Deformation Law And Spatial Effect Analysis Of Deep Foundation Pit With Convex Corner

With the development of deep foundation pit engineering,the depth of the foundation pit is getting deeper and deeper,and the plane size and shape are different.Many deep foundation pit projects will be designed with convex corners or with multiple continuous convex corners due to site constraints or functional requirements,the force and deformation of this type of deep foundation pit are more complicated.At the same time,as a three-dimensional space structure,the length,width and depth of the deep foundation pit will affect the stress and deformation of the foundation pit,and there is a significant spatial effect in the construction process of the deep foundation pit.However,foundation pit engineering is often regarded as a plane strain problem,using the traditional earth pressure calculation formula to analyze it,and directly applying the calculation results of the middle section of the foundation pit wall to the design of the entire foundation pit support system,ignoring the differences in the deformation of different sections of the deep foundation pit,making the design scheme conservative or unsafe.Although researchers have done a lot of research on the spatial effect of foundation pits,most of the research results of the spatial effect are based on the concave corner effect,and there is a lack of theoretical research on the spatial effect of the convex corner.There is still a lot of exploration space in the study of the deformation law of the pit.In this paper,by consulting a large number of specifications and documents,taking the foundation pit of an initial rainwater storage tank in Hefei as the engineering background,combining the actual monitoring data with the three-dimensional simulation results,to analyze the force-deformation characteristics and the convex corner effect of the deep foundation pit with convex corner.Based on the engineering case foundation pit model,the single factor analysis method is used to analyze the influencing factors of the space effect.The main work and research results of the article are as follows:（1）The research status of deep foundation pit deformation and space effect at home and abroad is summarized,and the research content and research significance are expounded in combination with the subject.（2）The basic theory of foundation pit deformation and the traditional earth pressure calculation theory are summarized,and based on the Coulomb active earth pressure formula in the traditional earth pressure theory,the earth pressure calculation formula considering the space effect and the calculation formula of the influence coefficient of the concave corner effect and the convex corners effect are deduced,which can quantitatively analyze the space effect of the foundation pit.（3）Combined with the project,relying on the foundation pit project of a rainwater storage tank in Hefei,the deformation characteristics of the foundation pit during the construction stage were analyzed by arranging the on-site monitoring data,mainly discusses the variation law of the deep horizontal displacement of the enclosure pile and the horizontal displacement of the pile top and the surface settlement with time,and compared with the numerical simulation results,the reliability of the calculation results of the three-dimensional model is verified.（4）The finite element analysis software（MIDAS-GTS）is used to simulate the excavation process of the deep foundation pit with an open angle,and the deformation of the retaining piles and the surrounding surface settlement deformation of the deep foundation pit with an open angle at different section positions are analyzed in detail.The results show that: The lateral displacement and surface settlement of the retaining piles at the convex corner are smaller than the deformation in the middle area of the convex corner,the convex corners are similar to the concave corners,which can restrain the deformation of the soil at the pit corners,and there is a significant spatial effect at the convex corners.On this basis,the deformation law in a certain range near the convex corner is further analyzed,and it is concluded that the influence range of convex corner effect on the lateral displacement of the retaining pile is about 2 times the excavation depth of the foundation pit,and the influence range on the surface settlement is about 1 time the excavation depth of the foundation pit.（5）Based on the engineering case model,using the method of single factor analysis,the factors such as the angle of the convex corner,the length of the convex corner,the depth of the enclosure pile into the rock,and the diameter of the enclosure pile were changed respectively,to discuss the influence of different parameters on the deformation properties of deep foundation pits with convex corner under the spatial effect,and the results provide guidance and suggestions for the design and construction of similar engineering support systems in the later stage.Figure [61] table [7] reference [59]...