Research On The Calculation Method Of Internal Force And Deformation Of Composite Soil Nailing Wall With Anchor Rod

Anchor composite soil nailing wall is a form of foundation pit support,which is composed of soil nailing,anchor rod and reinforced soil.Through the active application of prestress to anchor rod to reinforce foundation pit soil,the deformation of slope is effectively controlled,which has been widely used in engineering.However,the theoretical research of anchor composite soil nailing wall lags behind its application practice.Based on the needs of practice,this thesis simplifies the stress form of supporting structure from the measured data,assumes the position of sliding surface,and establishes the calculation method of internal force and deformation of anchor composite soil nailing wall based on Mindlin solution and deformation coordination condition.Through the comparison and analysis with the actual measured data in the project,the parameters of the supporting structure are adjusted,and the change law is analyzed,which verifies the feasibility of the calculation method.Further model tests are carried out to simulate the excavation process of composite soil nailing wall.The PLAXIS 3D finite element software is used to model and compare the calculation results.The test and numerical results verify whether some assumptions are reasonable,hoping to provide reference for the design optimization and construction of composite soil nailing wall.The main work and conclusions are as follows.(1)Through the calculation and analysis of the anchor composite soil nailing wall,it can be seen that the maximum increment of the axial force of the supporting rod always appears in the first working condition after the supporting rod is stressed;The axial force on the soil nail is double parabola along the axial direction,the maximum axial force on the soil nail appears in the middle and upper part of the foundation pit along the depth direction,and the axial force of the anchor is slightly less than that of the adjacent soil nail.(2)The horizontal deformation of anchor composite soil nailing wall increases gradually with the excavation of foundation pit,and the deformation of the upper part is larger than that of the lower part.The displacement of foundation pit decreases obviously at the location of anchor.The anchor can directly transfer the axial force to the surface layer,which greatly reduces the axial force of anchor and controls the lateral displacement of foundation pit;At the same time,prestress can share the earth pressure generated by excavation and control the deformation of other positions,so as to ensure the overall safety of foundation pit during excavation.(3)The resistance provided by the surface layer increases with the increase of the excavation depth,and its maximum value appears at the location of the anchor.(4)Through the analysis of numerical simulation,it can be seen that the prestress in the bolt composite supporting structure can share the unbalanced earth pressure on other supporting members and control the deformation of other positions;The horizontal displacement of foundation pit decreases with the increase of anchor prestress.When the prestress exceeds a certain limit,the supporting effect is not significantly improved.The axial force of soil nail and anchor decreases with the increase of prestress.(5)Through the theoretical calculation method,a series of internal force and deformation laws of anchor composite soil nailing wall can be obtained.Through the comparative analysis with the engineering examples,model tests and numerical simulation,it is found that all kinds of change trends are basically consistent,which proves the feasibility of the calculation method and the rationality of the theoretical assumptions in this thesis.The design of the engineering scheme can be optimized according to the method in this thesis.