Numerical Simulation On The Underexcavation Method Of Building Rectification

The building inclination will affect the normal use,and even collapse will occur in severe cases,resulting in a safety accident.Buildings with practical usage could be rectified within the tilting limit to meet the safety and functional requirements.The building rectification method generally involves lowering the higher part,lifting the lower part,or a combin of the two.The underexcavation method,as one of the main lowering the higher part method,has advantages of small construction risk,high economic benefit and easy control of inclination compared with other rectification methods.Therefore,it has been widely used in correcting engineering,but the theoretical research of the excavation method lags behind the actual engineering requirements,especially the plastic zone around the excavation hole and its deformation characteristics.In this paper,the test and simulation of soil settlement in the model box are carried out firstly.The settlement and stress curves of the soil under load are obtained.At the same time,the finite element model is used for the simulation analysis,which is in good agreement with the test results.The simulation analysis of the soil correction method laid the foundation.The finite element numerical simulation was done on the rectification model test,completed by our research group.The plastic zone and around the soil hole were analyzed under the condition of 800 mm,600mm and 400 mm,and compared with experimental results.The soil was simulated by Mohr-Coulomb model in the finite element model and the second orderfully integration element was selected.The lateral support of the soil is horizontally supported,the bottom is fixed end and the upper soil is free boundary.The research results show that the shape of the holes change from circular to elliptical under load,and the stress distribution between the soil pores is U-shaped.The stress decresses rapidly within 200 mm from the hole center,which tends to be gentle outside 200 mm,like an exponential type.The principal compression stress traces appear at the boundary both sides and above of the hole;this is consistent with the phenomenon of experiment that the stress transferred from the top of the hole to the sides of the hole.The principal tension trsce is mainly distributed on the oblique line of the hole.In the process of destruction,the excavation hole first enters the yield stage on both sides of the horizontal hole,then displaces and squeezes the shoulder soil,which causes the upper part of the soil to be transformed from compressive stress to tensile stress,and eventually leads to the soil settlement and.It is consistent with the phenomenon of soil correction test.Comparing the pressure around the pores with the results of the model of the correction model,it is found that the general trend of stress changes is consistent.The numerical calculation results of the earth pressure on the side of the hole are smaller than the test results,and the pressures of the upper and lower soils are basically the same.For the simulation effect of the correction of the three different hole spacings,the plastic zone of 400 mm spacing of holes is best,which can reduce the building rectification period.