原状黄土遇水及饱和后软化特征研究

A study of soften characteristics of wet and saturated loess

黄土由于特殊的结构性导致其水敏性,以往相关研究多采用室内试验的方法。文章以动三轴弯曲元试验系统对原状黄土和饱和黄土在各级围压下的剪切波速与轴向变形进行了测试,并对兰州市西固区某饱和黄土场地进行了现场钻孔及原位试验。室内及现场试验结果表明,黄土遇水模量软化,饱和黄土更具有触变性。进一步对比饱和粉土与砂土的剪切波速与标贯击数统计关系,发现饱和粉土由于触变性导致标贯击数较小,而剪切波速为小应变无损测试,最终表现为剪切波速相同的饱和粉土与砂土,粉土标贯击数显著小于砂土。

Structural loess is water sensitivity,and previous studies are almost made by laboratory tests. Using cyclic triaxial apparatus along with the bender element system,shear-wave velocity and axial deformation of undisturbed loess and saturated loess were tested under different confining pressures. Furthermore,a borehole and in-situ tests were carried out at a saturated loess site in the Xigu district near Lanzhou. The laboratory and in-situ test results show that loess will soften during wetting,and saturated loess presents thixotropy. By comparing the statistical relationship between the shear-wave velocity and SPT blow count of saturated silts with that of sands,it is found that SPT blow count for saturated silts are small due to thixotropy,and the shear-wave velocity is a small strain and non-destructive test. For the saturated silt and sand with an identical shear-wave velocity,the SPT blow count of the saturated silt is significantly less than that of sand.