outline (soil liquefaction)

8/18/2019 Outline (Soil Liquefaction)

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Chapter 1

PROBLEM AND IT’S SETTING

1.1Backgroun o! the Stu"

The composition, moisture, and compaction of soil are all major factors

in determining the erosivity during rainfall. Sediments containing more clay

tend to be more resistant to erosion than those with sand or silt, because the

clay helps bind soil particles together.

Liquefaction is commonly used to be describing all failure mechanisms

resulting from the build-up of pore pressure during undrained cyclic shear

of saturated soil (astro an !oulos "#$$%.

&y narrowest definition, true liquefaction refers only to the flow of soil

under static shear stress that e'ceeds the undrained, residual shear

resistance of a contractive soil (astro "#$%. Liquefaction of loose,

cohensionless soils can be observed under both monotonic and cyclic shear

loads.

)lthough earthqua*es often triggers this increase in water pressure, but

activities such as blasting can also cause an increase in water pressure.

+hen liquefaction occurs, the construction above it decreases the strength

and the ability of a soil deposit to support the soil.

roundwater, sand and soil combine during seismic sha*ing to form

liquefaction during a moderate to powerful earthqua*e. ) quic*sand li*e

soil is the result of this process. +hen liquefaction ta*es place under

buildings the foundations sin* and the building collapse. )fter the


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earthqua*e, the soil firms again and the water settles deeper in the ground.

)reas with sandy soil and groundwater close to the surface are far more at

ris* of liquefaction.

arthqua*es accompanied with liquefaction have been observed for

many years. n fact, written records dating bac* hundreds and even

thousands of years have descriptions of earthqua*e effects that are now

*nown to be associated with liquefaction. /owever, liquefaction has been

so common in a number of recent earthqua*es that is often considered to be

associated with them.

The effects of soil liquefaction on the built environment can be

e'tremely damaging. &uildings whose foundations bear directly on sand

which liquefies will e'perience a sudden loss of support, which will result

in drastic and irregular settlement of the building causing structural damage,

including crac*ing of foundations and damage to the building structure

itself, or may leave the structure unserviceable afterwards, even without

structural damage. +here a thin crust of non-liquefied soil e'ists between

building foundation and liquefied soil, a 0punching shear0 type foundation

failure may occur. The irregular settlement of ground may also brea*

underground utility lines. The upward pressure applied by the movement of

liquefied soil through the crust layer can crac* wea* foundation slabs and

enter buildings through service ducts, and may allow water to damage the

building contents and electrical services (nstitution of !rofessional

ngineers of 1ew 2ealand, 3445%.


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The soil holding &ato lementary School is slope and steep. +ithout

further studies of the soil, its properties, type of soil, particle si6e analysis,

liquid limit, plastic limit, moisture content, specific gravity, porosity, void

ratio and unit weight, the structure and lives of students and teachers are in

ris* since soil liquefaction and erosion are such things that is unstoppable

by human.

The researchers resolve in leading on this study is to ensure the safety of

the students and the structure, to give them *nowledge and awareness on

their surroundings particularly for probable soil liquefaction.

1.# State$ent o! the Pro%&e$

This study aims to evaluate the condition of the soil for the possible

occurrence of soil liquefaction and erosion. Specifically, this study is

e'pected to answer the following questions7

". +hat *ind of soil &ato lementary School has8

3. +hat properties of soil do &ato lementary School has8

9. +ill soil liquefaction and erosion occur on this *ind of soil and load8

:. ;oes the soil need to be stabili6ed for it to hold the school8

5. ;oes the site needed to be evacuated8

1.'Theoret(ca& )ra$e*ork

1.+ Scope an L($(tat(on, o! the Stu"

This study is e'pected only to evaluate the soil of &ato lementary

School for the possible soil erosion and liquefaction to occur. n addition,

n-situ Soil Sample

(ndependent


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the design of the erosion control wall will be reliable in case of soil erosion

to occur.

1.- S(gn(!(cance o! the Stu"

The researchers believe that the findings on the test will give *nowledge

and awareness to the students and teachers of &ato lementary School

about the land they are stepping everyday. This study will show them how

important the stability of soil not only for structures but also for the living

things above it. =or the parents of the students, it will give them assurance

that their children is in a safe place to study. Since any parents always wants

their children to be away from harm and danger. 1o parent in the world

wishes their son>daughter to be injured.

1. De!(n(t(on o! Ter$,

n this section, definition of terminology is given so that the readers of

this study will easily refer to this section which will provide definition of

words that they might find hard to understand.

Bore /o&e- a narrow shaft bored in the ground, either vertically or hori6ontally.

Ero,(t(0(t"- is the ability to cause erosion.

S(&t- a granular material of a si6e somewhere between sand and clay, whose

mineral origin is quart6 and feldspar.


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C&a"- is a fine-grained natural roc* or soil material that combines one or more

clay minerals with traces of metal o'ides and organic matter.

San- is a naturally occurring granular material composed of finely divided

roc* and mineral particles.

C"c&(c Shear- is the distribution of forces (a*a stresses% that change over time

in a repetitive fashion.

Monoton(c

Shear- forces in which it does not change throughout the period.

Punch(ng Shear- a type of failure of reinforced concrete slabs subjected to

high locali6ed forces.

Sta%(&(t" o! ,o(&- is the potential of to withstand and undergo movement.

/o&ocene Epoch- is the current geological epoch which started some "",544

years ago when the glaciers began to retreat.

Ce$entat(on- The new pore-filling minerals form ?bridges? between original

sediment grains, thereby binding them together.

Shear Re,(,tance- the ability to resist sliding failure.

Pheno$enon- a fact or situation that is observed to e'ist or happen, especially

one whose cause or e'planation is in question.

Saturate So(&- ) condition of soil in which all easily drained voids (pores%

between soil particles are temporarily or permanently filled with water

D(&ate- ma*e or become wider, larger, or more open.


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Su,cept(%(&(t"- the state or fact of being li*ely or liable to be influenced or

harmed by a particular thing.

Gra0e&&" ,o(&- soil composed mostly of gravel.

Per$ea%(&(t"- is a measure of the ability of a porous material (often, a roc* or

an unconsolidated material% to allow fluids to pass through it.

P&a,t(c L($(t- is the water content, in percent, at which a soil can no longer be

deformed by rolling into 9.3 mm ("> in.% diameter threads without crumbling.

L(u( L($(t- is conceptually defined as the water content at which the

behavior of a clayey soil changes from plastic to liquid.

2n(t 3e(ght- the weight per unit volume of a material.

)au&t- n geology, is a planar fracture or discontinuity in a volume of roc*,

across which there has been significant displacement as a result of roc* mass

movement.

Tre$or,- a slight earthqua*e.

Ep(center- the point where an earthqua*e or underground e'plosion originates.

So(& )a%r(c- is the geometric or spatial arrangement of individual soil particles

and voids while structure includes the organi6ation of soil constituents into

larger aggregates or compound particles.

Propagat(on- The motion of a wave throughout a medium or the transfer of its

energy.


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RE4IE3 O) RELATED LITERAT2RE

This chapter presents the supporting information and details that might

be needed to perform the research study.

)ccording to @oud and !er*ins, "#$, Soils deposited prior to the

/olocene epoch (more than "4, 444 years old% are usually not prone to

liquefaction, perhaps due to wea* cementation at the grain contacts.

Liquefaction is a phenomenon wherein mass of soil loses a large

percentage of its shear resistance, when subjected to monotonic, cyclic or

shoc* loading and flows in a manner resembling of a liquid until the shear

stresses acting on the mass are as low as the reduced shear resistance

(Sladen, "#5%.

Liquefaction results from the tendency of soils to decrease in volume

when subjected to shearing stresses. +hen loose, saturated soils are

sheared, the soil tend to rearrange into a more dense pac*ing, with less

space in the voids, as water in the pore spaces is forced out. f drainage of

pore is impeded, pore water pressures increase progressively with the shear

load. This leads to the transfer of stress from the soil s*eleton to the pore

water precipitating a decrease in effective stress and shear resistance of the

soil. f the shear resistance decreases less than the static, driving shear

stress, the soil undergo large deformations and is said to liquefy (Aartin et

atB Seed and driss "#3%.


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+hen dense sands are sheared monotonically, the soil gets compressed

first, and then it gets dilated as sand particles move up and over one another.

+hen dense saturated sands are sheared, impeding the pore water drainage,

their tendency of volume increase results in a decrease in pore water

pressure and an increase in the effective stress and shear strength. +hen

dense sand is subjected to cyclic small shear strains under undrained pore

water conditions, e'cess pore water pressure may be generated in each load

cycle leading to softening and the accumulation of deformations. /owever,

at lager shear strains, increase in volume relieves the e'cess pore water

pressure resulting in an increased shear resistance of the soil (&iswas and

1ai*, 34"4%.

haracteristics of the soil grains li*e distribution of shapes, si6es, shape,

composition etc. influence the susceptibility of a soil to liquefy. +hile sands

or silts are most commonly observed to liquefy, gravelly soils have also

been *nown to have liquefied (Seed "#$#%.

shihara ("##9% gave the theory that non-plastic soil fines with dry

surface te'ture do not create adhesion and hence do not provide appreciable

resistance to particle rearrangement and liquefaction.

Coester ("##:% stated that sandy soils with appreciable fines content

may be inherently collapsible, perhaps because of greater compressibility of

the fines between the sand grains.

!ermeability also plays a significant role in liquefaction. +hen

movement of pore water within the soil is retarded by low permeability,


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pore water pressures are li*ely to generate during the cyclic loading. Soils

with large non-plastic fines content are more li*ely to get liquefied because

the fines inhibit drainage of e'cess pore pressures. The permeability of

surrounding soils also affects the vulnerability of the soil deposit. Less

pervious soils such as clay can prevent the rapid dissipation of e'cess pore

water pressures that may have generated in the adjacent saturated sand

deposit. Sufficient drainage above or below a saturated deposit may inhibit

the accumulation of e'cess pore water pressure and hence liquefaction.

ravelly soils are less prone to liquefaction due to a relatively high

permeability unless pore water drainage is impeded by less pervious,

adjoining deposits (&iswas and 1ai*, 34"4%.

So(& &(ue!act(on Occurrence (n the Ph(&(pp(ne,

Liquefaction was widespread in various parts of 1orthern Lu6on during

the recent "D Euly "##4 !hilippine arthqua*e which registered a magnitude

of $. on the Fichter scale. The !hilippine government, through the

;epartment of nvironment and 1atural Fesources (;1F% and the

;epartment of Science and Technology (;GST% is underta*ing steps to

mitigate the effects of future major earthqua*e not only in areas affected by

the above mentioned event but also in other developed and liquefaction

prone areas in the country. !art of that effort is the project study reported

herein (Feyes et al, 34""%


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Soil liquefaction and associated ground deformations caused e'tensive

damage to residential buildings and lifeline facilities in many areas in

hristchurch ity (1ew 2ealand% during the 34"4 ;arfield arthqua*e.

Twenty years earlier, the "##4 Lu6on (!hilippines% earthqua*e also caused

widespread damage in ;agupan ity due to liquefaction. This paper

compares the liquefaction phenomenon observed in bot earthqua*es, with

emphasis on the characteristics of the sites affected by liquefaction, the

e'tent of ground deformations observed and the influence of liquefaction-

induced settlement and lateral spreading on the built environment (Grense,

34""%.

+ith the anticipated magnitude $.3 earthqua*e triggered by the +est


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+ithout having any magnitude of earthqua*e, liquefaction occurred in

&enguet ity. Large area of soil in the hill of &enguet move and slideHs

down from the hill. Aany houses and structures that have been constructed

in the lower level in the hill are totally damaged (!hilippine ;aily nquirer,

34"5%.

)ccording to ;eocampo, ;avao city specialist of the !hivolcs, 34"5

that, starting last year, we have been updating young active fault map since

it has been done a decade ago. Gne of the initial things that the geologists

have seen was the new active faults within ;avao ity.

;eocampo, 34"5 stated, we are not releasing this initially and we will do

additional surveys and maybe some trenching for the actual location of the

fault and then we will ma*e it official. The !hilippine fault 6one is a very

active fault, so although won0t say alarming, it0s best to be prepared all the

time as we *now earthqua*e canHt be predicted.

n addition, even tremors felt in the ity of Aati can have a greater

impact in ;avao, since the city0s underlying soil material is softer compared

to Aati. +hat will happen is, the intensity here in ;avao will be higher than

in Aati due to ground sha*ing even Aati has the epicenter (;eocampo,

34"5%.

)actor, A!!ect(ng So(& L(ue!act(on


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Since liquefaction is associated with the tendency for soil grains to

rearrange when sheared, anything that impedes the movement of soil grains

will increase the liquefaction resistance of a soil deposit. !article cementation,

soil fabric, and aging I all related to the geologic formation of a deposit- are

important factors that can hinder particle arrangement (Seed, "#$#%.

Some investigators use the term Jlimited liquefactionK for conditions

where large deformations after initial liquefaction are prevented by an increase

in the undrained shear strength (=inn "##4%.

Stress history may also contribute to the liquefaction resistance of older

deposits. Gverconsolidated soils having been subjected to greater static

pressures in the past, are most resistant to particle rearrangement and

liquefaction. Soil deposits subjected to past cyclic loading are usually more

resistant to liquefaction as the soil grains tend to be in a more stable

arrangement but some deposits may loosened by previous sha*ing.

n addition, the frictional resistance between soil grains is proportional

to the effective confining stress. onsequently, the liquefaction resistance of a

soil deposit increases with the depth as the effective overburden pressure

increases. =or this reason, soil deposits deeper than about "5m are rearly

observed to liquefy ( Crinit6*y et al. "##9%.

haracteristics of the soil grains( distribution of si6es, shape,

composition, etc.% influence the susceptibility of a soil to liquefy ( Seed, "#$#%.


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+hile liquefaction is usually associated with sands or silts, gravely soils

have also been *nown to liquefy. Founded soil particles of uniform si6es are

generally most susceptible to liquefaction (!oulos et al, "#5%.

+ell-graded sands with an angular grain shapes are generally less prone

to liquefy because of a more stable interloc*ing of the soil grains. Gn the other

hand, natural silty sand sediments tend to be deposited in a looser state, and

thus are more li*ely to e'hibit contractive shear behavior, than clean sands.

(Seed, "#$%.

Coester ("##:%, suggests that sandy soils with a significant fines content

may be inherently collapsible, perhaps due to the greater compressibility of

fines between sand grains.

n addition, as pointed out by Selig and hang ("#"% and Fobertson

("##:%, it is possible for a dilative soil to reach a temporary condition of 6ero

effective stress and shear resistance.

;uring an earthqua*e, the upward propagation of shear waves through

the ground generates shear stresses and strains that are cyclic in nature. f a

cohesionless soil is saturated, e'cess pore pressures may accumulate during

seismic shearing and lead to liquefaction. ( Seed and driss, "#3%.


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Ero,(on Contro& 3a&& a, counter$ea,ure to earthuake5(nuce &(ue!act(on an

So(& ero,(on

arthqua*e-induced liquefaction is a major cause of damage that needs

to be controlled by engineers. ) popular option for protecting against

liquefaction is the installation of gravel drains to relieve generated e'cess pore

pressures. sing these, it was possible to determine a time varying e'tent of

drain effectiveness, and a 6one of influence consisting of a conical volume of

soil from which draining fluid left the ground via the drain (niversity of

ambridge, 344:%

Soil erosion and surface runoff occurs as water moves along the ground.

The more e'posed the soil and the faster the rate of flow, the greater the

damage and the bigger the concern. t is imperative to ma*e certain a slope is

covered or planted so that erosion is minimi6ed. rosion is prevented by

shortening a potentially long slope into a sequence of more level steps. This

allows heavy rains to soa* in rather than run off, ta*ing soil with it. Thin* of

terraces li*e steps in an emban*ment. Soil is cut out of the hill to create the

level tread or landing area. )s with garden steps, the level area is not e'actly

level. Sloped terraces ought to be graded by about 3M perpendicular towards

the incline in order to gently direct drainage towards one side or the other.

(Landers, &. 34""%

Fetaining walls are yet another way to slow runoff and erosion but their

primary function is to support and retain an emban*ment. /owever, whatever


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the weight, it has to be strong enough to contain bac* the pressure of a great

amount of soil weight, yet porous enough to be suitable for adequate drainage.

(Landers, &. 34""%

MET/ODOLOG6

This chapter presents the methodology used in the study. Type of research,

research design, research equipment, research process and investigation of the

problem are here discussed.

n addition, a more precise definition of liquefaction as given by Sladen et

al ("#5% states that JLiquefaction is a phenomena wherein a mass of soil loses

a large percentage of its shear resistance, when subjected to monotonic, cyclic,

or shoc*ing loading, and flows in a manner resembling a liquid until the shear

stresses acting on the mass are as low as the reduced shear resistanceK

1.7 RESEARC/ DESIGN

The research design that was used in the study is e'perimental. )n

e'perimental research design is concerned with the e'amination of the

effect of the independent variable on the dependent variable, where the

independent variable is tested through the process to observe its effect to the

dependent variable.

1.8 S2B9ECTS:PARTICIPANTS


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n performing the e'periment> testing of in-situ soil, the researchers used

the soil samples from &ato lementary School through the use of data from

bore hole.

1.; RESEARC/ INSTR2MENTS

=or this study, borehole is needed. ) borehole is used to determine the

nature of the ground (usually below Dm depth% in a qualitative manner and then

recover undisturbed samples for quantitative e'amination.

Gbviously the information gained from a borehole is an e'tremely limited

picture of the subsurface structure. t is therefore essential to compare the

results obtained with those that could have been e'pected from the des* study.

The greater the number of boreholes the more certain it is possible to be of the

correlation and thus to trust in the results

)pparatus of Standard !enetration test7

". Tripod

3. Standard split-spoon sampler.

n consists of three parts7

a. ;riving shoe, about $5 mm long.

b. Steel tube about :54mm long, split longitudinally in two halves having

inner diameter as 9mm and outer diameter as 54mm.


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c. oupling at the top of the tube about "54mm long.

9. uide !ipe

:. ;rill rod

5. ;rop hammer weighing D9.5 *g.

Field Investigation

=ield investigation by the S!T was to be done at &ato lementary

School. The number of boreholes cone penetrometer test positions in each

location are as follows7

Location 1o. of &orehole S!T

&ato lemetary School 9 9

n the field investigation, S!T was conducted to obtain the necessary borehole

data needed for the study. n the same manner, the storage of data is categori6ed

into the S!T data. )ll data gathered using the washboring (S!T% method are in

the S!T Table. ;ata tables are stored in database files that are (conceptually% in

tabular form and containing all field and (in case of the S!T% laboratory test

data.

Drilling Procedure

The S!T was done in accordance with )STA specifications. =or each test,

a 3-inch (54. mm.% outside diameter split spoon sampler is driven a total

distance of " inches (:D4 m.% by means of a ":4 lb. (D9.5 *g.% driving head


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falling free from a distance of 94 inches ($D4 mm.%. The number of blows

needed to drive the sampler in D-inch ("59 mm.% increments is recorded and the

number of blows needed to drive the last "3 inches (944 mm.% is ta*en as the

1-value. Soil samples were recovered using the spoon sampler and were ta*en

to the soils laboratory for analysis and testing.

1.1< RESEARC/ PROCED2RE

Laboratory Test !rocedure

The laboratory tests performed on soil samples from the boreholes are

briefly described as follows7

". lassification of Soils for ngineering !urposes

The nified Soil lassification System (SS% was used to classify the

soils.

3. !article Si6e )nalysis

Soil is passed through a series of sieves and the weight of soil retained in

each sieve determined. ) graph is drawn relating the percent finer by weight

and the particle si6e on a semi-long scale. ;54 or equivalent particle

diameter (in mm% that equally splits the soil in coarser and finer fractions is

read off from this graph.

9. Liquid Limit

The liquid limit is the moisture content at the point of change between the

liquid and plastic states of the soil.

:. !lastic Limit

The plastic limit is the moisture content at the transition between the

semi-solid state and the solid state.

5. !lastic inde'

!N LL-!LD. Aoisture ontent


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+N (+eight of water > weight of oven-dry soil% ' "44M

.


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!a N "44 *!a

n should not e'ceed a value of ".$

BIBLIOGRAP/6

9u$p up = Hazen, A. (1920). Transactions o t!e A"erican #ociet$ o %ivil

&ngineers 83' 111*+.

9u$p up = -eologists arrive to stud$ liueaction . /ne es. 10 #ete"3er 2010.

4etrieved12 ove"3er 2011.

9u$p up = %!ristc!urc! areas to 3e a3andoned . T!e e 5ealand Herald . 5PA.

6arc! 2011.4etrieved 12 ove"3er 2011.

9u$p up = &H4P reco""ended rovisions or seis"ic regulations or ne

3uildings and ot!er structures (F&6A *+0). 7as!ington D.%.' ational Institute o

8uilding #ciences. 200*.

9u$p up = &199:+'200* &urocode Design o structures or eart!ua;e

resistance. Part +' Foundations, retaining structures and geotec!nical asects.

8russels' &uroean %o""ittee or #tandardisation.

200*. http7>>www.astm.org>Standards>;"5D.htm

9u$p up =


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9u$p up = 5atsua, 6onosagu (200+). 8eare, sot ground and t!e standard

enetration test (in aanese). Pu3lic 7or;s 4esearc! Institute.

Status of the borehole disposal project implementation in the !hilippines by Aaria


22/22

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outline (soil liquefaction)

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