| Summarizing up other people's previous experimental research of seasonal frozen soil and coarse-grained soil,considering the particularity of freezing thawing condition of frozen soil and the problems existed in the laboratory test of coarse grained soil,this paper proposes the improvement to the design of the test equipment,and a indoor test method and a set of special laboratory test equipment for the coarse-grained seasonal frozen soil.In order to test the strength,frost heaving pressure,the index of attenuation of freezing and melt cycles under different freezing degree and water content,seepage property taking account of freeze-thaw,coarse granular seasonal frozen soil in Xinduqiao along Sichuan-Tibet railway were selected as a representative of this kind of soil.So a complete set of test regulation was established.It was based on the description of the operation steps and precautions during experiment.The main conclusion are following:The dry density of the seasonal coarse particles in the dry or saturated water state is larger,showing the bimodal curve;The maximum dry density increase first then being stable with slight decrease,reaching the maximum value while maximum particle size ranged from 30mm?40mm.It is necessary to study hydro physical properties of coarse grained soil by using the equivalent substitution method.The experiment indicate that water holding capacity and permeability of this kind of soil are stable after significantly decreasing with the times of freeze-thaw cycle 13 and 2-3 respectively.Comparing the compressibility of soil under different working conditions,the saturated one is the lowest.The frost heave force increase with particle size and freeze-thaw cycle number.And it is being stable after 13 times.The frost heaving rate is under the control of moisture content and the higher the moisture is,the larger the rate is.It reach maximum at the saturation condition. |
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