Nonlinear Damage Analysis Of Masonry Structure With Soil-Coment Pile Caused By Shield Tunneling

It is inevitably that shield tunnel will affect the existing superstructure,and the existance of artificial foundations can reduce this impact.Therefor,it is more and more important to study the damage risk of superstructure with artificial foundation under different construction condition.In this paper,taking the settlement and damage of a masonry structure caused by tunneling in a section of Zhengzhou Metro Line 5 as an example,and based on the field test,the finite element method(FEM)and theorectical method,the nonlinear damage of masonry structure in the process of tunneling is studied.The main contents and results are as follows:(1)The reinforcement effect of soil-cement pile on surrounding soil and the influence of shield construction on existing masonry structure are analyzed by monitoring data of field test.The results indicate that the reinforcement effect of the soil-cement pile on the surrounding soil decreases with the distance from the soil-cement pile.The existing cracks in the extising masonry structure will gradually expand with the shield construction and become the main impact factor of safety,and most of them are concentrated on the side that first intersects with the tunnel.(2)The masonry structure model used in this paper is verified by relevant experiments,considering the change of ground loss rate caused by the reinforcement of cement-soil piles,and a three-dimensional finite element model of tunnel-soil-masonry structure is established to analyze the nonlinear damage of buildings.The results show that the settlement and crack location of buildings can be simulated well by using this model.The wall cracks mainly occurred on the side that first intersected with the tunnel,and the cracks gradually spread from the bottom of this side to the upper part and other facades of the building with tunneling.(3)The influence of angle between shield tunnel and building is studied by Limiting Tensile Strain Method(LTSM)and Numercial Simulation Method.By comparing the calculation results under different conditions,it is found that the damage caused by tunneling is greatest when the angle between the building and the tunnel is 90°.The maximum tensile strain value calculated by FEM is much larger than LTSM.The stress concentration at the openings such as doors and windows in the model leads to this result.Therefore,it is difficult to accurately reflect the atual damage level of the building by using the traditional damage assessment methods,and the method combined with the area occupied by the strain occurrence area in this paper is better.(4)The maximum tensile strain value of the building with foundation is calculated by the Winkler elastic foundation model and the Limiting Tensile Strain Method.The results show that the tensile strain of the building decreases significantly when considering the effect of foundation,and its influence dererase with the reduction of the angle between the building and the tunnel.