Experimental Research On Segregated Ice In Frozen Soil

Study on the phenomenon of segregated ice is the key to understand all kinds of complex phenomenon in frozen soil.Segregated ice is the result of water transfer in soil freezing process,which is the intrinsic embodiment of frost heave,and the amount of frost heave is determined by the amount of segregated ice.In order to study the formation rules of the segregated ice during freezing process,in this paper,a one dimensional one dimensional freezing test under different boundary conditions was carried out in the laboratory.Based on the analysis of the temperature field,displacement field and the distribution of water content measured at the end of the experiment,obtaining the formation rules of the segregated ice.The main research contents include:(1)Study on the one-dimensional continuous freezing test of the samples under the moisture field,temperature field and stress field three coupling action,according to the data collected by the temperature sensor and displacement sensor during the experiment and the measured data of the last lens after the experiment,obtaining the time and thickness of the final lens formation,analyzing the forming process of the final lens and the real image,the formation rules of the segregated ice under three field coupling is obtained.(2)In order to research the effect of the formation rules of the segregated ice under the overlying load and the linear cooling mode,three initial temperature of cold ends and three overlying load is selected for the orthogonal test.The change laws of the temperature field in the test specimen,the advance of the frozen front with time,the change rules of the frost heave and the moisture migration are analyzed and compared,which can obtain the formation laws of segregated ice under the condition of linear cooling.(3)Compared the internal temperature field,displacement field and the redistribution of water field under the constant temperature freezing mode,linear cooling mode and intermittent cooling mode.The thickness of the segregated ice and the real picture of the segregated ice were analyzed under three freezing modes,which obtain the formation law of segregation ice under different freezing modes.This study shows that in the continuous freezing mode,the evolution process of the segregated ice is divided into three stages.In the first stage due to the freezing front advancing too fast,the freezing of pore water in situ,not forming of the segregated ice.In the second stage,the freezing front moves down slowly,producing micro segregated ice uncontinuously.In the third stage,because the freezing front down development stably,water supply have enough time to transfer to the freezing front rear,forming segregated ice in the negative temperature effect,called the final lens.The formation rules of the final lens is that: when the water content is the same,the thicker of the final lens is and the earlier of the formation time with the smaller overlying load,the larger the temperature gradient.The segregated ice produced under the freezing conditions of the three modes is stratified and the segregation of ice from the top to bottom is getting thicker and thicker,and more amount of segregated ice is near the frozen front.In the comparative sample with the overburden load,the larger of the overburden load,the smaller of the amount of segregated ice and the amount of frost heave,and the larger of the length from the bottom layer to the bottom of the sample.This is due to the increase in the overburden load makes the growth and development of the segregated ice is more difficult,needing to overcome the internal earth pressure and overlying load,resulting in reduced amount of the segregated ice.The distribution of water content under the temperature distribution pattern,the linear cooling mode and the intermittent cooling mode were analyzed.From the top to the bottom of the sample,the moisture content increases first and then decreases,and the maximum moisture content appears at the position where the final lens body appears after the frozen front stabled.Through the analysis of the internal temperature change curve,the curve of the frozen front curve,the frost heave volume curve,the water content change curve and the thickness of the final lens body of the sample after the completion of the three freezing modes,which can obtain that thickness and frost heave are the smallest,the deepest frozen depth,water content distribution range is also the smallest,so intermittent cooling method is the most effective freezing pattern to control of the thickness of segregated ice and frost heave.