| With the accumulated experience in the design and construction of tunnels and underground engineering in recent years,the construction of highway tunnels in my country is developing towards a trend of larger cross-section.The tunnel structure will have a greater impact.This paper takes the Longquanshan large section highway tunnel as the research object,using methods such as data collection and investigation,theoretical analysis and numerical simulation,based on the single-hole blasting model to compare and analyze the blasting effect of different methods on the damage to the rock mass around the blasthole and the impact on the far field.The main research conclusions of this paper are as follows:(1)Based on the single-hole blasting finite element model,the three methods of fluidsolid coupling method,initial volume fraction method and equivalent load method were compared and analyzed from the aspects of surrounding rock fragmentation around the blast hole,calculation efficiency and influence on far-field structure.It verifies the feasibility of the equivalent load method in analyzing the impact of blasting on far-field structures.(2)Based on the equivalent elastic boundary derived from single-hole blasting,the peak load,attenuation model,action time,“group effect” and “difference effect” of singlehole blasting of different types of blastholes are comprehensively considered.The equivalent blasting load curve process of the tunnel excavation profile surface is determined,and the blasting load curve of a specific step sequence is obtained in combination with the tunnel blasting design.(3)The large-scale finite element software ANSYS/LS＿DYNA is used to establish a tunnel blasting numerical model under the conditions of different excavation steps and different clear distances,and the blasting load effect of different excavation steps is studied.The dynamic response characteristics of the lower leading tunnel and the trailing tunnel are compared and analyzed,and the influence of different clearance distances on the dynamic response law of the leading tunnel under the condition of step 1 is compared and analyzed.(4)Using the spectrum analysis method,the vibration velocity response characteristics and the Fourier dominant frequency distribution law of each monitoring point on the blasting side in different directions under the conditions of different clear distances and specific step sequences were studied.The continuous wavelet transform analyzes the vibration velocity curve of the key monitoring point controlling the vibration velocity direction(X direction)in the time domain,frequency domain and amplitude. |
