| In tunneling projects in Western China,the characteristics of deep burial,high in-situ stress and large deformation of soft rock are often presented.When the tunnel site is in layered soft rock,the blasting energy of rock mass can not be well controlled and utilized due to the influence of the structural plane.When the detonation wave passes through the structural plane,it will cause the attenuation of the detonation energy,which will lead to the difficulty of tunnel forming.If the control is not good,there will be a large area of roof fall,collapse,over-excavation and under-excavation around the tunnel contour,even to the safety of the constructors.All threaten.This will directly lead to the high cost of such tunnels,and the quality of blasting is difficult to guarantee.Therefore,the study of the influence of the structure of layered rock mass on the blasting excavation of tunnel rock mass has far-reaching significance for speeding up the design and construction progress,saving project investment,ensuring construction safety and the use function of lining structure,and has broad application market and prospects in the field of tunnel engineering.Taking the Ganjialiang Tunnel Site of Xi'an-Chengdu Railway as the research object,this paper carries out the following research work:(1)According to the hydrogeological and engineering geological survey data in the tunnel site area,the soft rock types and the stress level in the tunnel crossing area are preliminarily determined.Based on the geological conditions of tunnel engineering,the possible risks in tunnel construction are analyzed,which provides background support for numerical simulation.(2)The damage process of single hole blasting in layered rock mass is simulated by ANSYS/LS-DYNA dynamic finite element software.The development law of explosive cracks is obtained and the influence of different filling forms of structural planes on the development law and damage range of explosive cracks is analyzed.The single hole blasting damage simulation of layered rock mass under 15 MPa in-situ stress is carried out,and the development rule and damage range of blasting cracks under the coupling action of blasting dynamic load and geostress static load are obtained.The vibration velocity time history of each monitoring point in the blasting model is extracted,and the particle vibration velocity attenuation law caused by the propagation of blasting stress wave in rock mass under the action of intact rock mass,rock mass with structural plane and in-situ stress is obtained.(3)The dynamic response of tunnel blasting excavation is simulated by using the discrete element software 3DEC.The influence of rock thickness,structural plane strength,structural plane occurrence and in-situ stress on tunnel blasting excavation is analyzed.The range of plastic zone,displacement vector and the distribution of maximum principal stress in the process of tunnel blasting excavation are obtained.The particle velocity in surrounding rock above the arch,left side wall and under the floor of the tunnel is monitored,and the attenuation law of the particle velocity in all directions is obtained. |
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