Study On Construction Disturbance Of Diaphragm Wall Based On In-situ Tests And Numerical Simulation

The grooving construction of diaphragm wall will cause the change of engineering parameters of surrounding soil,and then make the soil disturbed.The study of the influence of grooving construction on various physical and mechanical parameters of soil is of great significance to the actual construction safety guidance and the control of the impact on the surrounding environment.Based on the fund project "evaluation and Engineering Application Research on construction disturbance of soft soil based on multifunctional CPTU in-situ test",and based on the open cut tunnel in the north section of Jiangyin Jingjiang Yangtze River tunnel,through the combination of on-site Rayleigh wave test,high-density electrical test,CPTU pore pressure static contact test and finite element numerical calculation,this paper analyzes the shear modulus,resistivity,cone tip resistance The law of shear strain,soil displacement and the range of disturbance area are studied.The main research contents and results are as follows:(1)Through Rayleigh wave test,the soil shear modulus before and after grooving of diaphragm wall and the disturbance law based on shear modulus are obtained.The results show that the shear modulus of soil decreases after grooving construction,the change of shear modulus of soil near the groove section and shallow part is more obvious,and the shear modulus of soil at the depth of 10-20 m basically does not change;Taking the disturbance degree of 10% as the boundary,the obvious disturbance area is mainly distributed in the shallow 5m;The disturbance degree of soil near the trough section is greater,up to about20%;The degree of disturbance decreases along the depth direction,and the degree of disturbance of soil within 8m in the shallow part is large and changes rapidly.(2)Through high-density electrical test,the soil resistivity before and after grooving of diaphragm wall and the disturbance law based on resistivity are obtained.The results show that the resistivity changes at different locations are different after the trench construction.The resistivity change of shallow 2m soil is more obvious than that of deep soil.The resistivity of soil within 2m near the trench section increases and that of soil in the distance decreases;The obvious disturbance area is located at the depth of less than 4m,and the disturbance degree of soil within 2m away from the trough section is the largest;The disturbance degree increases from small to large along the depth direction,and the soil disturbance degree reaches the maximum value of 40% at the depth of 7m.(3)Through the pore pressure static cone penetration test,the soil cone resistance,pore water pressure and soil disturbance law based on cone resistance before and after the grooving of diaphragm wall are obtained.The results show that the cone tip resistance and pore water pressure of the soil near the groove section change little before and after the groove is formed,and the variation trend with depth is basically the same,but there are great differences in cone tip resistance at some depths;Within the depth range of50 m measured at the hole position 2m near the trough section,most of the soil disturbance degree is 10%-40%,the disturbance degree in the aquiclude area(silty clay layer)is large,up to 40%,and the disturbance degree in a few areas is greater than 100%.(4)Through PLAXIS 3D calculation and analysis,the soil displacement,shear strain and soil disturbance law based on shear strain before and after grooving of diaphragm wall are obtained.The results show that the soil displacement and shear strain caused by the construction of diaphragm wall are mainly in the stage of grooving and excavation,and the soil displacement is basically horizontal displacement;The maximum displacement reaches 13 cm,the maximum shear strain is about 13%,and the shear strain concentration area occurs in the corner of the groove section and the soil at the bottom;The obvious disturbance area is mainly distributed within 5m from the trough section;The peak disturbance degree is located in the area without groove wall reinforcement,especially in the sandy soil layer rich in confined water,up to 28%,and the peak disturbance degree in the groove wall reinforcement area is only about 14%.(5)Through the comparison of field test and numerical simulation,the similarities and differences of soil disturbance law before and after grooving of diaphragm wall are obtained.The results show that different methods show that the disturbed area is distributed within 5m of the diaphragm wall;The numerical simulation results show that the disturbed area is mainly distributed in the reinforced area;The soil detected by high-density electrical test and Rayleigh wave test are located within the reinforcement depth of the tank wall,and the deep soil can not be detected;The area detected by CPTU test is 2m away from the diaphragm wall,and the results are close to the numerical simulation method.