Study On Properties Of Frost Heave And Thawing Settlement Of Cement-improved Silty Clay

Cement soil reinforcement method and artificial ground freezing method are the two most commonly used construction methods in geotechnical engineering,but both have their own shortcomings.The former is always going wrong in control of the groundwater seepage,Frost heaving and thawing settlement caused by the latter easily has an effect on the surrounding environment.With more and more complicate geological conditions confronted in the practical engineering,researchers are planning to combine the two methods,that is,reinforcing the ground with grouting first and then freezing them.Considering few research on frost heave and thawing settlement of cement-improved soils has been carried out by far,topic of this thesis,a series of studies on the frost heave and thawing settlement characteristics of cement-improved silty clay were carried out by means of the combination of laboratory test and numerical simulation.First of all,to investigate water content,permeability coefficient,freezing temperature and thermal conductivity of the cement-improved soil through the routine soil test and thermal physical parameters test,then summarize the rules of the parameters in different cement content and curing time,and for the subsequent frost heave and thawing settlement test and numerical simulation provides the necessary reference.Then,the single factor test and orthogonal test of the frost heave and thawing settlement of cement-improved soil which are conducted by self designed and processed indoor frost heave and thawing settlement test device,the influence of four factors such as cement content,curing age,cold junction temperature and water content on frozen-heave factor and thawing settlement coefficient,and the primary and secondary relationship as well as significant degree of each influence factor are obtained.At the same time,the law of the temperature field,displacement field and the distribution of water redistribution in the test process are obtained through the measurement of the temperature,displacement and the water content in different parts of the soil sample after the freezing test.Finally,based on the basic equations of frozen soil phase change temperature field and moisture field,a water and heat coupled model for saturated freezing soil is established.The modle is solved by the unidirectional freezing two-dimensional numerical modle which is established by the coefficient type partial differential equation interface in the COMSOL Multiphyscis mathematical module.The feasibility and effectiveness of this model is verified by comparing with the indoor frost heave test data.