Study On Parameters And Deformation Prediction Of HSS Model Of Lacustrine Sedimentary Soft Soil

With the accelerated development of urban underground space,various engineering safety accidents continue to occur,especially in areas where soft soil is widely distributed.Once an accident occurs,it will cause huge economic and property losses.Therefore,the study of foundation pit deformation becomes very important.Commonly used deformation prediction methods are mainly system analysis and numerical analysis.Therefore,the finite element software and extension cloud theory are used to analyze the deformation of the foundation pit.The Dianchi Lake Basin in Kunming is distributed with deep and very wide lacustrine sedimentary soft soil,which is mainly composed of peaty soil,silty clay,clay and silty layer.The constitutive model and its parameter selection have a great influence on the results of the finite element calculation.For the soft soil deposited in the lake facies,six common constitutive models are analyzed in this paper,and it is found that the small strain model(HSS)of hardened soil can fully consider the soil stress The influence of the path and the high nonlinearity of the soil modulus in the case of small strains have good applicability when simulating the excavation of foundation pits.Therefore,the HSS model is used to calculate the deformation of the foundation pit in Kunming soft soil site during numerical analysis.But for the regional soft soil layer with such characteristics in Kunming,especially the peat soil layer,there is almost no research on the parameters of the HSS model.In this paper,the undisturbed soil layer was taken indoors for triaxial test,compression test and some physical and mechanical index tests,as well as analysis of a large number of engineering geological survey reports collected,and the parameter value method of the HSS model was given,and two engineering examples were adopted.The rationality of parameter values is verified.The above research can provide reference for the design and construction of foundation pits in similar soft soil areas.In addition,it has important reference value for the investigation and selection of geotechnical engineering parameters.The main research contents of this article are as follows:(1)Comparing and analyzing various constitutive models,it is found that the small strain model of hardened soil(HSS model)can not only consider the plastic deformation and compression hardening of the soil,but also distinguish the characteristics of loading,unloading and stiffness with stress,so The HSS model was selected as the first choice model for analyzing the deformation of the soft soil foundation pits in the Dianchi Lake facies.(2)A variety of tests were carried out on undisturbed soil samples of typical soft clay peaty soil,silt and clay deposited in Dianchi Lake facies,combined with a large number of geological survey data analysis,HSS suitable for soft soil belonging to this area was given Model parameter value method.(3)Comprehensively analyze the deformation characteristics and laws of excavation,excavation,support,monitoring and other data of the foundation pits of multiple Kunming peat soil subway stations.And establish a model to calculate the numerical model,and take the horizontal displacement of the retaining wall,surface settlement,and settlement of surrounding houses as the research objects,compare and analyze the calculation results and monitoring results,analyze the rationality of the calculation results and verify the parameters of the HSS model Rationality.(4)Analyze the deformation characteristics of the peat soil site,select the 7 indicators that have the most significant impact,establish a settlement risk assessment index system,use the extension cloud model to evaluate the settlement risk of the peat soil site,and pass examples Verify the rationality and feasibility of the analysis method,and guide the construction,solve engineering problems,and eliminate potential risks.