Study On Blasting Vibratioin Response Of Excavation Tunnelwith Super-close-up And Over-span Of Smoke- Exhausting Cross-hole

This paper takes the Wenchuan-Maerkang high speed super close to the smokestack crosshole blasting project on the left side of the Ganyanggou tunnel as the research background,combining the actual situation of the scene to design the smokestack transverse hole blasting scheme,and then applies the numerical simulation method to the two steps respectively.The method and three-step bench blasting construction analyze the vibration response of the existing tunnel lining,and studying the dynamic response law of vibration velocity,vibration acceleration,displacement and stress of the existing tunnel lining,providing theoretical basis and technical support for engineering design and construction.In order to ensure the smooth construction of the safety line of the left line lining of the Ganyanggou tunnel and the smooth construction of smoke exhaust holes,and provide a favorable reference for other similar superclose-up and cross-tunnel projects in the future.The main research contents of the paper are as follows:(1)By referring to similar engineering examples at home and abroad,and combining the specific conditions of the smoke-exit tunnel construction of the Ganyanggou tunnel,a vibration threshold value of 7.0cm/s for blasting cross-hole tunneling in tunnels with super-near-up and cross-over tunnels was developed about safety control standards.(2)According to the geological conditions of the intersection and the mechanical properties of the surrounding rock,the two-step method and the three-step method were used to design two horizontal flue blasting tunnel blasting programs(borehole diameter,blasthole depth,guttering,single-dose,etc).The three-step method reserves the lower steps,after the construction of the upper and middle steps is completed,construction will be worked on the lower steps.(3)Using MIDAS/GTS software to simulate the blasting construction on the upper and lower steps of the two-step method for smoke stacking.To analyze the velocity,acceleration,displacement and stress of the lining particles in the existing tunnel under blasting vibration,studying the propagation law of blasting seismic wave.The results show that the peak velocity of the existing tunnel lining under the two-step blasting method is 7.97cm/s,which exceeds the vibration velocity threshold.After the explosion of the newly-built exhaust fume at the cross-hole face,the blasting vibration produced by it generates vibration speed loops and vibration acceleration loops at the existing lining vault,and the value decreases gradually from the inside to the outside.With the end of the blasting process,the vibration velocity circle and the vibration acceleration circle propagate symmetrically in the front and back sides of the existing tunnel,the numerical value gradually decreases.The stress wave generated by blasting propagates through the surrounding rock to the existing tunnel lining,stress value is gradually reduced from the surrounding rock to the lining,and the extreme stress of the lining appears at the dome.(4)Using software to simulate the blasting construction of the upper,middle and lower steps of the three-step method,and compare it with the blasting vibration response generated by the two-step bench blasting construction,studying on the attenuation of blasting seismic wave propagation due to the reservation of lower steps.The results show that under the three-step method,existing tunnel structure under the blasting construction of the upper,middle and lower steps is in a stable state,and the reserve of the lower step effectively reduces the vibration velocity,acceleration,stress and displacement of the existing tunnel lining particles.