Research On The Failure Mechanism Of Earth-cut Hole Based On Limit State Analysis

The complexity of the building foundation、long history、the errors of design and survey and so on can cause buildings to tilt.Inclined buildings would affect the function of the building,and even affect the stability and safety of the structure,so it is necessary to carry out the reinforcement and rectification treatment to avoid failure and collapse.At present,The under-excavation technique is widely used in the practical engineering of building rectifying.Through the observation of the settlement curve in the rectifying engineering,it can be found that the settlement value of soil will produce the limit state point under the action of the upper load,after which the settlement value increases rapidly.The limit state is mainly related to the properties of the soil 、 the cut hole spacing and the upper load.In identical soil conditions and the upper structure,the cut hole spacing is the main determinant of the limit state,and also determines the effect of the rapid tilting of the building.Firstly,In this paper,finite element displacement loading simulation and theoretical formula are combined to solve the ultimate strain and failure load of soil failure.Then the finite element limit state analysis method was applied to the numerical simulation of the under-excavation rectification experiment,and the vertical stress cloud map,vertical displacement cloud map and failure surface form of the excavation under different hole spacing of 800 mm,600mm and 400 mm in the experiment were obtained.and they agree well.In order to analyze the influence of different factors on the soil,the factor analysis of the limit state analysis method is carried out,and it is found that the internal friction Angle of the soil’s cohesion increases with the increase of the limit strain value,and the relationship is linear.The elastic modulus of soil decreases with the increase of the limit strain value and shows a quadratic function relation.Using the finite element software ABAQUS to rectify leaning building soil hole is analyzed under different load hole spacing,get under different working conditions on the surface of the damage evolution process,and obtain silt and clay under different load,the relationship leaning back limit state and the rule of hole spacing.The method is very useful in selecting the optimal hole spacing in practical engineering,so as to shorten the controlling engineering of the time limit for a project.Finally,according to the method of obtaining failure surfaces of limit strain,thenumerical simulation analysis of different hole spacing in the under-excavation rectification residential building is carried out,and the position,shape and evolution process of the soil failure plane around the excavation hole under different hole spacing are obtained.The range of hole spacing obtained is basically consistent with the actual hole spacing,which provides theoretical guidance for the actual rectification project.