Study On Construction Technology Of Mining Method And Milling Excavation Method Of New Railway Tunnel Adjacent To High Speed Railway

Mining method is commonly adopted in tunnel and underground engineering.Meanwhile,especially in approaching constructions controlled blasting is also widely used.In recent years,with the gradual decline of the distance between newly constructed structures and existing structures,approaching construction encounters more sever obstacles.In order to confirm the safety of the construction and existing structure,the mining method or milling-mining method can be replaced by milling method,which reduces the disturbance to surrounding rock and existing structures.When using milling method,the cutter depth of milling machine,cutting thickness and cutting method have a significant influence on the efficiency of construction.When using mining method,the blasting vibration will have a distinct adverse effect on existing structures.Therefore,analyzing the propagating law of blasting wave and the dynamic response of existing structure is of great importance on confirming the safety of blasting and reducing the vibration.Determining the applicability and working conditions of milling-mining method is important for improving the efficiency and safety of the construction.Based on the the Qishan Tunnel Project of Pumei Railway in this paper,the engineering problem is studied by means of data investigation,numerical simulation and field test.The main research contents and results are as follows:(1)Based on the method of particle flow discrete element,the rock breaking model of the milling cutter is established by PFC3 D software to carry out numerical simulation research.Through carrying out thorough and comprehensive scientific research on the cutter depth,cutting thickness and cutting method of milling machine,the effect of rock breaking,stress state of the milling cutter and operation state of the milling machine under different working conditions are explored.The reasonable adaptability of the lithology,the optimal cutter depth,the cutting thickness and the cutting method are obtained,and the key parameters of the milling method are proposed.(2)Through on the finite element software ANSYS/LS-DYNA,the blasting construction technology of the new tunnel adjacent to the high-speed railway tunnel and forced vibration of the existing structure are simulated and analyzed.The reasonable cyclic footage of the adjacent blasting construction is determined,and the dynamic response law of the lining structure of the existing high-speed railway tunnel under the influence of blasting vibration is explored.Based on the field monitoring data,the formula of blasting vibration velocity is obtained by using MATLAB fitting,which provides a criterion for evaluating the influence degree of the existing line by adjacent blasting construction.(3)Based on the finite element theory,the blasting construction model of the tunnel adjacent to the high-speed railway tunnel is established by the finite element software ANSYS/LS-DYNA.The generation and propagation of blasting vibration are simulated and the attenuation law of blasting vibration in the formation is explored.At the same time,the technology of hydraulic blasting and vibration reduction groove around the tunnel is simulated,and reasonable blasting vibration reduction measures are proposed.(4)For the homogeneous lithology or composite stratum conditions,the numerical simulation method is used to carry out scientific research on the comprehensive construction technology of milling-mining method.By analyzing the vibration velocity and stress state of each monitoring point under different excavation modes,it is clear that the combination of milling method and mining method can greatly reduce the impact of blasting vibration on adjacent existing structures.At the same time,the reasonable construction methods and applicable conditions for upper soft and lower hard strata are proposed.