CHAPTER 1: INTRODUCTION 1.1 Background of the Stud
The Philippines is located in the south-western portion of the Pacific marine territory, thus making it susceptible to any typhoon which had developed in the ocean. These typhoons brought several havocs to Filipinos, and one of these disasters which naturally-occurs in slightly stable slopes that consist of various types of soil is the lands landslid lide. e. Land Landsli slide de is a very very dang dangero erous us phen phenome omeno non n and and can caus cause e massiv massive e damages damages to nearby nearby infrast infrastruct ructures ures,, and even even to people’ people’s s lives. lives. ccord ccording ing to !avid !avid Petle Petley y, a profe profess ssor or of ha"a ha"ard rd and risk risk at !urh !urham am #niv #nivers ersity ity in #nite #nited d $ing $ingdom dom,, Philippines has lost %,&'( lives in ))* non-seismic landslides between )++% and )++. The The Phili Philipp ppine ines s also also rank ranked ed third third in terms terms of casua casualti lties es and and cases cases among among the % countries countries identified identified as key spots for non-earthuakenon-earthuake-related related landslides Philippine Philippine !aily /nuirer, ug. 0, )+)1. 2on2on-sei seismi smic c landsl landslid ides es usuall usually y occur occur durin during g or after after a massiv massive e rain. rain. 3lop 3lope e saturation by water is a primary cause of landslides. The ground takes much water which causes the increase of soil moisture. Then as the water content of the soil rises, the yield strength decreases and the soil particles loosen up with each other. #pon further analysis, when rainwater infiltrates a soil profile that is initially in an unsaturated state, a decrease in negative pore pressure, or matric suction, occurs. This causes a decrease decrease in the effective normal stress acting along the potential failure plane, which in turn diminishes the available shear strength to a point where euilibrium can no longer be sustained in the slope 4rense, )++%1.
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soil map of 5ukidnon produced by the 5ureau of 3oils illustrated that e6pansive soils, such as dtuyon clay, covers a large area of the national highway where it was constructed. The dtuyon clay is acidic strong brown clay with a relatively high plasticity of (07 and high amount of silt and clay. value of Plasticity /nde6 greater than (& 7 and fall between )+ 7 to %+ 7 range e6hibits high swell potential and high plasticity 5argasa et al, )+)1. 3ome portions of the national road, particularly around the municipality of 8ue"on, have different soil types such as 9acolod clay, La :astellana clay and other undifferentiated mountain soils. ;enerally, these types of clayey soils absorb significant amounts of water and deals considerable effect to its yield strength. /n order to evaluate the modified physical factors before a landslide occurrence, 3ultanov and $husanov )++1 proposed euations of state of soil prone to slum-type settlement, which take into account the degree of wetting in the initial stage. These euations were developed using models of deformation of the continuous and e6perimental results of cohesion and the angular coefficient of internal friction as well as the bulk compression and shear modulus. This study was revised by treating the yield stress as a function of water content for slip-prone clayey soils due rainfall and determined how yield stress is decremented by the water content.
1.! State"ent of the Pro#$e"
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The principal problem which paved way to the e6istence of this research proposal was the freuent manifestation of heavy rainfall in the island of 9indanao. s a result, soil profiles which were characteri"ed by clays and silts triggers landslides due to e6cess weight generated by water. The secondary problem that arose in this study was the lack of information to recogni"e the reasons that make an area susceptible to sliding and to acknowledge factors that trigger the movement of the rock or soil mass movement.
1.% O#&ect'(e) of the Stud
The primary ob=ective of this study is to provide corresponding yield stresses of soil for a ranged value of moisture content. The investigation will be conducted within the pro6imity of the 5ukidnon-!avao national highway, 9indanao, Philippines. The specific ob=ectives are as follows> . To determine the physical properties tterberg limits, ;rain si"e distribution1 of the soils in the certain points along the 5ukidnon-!avao national highway. ). To illustrate the correlation between the water content and yield strength of soil. (. To determine the critical soil moisture content in which landslide is about to occur. %. To determine the average daily rainfall intensity in order to postulate the probability of non-seismic landslide occurrences in the location of study.
1.* S'gn'f'cance of the Stud
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Landslides tragedies are becoming common nowadays? this implies that being aware of any landslide possibilities is necessary. This research will provide a better perspective of the soil’s status along the slightly stable slopes of the national highway connecting the provinces of 5ukidnon and !avao. The results of this study will supply sufficient information to nearby residences regarding the chances of landslide occurrence, thus reducing the risk of accidents and casualties. nother purpose of this assessment is to endorse the easiest way of ascertaining the yield stresses of various soils. This can be done by performing the slump test method and then using the Phasias and coworker’s formula. This procedure of calculating the yield stress is reduces efforts and time consumed, hence making it preferable than the conventional method. This study can also open new doors for further research about the several e6pansive soils at 9indanao, Philippines which can cause non-seismic landslides upon taking large accumulation of moisture.
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1.+ Sco,e and -'"'tat'on of the Stud
This study is limited on acuiring the yield stress of soils within the national road linking the provinces of 5ukidnon and !avao using the slump test method. The place of study will be distributed in si6 various areas in order to gain different soil samples that will elucidate the variations of soil properties covered by the highway. The pre-assessment tests to be conducted will be the tterberg limits test grain si"e distribution test, for these were the only related tests in this field of study. Then other associate tests will be performed to acuire the physical properties of the soil. The water content of the specimen collected will be measured. Then moisture will be manually manipulated in order for the soil specimen to reach the desired moisture range of (+ 7 to %+ 7, for the cause of determining the critical moisture content. The method which will be used in yield stress determination will be the slump test method. fter attaining the needed data during the testing process, we will use the Phasias and coworker’s e6pression in order to calculate for the yield stress. This study also emphasi"es to have a copy of the rainfall intensity records from P;-3 or other related institutions. @ith the aid of these documents, an average daily rainfall intensity rate can be deduced considering the respective areas studied. nd a conclusion can be arrived on the possibility of landslide occurrence along the stretch of the 5ukidnon-!avao national highway.
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CHAPTER !: REIE/ O0 RE-ATED -ITERATURE
!.1 Background of -and)$'de)
Landslides are defined as the mass movement of rocks, debris or earth along a sliding plane. They are characteri"ed by almost permanent contact between the moving masses and sliding plane 5utler, A0*? :ro"ier, A'%? and 3mith, AA*1. Landslides cause substantial economic, human and environmental losses throughout the world. B6amples of devastating landslides at a global scale include the A0) :alabria landslide in /taly, the A0+ Causcaran landslide in Peru 9c:all, AA)1, the A** berfan landslide in @ales, and the A'& rmero landslide in :olombia le6ander, AA(1.
!.! -and)$'de) due to S$o,e 0a'$ure)
ccording to 4rense )++&1, landslides induced by heavy rainfall often occur in marginally stable slopes that consist of various types of soil, such as colluvial and residual soils. 5ecause of its freuency and pro6imity to various infrastructure developments in landslide-prone areas, rainfall-induced slope instability is considered one of the most signiDcant geo-environmental ha"ards. /n order to understand the mechanism and conditions leading to these slope failures, a comprehensive testing program consisting of constant shear stress drained tria6ial tests and model slope e6periments was performed using sandy materials obtained from a former landslide site in Eapan. esults of both element tests and model e6periments clearly showed that slope failure is induced due to the development of pore-water pressure in slope. s soil moisture contents within the slope approach critical values, ground deformations are
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mobili"ed. Therefore, by properly selecting regions where soil moisture contents must be monitored, possibly in areas where seepage forces will develop, failure initiation in slopes can be predicted.
!.% Ph'$',,'ne) a) a -and)$'de Prone Countr
The Philippines ranks third in terms of casualties and cases among % countries identified as key spots for non-earthuake-related landslides, according to a professor of ha"ard and risk at !urham #niversity in the #nited $ingdom. !avid Petley, lead author of the recently released study, ;lobal patterns of loss of life from landslides,
‟
also identified Gthe mountain chains along the western edge of the Philippine 3ea plateH as among the global hotspots for landslides Philippine !aily /nuirer, )+)1.
!.* Character')t'c) of Adtuon C$a
study conducted by 5argasa, et al. )+1 showed that the overall geotechnical inde6 properties of dtuyon :lay show that it can be classified under the -0-* subgroup with group inde6 of %) of the 3CT4 3oil :lassification 3ystem and :C clay of high plasticity, fat clay1 in the #nified 3oil :lassification 3ystem. /t is acidic strong brown clay with a relatively high plasticity of (07 with high amount of silt and clay. value of Plasticity /nde6 greater than (& 7 and fall between )+ 7 to %+ 7 range e6hibits high swell potential and high plasticity . /n 5ukidnon, large areas of soil cover are dominated by dtuyon clay based on the soil map generated by the 5ureau of 3oils and @ater 9anagement 53@91. This type of soil has high potential to swell.
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!.+ Con(ent'ona$ 'e$d Stre)) Deter"'nat'on
To analy"e the stability of slopes during rainfall, it is necessary to know the change in the saturation ratio and the strength parameters of highly saturated soils. :onstant shear stress drained tria6ial tests on initially unsaturated sandy specimens were conducted to simulate the stress path followed by soil element in a slope during rainfall. /n these tests, total normal stress and shear stress essentially remained constant during the process of rainwater infiltration. /n addition to porewater pressure inside the specimen, a6ial and volumetric strains during water infiltration were e6amined. 4rense, )++%1
!.2 'e$d Stre)) Deter"'nat'on through S$u", Te)t
9ende"-3anche" et al conducted a study about yield stress evaluation as a function of water content for slip-prone clayey.
heights is called the slump height s1.
Ƭ y ¿
was calculated using the
Pashias and coworker’s e6pression.
8
@here I is the material density, where g is the gravity, C is the height of the frustum and s is the slump height.
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CHAPTER %: THEORETICA- 0RA3E/OR4
INPUT
Materials
Sand strainer Sieve no. ! Cassagrande cup device "AS#M D$%&! ' &() Cylindrical *ipe "&+( mm , %+( mm) Clayey soil "ta-en from different site) Specification
AS#M D$%&! ' &( standard test methods for liuid limit
PROCESS
Soil preparation from specified site Determination of physical and chemical properties Atterberg Limit Grain Size Distribution Determination of Yield Stress Data Gathering
OUTPUT
Yield Stress of Soil Soil Moisture vs. Yield Stress
Graph Critical Moisture Content for Landslide to occur
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CHAPTER *: 3ETHODO-O5
*.1 Pre,arat'on of Con)t'tuent 3ater'a$) *.1.1 So'$ Sa",$e)
;enerous uantities of disturbed soil samples will be gathered in si6 different points along the stretch of the 5ukidnon-!avao national highway and then will be taken to :entral 9indanao #niversity for the application of pre-evaluation processes. *.1.! Dr'ng Proce))
representative soil sample will undergo air-drying for about one week or until the e6ternal moist will be removed. Then, it will be brought to the 3oil and Plant nalysis Laboratory in the !epartment of griculture, :9#, 9aramag, 5ukidnon for oven-drying. fterwards, the moisture content of the specimen will be "ero. *.1.% S'e('ng
The oven-dried soil will pass through sieve number ' and )++. 3oil particles that will pass through sieve number ' will be used in the determining of the soil yield stress through slump test method. @hile the soil debris that will pass through sieve number )++ will be used in the tterberg limit and other related tests. *.1.* Storage and -a#e$$'ng
The sifted soil sample will be stored in a "ip-lock and will be kept in a room with a moderate temperature. :old environment must be avoided in order to prevent moist 11
development within the soil particles. 3pecimens should be labelled accordingly to avoid interchanging of samples. *.! Deter"'nat'on of So'$ Pro,ert'e)
The representative from soil samples will be e6amined in the laboratory for physical and chemical properties such as specific gravity, mean grain si"e, gravel content, sand content, fine content, coefficient of uniformity, coefficient of gradation, ma6imum void ratio, minimum void ratio and the like.
*.% Atter#erg -'"'t) *.%.1 -'6u'd -'"'t Te)t
Liuid limit will be tested by using cassagrande cup device with 3T9 !%(' J + standard test methods for liuid limit will be the basis for this test. 3oil sample will be put into the cassagrande cup of about ++mm in thickness and it will be separated eually in the middle by a spatula and it will be sprayed by a varying amount of moisture content for three trials. /t will be blown until the separated soil portions will be in contact for about )mm. The moisture content of the three trials and the numbers of blow with respect to the varying amount of moisture content will be plotted on a semi-logarithmic graphing paper. The moisture content corresponding to )& blows will determine the liuid limit of the soil.
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*.%.! P$a)t'c -'"'t and P$a)t'c't Inde7
Plastic limit and plasticity inde6 will be test by 3T9 !%(' J + standard test methods for plastic limit and plasticity inde6. The soil sample will be sprayed by varying water content for three trials at where it will crumble when rolled into threads about (mm. it will be oven dried in a kiln for the determination of water content. The average computed water content will give us the plastic limit of the soil. #sing the euation PI=LL-PL we can compute the plastic inde6.
*.* 'e$d Strength Co",utat'on
of the cylindrical frustum. Then the yield stress
Ƭ y
1 will be solved using Pashias et al
e6pression>
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@here I is the material density, g is the gravity, C is the height of the frustum and s is the slump height. fter calculating the yield strength, graph illustrating the correlation between yield strength and the moisture content will be made. Then the critical moisture content will be pointed out depending on the graph. *.+ Re$at'ng 'e$d Strength to Ra'nfa$$ Inten)'t *.+.1 Ac6u'r'ng Ra'nfa$$ Inten)'t Data
The records of the past rainfall intensity will be acuired at the Philippine tmospheric ;eographical and stronomical 3ervices dministration P;-31 or other related institutions. Preferably, the records will be from the past twelve months of )+) and should cover the location in which the study will be conducted. *.+.! A(erage Da'$ Ra'nfa$$ Inten)'t
From the data that will be obtained, the average daily rainfall intensity can be calculated. n assumption will be made that the average daily rainfall intensity will be the source of the water content of the soil and then we can conclude an optimum rainfall intensity that can cause non-seismic landslides at a certain place.
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CHAPTER +: 3A8OR ACTIITIES OR /OR4 P-AN
3onth)
Act'('t'e) 8u$ !91%
Aug. !91%
Se,t. !91%
Oct. !91%
No(. !91%
. Proposal of the pro=ect ). Preparation of materials (. :ollection and preparation of sample %. Testing of sample ;3!, tterberg limit, slump test1 &. ;athering of data *. nalysis of data 0. Preparation and submission of final report '. Final defend of pro=ect
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CHAPTER 2: BUD5ETAR A--OCATIONS
Co)t) of 3ater'a$) 3ater'a$)
Pr'ce
uant't
Tota$
3ieve
P0+++.++
)
P%+++.++
:ylindrical frustum
+
*
+
Total
K
P%+++.++
Co)t) of -a#orator Te)t) Sa",$e
Co)t ,er )a",$e
uant't
Tota$
3oil
P+++.++
*
P*+++.++
Total
K
P*+++.++
Other co)t) ;food and tran),ortat'on<: P%999.99 TOTA- COST =
P!%>999.99
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CHAPTER ?: E@PECTED OUTPUT
/n the work of 9ende"-3anche" et al, the soil samples that they have acuired have high contents of aluminium and silicon. 5esides, a low content of /ron and Titanium was observed in this material. /n its particle si"e distribution, *+7 of the particle si"es are in the range between (++ and )&+ microns, the +7 are in the interval )&+ J )(*+ microns, and the rest (+7 of the particle si"e is shorter than )++ microns. /n a plot of yield stress versus water concentration shown below, contents lower than (&.&7 of moisture content decreases the yield strength e6ponentially with concentration. t this point, it is practicable to e6plain an increment in the landslide risk, since the specimen has transformed from solid-plastic to solid-viscous behaviour. 9ende"-3anche" et al1
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RE0ERENCES: -
5argasa, , et al. )+)1. GBffects of 3ugarmill Lime 3ludge on the Permeability of
dtuyon :layH. - 5utler, E.> A0*, 2atural !isasters , ictoria, Ceinemann. - 9ende"-3anche" . et al. /nfluence of humidity on yield stress determination by slump test of slip-prone clayey soils and their relation with the chemical properties. A manuscript draft submitted for the course Applied Science. - Pashias 2., 5oger !. ., 3ummers E. and ;lenister !. E., AA*, fifty cent
-
rheometer for yield stress measurement, Eournal of heology, %+, *, 0A-'A. .P. 4rense, 3lope Failures Triggered by Ceavy ainfall, Philippine Bngineering
-
Eournal, submitted for publication )++%1 .P. 4rense, 3.B. 3apuay and B.5. 5illedo, :haracteristics of the )++% sedimentrelated disasters in 8ue"on Province, Philippines triggered by tropical cyclones,
-
Eournal of 2atural !isaster 3cience, submitted for publication )++&1 3Mnche" :rN", P., )++', nMlisis del esfuer"o de cedencia de
suelos
arcillosos como posible indicador de un derrumbe, 5achelor Thesis at B3F9, -
/nstituto PolitOcnico 2acional, 9O6ico. 3idle, .:, Pearce, .E and 4’loughlin, :.L .> A'&, Cill 3lope 3tability and Land #se, @ater esources 9onograph 3eries, 2o. , @ashington !.:, merican
-
;eophysical #nion. 3ultanov, $.3., $husanov, 5.B., )++, 3tate euations for soils prone to slump-type settlement with allowance for degree of wetting, 3oil 9echanics and
-
Foundations Bngineering, (', (, '+-'*. http://globalnation.inquirer.net/4!"#/philippines-ran$s-!rd-in-landslide-deaths
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