Study On Damage Law Of Surrounding Rock Under Blasting Load Of Cylindrical Charge In Tunnel Excavation

In order to control the damage effect of blasting excavation of urban subway tunnel on surrounding rock,based on the National Natural Science Foundation of China(51664007),taking the blasting excavation of Guiyang Metro Line 3 tunnel as the actual engineering background,on the basis of previous studies and theoretical analysis,this paper adopts the research method of numerical simulation and model test to study the blasting effect of cylindrical charge,The influence law of different charge structure on surrounding rock damage.Based on the damage theory of surrounding rock and RHT constitutive model,the concrete model test is carried out.Combined with numerical simulation,the dynamic response characteristics of rock mass under the blasting action of different charge structures are studied,and the influence of the change of decoupling coefficient on the damage of rock mass during blasting is studied.The damage law of surrounding rock under blasting load of cylindrical charge in tunnel excavation is explored.The main conclusions are as follows:(1)Through theoretical analysis,based on the elastic modulus defined by Taylor method,the damage variable of rock under the combined action of explosion stress wave and high-pressure detonation gas is defined.The damage range of rock during blasting with cylindrical charge is divided into four areas: serious damage,general damage,slight damage and no damage.(2)Based on the model test results,it is concluded that: with the increase of horizontal distance,the damage factor decays in a power function;due to the influence of free surface,the damage factor increases with the increase of vertical distance;the damage range of uncoupled discontinuous cylindrical charge is the smallest,and that of coupled continuous charge is the largest.(3)Based on the numerical simulation results of LS-DYNA,the damage law of rock under different charging structures is obtained,which is consistent with the results of concrete model test.The results show that with the increase of horizontal distance,the damage factor decays in power function;the damage range of rock mass in crushing area increases with the increase of decoupling coefficient,and the damage range of rock mass in fracture area decreases with the increase of decoupling coefficient;the closer to the free surface,the more serious the damage caused by reflected stress wave.