Study On The Excavation Stability Of Bridgefoundation Pit Excavated In Mining Subsidence Area

In mining subsidence area,After underground coal seams are mined,the upper soil will be resulted in disturbance and subsidence deformation.it has serious influence on the stability of the foundation bridge foundation pit's excavation.This paper takes the combined box frame bridge foundation pit engineering and the local engineering geological conditions in Huainan mining area as the research background.According to the local actual situation of the engineering,through using the numerical simulation of FLAC3 D,theoretical deduction and engineering application,systematically study the stability of bridge excavation in coal mining subsidence area,and analyzed the influence of remaining subsidence of the soil on the stability of foundation pit slope,and the calculation results are applied to the actual engineering.Finally,the reasonable reinforcement programs are put forward for the bridge foundation which does not meet the stability requirement.The paper has achieved the following main achievements:(1)The numerical simulation of FLAC3 D is used to calculate remaining subsidence of the soil deformation and the displacement of the foundation soil within a certain depth of the surface caused by coal mining in the later stage,which is used as a later stage to study the stability of bridge foundation pit excavation the boundary conditions.(2)Through using FEM numerical analysis,systematically analyzes the influence of the variation of mechanical parameters and the subsidence deformation of foundation soil caused by the remaining subsidence on the stability of bridge foundation pit excavated,In addition,the relationship between the remaining subsidence and the safety factor of the stability of the foundation pit of the bridge is obtained according to the comparative analysis of the results of different group numerical models.Based on this,the reasonable foundation pit slope of excavation of bridge foundation under the influence of remaining settlement in subsidence area is proposed.(3)Based on the basic calculation principle of several common limit balance method,the formula for calculating the safety factor of slope stability is deduced according to the deformation form of foundation soil in subsidence area.On this basis,the safety factor of the slope in the example is calculated,and the calculated results are compared with the numerical results of FLAC3 D.The above calculation method has certain engineering application value.(4)Combined with practical engineering,the stability of the existing bridge foundation pit under the influence of the remaining subsidence of the soil caused by the late coal seam mining is analyzed,and the reasonable reinforcement programs are put forward for the foundation pit of the mining subsidence area which does not meet the stability requirement.it is a great significance to the construction of bridge foundation pit in coal mining subsidence area.