Numerical Analysis Of The Influence Of An Open-Pit Mining On Adjacent Existing High-Speed Railway Bridges

The vibration of mine rock mass caused by human activities such as open-pit mining may affect the operation of existing high-speed railway bridges.Therefore,this paper relies on the problem that the mining of the ore body in Shangrao Duimenshan quarry has an impact on the operation safety of the adjacent existing Kunming-Shanghai high-speed railway.Based on the field investigation of the mining method of the ore body and the operation status of the adjacent Kunming-Shanghai high-speed railway infrastructure,this paper uses the combination of theoretical analysis,field investigation and numerical simulation to carry out the numerical analysis of the impact of vibration caused by different mining methods of open-pit mines on the safe operation of adjacent existing high-speed railways.Field investigation shows that mining may have a significant impact on the operation of adjacent high-speed railway bridges.Therefore,based on ABAQUS finite element numerical simulation,two different mining methods(blasting technology or stripping machine-scraper-rock breaker combined open-pit mining technology)are selected to establish a finite element model with high-speed railway bridges.The vibration velocity,displacement and deformation index and variation law of adjacent existing high-speed railway structures are calculated.It is proposed that the stripping machine-scraper-rock breaker combined open-pit mining technology is feasible for Shangrao quarry,and the impact on adjacent existing high-speed railway bridges is within the control range.Its technology can provide reference for similar open-pit mining.The main research contents are as follows :(1)The mining method of the ore body and the operation status of the infrastructure near the Kunming-Shanghai high-speed railway are investigated on site.It is obtained that the ore body in the mining area corresponds to the mileage of the Shanghai-Kunming high-speed railway from K482+339 to K482+419.The M2 ore body in the mining area is about 84 m away from the high-speed railway and is facing the railway bridge.The first mining method is to choose blasting,and the second is to choose hammer crushing,that is,stripping machine-scraper-rock breaking machine combined open-pit mining technology.(2)ABAQUS finite element software is used to establish a numerical analysis model of hammer weight impact,and the vibration response of open-pit mining impact load to adjacent existing high-speed railway bridges at different positions,hammer weight and drop height is analyzed.The numerical analysis results show that under the premise of hammer weight of2000,4000 and 6000 kg,the maximum vibration speed of railway box girder A1 measuring point caused by mining is 0.172cm/s,which is less than the specified safety vibration speed limit of adjacent high-speed railway bridge construction of 1.5cm/s.(3)It shows that it is feasible to adopt the combined open-pit mining technology of stripping machine-scraper-rock breaker in quarry.When the hammer weight increases by2000 kg,the maximum vibration velocity of box girder A1 measuring point increases by 6%,and the maximum vibration velocity of pier B1 measuring point increases by 6%.For every1 m increase in the drop height of the hammer,the maximum vibration velocity of the box girder A1 measuring point increases by 6%,and the maximum vibration velocity of the pier B1 measuring point increases by 6%.For every 20 m increase in the distance of the mining point,the maximum vibration velocity of the box girder A1 measuring point decreases by30%,and the maximum vibration velocity of the pier B1 measuring point decreases by 30%.The maximum vibration velocity of A1 measuring point of railway box girder caused by mining at 80 m is 0.225cm/s,which is far less than the vibration velocity limit of 1.5cm/s of adjacent high-speed railway bridge construction.(4)ABAQUS finite element software is used to establish the numerical model of explosive mining construction,and the vibration response of the open-pit blasting load to the existing high-speed railway bridge at different explosive quantities and positions is analyzed.The numerical analysis shows that the stress wave under the action of explosion load has a certain influence on the structure of the existing high-speed railway bridge during the propagation process.The nearest distance between the mine construction point and the edge of the high-speed railway cap is 84 m.The comparison shows that the maximum horizontal radial,longitudinal and vertical displacements of the high-speed railway bridge caused by blasting vibration are respectively 0.761 mm,0.681 mm and-1.753 mm.The displacement and deformation values are less than the standard limit of 20 mm.The peak value of vibration velocity caused by explosive mining technology is 2.826cm/s,which exceeds the safety value of vibration velocity of 1.5cm/s for the construction of adjacent railway bridges.Therefore,it is not recommended to use open-pit blasting.(5)The paper also studies the vibration response of the open-pit mining explosion load to the existing high-speed railway bridge at different explosive quantities and positions.The numerical results show that for 2000 kg increase in the explosion load,the maximum vibration velocity of the box girder A1 measuring point and the pier B1 measuring point increases by 8%and 8% respectively;the maximum displacement of box girder A1 measuring point and pier B1 measuring point increased by 32% and 27% respectively.For every 20 m increase in the distance between the explosion load and the mining point,the vibration velocity of the box girder A1 measuring point and the pier B1 measuring point is reduced by 30% and 25%respectively.The maximum vibration velocity and absolute displacement of box girder A1 measuring point and pier B1 measuring point are reduced by 32% and 30% respectively.