Direct Shear Box Test

Direct Shear Box Test Contents

Introduction Objective  Apparatus  Appara tus Description of Test Test Results Calculations Relevance to Geotechnics Soil Description and Conclusion References

Introduction

Shear strength is the property that enables a material to remain in euilibrium !hen its surface is not level" #Smith$ %&&'( The direct shear test is used to determine the shear  strength of soils on a predetermined failure surface" This test is used to measure the shearing resistance$ resistance$ un)drained shear strengt strength$ h$ and dilative and contrac contractive tive tendencies in soils" #*ratta et al$ %&&+( The results can then be used to determine the allo!able bear be arin ing g ca capa paci city ty of fo foun unda dati tion ons s an and d st stab abil ilit ity y of re reta tain inin ing g !a !all lls$ s$ cu cutt ttin ings gs an and d emban,ments" Objective

To determine the angle of shearing resistance of a sample of sand- the test may be carried out either dry or fully saturated but not any!here in bet!een" Apparatus

.otorised shear bo/ 0lectronic balance 1ori2ontal and vertical measuring gauges  Assorted steel !eights 3ever arm attachment Tamper  4roving Ring Description of Test

Three samples of the same soil are placed into the shear bo/$ !hich has t!o stac,ed suares to hold the sample" A confining stress is applied to the sample and the upper  suare is pulled laterally until the sample fails" The normal stress applied$ the vertical displacement and

proving

ring are

recorded at regular and freuent intervals"

5ormal Stress #,4a(6%7$&7&$&+7$& Sheat stress at *ailure #,4a(6%%$89:$&+9$&  Area ; '& < '& ; 9'&&mm% ; 9$' < =&)9 m%

>= ; %7$&?Area ; ':88$87 ,4a  >% ; 7&$&?Area ; =9@@@$@: ,4a >9; +7$&?Area ; %&@99$98 ,4a =; %%$8?Area ; '%%%$%9 ,4a  %; 9:$&?Area ; =&@99$98 ,4a 9; +9$&?Area ; %&%++$+@ ,4a

ɸB; tan)= #'%%%$%9?':88$87( ; 8=$@' Relevance to Geotechnical Design The relevance of this test is to determine !hether the soil !ill have enough shear strength to support planned construction !or,s upon it$ such as e/cavation$ emban,ments$ roads$ foundations and retaining !alls" The shear strength value that is calculated from this test allo!s the soil to be used in a !ay that !ill not be subjected to failure due to shear" Soil Description and Conclusion sing a =&/ hand lens the follo!ing visual description !as concluded6 < 4ale bro!n in colour  niformly graded particle si2es !ith no cohesion  4article si2es of less than %mm" To ES:7:9&6=::& the classification of the soil !as determined as6 4ale bro!n !ell graded medium angular uart2 sand"The direct shear test is one of many test methods used to determine the shear strength of a soil" Fith the results of this test$ the

angle of shearing resistance #ɸ B( can be determined and used to calculate the active lateral pressure coefficient #a( !hich is then used in the design of retaining !alls" References

Smith$ I" %&&'" SmithHs 0lements of Soil .echanics" @th 0d" Elac,!ell 4ublishing *ratta" %&&+$ Introduction to Soil .echanics 3aboratory Testing" CRC 4ress 3iu$ C" 0vett$  E" %&&&" Soil 4roperties6 Testing$ .easurement and 0valuation" 8th 0d" Carlisle 4ublishers Eritish Standards Institute =:::" ES7:9&6 =::: Eritish Standards Institute =:::" ES=9++6 =:::