evaluation of road landslide in iran and stabilization
TRANSCRIPT
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Evaluation of Road Landslide in Iran and Stabilization with Micropile
Ashkan Gholipoor Noroozi1,*
Phd student , Department of Civil Engineering, Najafabad Branch, Islamic Azad University, Najafabad,Isfahan, Iran
e-mail: [email protected]
Mehrali Khaledi2
Phd student , Department of Civil Engineering, Najafabad Branch, Islamic Azad University, Najafabad,Isfahan, Iran
e-mail: [email protected]
Alborz Hajiannia3 Assistant Professor, Department of Civil Engineering, Najafabad Branch,
Islamic Azad University, Najafabad, Iran. e-mail: [email protected]
ABSTRACT In this article, study about landslide axis of Yasouj- Esfahan which is located with geography specification of 31 degree and 3 minutes northern ,51 degree and 14 minutes southern and height about 1600 meter from sea surface. Restricted area of sliding case of study with the length of about 120 meter and width of 100 meter located in distance of 56 km northeast of Yasouj in the direction which is above mentioned. The aim of this study recognizing effective factors in case of building up the landslide and also investigation of existent slope stability and finally representation of suitable procedures for proper control of slope. In order to gain above objectives issues have accomplished study of mapping, geology, hydrology, geotechnical. According to obtained results of above study and also existent air photography of restricted study, provided different sectionals, in order to analysis stability of slope. Results of stability analysis shown that slope has low safety factor and high potential of (landslide). Regarding to consequences of stability analysis and field examination it seems that unsuitable drainage , lack of suitable executive accumulation , lack of high quality materials , traffic of loading , unsuitable slope ,abrupt slope , Soil erosion and existing faults have been effective factors in landslide. In following this research for instability states, studied the ways of making stability and finally after analyzing slope stability According to at the same time usage in direction of making stable to lay out a design suitable drainage system in upwards axis and executive micropile in downwards axis cross section have chosen as improvement of making stable. KEYWORDS: landslide; geotechnical examination; slope stability analysis; methods of making stable; micropile, drainage.
INTRODUCTION Natural landslide and also embankments that have made through human hand are phenomena that
occurred in many parts of the world. Land masses either earth or rock during landslide and replacement affected a lot of dangers on connection of roads and tunnels, floodways of water and
Vol. 22 [2017], Bund. 04 1266 sewage, telephone, electricity, and also buildings. Roads and tunnels that provide connection between parts o country because of topography (the physical features of an area of land especially the position of its river, mountain, etc.; the study of these features is a map showing the topography of the Island.) and geology and climatic transit through different parts of country. Therefore in comparison to other structures mostly expose to unstable natural earth down pipe and also embankments. Landslide and instable slopes caused destruction and road obstruction, or at least reduced quality and safety. And among consequences are a lot of costs for rebuilding and maintenance of roads. In case of critical state, it may cause life causality to whom that used roads. Villages and habitable state which are located in downwards slope are involved.
Different methods have been used to evaluate the performance and design of the various elements which are used as reinforcement in slopes.
Rowe and Soderman (1984), and Carsel and Parrish (1988) conducted substantial experimental work and obtained the Van Genuchten model parameters for different soil textural groups according to the USDA soil classification system. As a result of this work, laboratory particle size analysis can be directly related to the modeled parameters. Further, for geotextile, the Van Genuchten model parameters could be taken from the typical values evaluated from published data compiled by Iryo and Rowe (2003).
Ashkan GHolipoor Noroozi and Alborz Hajiannia in 2015 were investigated on the effect of vegetation on slope instability using finite element method and they show that with increasing the height of the root on Slope Surface and over the entire ground surface, the safety factor increased. The process of this increasing, the changing in height of roots from 1 m to 2 m, the safety factor reach to the top of 1 and with increasing and progression of plant roots in the depth of soil, safety factor of slope increased.
The use of piles as a stabilizing element to increase slope stability has been proved to be an effective solution in recent decades [Appolonia et al in 1967; De Beer and eallays in 1970; Ito and Matsui in 1975; Fukuoka in 1977; Wang et al in 1979; Ito et al in 1981 and 1982; Reese et al 1992]. The piles used in slope stabilization are considered as passive piles because they are usually subjected to lateral force arising from the horizontal movements of the surrounding soil. For passive piles, the problem is complicated because the lateral forces acting on the piles are dependent on the soil movements, which are in turn affected by the presence of the piles. A pile will function by its shear strength which is different from an anchor or soil nail.
Wei and cheng in 2009 were investigated on Strength reduction analysis for slope reinforced with one row of piles. In their paper, slope reinforced with one row of piles is considered. The critical slip surface is found to be divided into two parts when the pile spacing is small, and these two parts gradually get connected with the increase of pile spacing until a clear critical slip surface is formed. The critical slip surface of the piled slope is found to be usually shallower than the corresponding slope without pile, and this result is totally different from the previous results based on the maximum point of shear force where a very deep critical slip surface is obtained.
Also one method that has been used to improve the stability of slopes has been via the installation of micropiles. Micropiles are defined as small-diameter (typically less than300mm), drilled and grouted replacement piles that are typically reinforced (Bruce and Juran, 1997). A micropile is constructed by drilling a bore hole, placing reinforcement, and grouting the hole. Micropile technology has evolved continuously since its introduction by Fernando Lizzi in the 1950s. Over the past 60 years, advances in drilling equipment and techniques have extended the applicability of micropiles to infrastructure repair and seismic retrofit projects (Tsukada et al., 2006; Pinyol and Alonso, 2012).
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An element from a micropile with an unloaded shape of abcd is shown by the dashed lines in Figure. 1. The beam is subjected to pure bending and element changes in shape as shown by the solid lines. The length of element is given by dx and the deformation at any distance from the neutral axis is signified by Δ. The relative rotation of the sides of the element is given by the small angle dθ and the radius of curvature of the elastic element is signified by the length ρ. The symbol η is the distance from the neutral axis. The unit strain εx along the length of the micropile can be expressed as
εx = ∆dx
(1)
From similar triangles
ρdx
= η∆
(2)
Figure 1: Deformation shape of an element from a micropile [Sun et al in 2013]
Thus, the main aim of this present article that is analysis of slope stability and compilation the
way of solving the suitable procedure for making landslide stability. First of all, study of different topography, geotechnical, hydrology (the scientific study of the earth’s water, especially its movement in relation to land) geology (the scientific study of the earth including the origin and history of the rocks and soil of which the earth is made.) rising slide expressed restricted case study. Then analysis slope stability performed with usage of Geoslope software, and presentation methods of sliding slopes and introducing executive procedures in order to make stability. Finally, in this article presented case study of landslide.
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GEOTECHNICAL STUDIES IN LANDSLIDE MASSES For analysis slope stability awareness of condition under slope, geometric of slope properties
resistance and physical resistance. Situation of slope materials slope scale for underground water and …, are very necessary. In this research all activities and efforts have been applied generally under the title of geotechnical studies, and in this part wholly applied. Certainly, all performed activities in this phase would be comprehensive and gained results should be close to reality. In phase of slope analysis should be with most knowledge analyzed. In analysis of stability and making stable would be close to true. In this section presented most of performed geotechnical study under title at determination of geometric slope , control and measurement of probable slope replacement , determination of slope in superficial and under superficial conditions and determination of underground water level.
Determination of slope geometric In this research in order to find factors of occurred landslide and also in order to investigate and
analysis slope stability and presentation procedures of making stable, to gain slope geometric would be necessary. In this case we need topography maps of area. As the only available topography map of area was provided in scale of 1/25000 and gained geometric among these maps were not in sufficiently precise we decided to provide area topography in scale of 1/5000 and curve scale in distance of 1 meter. In this case the whole restricted of became slide in lattices of 10 meters were mapped by total station camera. This topography of slope geometric shown after occurrence of landslide (figure 2).
Figure 2: Topography map of landslide in restricted area
Appearance signs for recognizing landslide in restricted area
Recognizing superficial of embankment by using appearance signs would be helpfully in order to understand factors of instability. According experts expression of general administration of road and transportation in province, because of road movement to downwards, every year spent a lot of costs for repairing and Maintenance of this part of path direction (figure 3).
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Figure 3: Formation of splits in downwards of landslide in case to lay the road
foundation in this area has been built intervening wall with following specification.
-Length of wall 120 meters
-width of wall 1/5 up to 3 meter
-Width of foundation 3/5
- its height from 3 up to 7 meter variable
Figure 4 shown condition of intervening wall in downwards axis of yasouj-samirem.
Figure 4: Condition of intervening wall in downwards axis of yasouj-samirem
By using unsuitable soil, high height of embankment and also earth of landslide (marl) caused movement of road in zoning area and lack of performance maneuvers and necessary technical and engineering design in order for slope stability annually required a lot costs for repairing and Maintenance. The parts of axis which is mentioned above and large sliding in this section of road. Unfortunately, caused blocked in this path that which cannot be compensated financial and life damages (Figure 5).
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Figure 5: Shoulder replacement and guardrail axis impact of earth expulsion
STABILITY ANALYSIS DURING SLIDING In order to analyze landslide in three sections along path considered according figure 6. After
describing cross section by using restricted topography specification of earth, scale of underground water According to laboratory results and gained field inspection and geology reports that are rendered on table (1) in software which are consisting of state of being cohesion, angle of friction and specific weight and also in order to load the road, we used bridges loading policy. We considered most critical states. This loading consisted of linear loading as large as 60 KN/m and extensive as large as 5 KN/m2 .
Table 1: Specification of cross section materials section Type of soil
akpC φ 3/ mknγ
1
Dyke 0 32 19
Wall 100 45 22
Bed soil 6 27 20
2
Dyke 0 31 18.5
Wall 100 45 22
Bed soil 5 28 20
3
Dyke 0 32 19
Wall 100 45 22
Bed soil 6 27 20
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Figure 6: State of analyzed cross section
First section Minimum safety factors of this section according figure 7 are in static state of 1.101 and in
pseudo static method is 0.754 that According to mentioned coefficients this section is instable.
)a(
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)b(
Figure 7: Sliding linear and safety factor during sliding
in state: a) static and b) pseudo static method
Second section
Minimum safety factors of this section according figure 8 are in static state of 0.936 and in pseudo static method is 0.841 that According to mentioned coefficients this section is instable.
(b) (a)
Figure 8: Sliding linear and safety factor during sliding
in state: a) static and b) pseudo static method
Third section
Minimum safety factors of this section according figure 9 are in static state of 1.208 and in pseudo static method is 0.931 that According to mentioned coefficients this section is instable.
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(b) (a)
Figure 9: Sliding linear and safety factor during sliding
in state: a) static and b) pseudo static method Gained results from static analysis a pseudo method in primary slope in each section rendered
separately, in this issue considered scale of sliding minimum safety factor in order stability to encounter slide in static state 1.3 and in pseudo static method are 1. Regarding to gained analysis shown that in three sectional slide.
MAKING STABILITY OF 56 KM IN AXIS OF YASOUJ-ISFAHAN BY USING MICROPILE
According specification of earth geometric, geology usage of guard micropile is suitable method for encountering earth expulsion. Obviously improvement depth must be considered in such way that additional guarantee of suitable earth manner in critical condition such as earth quick, safeguarding of earth resistance to encounter additional loading and prevention of heterogeneous settlement should be economy. Therefore in this article we applied design of micro specification that rendered on table 2 up to table 4:
Table 2: Specification of micropile armature Type of steel No Yield stress (kPa) Area( 2cm )
Ultimate Force (kN)
AIII 32Φ 5104× 04.8 320
Table 3: Specification of micropile sheath Type of steel Outside diameter
(cm) Inner Diameter
(cm) Yield stress (kPa)
Area
(2cm )
Ultimate Force (KN)
37ST 6.7 8.6 5104.2 ×
05.9 220
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Table 4: executive details of micropile distance
between the micropile
Number of micropile
Length of micropile(m)
Distance from the tunnel (m)
section
m5.1@ 135 12 160-200 1
m5.1@ 360 12 200-260 2
m2@ 40 12 260-290 3
Analysis after stability
Minimum safety factor in first section in static state 1.30 and pseudo static method 1.029, minimum safety factor in second section in static state 1.319 and in pseudo static method 1.044 and minimum safety factor of third section in static state 1.325 an in pseudo static method 1.020 that regarding to mentioned coefficients corresponding to Figures 10 up to 12 these sections are stable.
(b) (a)
Figure 10: Slide linear and safety factor after making stability for first section
in state of: a)static state and b) pseudo static method
(b) (a)
Figure 11: Slide linear and safety factor after making stability for second section
in state of:a)static state and b) pseudo static method
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(b) (a)
Figure 12: Slide linear and safety factor after making stability for third section
in state of: a) static state and b) pseudo static method
CONCLUSIONS Among all making variant stability methods, Methods of drainage on superficial in upwards axis
in order to prevent saturate of mass earth and establishment of downwards axis by using micropile , in order to increase earth Shear strength in case of most executively methods , following are description of these methods.
A) Superficial drainage: in order to prevent penetration of water to downwards road channel must be with sharp slope and suitable dimensions to lay the foundation in upwards road in order to transport water to closer floodway.
B) Analysis after stability : to set forth a accomplishment procedure and gained results in case of introducing static analysis and pseudo static method by using micropile reinforcement and gained minimum safety factor shown cross _ section that slope is stable.
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Editor’s note. This paper may be referred to, in other articles, as:
Ashkan Gholipoor Noroozi, Mehrali Khaledi, and Alborz Hajiannia: “Evaluation of Road Landslide in Iran and Stabilization with Micropile” Electronic Journal of Geotechnical Engineering, 2017 (22.04), pp 1265-1276. Available at ejge.com.
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