Experimental Study Of The Freeze-Thaw Effects On Physical And Mechanical Properties Of Soils

It has become a common understanding that freeze-thaw cycling is a kind of weathering process which considerably changes geotechnical properties of soils due to cryogenic actions, and different temperature conditions may cause various results. Also the effect of freeze-thaw on the same soil of different dry density may be different. Therefore, the influence of temperature and dry density must be taken into account when selecting soil parameters for stability and deformation analysis of many geotechnical engineering problems in cold regions where newly exposed soil layers are bound to be submitted to freeze-thaw cycling. Because of the lack of study on the effect of freezing-thaw on soil mechanics, further study is needed.This paper takes two frost-susceptible soils, Lanzhou loess and Qingzang silty clay as study object. The freeze-thaw characteristics and the variation rules of their mechanical properties after freeze-thaw are studied considering two influencing factors, the freezing gradient and dry density. Experiments show that for Lanzhou loess, the characteristic indexes during freezing-thaw and the physical and mechanic properties change linearly vs. the temperature. With the increase in dry density, there is a critical dry density where the freezing-thaw indexes, the physical and mechanic properties remain constant before and after freezing-thaw. When the soil dry density is larger or smaller than the critical dry value, these parameters change in different ways. This is because the saturation water content is changing with the dry density, thus the effect of ice nucleation on effective stress conditions is different. Experiments also show that the variation rules for the two soils is more or less the same, only with small difference in values– the Qingzang silty clay is a little more sensitive to freeze-thaw cycling than Lanzhou loess.