A Field Experimental Study And Numerical Simulations Of The Relationships Among The Spatial Additional Earth Pressures And Deformations Of Retaining Structures For Deep Slender Foundation Pits

It is very important to have a correct understanding of the relationships among the earth pressures and the deformations of retaining structures for the support design of foundation pits.The existent soil pressures are still used to analyze the deformations of soils according to the current design methods of foundation pits,and the interactions among soils and retaining structures are not fully considered.In fact,the deformations of soils around the retaining structures are caused by the additional earth pressures rather than the existent earth pressures.This viewpoint has been preliminarily confirmed by excavation experiments conducted at Tianjin University.In order to verify the viewpoint further,a field model experiment of slenderer typed foundation pits in cohesive soils and a series of finite element numerical simulations were carried out.At the same time,the variation and relationships among the existent earth pressures,the additional earth pressure and the deformations of retaining structures were analyzed.The important works carried out in this paper are as follows:1.The existing research results about earth pressures and deformations of retaining structures were reviewed,at the same time,the calculation methods of the earth pressures and the main problems or shortcomings in the study of the relationships among the earth pressures and the deformations of retaining structures were summarized,and some improvements were put forward.2.Model experiments of deep slenderer typed foundation pits in field cohesive soils were carried out.The earth pressure,the deformations,the bending moment of retaining structures and their distribution during the excavation and surcharge loading were studied.The relationship between the measured earth pressure and the deformation of the retaining structure was analyzed.3.The corresponding three-dimensional finite element models about the deep slenderer typed foundation pits in field were established by using ABAQUS,and the numerical simulations of the earth pressures and deformations of the retaining structures were carried out when the foundation pits were excavated and the surcharge load was applied.4.The relationships among the additional earth pressures and the deformations of retaining structures during the excavation of deep slenderer typed foundation pits were further analyzed by comparing the results of the field model experiments and the numerical simulations.The main conclusions were obtained as follows through the above research of deep slenderer typed foundation pits: 1)The spatial existent earth pressures show nonlinear distribution characteristics,and the existent soil pressures are negatively related to the deformations of the retaining structures.2)The additional soil pressures are closely related to the deformations of the soils on both the frontal and back sides of the retaining structures,and the deformations among soils and the retaining structures are consistent.3)The surcharge load exerts great influence on the spatial earth pressures and the deformations of retaining structures.