Mechanical Response Of Typical Soil Under Impact Load Experimental Research And Theoretical Analysis Of Finite Feature Ratio

The mechanical response of soil under dynamic load is very different from that under static load,and the mechanical response characteristics are the important basis for foundation design.The in-situ soil testing technology has been highly valued by the geotechnical engineering community.For many problems existing in the traditional in-situ test,such as the Evd test technology,the impact load is small(the detection depth is small),the detection index is single,the actual detectable soil is limited,and the impact load duration is strictly limited.In this paper,a newly developed high-energy self-controlled impact load tester(TDE-300)was used to perform dynamic tests and theoretical analysis of finite characteristic ratios of two typical soils.In this paper,the research status of plate loading test and constitutive relationship between soils at home and abroad is first reviewed.Using high-energy self-controlled impact load tester(TDE-300),a new impact load test is performed on two typical soils.High-frequency impact load and displacement measurement system records the change of load and soil displacement at the instant of impact in the whole process.Combining with test data,it analyzes and discusses the mechanical response and deformation characteristics of the soil.Combined with the finite feature ratio theory,the deformation characteristics of the soil are performed.Research;then the test results,the results of the finite feature ratio model and the finite element simulation results were compared and analyzed.Finally,the new impact load test and the Evd test were compared.The main contents and research results of this paper are as follows:(1)New impact load test studyBy analyzing the response characteristics of the load and displacement of two different soils under high energy impact,the corresponding deformation moduli are determined at different stages of deformation,namely the initial dynamic deformation modulus Eid,i,and the dynamic deformation modulus of the linear segment Eid.The average dynamic deformation modulus Eid,m;According to the characteristics of the soil response and the test results,the vertical stress-strain curves of the two soils were obtained.(2)Study on the mechanical response characteristics of two typical soilsAccording to the new dynamic plate loading test and the dynamic response characteristics of soil,the relationship between the dynamic deformation modulus of soil and the strain rate of soil,the introduction of parameter ? establishes the empirical relationship between soil strain rate and dynamic deformation modulus;According to the empirical formula of dynamic deformation modulus,the formula for calculating the dynamic deformation modulus is obtained.The test results show that the geotechnical materials are typical sensitive materials,and the greater the strain rate of the soil,the greater the deformation modulus of the soil.(3)Theoretical analysis of finite characteristic ratios of two typical soilsBased on the theory of finite feature ratios,combined with test results,a curve-fitting and inverse analysis method was used to establish a finite relationship evolution equation for soils.Two kinds of soils were analyzed by finite element method.The results of finite feature ratios,finite element simulation results and experimental results were compared.The experimental results show that the results of the finite-feature ratio theoretical model,the finite element analysis results and the test results are in good agreement,and the finite-feature ratio model is the closest to the test results,which shows that the model is suitable for the deformation of clay and sand.The analysis and description of the features are ideal;but the deformation response is different,which is caused by the differences in the internal and external feature ratios of the media,and also shows the differences in the theoretical model.(4)Comparative analysis of new impact load test and Evd testThe relationship between the dynamic deformation modulus and the dynamic modulus of elasticity Eid of the new impact load test is much higher than that of the Evd Evd test,ie under the same experimental conditions: Eid/Evd?8.The establishment of this relationship provides a certain reference for the unified relationship between the parameters of the dynamic plate load test in the future.Comparison tests show that the impact depth of the new impact load test(TDE-300)is significantly greater than the depth of influence of the Evd test.The impact depth of the newimpact load test is 120 cm to 130 cm,while the depth of influence of the Evd test is 40 cm to50cm.