Research On The Spatial Effect Of L-shaped Corner Area Of Special-shaped Foundation Pi

In recent years,with China’s economic boom,the rapid growth of urban construction scale and the increasing tension of urban land resources,the development and utilization of underground space engineering has become one of the main directions of development.A large number of engineering practices and theories show that in the excavation process of shaped pits,the plan shape,geometry,excavation depth and excavation steps of the pit will cause the nature of the pit to change,and the corner effect will occur in the shaped variation area or corner area of the shaped pit,and the force of the support structure and the deformation of the surrounding strata caused by the excavation disturbance in such areas are greatly different from the regular area of the pit.Most of the different shaped pits have relative corner areas,and the relevant research and literature on them at home and abroad are relatively shallow,so it is necessary to study the corner areas of shaped pits.This thesis takes the spatial effect of L-shaped corner area of shaped foundation pit as the research target,and mainly studies the influence on the support system and ground disturbance under the interaction of negative and positive corners in the corner area of shaped foundation pit,and conducts relevant theoretical research on the change law of ground stress in the L-shaped corner area,and carries out indoor model tests of excavation in the corner area under the internal support system to analyse the deformation characteristics of soil and support structure.Taking specific engineering examples as the research background,the finite element software PLAXIS 3D is used to establish the L-shaped corner area model of the shaped foundation pit with internal support system,to summarise the deformation law of the support structure in the L-shaped corner area with different pit width to depth ratios under the action of the negative-positive corner,and to analyse the influence of the corner effect on the ground disturbance near the L-shaped corner area,the main research results and contents are as follows:(1)Simulate the excavation of the pit by applying horizontal virtual stresses,and use MINDLIN to solve the relevant calculation formulae in combination with the iso-substituted load method to solve the additional stresses and displacements in each direction near the L-shaped corner area of the shaped pit affected by horizontal unloading,and analyse the spatial distribution law of the ground disturbance in the corner area affected by the corner effect;(2)Through the indoor model test of excavation in the L-shaped area of the foundation pit,the study focuses on the horizontal displacement and internal force change law of the enclosure structure on the single positive corner side,and further analyzes the spatial distribution characteristics of the deformation and internal force of the enclosure structure in the L-shaped corner area of the internal support system under the interaction of the negative and positive corners by combining the actual measurement data of the engineering cases;(3)The three-dimensional simulation model of L-shaped corner pit with different depth to width ratios is established to simulate the excavation process of the pit.By comparing and analysing the horizontal deformation of the enclosure structure and the supporting axial force during the excavation of the L-shaped corner area of the pit with different depth to width ratios,the development and evolution law of the deformation characteristics of the enclosure structure under different excavation width conditions of the pit is studied to reveal the influence of the corner effect on the force deformation of the enclosure structure of the pit,and The study will reveal the influence of corner effect on the force deformation of foundation pit enclosure structure and verify it through corresponding engineering examples;(4)By establishing an L-shaped corner pit model,the excavation process of the pit is simulated,the vertical and horizontal stress trends of the soil at the bottom and side of the pit are compared and analysed during the excavation of the L-shaped corner area of the pit under different working conditions,and the spatial distribution pattern of the soil arch area and disturbance area of the ground is studied during the excavation process to reveal the influence of the corner effect on the ground disturbance caused by the excavation of the pit.