Study On The Harmfulness And Prevention Measures Of Groundwater Level Rise To Metro Stations In Loess Area

The groundwater level rise will cause certain harm to the underground structure,and the collapsibility characteristics of the loess under water conditions will further aggravate the damage degree of the underground structure.Therefore,it is apparent that studying the hazard of the rise of groundwater level to the metro station structure in the loess region and the prevention and control measures particularly important.This article mainly carried out some researches on the background of Xi'an Zhangba North Road subway station.The main research results are as follows:(1)Analysis of the hazard types of underground structure after rising water level,and summarizing the causes of hazards,there are two main reasons:First,the rise of water level leads to the weakening of soil parameters of surrounding rock mass of underground structures;second,the underground structures are affected by water loads.(2)The ABAQUS simulated the influence of the change of the groundwater level from the initial water level(3m below the floor)to the position of the roof to the structure of the subway station.According to the damage reasons,this paper reduced the soil parameters of the subway station structure,the water load and the surrounding rock.The joint action of body parameter reductions simulates the rise of the water level.The results show that the reduction of surrounding rock parameters has little effect on the structure of the subway station,and the main role of the influence on the structure of the subway station is the buoyancy force;as the horizontal and vertical stresses increase too much,they are at the top of the roof respectively.Destruction occurs at the position of the outer side of the side wall and the top of the middle plate;comparing the stress of the station structure under the reduced water load and surrounding rock parameters,it can be seen that the main factor of the structural failure of the subway station is the water buoyancy load.(3)The effect of groundwater pipeline leakage on the structure of the subway station when the underground pipelines are Om,3m,6m,and 9m away from the subway station structure is simulated.The results show that the groundwater pipeline at different locations does not have a large stress increase in the subway station structure,but it will result in the structure the overall tilt,and the largest difference between the two sides of the structure to reach 100mm,so the safety of the subway station operations may have a certain impact.(4)Whether it is water supply or groundwater pipeline leakage,the water level will rise and the structure of the subway station will be destroyed.In order to avoid structural damage,the natural water supply will increase the water level using ABAQUS to simulate the changes in the structure of the subway station before and after the application of the anchor rod.The influence of pipe leakage caused by water level rise was changed by the effect of ABAQUS simulation grouting treatment before and after the subway station structure,and the force characteristics and displacement changes of the subway station structure were significantly reduced after taking measures.