杭州软土的基本力学特性

Engineering properties of Hangzhou clay

杭州软土体具有含水量高、强度低、压缩性高、渗透系数低、变形稳定历时较长等特点。为系统的研究杭州软土的物理、力学特性,以杭州紫金港隧道某段附近从地表到20 m埋深范围内的土层为研究对象,选用一维固结试验和三轴排水、不排水剪切试验系统研究了杭州软土的压缩特性和三轴剪切特性。试验结果表明,该区域软土天然含水量高,随着埋深的增加,含水量和孔隙比呈现逐渐减小的趋势;随着深度的增加,4~10 m范围内的土体压缩指数变化不大;而在12~16 m深度处,土体有轻微的结构性,因而压缩指数相对大一些。16~20 m的土体,由于土体的先期固结压力比较大,土体比较密实,压缩指数较小;杭州黏土的M值主要分布在1.0~1.5之间。其中17m土体的M值最小,其平均值在1.0左右;8 m、14 m和19 m土体的M值较大,略小于1.5。

Hangzhou clay behaves the properties of high water content, low strength, high compressibility, low permeability and long duration of stability of deformation. To study systematically the physical and mechanical characteristics of Hangzhou clay, laboratory investigations were carried out on the clays from ground to the depth of 20m around the Zijingang tunnel. The tests contain 1D oedometer tests, triaxial drained tests and triaxial undrained shear tests. The results show that ： The water content is very high for the clays, and the water content and void ratio are decreasing along with the depth of the clays. Along with the depth, the compression index for the clays between 4 -10 m is almost constant; however, due to the exists of soil structure for the clays at 12 ~ 16m, the compression index is larger. For the clays at 16 -20 m, due to the higher preconsolidation pressure, the density is denser and correspondingly, the compression index is smaller. The value of M is in the range of 1.0 - 15. For the clay at 17 m,its M is smallest,the value is about 1.0; the values of M for the clays at 8 m,14 m and 19m are larger,and the average M is slightly lower than 1.5.