不同取样直径下软土物理力学特性室内对比试验分析

以宁波市轨道交通4号线岩土工程勘察项目为依托，采用软土地区目前普遍使用的敞口薄壁取土器，对两种不同直径取样器（75、100 mm）下采取的软土开展了室内对比试验。基于室内对比试验结果，分析了两种取样直径下软土物理力学性质指标取值的差异性及其产生机理；采用附加体积应变法对两种直径下土样的扰动程度进行了分析评价。结果表明：与直径100 mm的取土器相比，直径75 mm取土器获得的土样含水量、孔隙比有一定程度降低，降低幅度均为9%；密度、压缩模量及抗剪强度指标有一定幅度的增加，增加幅度2%～21%；土样的体积应变均值分别为6.4%、6.6%，扰动程度评价均为很大；大直径取土器获得的土样较小直径土样更接近于软土实际性状。

Comparative lab-testing of physical and mechanical properties of soft soil at different sampling diameter

Based on Ningbo rail transit Line 4 geotechnical investigation project, comparative lab-testing was conducted on soft soil taken at two different diameters (D= 75mm, D= 100mm)with the open thin wall samplers commonly used in soft soil areas. Based the test results, the differences of indexes of physical and mechanical properties of soft soil at two sampling diameters and their mechanism were analyzed; the additional volumetric strain method was used to analyze and evaluate the disturbance of soil samples at two different diameters. The results show that the water content and void ratio of the soil sample with the diameter of 75mm reduced to a certain extent with the reduction range of 9% compared with the soil sampler with the diameter of 100mm; the density, compressive modulus and shear strength index increased to a certain extent with the increasing of 2% to 21%; the average volumetric strain of soil samples was 6.4% and 6.6% respectively, and the degree of disturbance was very large; the soil samples which were obtained by the large diameter soil sampler was closer to the actual properties of soft soil than the small diameter soil sampler.