Fractal Analysis Of Crack Propagation Of Reinforced Concrete Beams Under Uneven Ground Subsidence Caused By Tunnel Construction

During the construction of the subway tunnel,the surrounding strata is disturbed and the surface is deformed.The buildings in the affected area of the surface deformation are affected by the surface deformation and have additional stress.The concrete material used in the buildings,under the action of the internal force,will crack and expand into a macroscopic crack,thus affecting the safe use of the buildings.In order to study the law of the crack propagation of the surface cracks under the action of additional internal force,this paper will simplify the internal force in the study.Based on the four-point bending beam test of reinforced concrete and the finite element simulation,the crack propagation of the component under pure bending moment is studied.Combined with fractal theory knowledge,from the perspective of fractal geometry,describes the relationship between concrete cracks and component characteristics.The specific research work is as follows:(1)Based on the influence of tunnel construction on the surface,the finite element simulation is used to simulate the internal force of the surface building caused by tunnel construction.Due to changes of the internal force of the building,resulting in cracks in the components,thus established the link between building cracks and tunnel construction.(2)Surface deformation caused by tunnel construction,resulting in uneven settlement of the building foundation,so that the building internal force changes.Combined with this principle and the reinforced concrete four-point bending test,the internal force is simplified.The crack propagation law of the member beam under the action of pure moment is studied by experiment and the experimental results are compared with the calculated values.(3)Based on the fractal geometry theory,the fractal dimension of the crack of the test beam is calculated,and the fractal dimension is established connection with the corresponding experimental data.And the relationship between the fractal dimension of the crack of the component beam and the load,the mid-span deflection,the reinforcement stress are established.(4)The extended finite element method is used to simulate the NO.a crack in the test,and the accuracy of the test is verified by comparing the experimental data.It also proves the practicability of extended finite element method in simulating crack propagation.(5)Summarize the relationship between the development of cracks in building components and tunnel construction,and put forward the next work outlook.