上覆荷载作用下末透镜体演变规律试验

Tests on characteristics of final ice lens at different overburden pressures

土体冻胀量由原位冻胀、不连续冰透镜体、末透镜体构成,末透镜体厚度是构成土体冻胀量的决定性因素。选取兰州饱和粉质黏土、黏土进行上覆荷载作用下的冻胀试验,采用可视化、图像二值化处理方法对饱和试样冻结过程中的末透镜体演变规律进行分析。试验结果表明:土体类型相同时,末透镜体厚度随上覆荷载的增大而减小;上覆荷载相同时,粉质黏土末透镜体厚度大于黏土。将末透镜体生长过程视为准静态过程,由固体表面水膜热力学理论推导可知,等效水压力、土体导湿系数是影响末透镜体分凝速率的根本原因。通过数据拟合,得到末透镜体平均分凝速率与上覆荷载之间的定量函数关系。

Frost heave consists of in-situ heave,discontinuous ice lens and final ice lens.Thickness of final ice lens is the key factor influencing on frost heave.In order to study on the characteristics of final ice lens at different overburden pressures,the tests using saturated Lanzhou silty clay and Lanzhou clay were carried out.The evolution of final ice lens was analyzed by using visual equipment and the binarization method of images during the freezing process of saturated samples.The results indicated that the thickness of final ice lens decreased with the increase of overburden pressure for the same soil types,and the thickness of final ice lens in saturated Lanzhou silty clay is larger than that in Lanzhou clay at the same overburden pressure.Equivalent water pressure and hydraulic conductivity are the key factors to the segregation rate of final ice lens when regarding lens growth as a quasi-static process and using the thermodynamic theory for the liquid layer near a substratum.At last,the fitting functions between average segregation rate and overburden pressure are acquired.