不同取样方法下饱和软土物理力学性状对比试验分析

COMPARATIVE EXPERIMENTAL MECHANICAL PROPERTIES OF SATURATED SOFT SOIL UNDER DIFFERENT SAMPLING METHODS

不同取样方法获得的同一饱和软土的物理力学指标存在一定的差异。以软土地区轨道交通岩土工程勘察项目为依托,采用岩芯管包样、厚壁取土器、敞口薄壁取土器等3种取样方法,对采取的软土土样开展室内对比试验。基于室内试验成果,从物理力学性质角度对比分析了3种取样方法下同一指标之间的规律性及差异性;在对试验成果综合分析的基础上,结合不同取样方法下饱和软土结构组成变化,对指标差异性的内在机理进行相关分析。结果表明:包样和厚壁样的物理性质指标基本一致,抗剪强度指标高于薄壁样2.1%~20.3%;与薄壁样相比,包样和厚壁样的含水量、孔隙比有所降低,降低幅度均为10%左右,密度有小幅度增大,幅度约为3%,抗剪强度指标有所提高,提高幅度6.9%~68.3%;取样方法引发饱和软土固、液组成成分的所占比例的变化是导致其物理力学性质指标产生差异的根本原因。

There are some differences in the physical and mechanical properties of the same saturated soft soil under different sampling methods.Relying on geotechnical engineering survey projects for rail transit in soft soils,three sampling methods were adopted to carry out indoor comparative test on soft soil samples.The methods were the core tube sampler,the thick-wall sampler and the open thin-wall sampler.Based on the laboratory test results,the regularity and difference between the same indicators under the three sampling methods were compared and analyzed from the perspective of physical and mechanical properties.Based on the comprehensive analysis of the test results,combined with the changes of saturated soft soil structure under different sampling methods,the internal mechanism of index difference was analyzed.The results show that the physical properties of the core tube sample and thick-wall samples are basically the same,and the shear strength index is 2.1%~20.3%higher than these of the thin-wall samples.Compared with those of the thin-wall samples,the water content and porosity ratio of the core tube sample and thick-wall samples are reduced by about 10%,density has a small increase,about 3%,and the shear strength index has improved,an increase of 6.9%~68.3%.The change of solid and liquid composition in saturated soft soils caused by sampling method is the root cause of the difference in physical and mechanical properties.