Numerical Simulation And Theoretical Analysis Of Damage Caused By Blasting Damage Of Tunnel Surrounding Rock

With the emphasis on deep underground engineering in China,the construction of water conservancy and hydropower projects under deep tunnels and deep high stress conditions has developed rapidly.Blasting is one of the important means of excavation of deep underground rock mass.The mechanical properties of surrounding rock are deteriorating under cyclic blasting.The continuous accumulation of damage induces instability of the surrounding rock,causing tunnel collapse and threatening the safety of engineers.The progressive failure of the rock mass surrounding the tunnel under cyclic blasting is studied,which has important guiding significance for revealing the failure mechanism of rock mass,the deterioration of mechanical properties and the design of supporting structure.This paper relies on the National Natural Science Foundation of China,"Research on the damage evolution mechanism of tunnel surrounding rock under cyclic blasting load(51579142)".Through the basic theory and LS-DYNA numerical simulation analysis,the damage of surrounding rock under the dynamic load of cyclic blasting is discussed.The specific research results are as follows:(1)Summarize the related achievements in the theoretical and numerical simulations of cyclic blasting dynamic loads acting on the surrounding rock of the tunnel at home and abroad,and point out the existing deficiencies and problems.(2)Based on the basic theory of rock mass failure under blasting,the variation process of explosives over time and the progressive failure of rock mass are discussed,and the variable D of damage damage of surrounding rock is determined.(3)Perfecting the constitutive relationship of brittle rock materials by means of generalized Hooke's law;by using the maximum tensile strain criterion of rock mass and the Moore-Coulomb criterion of rock mass to judge the progressive failure of rock mass under cyclic blasting,The different values of the damage variable D(D0?D?1)are used to characterize the damage of the rock mass:when D=D0,the rock mass has the initial damage rock mass(D0 Can be equal to 0,at which time the rock mass is a complete rock mass);when D0<D<1,the rock mass has different degrees of damage damage under the initial damage;when D=1,the rock mass is completely destroyed and fracture occurs.Through the damage accumulation(?),the continuous cumulative damage damage of the tunnel surrounding rock under cyclic blasting is characterized.(4)With the help of LS-DYNA finite element software,it is revealed that the stress peak exists in the blasthole under the blasting action and radiates to the surrounding radiation.The rock mass is seriously damaged in the Y direction than in the X direction,and its failure mode is mainly caused by compression shear failure,accompanied by tensile failure.(5)By comparing the single-blast and cyclic blasting to the rock mass destruction,it reveals that the rock mass damage has obvious memory,although the rock mass damage is continuously attenuated,but the damage continues to accumulate.It shows that the macroscopic instability phenomenon of underground rock mass engineering is caused by the cumulative damage of rock mass caused by cyclic blasting,not caused by one blasting.(6)By comparing the damage damage of surrounding rock by 6 and 4 parallel blasting blasting,it is found that the damage of the surrounding rock by the six blastholes is more severe and the scope is more extensive,but the difference is mainly concentrated in the previous few times.Cyclic blasting,with the increase of the number of blasting cycles,the damage of the same surrounding rock is gradually attenuated,and the damage degree tends to be the same.Based on the basic theory of rock blasting,this paper makes a corresponding discussion and research on the damage of surrounding rock under cyclic blasting dynamic load by means of LS-DYNA numerical simulation,and further explores the cumulative damage and damage of rock mass and surrounding rock support.A certain theoretical guiding significance,to provide a certain reference for the realization of tunnel blasting construction technology innovation.