The Study On Hollow Effect Of Ground Vibration Under Blasting Load In Shallow Tunnel

The blasting vibration is considered to be the biggest negative effect for tunnel construction using drilling and blasting method.In the construction of shallow tunnel,the blasting vibration of the surface effect is more obvious because of the buried depth of the tunnel.The incomplete understanding of the propagation law of blasting seismic wave on the surface may lead to the buildings destroyed due to excessive vibration intensity which caused a serious engineering accident.The hollow effect of shallow tunnel caused the surface vibration presenting regional changes.The blasting vibration on the surface of the tunnel behind tunnel face is greater than the symmetric position of the surface vibration velocity.Taking the project of Douziwan shallow tunnel through the Qiaoqiaowan reservoir for Chengdu-Guiyang passenger railway as the background,experiment test of vibration effects on the surface and numerical simulation by computer are utilized to research the study of hollow effect of ground vibration under blasting load in shallow tunnel.The surface vibration velocity caused by cutting blasting is greater than others through the analysis of the vibration wave curves by experiments.Cutting blasting is the key case of the vibration intensity.The velocity amplification index of hollow effect has been put forward as the standard of amplification effect caused by hollow effect.Through the study of numerical simulation,putting forward the method of putting blasting load and boundary conditions,the change rule on tunneling direction of hollow effect and the area influenced by the hollow effect on the surface of the shallow tunneling have been got.Putting forward the vibration damping technology of wedge cut to weaken the effect of the surface vibration amplification caused by hollow effect and applied the method to the construction of Guangzhou metro line twenty-one.