真空预压下软土地基的固结特性和沉降计算方法  

Consolidation characteristics and settlement calculation method of soft soil foundation under vacuum preloading

作　　者：王思刘 张冬琪 陈纪胜 黄欣 王靖博 傅旭东[1] WANG Siliu;ZHANG Dongqi;CHEN Jisheng;HUANG Xin;WANG Jingbo;FU Xudong(School of Civil Engineering,Wuhan University,Wuhan 430072,China)

机构地区：[1]武汉大学土木建筑工程学院,湖北武汉430072

出　　处：《铁道科学与工程学报》2022年第3期674-682,共9页Journal of Railway Science and Engineering

基　　金：国家大学生创新创业训练计划(202010486059)。

摘　　要：地基在真空排水预压条件下产生负的孔隙水压力,但其沉降计算是将膜下真空度作为等效荷载作用于地基上,按照堆载预压沉降计算方法进行的。因此,研究负孔隙水压力下土体的三向固结特性与沉降计算方法具有重要意义。对负孔隙水压力下的典型饱和软黏土样进行三向固结试验和标准固结试验,并将试验结果进行对比分析。建立真空排水预压固结微分方程,根据排水砂层和竖向砂井的边界条件对微分方程进行求解。基于按应力定义的固结度,提出考虑负孔隙水压力和土体三向变形影响的固结沉降计算方法。开展真空排水预压室内模型试验,并根据试验结果确定计算参数的取值范围。研究结果表明:三向固结试验测得的固结系数在3×10;cm;/s~4×10;cm;/s之间,是标准固结试验测得的固结系数的40倍左右;真空预压排水条件下的竖向和径向固结微分方程与砂井固结理论方程具有相同的形式,但排水边界的孔隙水压力为负值;所提出的沉降计算方法得到的固结沉降计算值与实测值最大误差为12%,总沉降修正系数为0.98~1.18时计算值与实测值吻合较好。研究结果对于准确确定真空排水预压法预压工期和工后沉降具有一定参考价值。The foundation produces negative pore water pressure during vacuum drainage preloading, but its settlement calculation is carried out by taking the vacuum under the membrane as the equivalent load on the foundation and according to the settlement calculation method of surcharge preloading. Therefore, it is meaningful to study the three-dimensional consolidation characteristics of soil under negative pore water pressure and the settlement calculation method. Three-dimensional consolidation tests and standard consolidation tests were performed on typical saturated soft clay samples. The results were compared and analyzed. The differential equation for vacuum drainage preloading consolidation was established, and was solved under the drainage sand layer and vertical sand drain boundary conditions. Based on the degree of consolidation defined by stress, a calculation method of settlement considering the influence of negative pore water pressure and three-dimensional deformation of soil was proposed. The vacuum drainage preloading model test was carried out, and the value range of calculation parameter was determined according to the test results. The results show that the consolidation coefficient in the three-dimensional consolidation test is mostly around 3×10;cm;/s~4×10;cm;/s,which is about 40 times of standard consolidation test. The vertical and radial consolidation differential equations have the same form as the sand drain consolidation theoretical equations. The pore water pressure at the drainage boundary is negative. The maximum error between the consolidation settlement value obtained by the proposed settlement calculation method and the measurement is 12%. When the total settlement correction coefficient is0.98~1.18, the calculated value is in good agreement with the measured value. The research results have a certain reference value for accurately determining the preloading construction period and post-construction settlement of the vacuum drainage preloading method.

关 键 词：真空排水预压法 负孔隙水压力 三向固结试验 模型试验 固结度 

分 类 号：TU470[建筑科学—结构工程]