土的工程绪论土的工程 (135).pdf
4.6 The relationship between foundation settlement and timeIn engineering practice,it is often necessary toestimate the settlement of buildings,roads and otherprojects after completion or a period of time,as well asthe time required to achieve a certain settlement,whichrequires to solve the relationship between settlement andtime.Consolidation of saturated soil土力学土力学Soil MechanicsSoil MechanicsProf.Prof.H.J.LiaoH.J.LiaoUsually during the construction period,differentgrounds lead to different settlements.For example,theground settlement of gravel soil and sand has beenbasically completed during the construction periodbecause of low compressibility and high permeability.For the thick saturated clay ground,the settlementoften takes several years or even decades to reachstabilitybecauseofthesmallvoidsandhighcompressibility.土力学土力学Soil MechanicsSoil MechanicsProf.Prof.H.J.LiaoH.J.LiaoFor saturated soil,settlement is related to theescaping of water.Because the void is full of water,under the effect of load,part of the water in the voidmust be discharged so that the soil can be compacted.Therefore the time needed for pore water drainageis related to the distance of soil drainage,soil particlesize,voidsize,soilpermeabilitycoefficient,load,compressibility coefficient and so on.土力学土力学Soil MechanicsSoil MechanicsProf.Prof.H.J.LiaoH.J.LiaoThe consolidation of saturated soil,including:1)The gradually discharge of free water in the soil voids；2)The gradually decrease of the void volume；3)The excess pore water pressure,gradually transfers tothe soil skeleton to bear and become the effective stress.It is a process in which the consolidation,drainage,compression and stress transfer of saturated soil are carried out simultaneously.土力学土力学Soil MechanicsSoil MechanicsProf.Prof.H.J.LiaoH.J.LiaoIt can be seen that the consolidation of saturated soil is a process of pore water pressure dissipation and gradually transfer to effective stress.t=0u=z;=0u+=z0 t+u0u +=z t+u=0;=zu+=zzConsolidation model of saturated soilPistonContainerWaterSpringStatementStatement:Thanks for some pictures and materials fromthe Internet used in this courseware only for teaching.
