Study On Earth Pressure At-rest Characteristics Of EPS Particles Light Weight Soil

EPS particles light weight soil is a kind of light geotechnical material,which is composed of expanded polystyrene?EPS?particles,cement,water and remolded soil.As a result of light weight soil has plenty of advantages,such as light weight,high strength,self-reliance,easy construction,buffering,adjustable strength and deformation modulus.At the same time,the light weight soil can be cleared up a large number of polymer compounds?such as discarded foam and waste tires?,treated the uneven settlement of soft soil foundation,expanded old road expansion,filled the wall back,landfilled the pipeline,constructed artificial floating landscape and other engineering fields.So the light weight soil is widely used in foundation engineering,subgrade engineering,slope engineering,pipeline engineering and landscape engineering.At present,many scholars have made a lot of achievements in the study of the basic physical properties,static and dynamic strength characteristics,static and dynamic deformation characteristics.However,there are still some work need to be done in the study of compaction characteristics and earth pressure characteristics of light weight soil.In this paper,the loess in Yangling area of Shaanxi province is used as the remolded soil,cement as the curing agent,EPS particles as light weight materials,to prepare EPS particles light weight soil.Through compaction test,indoor at-rest earth pressure coefficient test and outdoor retaining wall model test.The at-rest earth pressure,the coefficient of at-rest earth pressure and the settlement deformation characteristics of light weight soil are studied under the optimum water content.The conclusions are:?1?For three kinds of light weight soil with different EPS particles contents,four kinds of compaction tests are carried out:standard light-type,standard heavy-type,small light-type and small heavy-type,and the volume compression ratios of EPS particles are measured after four kinds of compaction tests.The results show that the dry density and the wet density of light weight soil increases at first and then decreases with the increasing of water content for the three mixed ratios light weight soil under four kinds of compaction tests,and their curve shapes are similar to parabola,and the optimal water content was basically the same.Under the influence of“size effect”of compaction cylinder,the maximum dry density is different,but the difference is small.Compaction type has little influence on the optimum water content and maximum dry density of light weight soil.Under compaction action,the EPS particles volume compression ratio decreases with the increasing of the water content and the EPS particle content,and the volume compression ratio variation range of EPS particles is 0.955%?31.174%.It is feasible to determine the optimum water content and the maximum dry density of light weight soil by using small-type compaction test instead of standard compaction test.?2?The lateral compression test is carry out by using the K₀consolidation instrument for different proportion of lightweight soil.Compared with remolded soil,due to the solidification effect of cement and the weight reduction effect of EPS particles in light weight soil,the light weight soil have self-supporting property and lightweight property,and its lateral stress and K₀can be greatly reduced.The measured coefficient of at-rest earth pressure of each ratios of light weight soil is between 0.14?0.31,only 1/3?1/2 of the theoretical calculation value of Jaky formula,and the measured coefficient of at-rest earth pressure of remolded soil is 3/4 of the theoretical calculation value.The coefficient of at-rest earth pressure of light weight soil is not constant,but closely related to loading and unloading path,vertical stress,EPS particles volume ratio and cement ratio.When the EPS particles volume ratio and the cement ratio are constant,the coefficient of at-rest earth pressure of light weight soil increases with the increasing of vertical stress and finally tends to stable value.In the unloading process,the coefficient of at-rest earth pressure first increases slowly and then increases rapidly with the decreasing of vertical stress.When the volume of EPS particles is large,the coefficient of at-rest earth pressure is greater than 1.When the vertical stress is the same,the lateral stress and the coefficient of at-rest earth pressure increase with the increasing of EPS particle volume ratio and the decreasing of cement ratio.At the end of unloading process,the residual lateral stress of light weight soil increases with the increasing of EPS particles volume ratio and the decreasing of cement ratio.?3?In order to study the earth pressure at rest characteristic and deformation characteristic of remolded soil and light weight soil with two different EPS particles contents?0.32%,0.81%?,the outdoor model test of retaining wall is carried out.The results show that the vertical earth pressure and lateral earth pressure of remolded soil and light weight soil increase linearly with the increasing of filling depth before loading and unloading,and the difference between the measured value and the corresponding theoretical calculation value is small.After curing,the light weight soil have self-supporting property,and the influence depth of load on light weight soil is limited.In this test,the load influence area depth of light weight soil is about 75cm.In the process of loading and unloading,when the depth of filler is less than 75cm,the vertical and lateral earth pressures of light weight soil increase or decrease obviously with the increasing or decreasing of load.When the depth of fill is greater than 75cm,the increase or decrease of vertical and lateral earth pressure of light weight soil are small.The measured values of the coefficient of earth pressure at rest of remolded soil and two kinds of light weight soil are non-linear distribution behind the retaining wall,which are in the range of 0.27?0.74,0.34?0.45 and0.29?0.42 respectively.There is a big deviation between the measured values and the theoretical values of the coefficient of earth pressure at rest.The coefficient of earth pressure at rest for light weight soil decreases with the increasing of EPS particles contents.The vertical settlement deformation of remolded soil decreases with the increasing of filling depth,which is generally between 0?21.5mm.The vertical settlement of two kinds of light weight soil formed by curing has no obvious change under load,generally between0?2.8mm and 0?3.9mm respectively.Compared with remolded soil,due to the solidification effect of cement and the weight reduction effect of EPS particles,the light weight soil have self-supporting property and lightweight property,and its earth pressure at rest and the coefficient of earth pressure at rest can be greatly reduced,which can meet the requirement of weight loss and enhancement in retaining wall engineering.