earthpressureat-rest(静止土压力)

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1、第六章土压力Chapter6EarthPressureInthislecture,we’lllearnCoefficientsofearthpressure(土压力系数)Relationshipbetweenwallmovement&earthpressure(墙体移动与土压力的关系)Earthpressureat-rest(静止土压力)Rankine’searthpressuretheory(朗肯土压力理论)6.1Earthretainingstructures(挡土结构物)Soilnailedwallforacutslope(土钉墙)Bridgeabutment(桥台)Quayw

2、allforcontainerterminal(码头的岸墙)Deepexcavation–diaphragmwall(深基坑–地下连续墙)Deepexcavation–sheet-pilewall(深基坑–板式挡土墙)6.2CoefficientofEarthPressure(土压力系数)isunitweightofsoilandzisdepthofsoilH地面M’h’v土压力竖向有效应力AA’CBB’C’Backfill(填土)EarthPressureAt-Rest(静止土压力)whenawalldoesnotmoveatall,i.e.itis“atrest”[AA’]

3、(墙体没有位移)ActiveEarthPressure(主动土压力)whenawallmovesawayfrombackfill[AA’toBB’](墙体离开填土方向)PassiveEarthPressure(被动土压力)whenawallispushedagainstbackfill[AA’toCC’](墙体向填土方向挤压)1.WallMovement(墙体的移动)Howtoevaluatethecoefficientsofearthpressure?怎样计算土压力糸数?Assumptions(假定):-nogroundwatertable(没有地下水)-nomovementofw

4、all(墙体没有位移)Lateralearthpressure(土压力)[´h]actingonthewallis:whereisunitweightofsoil,HisdepthofsoilandKoiscoefficientofearthpressureatrest(静止土压力糸数).´v´h´6.3EarthPressureatRest(静止土压力)Jaky(1944)proposedfollowingempiricalexpressiontoestimateKofornormallyconsolidatedsoil(估计正常固结土的Ko的经验公式):where´is

5、effectiveangleofinternalfriction(有效內摩擦角)Lateralearthpressure[´h]increaseslinearlywithdepthandtotallateralforce(总合力)[Po]exertedonthewallis:Followingassumptions(假定)aremadetodevelopRankine’searthpressuretheory.Wallisrigid,vertical,frictionlessandextendstoaninfinitedepth(墙背竖直和光滑)Backfillisadry,hom

6、ogeneous,isotropicandcohesionlesssoil(填土是无粘性土,干,均质和各向同性)Soilsurfaceishorizontal(水平表面)andtherearenoshearstressesonhorizontalandverticalplanes,i.e.horizontalandverticalstressesareprincipalstresses(水平和竖直方向为主应力方向)6.4.Rankine’sEarthPressureTheory(朗肯土压力理论)Infigureontheright,redcirclerepresentsinitial

7、stressstateorKoconditionofelementA(右图的红圆代表土单元A的初始或静止状态)WallismovedawayfromelementAtoB(墙体从土单元A方向离开)´hwillreducebut´vwillremainconstant(´h减少,但´v不变)Mohr’scirclewillexpanduntiltouchingCoulombfailuresurface[representedbybluecircle]