基于修正剑桥模型的真空预压表面硬壳层不排水抗剪强度分析  

Analysis of the undrained shear strength of hard crust in vacuum preloading based on Modified Cam Clay(MCC)constitutive model

作　　者：陈富[1,2] 李宁 CHEN Fu;LI Ning(Harbin Institute of Technology,Harbin,Heilongjiang 150001,China;CCCC First Harbor Engineering Co.,Ltd.,Tianjin 300461,China)

机构地区：[1]哈尔滨工业大学,黑龙江哈尔滨150001 [2]中交第一航务工程局有限公司,天津300461

出　　处：《地基处理》2021年第4期271-276,共6页Journal of Ground Improvement

摘　　要：真空预压是一种广泛应用的深厚软土地基处理方法,表面硬壳层对于真空预压的沉降量和地基稳定性有着重要影响。本文基于修正剑桥本构模型分析表面硬壳层抗剪强度较高的原因。表面硬壳层的成因主要包括真空预压加固前天然形成和真空预压固结过程中形成。天然形成的表面硬壳层主要是由于地下水位降低和水分蒸发等因素使表层土体处于超固结状态,通过调整超固结比OCR沿深度的变化能够很好拟合十字板不排水剪切强度曲线,从而将不排水抗剪强度引入到岩土工程有效应力分析中。真空预压过程中形成的表面硬壳层是由于竖向排水距离和塑料排水板弯折等因素导致在相同时间内深层土层的固结度小于表层土层。随着真空预压固结时间的增加,深层土层固结度逐渐增大,抗剪强度随之增长,真空预压的表面硬壳层现象变得不明显。Vacuum preloading is a widely used technology for deep soft soil foundation treatment.The hard crust has an important impact on the settlement and foundation stability of vacuum preloading.Based on Modified Cam Clay(MCC)constitutive model,the reason of higher shear strength of hard crust is analyzed.The hard crust is formed by two ways,which includes the naturally weathering before vacuum preloading,and consolidation in the process of vacuum preloading.The naturally formed hard crust is mainly due to the reduction of groundwater level and water evaporation,which makes the surface soil in an over consolidated state.By adjusting the change of over consolidation ratio(OCR)along the depth,the undrained shear strength profile of vane is well fitted,so that the undrained shear strength is introduced into the effective stress analysis of geotechnical engineering.The hard crust which is formed in the process of vacuum preloading is due to the consolidation degree of deep soil layer which is less than that of surface soil layer because of the factors such as vertical drainage distance and bending of plastic drainage plate.With the increase of consolidation time of vacuum preloading,the consolidation degree of deep soil layer gradually increases,the shear strength increases accordingly,and the hard crust phenomenon of vacuum preloading becomes unobvious.

关 键 词：真空预压 修正剑桥本构模型 表面硬壳层 固结度 超固结 

分 类 号：TU472[建筑科学—结构工程]