Research On Influence Of Circular Diaphragm Wall Joints On Mechanical Performance Of Wall

With the rapid development of engineering construction,foundation pit engineering has gradually become a hot topic in the field of geotechnical research.The increase in the depth of foundation pits and the complexity of construction conditions urgently requires more stable support forms.Because of the significant arching effect of the circular ground wall,the structure is mainly compressed in the circumferential direction,and has excellent stability under good enclosure and impermeability.It is widely used in foundation pit support of various large-scale projects;but The circular ground connecting wall is a cylinder-like body formed by pouring in divided groove sections.The rigidity of the joint between the groove sections is different from that of the wall,which causes the circular ground connecting wall to reduce the circumferential rigidity,and then exerts the "arch effect".Causes the impact and changes in the mechanical properties of the structure;in addition,the number of joints will also affect the size of its hoop stiffness,and it is necessary to study this.Using structural symmetry,indoor model tests are carried out on the semicircular ground connecting walls of various joints.By analyzing the hoop direction of the wall and the joints,the stiffness reduction factor at the joints is established,and then the test model is established with MidasGTSNX software.The three-dimensional numerical model is calculated and analyzed,and the reliability of the numerical calculation model is verified through the comparative analysis of the calculation results and the test results.The main research contents of this paper are as follows:(1)Pouring semicircular ground wall models with different joint forms and different joint numbers,and measure the circumferential and vertical strains at the wall and the joints under the condition of graded loading.Based on the equal axial force of the wall under the uniform load,the circumferential stiffness ratio between the joint and the wall is calculated,and the circumferential stiffness at the joint is obtained indirectly,and then different joint forms and different numbers of stress values are compared.The hoop stress,vertical stress and radial displacement of the wall under the influence of the joint change with the magnitude of the load.(2)Midas GTSNX is used to establish a numerical model for calculation according to the boundary conditions and loading size of the indoor test and the wall parameters.The stiffness of the joint unit is reduced according to the ratio of the stiffness of the joint to the wall body obtained from the experiment.Obtain the variation law of wall stress and displacement with depth of different forms and different numbers of joints.Comparing the results of the test and the numerical calculation,the two are quite consistent,indicating that the method of reducing the stiffness of the joint element according to the stiffness of the wall is feasible.(3)Through the comparative analysis of the numerical calculation results,the influence law of the different joint forms and the number of joints on the mechanical performance of the circular ground connecting wall is obtained,and the test results are supplemented.The form and number of joints affect the rigidity of the circular ground wall to varying degrees.The research in this article provides a reference for the design of joints and ground connecting walls.