基坑开挖过程中的土体体积变化试验

Test of Soil Volume Changes During Process of Excavation

为了深入研究基坑开挖过程中周围土体的体积变化情况,采用英国GDS公司生产的STDTTS+UNSAT(7 kN/1700 kPa)型号三轴测试系统针对基坑开挖过程中土体卸荷的应力路径进行试验研究,分析了不同初始有效应力、不同应力路径条件下土体卸荷体积变化规律,得出主动区、被动区土体随轴向应变增加经历相同的过程,但体积变化量存在显著差别;并进一步从土体内部结构的角度探讨了产生这一现象的原因,得出重塑土在制样过程中也产生结构性,在垂直向上呈现的似“环形”结构以及水平向表现为均匀分布,且随各向同性固结压力增加或单向卸荷而逐渐丧失.

In order to thoroughly study volume change rules of soil around deep excavation during the course of excavation, STDTTS＋UNSAT（7 kN/1700 kPa） triaxial test system produced by GDS corporation in UK was adopted to research into the stress paths of soil unloading around deep excavation and to analyze the rules of volume change induced by soil unloading under the conditions of different initial effect stress and stress paths. The result shows that soils in both active and passive areas have the same process with the increase of axial strain, but the change in quantity is obviously different. The reason of such phenomena was further discussed from the inside structure of soil body. It can be concluded that the reconstituted soil during the sample making process still form a new structure, which show a ring-like structure in vertical direction and a uniform distribution in horizontal direction, and gradually disappear with the increase of isotropic consolidated stress or unidirectional unloading.