Mechanism Analysis Of The Whole Process Of Cement Soil Failure Based On CTS Model

The scale of foundation pit enclosure system is more and more improved with the development of geotechnical engineering in recent years.However,the number of cement mixing pile construction accidents increases gradually due to the rapid development of underground engineering and the poor geological conditions of the soft soil in the coastal areas.The finite element software PLAXIS is widely used in the finite element analysis of geotechnical engineering projects in coastal cities such as Hangzhou,but the constitutive model of cement mixing pile is often used as an approximate substitute for the constitutive model of soft clay,which makes the results of finite element analysis not accurate and their credibility is questioned.In order to more clearly understand the changes in the mechanical behavior of the cement mixing pile from construction to destruction,this article uses cement and kaolin as raw materials,uses indoor geotechnical tests and numerical analysis methods as means,and uses test equipment and finite element software PLAXIS as tools.First,the constitutive model of the cement soil is determined.Secondly,the parameters of constitutive model of soil-cement were calibrated by indoor geotechnical test,and then the nonlinear behavior of soil-cement was analyzed by numerical simulation.Finally,the application analysis of the cement soil construction case is carried out,and the combination of theory and experiment is realized and applied complete process for actual engineering analysis.The main contents of this paper are as follows:The constitutive model of soil-cement was determined.The various constitutive models applicable to soil in the finite element software PLAXIS are introduced in detail,and the differences of the models in reflecting the mechanical behavior of soil are obtained.Combined with the laboratory test results,so CTS model is finally selected for numerical simulation analysis of soil-cement mechanical behavior.Experimental study on constitutive model parameters of soil-cement.Firstly,the compaction test,unconfined compressive strength test,splitting test and semicircle bending test were tested.Secondly,the load-displacement curve and stress-strain curve of cement soil in different age and different cement content were fitted by Origin software.Then combining with empirical formulas,the constitutive model parameters of soil-cement were calculated.Study on nonlinear behavior of soil-cement.Firstly,the finite element model of numerical analysis was constructed by referring to the research results of existing scholars.Secondly,the displacement field,plasticity point distribution and load-displacement curve of cement-soil under compression and tension was analyzed.And the sensitivity of the parameters influencing the mechanical behavior of soil-cement under pressure was analyzed.Analysis of nonlinear failure mechanism of gravity soil-cement retaining wall and study of reinforcement scheme.Based on the collapse accident of a gravity-type cement-soil retaining wall in Hangzhou,the mechanism of the instability of the project is explained by the elastic-plastic and elastic-plastic damage behavior of cement-soil.Based on the experience of foundation pit reinforcement,the finite element method was used to study the effective measures to improve the rigidity of gravity cement-soil retaining structure.