Study On Macroscopic And Microscopic Deformation And Settlement Mechanism Of Silt Lightweight Soil Under Cyclic Loading

In recent years,the siltation phenomenon of the irrigation system and medium to small rivers in many important river basin passage areas in China have been more serious.If the collected dredged silt is piled or discarded randomly,it will not only occupy a large amount of cultivated land,but also cause many environmental problems,such as pollutant diffusion,river pollution and air pollution.So,it is urgent to adopt safe and environmentally friendly treatment measures to solve these problems.The silt lightweight treatment technology can treat the silt as a “resource”.The silt lightweight soil is a kind of synthetic filler prepared by adding expanded polystyrene sheet(EPS)and curing agent.As a new type of environmentally-friendly soil,it has the advantages of light weight,high strength,fluidity before solidification,easy construction and self-reliance after solidification.It can not only realize "turning waste into treasure" of silt,but also effectively solve the problems of environmental pollution caused by silt stacking.The research contents and results of this paper are as follows:(1)In this paper,the fitted cosine waveform load is selected as the cyclic load type.Through the indoor consolidation test and the triaxial test,the effects of different cement content,confining pressure,EPS content and EPS particle size on the macrostructure and microstructure deformation characteristics and shear strength of silt lightweight soil under certain cycle periods are revealed.It is found that the effect of EPS particle content and particle size on the meso-deformation of silt lightweight soil is the most significant under different cycles.When the EPS content difference is 2.0%,the volume deformation of silt lightweight soil differs by a maximum of 4.1%.With the increase of EPS particle size,the proportion of total volume variable of EPS particle decreases gradually,and the maximum proportion of EPS particle deformation is about75%.(2)Based on the parameters obtained from the tests,the numerical simulation of the meso-multiphase deformation mechanism and the dynamic evolution law of stress and strain of the silt lightweight soil internal EPS particles under cyclic loading were carried out by the finite element software ABAQUS,and the results are compared with those of indoor tests.The study further shows that with the increase of cyclic period,the deformation of EPS particles is dominant in the whole deformation process,accounting for 55%~75% on average,while the volume deformation of consolidated soil accounts for a small part.(3)In view of the complexity of the composition of silt lightweight soil,according to some assumptions of Terzaghi's one-dimensional consolidation theory,a silt lightweight soil one-dimensional consolidation theory model is established.And the relevant mathematical model,consolidation equation and the non-linear function coefficient ? about different EPS particles content between volume deformation and drainage were derived.Then,according to the initial boundary conditions of the model,the one-dimensional consolidation analytical solution and settlement expression of the silt lightweight soil foundation under cosine load are obtained by Fourier series method,variable separation method and Maple mathematical programming software.(4)The three-dimensional silt lightweight soil roadbed model was established by using ABAQUS software.The dynamic deformation of each layer structure under vehicle load and its post-construction settlement characteristics were systematically analyzed.And the dynamic deformation law and distribution characteristics of the silt lightweight soil roadbed under dynamic loads are revealed.By comparing the theoretical calculation results and numerical simulation results,it is found that the results obtained by the two methods are almost the same in the initial stage of loading.With the increasing of loading time,the results of numerical simulation are slightly smaller than those of theoretical calculation,but these deviations are within the allowable range of errors.