Analysis Of Internal Force,Deformation And Spatial Effect Of Pile Anchor Supporting Structure

In the practical foundation pit engineering,the internal force and deformation of the foundation pit support structure are affected by many factors,such as the dimensions in the three directions,the excavation mode of the foundation pit,the form of the support structure,and the parameters of the support structure.In the design process,in order to simplify the calculation,the foundation pit are think as a two-dimensional problem to analysis,this simplification in the Angle of the pit foundation pit have bigger difference,in the actual situation in order to control the project cost at the same time satisfy the current buildings densely populated area to control the deformation,the factors which influencing foundation pit deformation need a more depth research.Therefore,it is necessary to establish a three-dimensional model and study the internal force and deformation law of the supporting structure at the corner of the foundation pit combined with practical engineering.Aiming at the above problems,this paper mainly completed the following work:(1)According to the soil arch effect of pile row support structure,the soil pressure at the pile side is divided into two parts,the earth pressure directly caused by the soil behind the pile and the indirect earth pressure transmitted by the soil arch.The formulas for calculating the vertical average stress and the soil pressure at the pile side are given.(2)The top surface of the foundation pit is simplified into a trapezoid shape during failure,and the distribution of soil pressure within th,e influence range of pit Angle effect under the limit equilibrium state is analyzed.The influence coefficient of,pit Angle effect is given to reflect the influence degree of pit Angle effect.(3)The internal force,deformation and soil settlement of pile-anchor support structure are calculated,and the distribution rules of th,e above three directions are discussed respectively.(4)The 3d models of different excavation sizes,supporting stiffness and different excavation methods were established respectively,and the influence of these factors on the spatial effect was analyzed.(5)Based on the design and monitoring results of the foundation pit project of gloria plaza hotel,the excavation process in the HIJ area of gloria plaza hotel was simulated by FLAC 3D,and the simulation results were compared with the monitoring data.The research results are summarized as follows:(1)The action principle of soil arch effect is analyzed.By simplifying the foundation pit model,the solution formula of vertical average stress and soil pressure at pile side considering soil arch effect is given.(2)Combining with the shape of the sliding crack body and the principle of limit equilibrium when the foundation pit is destroyed,the influence coefficient of the pit Angle effect is obtained,which can be used to express the influence degree of the pit Angle effect.(3)By simulating the foundation pit calculation examples with different excavation sizes,supporting stiffness and different excavation methods,it is found that when the excavation depth of foundation pit is relatively shallow,the above factors have no obvious influence on the pit Angle effect,and the soil pressure distribution pattern of pile body is basically consistent with the gravity retaining wall.When the excavation of the foundation pit reaches the design depth,increasing the width of the foundation pit will weaken the constraint on the direction of the long side of the foundation pit.When the width of the foundation pit increases to 3 times the excavation depth,the influence of the change of the excavation width on the direction of the long side of the foundation pit will no longer change.When sublevel excavation is adopted,the soil mass reserved in the foundation pit can play a supporting role.By setting a reasonable excavation sequence,appropriate soil mass is reserved to effectivel control the deformation of the foundation pit.When the lumbar beam with different stiffness is used for simulation,it is found that the increase of stiffness can increase the influence range of pit Angle effect to a certain extent,but when the stiffness is too large,it will lead to uneven stress of foundation pit support structure.In the design of foundation pit excavation and support,the calculation formula derived in this paper can be referred to.Considering the effect of the pit Angle in the foundation pit Angle area,and setting the excavation sequence reasonably,the support stiffness enables the deformation of the foundation pit to meet the design requirements as well as the requirements of deformation coordination.