An Overview of Soil Mechanics - IIT Kanpur

1 An OverviewAn OverviewAn OverviewAn OverviewofofofofSoil MechanicsSoil MechanicsSoil MechanicsSoil MechanicsDr. P. K. BasudharDr. P. K. BasudharDept of Civil EngineeringIIT KanpurSoil Problems soil Problems soil Problems soil Problems &&SolutionsSolutionsA Preview of A Preview of soil BehaviorSoil BehaviorPioneers inPioneers inSoil MechanicsSoil MechanicsSoil MechanicsSoil MechanicsCIVIL ENGINEERSOILCIVIL ENGINEERSOILENCOUNTERSWHERE ?CIVIL ENGINEER SOILCIVIL ENGINEER soil soil AS AENCOUNTERS FOUNDATION CONSTRUCTION MATERIALCONSTRUCTION MATERIAL soil RETAININGSPECIAL PROBLEMS SPECIAL PROBLEMSFOUNDATIONSFOUNDATIONSFOUNDATION SFOUNDATIONS WHAT ARE FOUNDATIONS?WHAT ARE FOUNDATIONS? TYPES OF FOUNDATIONSSHALLOW FOUNDATIONS SHALLOW FOUNDATIONS DEEP FOUNDATIONS MAIN PROBLEM IN THE DESIGN TO PREVENT SETTLEMENT TOTAL SETTLEMENT DIFFERENTIAL SETTLEMENTSHALLOW FOUNDATIONSSHALLOW FOUNDATIONSSHALLOW FOUNDATIONSSHALLOW FOUNDATIONS StructuralStructural loadsloads arearecarriedcarried bybythethe soilsoildirectlydirectlyunderunderthethe structurestructureDEEP FOUNDATIONSDEEP FOUNDATIONSDEEP FOUNDATIONSDEEP FOUNDATIONS UsedUsedtotocarrycarrythetheUsedUsedtoto ca yca yteteloadsloads toto firmfirm soilsoil atatsomesome depthdepthppClassic case of bad foundationClassic case of bad foundationClassic case of bad foundationClassic case of bad foundation showsshows thethe PalacioPalacio dede laslasggBellasBellas Artes,Artes.

2 MexicoMexico CityCity TheThe22mmdifferentialdifferentialsettle mentsettlementbetweenbetweenthethestreet streetsettlementsettlementbetweenbetween thethestreetstreetandand thethe buildingbuilding onon thethe rightrightnecessitatednecessitated thethe stepssteps whichwhichwerewereaddedaddedasasthethese ttlementsettlementwerewereaddedaddedasas thethesettlementsettlementoccurredoccurr ed TheThe generalgeneral subsidencesubsidence ofofthisthispartpartofofthethecitycityis is77mmthisthispartpartofofthethecitycity isis77mm (Photograph(Photograph complimentscompliments ofofRaulRaul Marsal)Marsal)Example of Shallow foundationsExample of Shallow foundationsExample of Shallow foundationsExample of Shallow foundations FigFig showsshows thethe MITMIT studentsstudents centrecentre MatMat foundationfoundation FloatationFloatationtechniquetechnique FloatationFloatationtechniquetechniqueMa in FactorsMain JustJust howhow deepdeep intointo thethe soilsoil shouldshould thethe buildingbuilding bebeplaced?

3 Placed?placed?placed? WouldWould thethe excavationexcavation havehave toto bebe enclosedenclosed byby aawallwallduringduringconstructionconstr uction totopreventpreventcavecave--insins ofofsoil? soil ? WouldWould itit bebe necessarynecessary toto lowerlower thethe waterwater tabletable ininorderorder toto excavateexcavate andand constructconstruct thethe foundationfoundation and,and,ififsosohthtme nsme nssho ldsho ldbebesedsedtotoomplishomplishthisthisif ifso,so,whatwhatmeansmeansshouldshouldbe beusedusedtotoaccomplishaccomplishthisth isloweringlowering ofof thethe groundground waterwater(dewatering)?(dewatering)? geda geooda ageda agetotoadjace tadjace tbdgs?bdgs? HowHow muchmuch wouldwould thethe completedcompleted buildingbuilding settlesettle andandwouldwould itit settlesettle uniformly?

4 Uniformly? ForForwhatwhatstressesstresses andandwhatwhatstressstress distributiondistribution shouldshouldthethe matmat ofof thethe buildingbuilding bebe designed?designed?Example of Deep foundationsExample of Deep foundationsExample of Deep foundationsExample of Deep foundations MITMIT materialmaterial centrecentre hashasdeepdeeppilepile foundationfoundationpppp ReasonsReasons Basement space not Basement space not desirabledesirable No sand and gravel at No sand and gravel at hihithe sitethe site Not to disturb Not to disturb underground utilitiesunderground utilitiesunderground utilitiesunderground utilities PointPoint bearingbearing pilepile FrictionFrictionpilepilepp AugeringAugeringMain FactorsMain FactorsI What type of pile should be used?

5 I What type of pile should be used?Main FactorsMain FactorsI. What type of pile should be used? I. What type of pile should be used? 2. What was the maximum allowable load for a pile?2. What was the maximum allowable load for a pile?3 At h t p inh ld th pilb dri n?3 At h t p inh ld th pilb dri n?3. At what spacing should the piles be driven? 3. At what spacing should the piles be driven? 4. How should the piles be driven? 4. How should the piles be driven? 5. How much variation from the vertical should be 5. How much variation from the vertical should be permitted in a pile? permitted in a pile? 6. What was the optimum sequence for driving piles? 6. What was the optimum sequence for driving piles? 7. Would the driving of piles have an influence on 7.

6 Would the driving of piles have an influence on adjacent structures? adjacent structures? Example of Embankment Example of Embankment on Soft Soilon Soft soil soilsoil PreloadingPreloadingtechniquetechnique PreloadingPreloadingtechniquetechnique ShearShear rupturerupture shouldshouldnotnotoccuroccurMain FactorsMain Factors11 HowHowhighhighaafillfillcouldcouldbebepl aced?placed?Main FactorsMain HowHow fastfast couldcould thethe fillfill bebe placed?placed?33Wh tWh trrththmimmmimmlplpfrfrththfill?fill? CouldCould thethe fillfill bebe placedplaced withoutwithout employingemploying specialspecialthithitttitididiththftftfd tifdtitechniquestechniquestotocontaincon tainorordraindrainthethesoftsoftfoundati onfoundationsoil? soil ?55 HHhhldldhhfillfilll?l? muchmuchwouldwouldthethefillfillsettle?

7 Settle? HowHow longlong shouldshould thethe fillfill bebe leftleft inin placeplace inin orderorderhhhhfdifdibbddhhthatthatthethe foundationfoundationbebe compressedcompressedenoughenoughtotoperm itpermit constructionconstruction andand useuse ofof thethe tank?tank?Example of Foundation HeaveExample of Foundation Heave OccursOccurs whenwhen foundationfoundation soilsoil expandsexpands whenwhen thetheconfiningconfiningpressurepressure isisreducedreducedandand//ororthethewate rwatercontentcontentconfiningconfiningpr essurepressureisisreducedreducedandand// ororthethewaterwatercontentcontentofof thethe soilsoil isis increasedincreased AridArid regionsregionsgg PresencePresence ofof montmorillonitemontmorilloniteMain FactorsMain Factors ProperPropersizesizecapacitycapacityleng thlengthandandspacingspacingofofthetheMa in FactorsMain FactorsProperPropersizesize,capacity,,ca pacity.

8 Lengthlengthandandspacingspacingofofthet hepilespiles TheThepilepileshouldshouldbebelonglongen oughenoughtotoextendextendbelowbelow TheThepilepileshouldshouldbebelonglongen oughenoughtotoextendextendbelowbelowthet he depthdepth ofof thethe soilsoil thatthat wouldwould expandexpandThThdhdhldldiihhhhhh TheThedepthdepthselectedselectedininsuch suchaawaywaythatthatthetheconfiningconfi ning pressurepressure fromfrom thethe soilsoil overburdenoverburdenlliiiildldiiffi iffi iplusplus minimumminimumloadloadisissufficientsuff icienttoto preventpreventexpansionexpansionCONSTRUC TION MATERIALCONSTRUCTION MATERIALCONSTRUCTION MATERIALCONSTRUCTION MATERIAL Select proper type of soilSelect proper type of soil Method of placementMethod of placement Control of actual placementControl of actual placement Control of actual placementControl of actual placement FillingFillingggExample of an Earth DamExample of an Earth Dam Two main zonesTwo main zones Clay coreClay coreyy Rock toeRock toe Gravel filterGravel filter Rock facingRock facing Zoned earth dam & homogeneous earth damZoned earth dam & homogeneous earth damMain FactorsMain WhatWhat shouldshould bebe thethe dimensionsdimensions ofof thethe damdam toto givegive thethe mostmostMain FactorsMain Factorseconomical,economical, safesafe structure?

9 Structure? WhatWhat isis thethe minimumminimum safesafe thicknessthickness forfor thethe gravelgravel layers?layers? anyany swellingswelling ofof thethe clayclay corecore toto aatolerabletolerable amount?amount? WhatWhat moisturemoisture contentcontent andand compactioncompaction techniquetechnique shouldshould bebeemployedemployedtotoplaceplacethethe gravelgravelandandclayclaymaterials?mate rials?employedemployedtotoplaceplacethet hegravelgravelandandclayclaymaterials?ma terials? WhatWhat areare thethe strengthstrength andand permeabilitypermeability characteristicscharacteristics ofof thetheconstructedconstructed dam?dam? timetime andand depthdepth ofof waterwater inin thethe reservoir?reservoir? HowHow muchmuch leakageleakage would,would, occuroccur underunder andand throughthrough thethe dam?

10 Dam? ,What,ififany,any, specialspecialrestrictionsrestrictions onon thetheoperationoperation ofofthethereservoirreservoir areare necessary?necessary?Example of a Reclamation StructureExample of a Reclamation StructureExample of a Reclamation StructureExample of a Reclamation Structure NonNon--availabilityavailabilityofofyygo odgood buildingbuilding sitessites HarborHarborandandterminalterminalHarbor Harborandandterminalterminalfacilitiesfa cilities HydraulicHydraulicfillingfilling HydraulicHydraulicfillingfillingMain FactorsMain FactorsMain FactorsMain HowHow deepdeep shouldshould thethe sheetsheet pilepile wallwall penetratepenetrate thethe foundationfoundationsoil? soil ? HowHow shouldshould thesethese pilespiles bebe bracedbraced laterally?laterally? ,, ,,howhowshouldshould thethe exitexit ofof thethe dredgedredge pipepipe bebe locatedlocated inin orderorder toto getgetthethe firmerfirmer partpart ofof thethe fillfill atat thethe locationslocations wherewhere thethe maximummaximumfoundationfoundation loadsloadswouldwould bebeplaced?