final report of geology

ACKNOWLEDGEMENT

TRIBHUVAN UNIVERSITY

INSTITUTE OF ENGINEERING

PULCHOWK CAMPUSDEPARTMENT OF CIVIL ENGINEERING

A FIELD REPORT ON

GELOGY

SUBMITTED BY SUBMITTED TO

AMRIT AACHARYA (063BCE005)

BIJAY SUBEDI (063BCE017)

BIKRAM K.C. (063BCE018)

BIR BDR. BOHRA (063BCE024)

September 10, 2008TABLE OF CONTENTS1. Introduction ...........6-71. Introduction

2. Objectives of study

3. Location of study area

2. Study of Mass Movement and study of Preventive and corrective measures ..8-181. Mass movement

2. Types of mass movement

3. Causes

4. Classification

5. Preventive and corrective measures

6. Description of each location

7. Location A

8. Location B

9. Location D

10. Field observation

11. Sketch

3. Measurement of Attitude of planner features of rock ....19-221. Rocky outcrops and Exposures2. Planner features

3. Attitude of planner features

4. Types of geological compass5. Measurement of attitude of planner features in rock outcrops at Location E4. Identification of Rocks in the field .23-321. Rock

2. Classification of rock

3. How to identify rocks in the field

4. Types of rocks identified in the field

5. Rock identification form

6. Civil engineering significance of each rock types observed in Malekhu field

5. Geology of the study area ..34-371. Regional geological framework

2. Geological information

3. Rock types in the formation

6. Study of geological structures in the field ..38-431. Geological structures2. Types of geological structures

3. Types of geological structures observed in the Malekhu area

4. Unconformity

5. Fold

6. Fault

7. Thrusts

8. Sketch, photographs, description of location

9. Civil Engineering Significance of each geologic al structures

7. Study of river channel morphology 45-481. River morphology

2. Types of river morphology

3. Features developed by river channel

4. Civil engineering significance of river channel

5. Sketch, photographs, description of location

8. Engineering Geological studies of the rock outcrops .49-541. Define engineering geology

2. Importance of engineering geology in the field of civil engineering

3. Engineering geological data

4. Parameters of engineering geological data9. Rock mass .55-581. Definition

2. Rock mass classification systems

3. Q-system

4. RMR-system

5. Parameters of RMR-System

6. mass classification system in the Malekhu area

7. Rock mass class in the Malekhu area

8. Photographs, description of location10. Conclusion .59-60PREFACE

Engineering Geology is an applied discipline of geology which is concerned with the application of geological knowledge to engineering problems .The selection of suitable sites for bridges, tunnels, dams, roads along hill slopes etc, are only successful with the application of geological knowledge . e.g. to design reservoir, determination of suitable location, slope stability, and determination of earthquake, flood, and subsidence danger areas considered for roads, pipelines, or other engineering works should be known for construction purposes. It helps an engineer in planning, designing and construction, in safer, stable and economic way. Therefore Geology is an important topic for civil engineers. Civil Engineer is only responsible for studying the stability of the infrastructures in different types of land geology including rock, their slope and many other things. So only theoretical knowledge is not sufficient to enrich the civil engineers about practical problems and their solutions. For producing satisfactory results of any work practical knowledge is of foremost importance. Therefore a thorough knowledge of actual field visit counts for its credit. Geology deals with rocks and their origin, structure, orientation, strength, stability, hardness, weathering property, etc. It also deals with minute study of rocks structure including faults, folds, joints, beds, and other discontinuities. Engineers should have knowledge of topographic map for proper location of site and other activities. It is therefore very essential to make field visits. The three day Malekhu tour enables us to learn the various geological conditions related to Engineering point of view. The scope of field study outline before were fully made with the co-operation of faculty member and Malekhu possess wonderful geological diversities and almost all type of rock structures and geological factors like rivers, hills, slopes and sedimentations, were available to study within small area. At last but not least we are very grateful to our respected teachers and lectures that helped in completing this three day visit in a very responsible manner and gave us much important knowledge in a very short period of timeACKNOWLEDGEMENT

We are very much thankful to the Department of Civil Engineering for conducting such a fruitful visit on the Malekhu area that has given us golden opportunity to gain the knowledge on different aspect of geology which plays an important role in completing any civil engineering projects. We especially express our gratitude to our respected teachers Mr. Prakash Chandra Ghimere and Mr. Ajay sir for their special guide line in recognizing local geological conditions and their descriptions, well co-ordination, valuable suggestion.

We would also like to thank our friends and seniors who helped us directly and indirectly in the successful completion of Malekhu field visit and preparation of the report through any kind of means.

1. INTRODUCTION

Since the Engineering works should be implied on the field, so it is a must for an engineer to know about the field before he starts his activities. And the knowledge of the geological condition for an engineer is provided by a branch of geology known as Engineering Geology.

Engineering Geology is an applied discipline of geology which is concerned with the application of geological knowledge to engineering problems .The selection of suitable sites for bridges, tunnels, dams, roads along hill slopes etc, are only successful with the application of geological knowledge . e.g. to design reservoir, determination of suitable location, slope stability, and determination of earthquake, flood, and subsidence danger areas considered for roads, pipelines, or other engineering works should be known for construction purposes.

Engineering geology is now established as an interdisciplinary branch of science & engineering. In other way, it is an interdisciplinary profession in which the Engineering Geologist works closely with must understand and respond to the needs of the civil engineer. It is closely related with urban geology and deals with the impact of human activities on the physical environment.

Engineering works that lack the benefit of geologic input are likely to cost more than necessary, function below their expected optimum or fail altogether. This is not to say that only geologic factors are important consideration in the failure of the design & construction of engineering works. Unfortunately, examples are far too common in which lack of geologic information is at the root of problems encountered during development.

This branch as well includes the investigation of sites for the proper stability of structures. It helps an engineer in planning, designing and construction, in safer, stable and economic way.1.1. OBJECTIVES OF STUDYThe main objectives of three days field visit were: - Measurement of dip amount and strike of rocks

Engineering geological studies along the large scale geological discontinuity (the Mahabharata thrust)

Study of landslides

Geomorphology of river channel

Rock identification in the field

Study of the bedding planes, faults and joints, the rocky outcrops.

Study of rock slopes along the road corridor

The rock mapping techniques of the rocky outcrops and so on.

1.2. METHODOLOGY

The only methodology implemented in this study is direct field visit methodology. The true inspection with the detail field visits was done to know the real nature of the geological structures .The field inspection method includes the collection of samples, description of the collected samples via different criterias ,testing the vegetation of the area etc. The inaccessible places were also studied by the inferred method i.e. following the study of area through maps predominantly.

1.3. LOCATION OF STUDY AREA

The location of our field study was Malekhu, west from the Kathmandu, along Prithvi highway in Dhading district. The location politically lies in Dhading District. This Site is suitable place for our study as it provides mixed diversity within a small range of area. Our main study area was Malekhu and nearby which covers about 110 sq Km and lies in between 270 25 - 270 52 latitude and 840 48 - 84 0 59 longitude.

Fig:- map of Nepal2. STUDY OF MASS MOVEMENT AND STUDY OF PREVENTIVE AND CORRECTIVE MEASURES2.1. MASS MOVEMENT

Mass movement or mass wasting is movements of rock waste, bed rock, soil or mud which usually occur along steep-sided hills and mountains under the influence of gravity. This sudden flow of rock wastes is mainly due to their position, gravitational forces as well as due to the water presence. 2.1 TYPES OF MASS MOVEMENTThere are three types of mass movements:-

i. Slope failure

ii. Debris flow

iii. Landslides

i. Slope failureThe down slope movement of rock wastes, weathered surface soil layer in a small dimension and rapid movement influenced by surface and sub-surface water is called Slope Failure. It often takes place in weathered surface and sandy soils. Its velocity is about 10 mm per day which is very high. Crest, scarp, debris, tension cracks etc. are the chief components of slope failure. The preventive measures applied in these cases are like trimming of debris, reinforcement of slope, decreases in rate of percolation (by increasing speed of flowing water on surface) etc.

Slope failure depends mainly upon the following factors

a. Angle at which it is sustaining

b .height

c. Material d. Strength. e. Water stress in the pores.The slope failure loosen the rock mass and the open the stress relief joints or fractures. The mass resulted due to the slope failure moves parallel the failure plane. So far as the impact of the net load due to the mass is concerned, along the slope component mgCos act, which in one way is the driving force of the debris, resulted. The component of mgSin acts vertical to the plane of slope (where =Angle of the slope with respect to the horizontal plane). The net impact, say E, due to the failure is:

E=

Clearing the debris is considered as the best solution in case of slope failure along the road, but it could sometimes lead catastrophic landslides.

Fig: Slope failureii. Debris flow

Debris flow is the rapid down slope movement of enormous amount of viscous soils and boulders either mixed or separately. it is the flow of deposited and eroded sediments along the stream. When the shear strength of the hill slope material considerably reduced the rapid movement of solid earth material including large volume of water can take place such a flow including complex debris are called debris flow. If the material is fine the phenomenon is called earth flow .The slow but continuous movement of the slope containing the thicker soil layer without distinct slip surface is recognized as creeping. The major role in debris flow is of gravity and pours water so it generally occurs in monsoon.

Preventive measures: Water percolation safety and consequence reduction in pour-water pressure.

FIG: - DEBRIS FLOWiii. LandslideA landslide is the movement of a mass of rock, debris or earth down a sloppy slip surface under the influence of gravitational force. It occurs in gentle slope in large dimension in slow and continuous manner.

Fig: - landslidesAll landslides are the result of failure of the soil and rock materials that make up the hill slope and they are driven by gravity. They can vary in size from a single boulder in a rock fall or topple to tens of millions of cubic meters of material in a debris avalanche. Landslides can be triggered by natural causes or by human activity.

Wasting of mass caused by slope angle, role of gravity, pour water pressure and consequence saturation of fine clay etc. is called landslide. They seem natural and same material is flowing continuously. Multiple scarps can be seen in landslide.

Slip surface of landside

The slip surface of landslide can be found out

a) By visual inspection:It includes, Convexity of slope, concentric type of scarp, Planes of seepage, Clay horizon can be seenb) Geophysical investigation c) By propagating wave inside soil.d) By core drilling e) Pit/trench constructionClassification of landslide

Landslide may be classified on the basis of type of movements and materials into the following types: Types of movement Type of material

Bedrock Engineering soil

Predominantly coarsePredominantly fine

Falls

Rock fallDebris fallEarth fall

TopplesRock topplesDebris topplesEarth topples

SlideRotationalFew unitsRock slumpDebris slumpEarth slump

TranslationalMany unitsRock block slide

Rock slideDebris block slide

Debris slideEarth block slideEarth slide

Lateral spreadRock spreadDebris spreadEarth spread

FlowsRock flow(deep creep)Debris flowEarth flow

ComplexCombination of two or more principal types of movement

Causes of landslides

The main cause of landslide is the force of gravity. It has been observed that softer and unconsolidated rocks are more affected generally unable to withstand the pull of gravity. Landslide may be caused due to:

a. Water content.

b. Overloading c. Structural textures. Geological causesMorphological causesPhysical causesHuman causes

Weak materials

Sensitive materials

Weathered materials

Sheared materials

Jointed or fissured materials

Adversely orientated discontinuities

Permeability contrasts

Material contrastsSlope angle

Uplift

Rebound

Fluvial erosion

Wave erosion

Glacial erosion

Erosion of lateral margins

Subterranean erosion

Slope loading

Vegetation changeIntense rainfall

Rapid snow melt

Prolonged

precipitation

Rapid drawdown

Earthquake

Volcanic eruption

Thawing

Freeze-thaw

Shrink-swell

Ground water changes

Soil pore water pressure

Surface runoff

Other mass movementsExcavation

Loading

Drawdown

Land use change

Water management

Mining

Quarrying

Vibration

Water leakage

deforestation

mining

Definition of Landslides features

a. Crown:-

The Practically underplayed material adjacent to highest part of main scarp.b. Main scarp:-

A Steep surface on undisturbed ground at upper edge of landslide cause by movement of displaced material; it is visible part of surface of rupture. c. Top:-

The Highest point of contact between displaced materials and main scrap.

d. Head:-

The Upper parts of the landslide along contact between displaced material and main scarp.

e. Minor scarp:-

A Steep surface on displaced material of landslide produced by differential movements within displaced material.

f. Main body:-

The Part of displaced material of landslide that over lines surface of rupture between main scarp and toe of surface of rupture.

g. Foot:-

The Portion of landslide that has moved beyond the toe of surface of rupture and over lies original ground surface.

h. Toe:-

The Lower, usually curved margin of displaced material of a landslide most distant from main scarp.

Prevention of landslide

Retaining wall: Retaining walls can be constructed at the landslide expected area. However it is costly. Even then it should be constructed at the place which does not have differential movement. By reducing Q:By bringing about reduction in pore water pressure(Q) also, we can avoid landslide. Construction of surface drainage from the area behind the scarp: We should construct surface drainage from the area behind the scarp so that water does not enter into the crack and thereby also does not affect the pore water pressure. The drain should however be maid above the crack for this purpose. Avoid disturbing mechanical equilibrium condition: Landslide occur due to disturbance in mechanical equilibrium. Thus one should avoid doing such a thing so that pore water pressure does not develop. Construction of Gabion wall: Gabion wall should be constructed at the place of differential moment. If retaining wall is however maid, it will be waste of money. Gabion wall can also be constructed at a place which has developed pore water pressure. At a place where pore water pressure exists, a small hole should be made before construction of gabion wall. Though most of the reasons given above for the occurrence of landslide are true, some may be stated otherwise. For eg. It is not always true that construction of road results in landslide, Sometime nature itself may bring about devastating landslides.

In addition to above stated things one should also know certain important features of landslide. When we look at the place of landslide, if we see too many scraps, we can conclude that many landslides may have been gone at that place. Age of landslide can be recognized by the degree of weathering of the rock at the place of its occurrence.

2.2 Causes of mass movement i. Natural Factor

Steep Slope

Heavy and concentrated precipitation (maximum rainfall).

Undercutting of banks by river and streams.

ii. Material of Slope and Shear Strength of Material

iii. Presence of Soft and Weak Rock.

Alternate layer of weak and strong rock.

High grade weathering rock.

Heavily fractured rock.

High porous rock.

iv. Construction Activities (Artificial Cause)

Road in mountainous area.

Water canals in steep slope.

v. Improper Land Use

Agricultural practice, irrigation in slope area.

Quarrying of constructional materials.

Over grazing.

Deforestation.

2.3 Preventive and corrective measuresThere are several methods for controlling mass movements. The method depends upon the factors like nature of the slide, the underlying causes for it, the nature and amount of material likely to be involved in it and economic considerations. vi. For Artificial Slopes

Construction of breast wall is below the road, gabion wall, retaining wall, etc.

Surface drainage (Cascade drain, canal, etc.).

Sub-surface drainage (Weep hole in retaining wall).

Slope trimming (Flattering, benching).

River structure work (Check dam).

Bio-engineering concept of soil stabilization

Suitable vegetation in slope

Hardening

vii. For Natural Slopes

River structure work (Check dam).

Benching and diversion.

Re-vegetation.

Bio-engineering grass seeding, a forestation. 2.4 Case study2.5.1 Khatri Pauwa (Chainage 17km from Kathmandu) In this place we found that there was certain landslide towards the downward during the monsoon season. So as safety measures were taken by building the composite retaining structures of cement masonry and gabion walls around the region where the landslide has occurred. The landslide had occurred in the side slope of a small valley.

Fig: -Chainage 17km from KathmanduA large amount of loose material was deposited over the retaining structure which was obtained from landslide. The area was composed of hard soil and soft rock with fractures in rocks. During the monsoon season, the rain water had flown in the area weakening the rocks by flowing inside the cracks and the steep slope further added in the rupture of hill site. Geological material present there was also of low load bearing capacity due to presence of the fractured rock. Dynamic load due to the moving vehicle further increased the danger the failure of the site; some of the consequences followed them such as the traffic interruption during the monsoon season, economic loss as we have to rebuild the road or the construction site after the landslide damage. Thus we have to make some preventive measures in order to minimize the consequences as far as possible. For this purpose first we have to build the breast wall taking in the account of factor of safety.To stop further landslide bio-engineering works were done on the surface of landslide. Even after building of stabilizing structures we also add protection measures such as surface drain friction angle vegetation such as herbs are planted which now called bio-engineering. The self weight of the gabion wall hampers the equilibrium of the material and the structure. The protection measure is applicable only for the falling material but not for the equilibrium structure.

It includes the mass wasting of hill slopes process in which predominance of P.E. has been disturbed by shifting the position of mass, failure. 2.1.2 Belkhu Khola

This was the second station of our study along the Prithvi highway. It was the place where Belkhu and Trishuli River meet .The flow direction of Belkhu River was perpendicular to the flow direction of Trishuli River up to the point of confluence.

fig: - Belkhu river along Tribhuvan highway

At this location mainly the downstream of the bridge and the right bank of Trishuli River has been observed. The place was heavily affected by the rainfall of 1994 .The bridged washed away and the condition we see is the period of over nine years. The things found upon the observation listed below:

Poor settlement downstream the bridge.

Life may have been lost during the disaster.

The debris flow may have washed out the bridge.

There was mass movement along the river bank.

Description of opposite bank.

i. The bank is of well-graded material having vertical slope.

ii. It seems to be stable to period before.

iii. The soil may have exposed for about of 1000 years because of its red color.

iv. The brown color shows that there may the recent exposure.

v. The clear line in the middle of the area passes horizontally along the river direction having the vegetation to the particular area shows that the strata laid horizontally.

vi. The material shows contrast color.There is risk of being falling so should be alert all the time.

2.1.3 Dhading besi bridgeThe picture shows that the mass movement occurred due to flow of water into the mass from the top side of the mass though cracks. The land slide was about 50m. In length and we found very different soil condition in short interval. There was rock exposure at the bottom of beginning point of the landslide above which loose soil was there. A bio-engineering method of protection was applied there along with good management of surface water providing side drain and cascade drain. At the middle of the land slide stone masonry wall was constructed over which huge mass of the landslide was protected. We also saw a small portion eroded by flow of water. Dry stone masonry wall was provided there. At the end of the land slide gabion wall was provided to protect the landslide. Vegetation was grown enough there and few trees were there which shows that, that portion of landslide was in naturally stable condition. Further possibility of mass movement was protected there by draining water form top side of the mass and leaving some gap near the zone to prevent the further mass movement by pressure due the moving vehicles on the road at upside of slope. The location of the place is 3Km. form Malekhu towards Gajuri. It includes the tension cracks on the roadside by which water entered in the road. There is presence of vegetation on both sides of the mass movement side.

Fig: - 42 km along Prithvi highway2.1.4 MALEKHU (Ch 68+000) In Malekhu there is an exposure/outcrop of rock. We can see number of discontinuities sets in outcrops. Due to rock failure there was movement of rock particles to prevent rock fragments falling to road gabion wall has been built along the side of the road. The individual rock was found to be strong but due the presence of number of discontinuities the whole rock mass was unstable. The landslide has length of about 60m. A huge mass was deposited behind the gabion wall. The gabion wall was constructed not for retaining purpose but to prevent the rock fragments coming to the road. Thus the wall served as the catch wall. Some vegetation and few trees were grown at the beginning of the landslide but remaining portion was fully rocky portion with number of discontinuities. The movement of heavy vehicles also affected the stability of the rock mass. There was possibility of further movement of rock mass towards the road, which could produce serious problem in future in rainy season.

Fig:- Malekhu3 Measurement of attitude of planner features of rock2.1. Rock Exposures and Rock outcrops

Rock exposure is the naturally visible rock to the surface of the earth .Solid rock is not exposed anywhere on the surface of the earth; it is often covered by thin r thick layer of alluvium or soil .IN some places, alluvium or soil may be spread for thousands of square kilometers and the bed rock may not be visible anywhere.

An Outcrop is defined as the artificial exposure of the geological units on the surface of the earth. It is major source of data where we can measure attitudes of geological materials easily. Generally the rock outcrop is natural while the rock exposure is human induced.2.2. Planar features at rocky outcropsThe distinct visible marks or features of the rock outcrops are known as the planner feature of the rock outcrops. The Planner features have the significant importance for the study of the structural features .There are different planner features, which we can see in the rock outcrops.2.2.1. Bedding plane

The layers which are easily distinguished on the basis of variation in color, composition and grain size is known as bed. The plane of this bed or strata is known as bedding plane .It has fundamental significance in the study of structural features of sedimentary rocks. The different beds are distinguished from each other by difference in mineral composition, variation in grain size texture, difference in color and variation thickness.2.2.2. Foliation plane The segregation of minerals into layers or bands of contrasting mineralogical composition is known as foliation. The plane of these different bands occurred in metamorphic rock is known as foliation plane. Foliation plane is generally formed by dynamo-thermal metamorphism of coarse-grained igneous and sedimentary rocks at progressive stages of the process.

2.2.3. Joints

The rupture surface present after the cracks is known as joints .These are the divisional planes or factures ,which divide rocks into parts or blocks without transverse movement of blocks. There may or may not be small movement in the blocks perpendicular to the facture surface.

2.3. Attitude of planner features Attitude:

Orientation of linear and planner surfaces in horizontal direction with respect to north and in vertical plane with reference to horizontal is known as attitude.

Orientation of linear features

Trend: The orientation of horizontal projection of the linear feature measured with respect to the north is called trend.Plunge: The angle of inclination measured of its own linear features horizontally is called plunge.

Orientation of planner features

Strike: The line of intersection of the bedding plane with the horizontal is called the strike line and its orientation is called the strike. The true dip and strike is always perpendicular to the each other.

Dip amount and dip direction: The angle made by the strata of the rock out crop or any geological unit to the horizontal is called dip amount and its orientation with respect to the north is called dip direction.

2.4. Types of Geological compass

The geological compass is the combination of clinometers and compass. (Clinometers is an instrument used to measure inclination of surface). This geological compass is used to measure attitudes of outcrops.

Types of geological compass:

a) Clinometer compass:

Consists of clinometers and compass with no leveling advantages. Easy to handle but the possibility of errors is high. No corrections can be applied. Its use can be time consuming because we have to keep in two positions to take attitudes.

b) Brunton compass:

It is derived from its company name. It is also like clinometers but provided with leveling device.

c) Clar compass:

Scale of measurement of inclination is on the side of compass. So, efficiency is double since we can read both data at the same time. It is also provided with leveling device.

d) Ptyberger frager compass:

Combination of clinometers and prismatic compass with help of this compass both the dip amount and dip directions components can be measured simultaneously in a single measurement.

e) Digital compass:

When we keep it in the outcrop in the proper manner, it gives attitudes in the digits, and hence highly efficient.

Digital compass attached to personal computers:

We dont need to write data also. Data are recorded directly on the word-pad or personal computers.

The geological compass used by our group is clinometers compass. Due to its nature, there may be error in the measured outcrop data.

2.5. Measurements of attitudes of planner features in rock outcrops at location The measurement of the orientation of the planar features i.e. rock outcrops is done on the field. It is measurement of its attitude, which helps us to know the actual position of the planar feature on the earth.

Left bank of Malekhu Khola about 40m upstream of old bridge, we measured the attitudes of the planner features.

S.N.Dip DirectionDip AmountAttitudeRemarks

1N 18 W7676/18J

2S 17 E8080/17B

3S 16 E7070/16B

4S 19 E7474/19B

5S 84 E6565/84J

6S 70 W 5656/70J

7S 22 E8181/22B

8S 50 E8181/50J

9S 9 W9090/9B

10S 10 E8484/10B

11S 80 E5858/80J

12S 15 E8181/15B

13S 88 E5656/88J

14S 12 E8686/12B

15S 80 E7979/80J

16S 88 E3737/88J

17N 79 E3838/79J

18N 86 W8787/86B

19S 9 E8787/9B

20N 72 E7474/72J

21N 85 E5555/85J

22W 82 N7676/72J

23S 17 E8080/17B

24S 16 E7070/16B

25S 19 E7474/19B

26S 84 W6565/84J

27S 70 W5656/70J

28S 22 E8181/22B

29S 50 E8181/50J

30N 72 E7474/72J

31E 5 N5555/5J

32S 22 E8181/22B

33S 50 E8181/50J

34S 16 E7070/16B

35S 19 E7474/19B

36W 82 N7676/72J

37S 17 E8080/17B

38N 86 W8787/86B

39S 9 E8787/9B

40N 72 E7474/72J

B= bed

J= joint

Note: The direction of strike is perpendicular to dip direction

3. Identification of Rocks in Field3.1. Rock

Rock is defined as the naturally forming, hard and compact solid aggregates or assemblage of minerals forming the crust of the earth. It is said to be monomineralic rock if it is formed from assemblage or aggregates of only one mineral and multimineralic if it is formed from more than one mineral.

3.2. Rock TypesAll the rocks found in nature are not the same. Even a small area contains large number of rocks varieties. One rocks differ from other in color, strength, crystal structure, composition, porosity, hardness and specific gravity, cleavage, fracture, grain size etc on the basis of the variations, rocks are classified into different classes.

On the basis of rock origin, they are classified as: -

3.2.1. Igneous rock

Those rocks, which are formed from a hot, molten material by the process of cooling and crystallization called magmatism on or beneath the surface of earth is called Igneous rock.

These are the rocks formed by the solidification of magma either under neat the surface or above it: accordingly they are divided into two groups:

a. Intrusive bodies: which are formed underneath the surface of the earth

b. Extrusive bodies: which are formed due to consolidation of magma above the surface of the earth. These are also known as volcanic rocks

On the basis of the depth of formation, intrusive rocks are of two types

Plutonic rocks: which are formed at very depths.

Hypobysal rocks: which are formed at shallow depths.

On the basis of chemical composition of the minerals of the rocks.

Acidic rock: If silica content is >66%

Intermediate rock: If silica content is 52-66%

Basic rock: If silica content is 45-52%

Ultra basic rock: If silica content is 95%) of three types: Sandstones, mud rocks and carbonate rocks.Broadly sedimentation includes:

Compaction: - Decrease in volume by weight of overlying sediments.

Lithification: - Change of loose sediments into rock.

Cementation: - Joining of sediments with fine materials.

Digenesis: - Cementation, Compaction and finally growth of new minerals.

Sedimentary rocks can be classified as:

a. Clastic (Detrital) Rock

b. Non-Clastic Rock

3.2.3. Metamorphic Rock

Those rocks formed by the alteration of the pre-existing rocks by the process of metamorphism are called metamorphic rocks.

Metamorphism is a natural process by which existing rocks are altered into new rock under the influence of pressure, temperature and chemical reaction. In rock, the minerals have preferred orientation3.3. How to identify rocks in the field

Rocks can be identified in the field with the following tips and points:-

Igneous Rock:

1. No bedding planes.

2. Random orientation of minerals and self-interlocked.

3. Hard and massive.

4. Usually contain much feldspar

5. Entire absence of fossils.

6. have heat effect on the country rock

7. huge massive body cross-cut into another rock

Sedimentary Rock:

1. Random orientation of minerals and sediments.

2. Sediments and minerals are cemented by fine matrix.

3. Have thick bedding planes.

4. Generally, soft, stratified i.e. characteristically bedded.

5. Fossils common

6. Stratification, lamination, cross bedding. Ripple marks, mud-marks etc are the usual structures.

7. No effect on the enclosing or the top and bottom rocks.

8. Quartz, clay minerals, calcite, dolomite, hematite are the common minerals.

E.g.: - calcite, limestone, magnetite, sandstone, shale, etc.

Fig:- sandstone Fig:- limestoneMetamorphic Rock:

1. Preferred orientation of minerals.

2. Have foliation planes i.e. thin folia of minerals.

3. Have rock cleavage.

4. Foliated, gneissose, schistose, granular lose, slaty etc are the common structure.

5. In this case fossils are rarely preserved in rocks of sedimentary origin except slate.Types of metamorphic rocks:-GneissIt is the rock with dark and light streaks or bands in alternating specific gravity are variable. Garnet (like mustard seed) can be seen in the rocks. The grain is medium or coarse. The structural feature is called gneissosity.

Fig:-Gneiss

Schist It is the rock that has extremely variable color and specific gravity. The dominant constituent is calcite. Others are mica, quartz and special minerals like muscovite (white colored), biotite (black colored), and chlorite (green colored). The rock is fusible and the property is called schistosity.

SlateIt is a black rock with low or medium specific gravity. Flaky minerals are quite abundant and others are hard to distinguish. The rock is compact and can be scratched by knife. It has foliation with slaty cleavage.

Fig:-Slate

Phyllite

It is a greenish and soft type of rock. It is layered and foliation plane is quite dominant with incompetent beds (the thickness less than 1cm is called foliation other it is called bed). No distinct grains can be seen. It is an igneous rock that has changed into metamorphic rock.

Fig :-phyllite QuartziteIt is usually light colored with shades of gray, yellow. It has medium specific gravity (i.e. S.G. =7). It has quartz, as major constituents while others are mica, feldspar. It is medium grained and the texture is massive and granular.

Fig :- quartzMarble It is derived from the latin word a shining stone. It is also a paarametamorphic rock. It is the rock of medium specific gravity, which is light colored. The major component is calcite. Texture is massive and granular. A knife can scratch it.

Fig :- Marble3.4. Types of rock identified in the fieldMajor metamorphic rocks identified in the field were Slate, Phyllite, Schist, Gneiss, Marble Slate: - Smooth and slaty cleavage, fine-grained texture. It can be split-up into smooth thin sheets. Due to its low crushing strength it is also used as building material. It was found at a distance of five hundred meter north of highway.Phyllite: - It is the fine-grained metamorphic rock. Slaty cleavage with soapy touch. Essential minerals are mica, quartz, horn blend etc. This is found at the south from the highway along the stream.

Dark green type of phyllite was found in the Robang Formation(RB).Schist: - It is formed by the dynamic metamorphism of shale. It is available in light colors and closely spaced foliation planes. Platy and flaky minerals arranged in regular layers.

Gneiss: - They are the coarse grained foliated rock formed by the dynamic metamorphism of the sandstones, conglomerates and granites. They are characterized by the inspection of segregation of minerals into layers. Contrast in color, texture and composition. They are massive. In Malekhu it was found at a distance of four thousand six hundred fifty meter south from the highway. The gneiss was found in the boulder as an eye structure and so called Augen Gneiss. This was found on the Kulekhani formation (ku) of Bhimphedhi group.

Marble:- Marble is essentially a granular rock composed chiefly of recrystallized calcite. It is characterized by a granular structure. Marble often show banded structure. Marbles are commonly used in building constructions in the form of blocks, slabs, aches, and as chip for flooring. It is also used as decorative and ornamental purpose. In Malekhu it was found at a distance of three thousand two hundred seventy five meter south from the highway.

Quartzite: - Quartzite is a granular metamorphic rocks composed mainly of the intercultural grains of quartz. The name Orthoquartizile is used for a sedimentary rock of similar composition but of different origin; it has siliceous cement. It contains sub-ordinate amount of micas, feldspars, garnet and some amphiboles which result from the impurities of the original sandstone during the process of metamorphism. The rock is generally very hard, strong, dense and uniformly grained. It finds extensive use in building and road construction..

Different types of Sedimentary rocks found in the field of study are as follows:-

Limestone: - These are the most abundant sedimentary rock formed from the non-elastic group and are composed of chiefly calcium carbonate. However the presence of dolomite, quartz, feldspar and iron oxides is rather a common mineral. Limestone is a primary source of materials for the manufacture of Portland cement and for a wide variety of limes. Its other uses are in the Metallurgical industries as a flux.

It was found along the Prithvi Highway towards Gajuri as the Robang Formation (RF) as a Malekhu Limestone Formation (ML) in the Upper Nuwakot Group.

Sandstone: - Sandstone is a mechanically formed sedimentary rock. It is formed by the cementation of the sand particles of sized between 1/10mm to 2mm in diameter. Sandstone is perhaps the most familiar of all the rocks as it is usually quarried and used more than any other rock, for all types of buildings. The various varieties of sandstone are named after the cementing material. E.g. Siliceous Sandstone, Ferruginous Sandstone, Calcareous Sandstone, Argillaceous Sandstone etc.

Breccias: - Breccias are a mechanically formed Sedimentary rock consisting of the angular fragments. These sediments are heterogeneous in nature; cemented together by clay; iron oxide, silica or calcium carbonate and are generally of more than 2 mm size. Because of the heterogeneous character they are not used as building stines but some of the varieties which are susceptible to polish can be used for ornamental works.

Igneous Rocks found in the field of study are described below:

Granite: - Granite may be defined as the Plutonic light colored igneous rock. These are among the most common igneous rock. Two most common and essential mineral constitutes of granite are Quartz and Feldspar. The first is always recognized by its vitreous luster, with MHN 7 and cleavage less wide translucent appearance. Feldspar, forming Granite may be of two types: K-Feldspar, commonly Orthoclase and the soda bearing Plagioclase Feldspar like Albite and Oligoclase. Feldspar microcline may occur in some granite.Agra Granite was found in the right bank of Malekhu Khola south west of "Chhapan Danda".3.5. Rock identification formFor rock 1S.no. ParametersCondition

1. Color Grayish

2. TextureNon-crystalline

3. StructureFoliation plane

4. Grain sizeFine

5. Specific gravityLow to medium

6. Acid testNo reaction

7. Mineral composition

8. OriginMetamorphic

9. Engineering properties

10. IdentificationSlate

11. UsesRoofing

FOR ROCK 2

S.no. ParametersCondition

1. Color White

2. TextureCrystalline

3. Structurebedding plane

4. Grain sizeMedium

5. Specific gravityHigh

6. Acid testVigorous reaction with acid HCl

7. Mineral compositionCalcite

8. OriginSedimentary

9. Engineering propertiesHigh strength and permeable

10. IdentificationLimestone

11. UsesManufacture of mortars, cements as well as fertilizers in white wash

For rock 3

S.no. ParametersCondition

1. Color Dark green


3. StructureFoliation plane sloty

4. Grain sizeFine to medium

5. Specific gravityHigh


7. Mineral compositionHorne blende


9. Engineering propertiesHigh strength

10. IdentificationAmphibolites

11. UsesDimension stones

For rock 4S.no. ParametersCondition

1. Color Silver white


3. StructureFoliation plane

4. Grain sizeMedium to coarse



7. Mineral composition


9. Engineering propertiesLow strength

10. IdentificationPhyllite

11. Uses

For rock 5S.no. Parameterscondition

1. Color Dirty white

2. Texturecrystalline

3. StructureFoliation plane and slaty cleavage

4. Grain sizemedium

5. Specific gravitymedium


7. Mineral compositionQuartz


9. Engineering propertiesDimension stone, foundation stone

10. Identificationquartzite

11. UsesRoofing

For rock 6

S.no. Parameterscondition

1. Color Silver white


3. StructureFoliation plane Schiestosity

4. Grain sizecoarse



7. Mineral compositionGranite, chlorite, quartz


9. Engineering propertiesLow strength

10. IdentificationSchist

11. Uses

For rock 7S.no. ParametersCondition

1. Color White


3. StructureBedding plane

4. Grain sizeCoarse

5. Specific gravitymedium


7. Mineral compositionCalcite


9. Engineering propertiesHigh strength

10. IdentificationMarble

11. UsesRoofing, decoration and manufacturing of cement

4. Geology of Study Area

Geologically, Malekhu contains many geological peculiarities like joints, faults, different types of rocks, streams and amazing flow direction of the Malekhu River.

TOPOGRAPHYMalekhu is a small village on Dhading district about 70km south west of Kathmandu and lies at latitude of 27degree 45 minute 50 second and longitude of 84 degree 49 minute 5 second to 84 degree 50 minute 50 second. It is situated at the bank of Trishuli and Malekhu River. The Trishuli River is flowing from east to west and Malekhu River from south to north that finally emerges into Trishuli River. Malekhu River at a distance of about 3km from Malekhu bazaar. The Trishuli River seems to be flowing linearly with some occasional meanders.

Malekhu lies in the region of lesser Himalayas, one of the morho-tectonic zone of Nepal. Siwaliks and higher Himalayas are its neighboring morpho-tectonic zones. Main boundary thrust (MBT) in south separates the Siwaliks and the Lesser Himalaya and the Main Central Thrust (MCT) in north separates the Higher Himalaya and Lesser Himalaya. The MBT is itself an active fault that has brought older rocks of lesser. Himalayas to Siwaliks.

The lesser Himalayas are mostly composed of unfossiliferous, sedimentary and meta-sedimentary rock such as slate, phyllite, schist, quartzite etc. There are also some intrusions of granite.

The lesser Himalayas of Nepal vary from east to west in stratigraphy, structure and magmatism. The eastern Nepal is characterized by development of extensive thrust sheet of crystalline rocks that have traveled southward. In central Nepal, a large thrust sheet called Kathmandu Nape covers a wide area around the Kathmandu region. Malekhu lies in the vicinity of Mahabharata thrust, which lies between Indian and Tibetan plates and thus landslides are quite common here. In few places the Mahabharata range is intercepted by major Rivers through which all the water from Nepal originating from north drain to south. The Mahabharata region is characterized by concentration of population along the ridge and gently dipping northern slopes.

CLIMATEThe climate of Malekhu has a typical sub-tropical. The vegetations consist of deciduous trees like chilaune, sal etc grasses and bushes. Malekhu is a river valley extending from east to west along the Trishuli River and most of the inhabitants are concentrated on the southern part. This causes lack of direct sunshine and foggy mornings.

4.1. Regional geological frameworkMalekhu is a small village on Dhading district about 70km south-west of Kathmandu and lies at latitude of 270 45 50 to 270 50 38 and longitude of 840 49 05 to 840 50 50. It is situated at the bank of Trishuli and Malekhu River. The Trishuli River is flowing from east to west and Malekhu River from south to north that finally emerges to Trishuli River. Malekhu River also has a tributary namely Apakhola which meets Malekhu River at a distance of about 3km from Malekhu bazaar. The Trishuli River seems to be flowing linearly with some occasional meanders. Malekhu lies in the region of lesser Himalayas.

Malekhu lies in the vicinity of Mahabharat thrust, which lies between Indian and Tibetan plates and thus landslides are quite common here. In few places the Mahabharat range is intercepted by major rivers through which all the water from Nepal originating from north drain to south. The Mahabharat region is characterized by concentration of population along the ridge and gently dipping Northern slopes.

Malekhu has a typical subtropical climate. The vegetations consist of deciduous trees like chilaune, sal, etc. grasses and bushes. Malekhu is a river valley extending from east to west along the Trishuli River and most of the inhabitants are concentrated on the southern part. This causes lack of direct sunshine and foggy mornings.

4.2. Recognition of Geological UnitsFollowing geological units were recognized in the field during field visit:

i) Benighat Slate:

The name is derived from the village Benighat at the confluence of Budhigandaki and Trishuli River.

This formation consists of grey to black slate. In some places it is highly carbonaceous (graphite), also it is calcareous and dolomitic at the lower part .Inter collation of quartz vein 2cm to 4 cm thick is also observed in some places. The beds are not thicker than 5cm to 7cm in this formation .this formation is about 500 m t0 300m thick .

Attitude of bedding plane

Strike:

E-WDip direction: S

Dip amount:860

It was found on thopla Khola and Dhading Road.

After 300m from suspension bridge over Trisuli River, calcareous beds of Benighat slate is observed this was fine grained yellowish grey in color and highly fractured and jointed.


Strike:

N 850 E S 850 WDip direction: N 50 W

Dip amount:750

The difference in attitude in Benighat slate indicates that these may be fault of fold in this formation.

ii) Malekhu Limestone:

It is named after the Malekhu village near Kulekhani village. Main lithology is schist, quartzite and carbonates in varying proportion and they form white colored marble. Cross bedding is also found near the middle part of formation.

About 400m far from the bridge over Malekhu Khola, nearly vertical beds of dolomitic limestone of grayish color were observed


Strike:

N 700 E S 700 WDip direction: S 200 E

Dip amount:750

About 200m from the previous location along Malekhu Khola towards upstream, We observed a fault plane .Left side of the fault plane composed of limestone of whitish yellow color and the right side of the fault plane composed of grayish white phyllitic limestone .The fault plane composed of mylonite bressia .Nearly 200m from the fault plane, there is a transitional contact between Malekhu Limestone and Robbang Formation.


Strike:

N 700 E S 700 WDip direction: S 200 E

Dip amount:900

iii) Robbang Formation

The name derived from the village Rogbang in Dhading district. Along Malekhu Khola, on right bank about 500 m .from the Prithvi highway, near Malekhu limestone and dark green phyllite of robang formation was observed from where river bends sharply.

Main lithology is phylite and yellowish quartzite called dunga quartzite which is highly jointed. Phyllite is gradually replaced by massive yellowish towards south .Some phyllitem beds are black in color due to graphite .Nearly middle part of the formation ,we observed was Amphibolites, a metamorphic product of basic intrusive rock-dolerite.

The thickness of this formation is about 200 m to 1000m.


Strike: N 550 E-S 550 WDip direction: S 350E

Dip amount: 500Attitude of bedding plane at dunga Quartzite:

Strike: N 800 E-S 800 WDip direction: S 100EDip amount: 900It is found along Prithvi Highway towards Gajuri

About 500m far from the Malekhu, the contact between Robbang Formation and Malekhu Limestone is found which transitional contact.


Strike: N800 E-S 800 WDip direction: S 100EDip amount: 750

About 100m far from the contact, Amphibolites a metabasic rock is observed which is weathered and is olive and muddy in color with

contact of metabasic rock and quartzite is observed. It may be Dunga Quartzite.

Attitude of bedding plane at dunga Quartzite:

Strike: N 850 E-S 850 WDip direction: S 50EDip amount: 850

iv) Raduwa Formation

The name is derived from the village Raduwa in Dhading district .This name was first used by Stocklin and Bhattarai at 1971

A highly fractured zone of Mahabharat Thrust exposed at right bank of Malekhu Khola, every fine, grey to black mylonite is observed. This separates Robbang formation of Nuwakot Complex and Raduwa Formation of Kathmandu Complex.

The main Rock type of this formation is mica-schist of coarse crystalline of dark grey color due to predominant micaceous minerals. Near MBT garnetiferrous schist is also observed which is perfectly foliated .This formation is about 1000m thick.


Strike: N 750 E-S 750W

Dip direction: S 150 EDip amount: 750

v) Bhainsedovan Marble:

This formation is named after the village Bhainsedovan on the Tribhuvan Highway. It is in contact with Raduwa formation. Well exposed marble is in front of dharapani. It is metamorphic equivalent of limestone and so white in color, crystalline in texture associated with pyrite mineral. It is about 800 m thick.

Attitude of bedding plane Strike: N 700 E-S 700 W

Dip direction: S 200 EDip amount: 700

4.3. Engineering significance

The study area Malekhu has great importance from the engineering point of view. This area being in the lesser Himalayan at an average height of 2200m to 3300m from the mean sea level has grate possibilities of constructing dams and reservoirs. Such as example of the construction is Kulekhani hydro power station.

The other having engineering significant is that the area is bounded by M.B.T. differentiating it from the Siwalik region and M.B.T. differencing if from the higher Himalayas. The earth quake in this region is bit lower that that of Siwalik and quaternary basin containing H.F.T,M.F.T. having large number of faults there by has high chance of earthquake. As M.B.T. is less active than H.F.T./M.F.T, the quake in this region is more prominent. The weak the point of areas is i.e. composes of low graded metamorphic rocks and phyllite are predominant. The phyllite has low bearing capacity and be easily weathered, there by having gentle slope.

5. Study of the Geological Structures in Field

We all know that the earth is a dynamic body. So different types of external and internal forces act upon the earth due to various geological processes like earthquakes, volcanisms etc. Due to such activities along with gradual shrinkage of interior of earth, causes structural changes on the rocks lying on earths crust to displace and distort. Such structures are called geological structures e.g. Folds, faults, joints etc. There are two types of deformation structures:-

Continuous deformation structures: - These are the product of plastic and viscoplastic deformations e.g.: Folds, Veins, Foliation, and Cleavage etc.

Deformation structures: - These are the product of brittle deformation e.g. Joints, Faults etc.5.1. Unconformity Unconformity is the plane of discontinuity that separates two rock sequences, which differ notably in age. When the rocks are formedcontinuously or regularly one after the another with break or depositional gap between the two conformable sequences, it is called unconformity. It occurs mainly due to erosion, deposition and tectonic activities. It develops in the three stages in which under the first stage older rock forms whereas in the second stage upliftment and surfacial erosion of the older rock occurs. In the last stage younger succession of beds forms after long time interval above the surface of erosion. There are three types of unconformity :-

Parallel unconformity

Angular unconformity

Non conformity

5.2. Folds

Any bend or flexure on rocks formed by plastic or viscoplastic deformations, which changes dip amount and often changes dip direction of rocks are called folds. They may be formed due to- tangential compression, intrusions, differential compactions etc.

Folds can be classified on different basis. On the basis of attitude of fold, they may be classified as:-i. Plunging fold

ii. Non plunging fold

iii. Doubly plunging fold

On the of upward and downward bend it is classified as:-i. Anticline fold

Fig:- anticline fold

ii. Syncline fold

Fig:-syncline fold

5.2.1. Recognition of folds in the field:-

Visual inspections

Repetition and omission of beds

Measuring attitudes of beds of rocks and plotting them in map and taking cross-section

Recognition of folds during excavation of tunnels/construction of roads

5.3. FaultsEarthquakes result from movement along a fault. Faults and earthquakes are cause and effect. The sense of motion on faults describes how the block moves relative to each other. Faults may move along preexisting fracture or may form a new one. There are 3 basic types of faults: normal, reverse, and strike-slip. Normal and reverse faulting result in vertical slip, while strike-slip faulting results in horizontal slip. In nature, motion is seldom absolutely along one direction. There can be a combination of vertical and horizontal slip, which would make the movement along the fault oblique. Normal faults: Normal faults are associated with extension. A good example of normal faulting is the Basin and Range topography of the western United States. The western part of the North American plate has been pulled apart into a series of "blocks". Most Basins and Range structures result from the tilting of these blocks. A major Basin and Range fault zone is the Wasatch Fault zone, which is 220 miles long (360 kilometers) and extends from Utah into Idaho.

Reverse faults: Reverse faults are associated with compress ional forces- 2 plates or fault blocks pushing towards each other. One side ends up on top! Thrust faults are reverse faults that move up a shallower angle than ordinary reverse faults.

Strike-slip faults: Strike-slip faults are associated with shear stresses. One side of the fault "slides" past the other. "Sometimes" it is fairly easy to recognize where movement on a strike-slip fault has occurred. The photo below shows a creek located along the San Andreas Fault. The zigzag effect (offset) of the creek channel is the result of movement along the fault.

Structures formed during faulting:

i. Slicking slides:-

They are the linear features developed in the fault plane, in which the relative displacement takes place.

ii. Fault gauge:-

It is the finely pulverized, clay like powdered rock material formed due to rubbing and shearing of block during faulting process.

iii. Fault breccias:-

The crushed (but not powdered) angular fragmentary material during faulting and found near the base of the up-thrown block is called fault breccias. Very often, such angular fragments are embedded and cemented in the fault gauge and forms a rock-like mass again, which is also called fault breccias.

iv. Mylonite:-

It is extremely fine grained and very hard, coherent type of rock formed due to faulting. It is also called micro-breccias.

Recognition of faults in the field:-

i. Discontinuity of the structures

ii. Repetition or omission of beds

iii. Silicification and mineralization

iv. Presence of slickenside

v. Characteristics feature of faults; fault gauge, fault breccias, Mylonite

etc. indicates existence of faults

vi. Difference in sedimentary faces

vii. Physiographic features:

a) Offset ridges b) Fault scarp

c) Pediment scarp

d) Offset stream e) Aligned spring f) Alluvial fan

g) Monocline h) Triangular facet

5.4. Joints

These are the ruptures/fractures without any remarkable displacement or even if negligible is there, it is perpendicular to the fracture plane. Joint intersect the existing structures like foliation, beddings etc. Joints are relatively smooth fracture; they are present in most consolidated rocks of igneous, metamorphic and sedimentary origin.

Joint sets: - Series of parallel joints are called joint sets.

Joint system: - A group of intersecting joint sets is called joint system.

Conjugate joints:-

Two sets of joints, which are nearly perpendicular to each other and produced by the same stress system, are called conjugate joints.

5.5. Vein

The filling of the minerals in between the fault planes produces a new structure, which is called vein. Veins may have valuable minerals like gold, copper, diamond, silver etc so it is important for the economy of the country.

5.6. Thrust

A kind of reversed fault in which hanging wall has actually moved up relative to the footwall is called thrust e.g. Mahabharat thrust separates Nuwakot complex and Kathmandu complex. These thrusts are formed due to actual movement of hanging wall in upward direction.

5.7. Engineering significance of geological structures

5.7.1. Fold

For the foundation of dam on the large fold, the flank which is dipping towards downstream is unfavuorable and the one which is dipping downstream is comparatively safer.

In tunneling, if the tunnel passes through the syncline, then the stress is exerted more on the side than the crown, while in anticline condition, tensional fracture may be developed on the crown causing over break.

In synclinal aquifer, the groundwater potential is higher and in antisynclinal, the same is reverse.

In folded area, there is possibility of rupture due to action of further stress.

5.7.2. Fault Fault causes considerable fracturing and shattering of rocks along the fault zone. This means they are not compact and massive. These places are very weak and hence unfit as foundation sites for withstanding heavy loads.

The most dangerous problem of faulting is that it may occur in the same place again. This means the faulted ground is unstable as long as the fault remains active. So in such places no civil engineering foundation will be safer and stable.

Generally, faults are accompanied by earthquakes which cause severe shaking of ground.

Since faults bring different rocks together, there will be no homogeneity of physical characters. Foundation across these areas is undesirable.

5.7.3. Joints

The sites where joints are found are weak physically.

Through these joints water is likely to percolate into the rock and saturate it. This may cause the decay of rock. This may cause the site unsuitable for bridge, dam construction.

6. Study of River Channel Morphology6.1. River morphologyThe surface water flowing in course of their own are known are known as streams and the large stream flowing through extensive area and receiving water from smaller side streams is known as river .The defined course followed by river is known as the river channel.Factors Responsible for River Channel Morphology

Discharge: The volume of water flowing per unit time is known as discharge. The discharge of water may affect for the river channel morphology. The activities of river may depend on the discharge of water .The high discharge water may cause erosion, transportation and deposition in high rate, which activities ultimately may affect for the river channel morphology.

Velocity: The velocity has the significance role for river channel morphology .The fast moving rivers are capable of erosion and carrying a greater amount of materials. The velocity itself depends on the gradient and discharge of river.

Lithology: The nature of rocks along the channel and side may effect for the river channel morphology. Some types of rocks are more easily eroded by river water .The river channel, which passes through the limestone, will be straight

Activity of River

When a river flows continuously in its way it carries out different activities along with its continue flow. The activities of river are different indifferent places according to the velocity of river, gradient of river and energy of flow .There are three different activities generally done by the river.

i) Erosion ii) transportation and

iii) deposition.

The water flowing in a river along its seaward journey erodes the land over which it flows, brings about its chemical decay, denudes rock, and transports the rock debris, which formed during erosion and weathering and finally deposits the transported materials under the favorable conditions. Hence the Eros ional and depositional can be divided as follows:

i) Erosional features

Hydraulic action

Abrasion

Attraction

Solution

ii) Transportation

The process in which the river carries erosional materials from one place to another is called transportation.

iii) Depositional Features:

The discharge of river gradient of its valley floor is responsible for the velocity of channels. Hydraulic action of the river is the breaking down of the rock mass due to the continuous impact of the moving water along the channel. The water running along the river channel contains some amount of rock fragments, the large boulders and pebbles roll along the valley floor. The rolling boulders and pebbles naturally rub themselves against the valley floor during the travel while in suspension impinges periodically upon the floor of the river valley. Such impacts are responsible for the mechanical wear and tear of rocks forming base and adjustment of river channel. The process of mechanical breaking down of bedrocks due to the impacts is known as abrasion. The process of mechanical breaking down of the transported rock-fragment due to impinging themselves is attraction. A river along its seaward journey traverses through a vast country or naturally comes across varieties of country rocks along its path of travel. Some rocks are practically insoluble but other are soluble in running water containing dilute acids, carbonate rocks like limestone are attacked by running water. In less soluble rocks some of the soluble constituents are slowly remained in solution as a result rock mass is rendered weak and subjected more conventionally further erosion. Running water transports load due to kinetic energy associated with its flow. The exact magnitude of energy depends upon the gradient of the valley floor shape and size of channel and discharge of as soon as the velocity of the running water decreases its transporting capacity is proportionally reduced and as a result part of its load is dropped down.

6.2. Types of River Channel MorphologyMainly there are three types of river channel. They are,

i. Straight: - The River follows in a straight path in its high energy level. In this case erosion is predominant and the velocity of river is maximum. In hilly region, the river follows in straight path.

SHAPE \* MERGEFORMAT

Fig:- Straight riverii. Meandering: - In this type of flow, the river follows the path like as snakes movement. In the valley region, the river follows the meandering path. Erosion and deposition take place side by side in the same time.


Fig:- Meandering river

iii. Braided: - In this type of Flow the river follows multiple channel. Deposition is predominant in this flow .The braided river tends to be very wide and relatively shallow. The river follows this type of path in Terai region.


Fig:- Braided river Features Developed by Rivers

Delta:

When a river ultimately meets the sea or lake, the flowing water looses its velocity and has therefore no other way to drop down the balance of its load right at its point of emergence at the mouth if river. Such depositions naturally initiates under Natural conditions. The formation of land mass is approximately triangular in shape; are called deltas. Deltas are seemed low elevated on the mouth of river.

Fig:-Delta deposit Fan:

Likewise delta, fans are also the triangular landmass deposition at the meeting point of rivers. These are high elevated as compared with deltas. If gradient of both rivers are approximately same fans can be formed.


Fig:- Fan deposit

Ox-bow lakes:

If only a narrow strip of land separates individual loops of meandering stream from each other, then during large water discharging time the river has tendency to flow straight; isolating the loop on one side. That isolated loop forms a lake called Ox-bow Lake.


Figure 4:- Different Stages of Formation of Ox Bow Lake7.4 Civil Engineering Significance of River Channel

A civil engineer has to face different types of river channels for the construction of different types of civil engineering projects as well as for the survey of availability of construction materials. If a bridge is to be constructed on a straight river, it is not applicable to make foundation in the river channel as scouring is intense along the path. As side cutting is lower in such case, an arc bridge may be good. For example, Meeteri Bridge constructed over the Bhotekoshi River is an arc bridge which joins Nepal and China.

In the meandering river, if the bridge is constructed in a curve portion, then the foundation on the striking bank may be affected. In such case the site for bridge can be chosen in the straight portion of the river.

In case of braided river, a span of bridge is high with many pillars on the river path. For hydropower site, in Straight River run off type hydropower is applicable. In meandering type, both run off and reservoir type hydro powers are suitable depending to site condition.

, the availability of construction materials also detects the type structures. For example, due to the availability of granite boulders, a gravity dam is constructed to make reservoir of Kulekhani Hydropower Project.

7. ENGINEERING GEOLOGICAL STUDY OF THE rock outcrop

7.1. Engineering Geology

Engineering Geology is the branch of geology which deals with the application of geological knowledge in the field of civil engineering for the construction of infrastructures such as road, bridge, dam reservoir etc. Engineering is defined in the statutes of the IAEG as the science devoted to the investigation, study and solution of the engineering and environmental problems which may arise as the result of the interaction between geology and the works or activities of man, as well as of the prediction of and development of measures for the prevention or remediation of geological hazards.7.2. Importance of Engineering GeologyGeology in civil engineering is concerned with the engineering behavior of earth materials. It includes investigating existing subsurface conditions and materials; assessing risks posed by site conditions; designing earthworks and structure foundations; and monitoring site conditions, earthwork and foundation construction.

A typical geotechnical engineering project begins with a site investigation of soil, rock, fault distribution and bedrock properties on and below an area of interest to determine their engineering properties including how they will interact with, on or in a proposed construction. Site investigations are needed to gain an understanding of the area in or on which the engineering will take place. Investigations can include the assessment of the risk to humans, property and the environment from natural hazards such as earthquakes, landslides, sinkholes, soil liquefaction, debris flows and rock falls.

7.3. Engineering geological data

There are some factors whose condition in case of rock are observed and recorded in order to determine the age of the rock is simply known as engineering geological data. These data also helps us to determine the present condition and the nature of the rock.

8.4 Importance of engineering geological dataPurpose specific geological data collected from field (rock mass) which can be quantified and used as design parameter. It is quantities diagnosis of an area. It must be purpose specific. Site investigation is the investigation of particular area for specific purpose data collection. It is very essential to draw any engineering geological map or to solve any geological problems.

We always deal with a rock mass not only with a block of rock. Rock mass means intact rock with its discontinuities. In many cases, the technicians are in dark in this aspect. He or she collect a piece of sample and take it to the lab and conclude his/her result. This is not a correct way to publish any geological decision. In fact, it is much more important to know the entire rock mass up to our concern.

7.4. Parameters of engineering geological data

Rock type: -1. Sedimentary

2. Igneous

3. metamorphic

Rock strength: -

1. High

2. Medium

3. Low

Weathering grade: -1. Fresh weather (w0)

2. Slightly weathered (w1)

3. Moderately weathered (w2)

4. Highly weathered (w3)

5. Completely weathered (w4)

6. Residual soil (w5)

Rock Quality Designation (R.Q.D): -It is expressed in percentage. The expression for RQD has is:

RQD=115-3.3*JvWhere Jv = Joint volume. I.e. number of joint per unit volume.

Spacing of discontinuity: -It is expressed in cm and all the discontinuity is taken under considered area.

Aperture or separation of discontinuity: -1. Tight (30cm)

Infilling materials of Discontinuities

Persistence(Continuity)

Roughness of discontinuity: -1. Smooth

2. Rough

3. Very smooth

4. Undulated

Number of joint set

Orientation of joint set

Orientation of discontinuities is the attitude of the discontunities.Depending upon the slope of discontunitiy rock has different strength at the different direction.If the direction of the discontinuity is in the same direction as the rock mass ,it is an unfavorable condition.But if the discontinuity is in opposite direction to the rock mass,it is a favorable condition.

Expressed including dip amount and dip direction, (i.e. dip amt/dip dir)

Ground water condition: -1. Dry

2. Dripping

3. Seepage

4. Flowing

5. Damp/wet

8.4 Geological engineering data in the field

S.N.ParametersPropertiesRemarks

1Rock typeSedimentary

2Rock strengthHigh

3WeatheringW1

4R.Q.D. test62.2

5Spacing of discontinuity 5.5,2.5,23.5,6.8,3.5,10In cm

S.N.Parameters6

Aperture of discontinuity

tight

7

Infilling materials

Calcareous

8

Persistence

90%

9

Roughness of continuity

Rough

10

No. of joint set

3

11

Orientation of joint set

83/165, 5/251, 19/65

12

Ground water condition

Dry

PropertiesRemarks


2Rock strengthMedium

3WeatheringW2

4R.Q.D. test82

5Spacing of discontinuity 9,10,6,3.5,12.5,6In cm

6

Aperture of discontinuityTight

7Infilling materialsClay

8Persistence95%

9Roughness of continuitySmooth

10No. of joint set3

11Orientation of joint set80/162,24/72,56/77

12Ground water conditionDry



2Rock strengthHigh

3WeatheringW1

4R.Q.D. test75.4

5Spacing of discontinuity16,15,9,14,9,3,5,10,7In cm

6Aperture of discontinuityWide


8Persistence90%


10No. of joint set3


12Ground water conditiondry



2Rock strengthHigh

3WeatheringW1

4R.Q.D. test82

5Spacing of discontinuity15.65,13.2In cm.

6Aperture of discontinuityTight

7Infilling materialsClay and sand

8Persistence50%


10No. of joint set3





2Rock strengthHigh

3WeatheringW1

4R.Q.D. test83

5Spacing of discontinuity3,5.9,2,8,4.6,12In cm.

6Aperture of discontinuityTight


8Persistence70%


10No. of joint set3



8. ROCK MASS8.1. DefinitionThe collective mass formed by the rock material (intact rock and discontinuities is called rock mass. So the rock exposed on the outcrop is not rock, in fact it is the rock mass. Rock materials (intact rock) are a part of rock mass. Since in actual practice discontinuities are present, rock material alone doesn't exists in nature.

Rock mass is a mass of rock interrupted by discontinuities with each constituent discrete block having intact rock properties. Rock masses are heterogeneous because of different rock types, presence of discontinuities, and varying degree of weathering.

Rock Mass = Intact Rock + DiscontinuitiesThe objectives of rock mass identification are to

Identify the most significant parameters influencing the behavior of a rock mass.

Divide a particular rock mass formulation into groups of similar behavior rock mass classes of varying quality.

Provide a basis of understanding the characteristics of each rock mass class

Relate the experience of rock conditions at one site to the conditions and experience encountered at others

Derive quantitative data and guidelines for engineering design

Provide common basis for communication between engineers and geologists

8.2. Rock Mass Classification Systems: -

During the feasibility and preliminary design stages of a project, when very little detailed information is available on the rock mass and its stress and hydrologic characteristics, the use of a rock mass classification scheme can be of considerable benefit. At its simplest, this may involve using the classification scheme as a check-list to ensure that all relevant information has been considered. At the other end of the spectrum, one or more rock mass classification schemes can be used to build up a picture of the composition and characteristics of a rock mass to provide initial estimates of support requirements, and to provide estimates of the strength and deformation properties of the rock mass. It is important to understand the limitations of rock mass classification schemes (Plastron and Brooch, 2006) and that their use does not (and cannot) replace some of the more elaborate design procedures. However, the use of these design procedures requires access to relatively detailed information on in situ stresses, rock mass properties and planned excavation sequence, none of which may be available at an early stage in the project. As this information becomes available, the use of the rock mass classification schemes should be updated and used in conjunction with site specific analyses.

Engineering rock mass classification

Rock mass classification schemes have been developing for over 100 years since Ritter (1879) attempted to formalise an empirical approach to tunnel design, in particular for determining support requirements. While the classification schemes are appropriate for their original application, especially if used within the bounds of the case histories from which they were developed, considerable caution must be exercised in applying rock mass classifications to other rock engineering problems.

Terzaghi's rock mass classification

The earliest reference to the use of rock mass classification for the design of tunnel support is in a paper by Terzaghi (1946) in which the rock loads, carried by steel sets, are estimated on the basis of a descriptive classification. While no useful purpose would be served by including details of Terzaghi's classification in this discussion on the design of support, it is interesting to examine the rock mass descriptions included in his original paper, because he draws attention to those characteristics that dominate rock mass behavior, particularly in situations where gravity constitutes the dominant driving force. The clear and concise definitions and the practical comments included in these descriptions are good examples of the type of engineering geology information, which is most useful for engineering design.

Terzaghi's descriptions (quoted directly from his paper) are:

across sound rock. On account of the injury to the rock due to blasting, spalls may drop off the roof several hours or days after blasting. This is known as a spalling condition. Hard, intact rock may also be encountered in the popping condition involving the spontaneous and violent detachment of rock slabs from the sides or roof.

Stratified rock consists of individual strata with little or no resistance against separation along the boundaries between the strata. The strata may or may not be weakened by transverse joints. In such rock the spalling condition is quite common

Moderately jointed rock contains joints and hair cracks, but the blocks between joints are locally grown together or so intimately interlocked that vertical walls do not require lateral support. In rocks of this type, both spalling and popping conditions may be encountered.

Blocky and seamy rock consists of chemically intact or almost intact rock fragments which are entirely separated from each other and imperfectly interlocked. In such rock, vertical walls may require lateral support.

Crushed but chemically intact rock has the character of crusher run. If most or all of the fragments are as small as fine sand grains and no recementation has taken place, crushed rock below the water table exhibits the properties of a water-bearing sand.

Squeezing rock slowly advances into the tunnel without perceptible volume increase. A prerequisite for squeeze is a high percentage of microscopic and sub-microscopic particles of micaceous minerals or clay minerals with a low swelling capacity.

Swelling rock advances into the tunnel chiefly on account of expansion. The capacity to swell seems to be limited to those rocks that contain clay minerals such as montmorillonite, with a high swelling capacity. 8.3. Q-System of rock mass classificationThe Q-system of rock mass classification was developed in Norway in 1974 by Nick Barton, Lien, R., and Lunde, J at NGI (Norwegian Geotechnical Institute). The system was developed on the basis of an analysis of 212 tunnel case histories from Scandinavia. It is a quantitative classification system and is an engineering system facilitating the design of tunnel supports. Q-system use six different parameters to assess the rock mass qualityIt is a quantitative classification system and is an engineering system facilitating the design of tunnel supports. Q-system use six different parameters to assess the rock mass quality. The parameters are:

Rock Quality Designation RQD

Joint set number Jn

Roughness of the most unfavorable joint or discontinuity Jr

Degree of alteration of filling along the weakest joint Ja

Water inflow Jw

Stress Reduction Factor SRF

Then Q-factor can then be calculated as: Q =Retrieved from "http://en.wikipedia.org/wiki/Q-system"

8.4. RMR-System of rock mass classification

The Rock Mass Rating (RMR) system is a geomechanical classification system for rocks, developed by T.Z. Bieniawski between 1972 and 1973.

The following six parameters are used to classify a rock mass using the RMR system

Uniaxial compressive strength of rock material

Rock quality designation (RQD)

Spacing of discontinuities

Condition of discontinuities

Groundwater conditions

Orientation of discontinuities

Each of the six parameters is assigned a value corresponding to the characteristics of the mountain. These values are derived from field surveys. The sum of the six parameters is the "RMR value", which lies between 0 and 100.Rock Mass Rating has found wide application in various types of engineering projects such as tunnels, slopes, foundations, and mines. It is also adaptable for knowledge-based expert systems.

Below is the classification table for the RMR system.

RMRRock quality

0 20Very poor

21 - 40Poor

41 - 60Fair

61 - 80Good

81 - 100Very good

10.0 conclusions

Our geological tour conducted on (11-13)th of jestha for group(A/B) was very helpful in understanding and comparing the landslides, slope failure and debris flow practically in the field. We were also able to understand different terms and terminologies that we were not able to understand in the theory classes. From the field visit we also knew about the strike, dip of the bedding plane, their orientation and their origin.

The three day Malekhu tour enables us to learn the various geological conditions related to Engineering point of view. The scope of field study outline before were fully made with the co-operation of faculty member and Malekhu possess wonderful geological diversities and almost all type of rock structures and geological factors like rivers, hills, slopes and sedimentations, were available to study within small area.

In the Malekhu site visit, our main objective was to understand the geology of the entire country through the small area. The tour was also intended to give an insight to the various trouble cause of geological failure during the civil engineering construction. Many geological structures like Benighat Slat, Malekhu Lime Stone, Robang Formation, Radhuwa Formation, etc. are studied in the field along with their main Lithology boundary condition and exposure place. The area was found full of metamorphic rocks like Phyllite, schist, gneiss, slate, quartzite, etc. rocks were found.

Therefore from this tour, we were successful in obtaining the great knowledge regarding to the different geological activities, their effect, causes and their preventive measures related to the subjective matter.At last we had concluded that Malekhu and its surrounding is the answer for geological curiosity. Actually, the Malekhu is small in area but it has large amount or numbers of the geological phenomenon and hence it can provide broad knowledge for the learners.

Along the Malekhu River, we found sedimentary rock and gradually metamorphosed from Phyllite to crystalline schist and along the way to Dhading, it gradually metamorphosed to lime stone to Phyllite and then to slate.

Every major bed was dipped in north direction. This proved the tectonic movement along the way from south to north.

Besides this, we have learnt different methods of geological data collection measures and the way, how rock mapping is done.

Handling the compass and to measure the attitude of rock outcrop is now very easy to us.

By the river channel morphology we knew that, how the river flows, what are the factors affecting erosion and deposition and how it occursReferences:-

1. Old reports

2. Engineering Geology (By Prakash Chandra Ghimire and Mahesh Sing Dhar)

3. Field Manual Prepared by:

Mr. Amrit Aacharya Mr. Bijay subedi

Mr. Bikram K.C. Mr. Bir Bahadur Bohra

Channel Deposit Bar

Point Bar Deposit

Striking Bank

Depositional Bank

River

Sea

Delta

Malekhu

13

final report of geology

Documents

field of civil engineering

rock types

engineering geological

types of geological

study of geological

engineering works

classification of rock

preface engineering