基于孔压实测资料的真空预压机理及沉降计算探讨

Discussion of the mechanism of vacuum preloading and settlement calculation based on measured values of pore water pressure

分析真空预压工法下土体孔隙水压力实测资料,建议将其作用过程分成三个阶段:真空吸力导致浅层土体渗透固结,并对深层土体产生"堆载"效应;浅层土体固结稳定,深层土体由受"堆载"效应向受"负压"效应过渡;深层土体在"负压"效应下产生渗透固结,并达到稳定平衡。认为真空预压法作用机理的根源并不是单独的流体渗流场产生的负压差,而是不同时段"正压"和"负压"共同作用以及在该工法水位下降现象下两种"压力"互相叠加发生的。建立了一维"双弹簧"真空固结模型,进行了土体固结分析,认为该模型能反映真空预压加固软基作用机理。获得了适合真空预压法下土体沉降的计算方法,用此法进行了沉降计算,结果比较符合实际情况,也证明了机理的合理性。

Measured values of pore water pressure in soil under vacuum preloading were analyzed.Action process of vacuum preloading was compartmentalized three phases.They were seepage consolidation in the upper part of the soil and＂surcharge load＂effect in deep soil by vacuum suction,consolidation stabilization in the upper part of the soil and transformation of＂surcharge load＂effect to＂negative pressure＂effect in deep soil,seepage consolidation in deep soil under＂negative pressure＂effect and to balance.Action mechanism root of vacuum preloading was not negative pressure difference solely,which was produced by seepage field.The root was＂positive pressure＂action and＂negative pressure＂action together during different period.The root also included the two pressures superposition under the especial phenomenon of vacuum preloading： water level falling.＂Two springs＂vacuum consolidation model of one dimension was established and was applied to analyzing soil consolidation.The model can reflect action mechanism of vacuum preloading well.Settlement calculation method was obtained and applied to calculating soil settlement.Compared measured value,the result was favorable and showed that mechanism of vacuum preloading in this paper was reasonable.