Evolution Law And Mechanism Of Static Earth Pressure And Compression Characteristics Of Unsaturated Silty Clay

Most of the lateral retaining structures are subjected to static earth pressure in normal use,so it is necessary to obtain the value of static earth pressure to guide the design and construction.However,the theory of unsaturated soil pressure is not perfect,and the results obtained by calculating unsaturated soil parameters according to the theory of saturated soil are not accurate.In addition,there are few studies on static soil pressure of unsaturated soil in the process of humidification,and the data is insufficient,and the influence of various factors in the process of humidification is not clear.In addition,there are few studies on the compressive properties of unsaturated silty clay,especially on the collapsibility of unsaturated silty clay.The variation law of the compressive properties of unsaturated silty clay is not consistent with that of unsaturated silty clay.Therefore,it is urgent to study the static earth pressure and compression properties of unsaturated soils,so as to establish corresponding experimental measurement methods and master the static earth pressure and its coefficient in the process of wetting,as well as the evolution law of compression properties.This project intends to take the silty clay in Beijing as the research object,and explore the evolution law of static earth pressure and compression properties of unsaturated silty clay under the action of wetting and drying through laboratory tests.Based on the test data and through in-depth analysis,the results obtained are as follows:（1）The basic soil properties and pore structure of unsaturated silty clay were measured.The basic physical properties of soil are measured.The SWCC curves under different compaction degrees were measured by the combination of filter paper method,pressure plate method and WP4 method.The inversion data of NMR signal intensity of soil under different compaction degrees and water content conditions were measured by using NMR instrument,and the distribution change law of soil pore size was further obtained.（2）K₀ compression test,ordinary compression test and post-compression nuclear magnetic resonance test were carried out in the process of dehumidification.It was found that the K₀of unsaturated silty clay was mainly affected by the early consolidation pressure,saturation and compacting degree,and the internal mechanism was summarized and analyzed.The variation law of compression index with saturation,water content,suction and compaction degree was obtained.The effect of compaction process on the pore structure of soil sample was analyzed by comparing the pore structure before compression.（3）Carry out experimental studies on the influence of different overburden loads and initial saturation on static soil pressure,compression properties and collapsibility properties after wetting and saturation under wetting conditions.The increment calculation model of wetting soil pressure considering overburden load and initial saturation is obtained,and the influence law of overburden load and initial saturation on soil pressure,K₀,collapsibility coefficient,compression index and compression modulus in wetting process is sorted out.（4）By comparing the preliminary consolidation pressure determined by the traditional specification with that determined by the K₀ compression test,it is found that the two results are highly consistent,so a new method to determine the preliminary consolidation pressure by using THE K₀ compression is proposed,which can make up for some shortcomings of the traditional method.