Deep Hole Blasting Effect Evaluation For The Boulder Of Subway Tunnel And Hole Network Parameter Optimization Method

With the rapid development of urban rail transit and the popularization of shield technology in tunnel construction,the construction of tunnels is facing more complex geological conditions and new challenges."Granite strata,local bedrock protrusions and local high-strength granite" solitary stones ".Difficulties in the safe and smooth excavation of the shield.In order to ensure the smooth excavation of the shield,the deephole blasting method on the surface is used to blast and remove the lone rock.The problem of blasting and breaking of solitary rock is very complicated.In order to achieve the best blasting effect of solitary rock,it is necessary to study: the dynamic breaking process and crack propagation mechanism of solitary rock under blasting impact load;Design parameter optimization method.Based on the explicit dynamic numerical simulation software Autodyn and LSDYNA,the deep hole blasting of the boulder is numerically simulated,and the fluidsolid coupling analysis method is used.The Johnson-Holmquist damage constitutive model describing the dynamic response of brittle materials is selected as the mechanical constitutive model of the rock mass.The Euler network is used to model the fluid field(explosive,air field,water medium field)in blasting and to analyze the fluid-solid coupling with the rock mass.The damage variables of rock mass units are used as physical quantities to describe rock mass breakage.Through the spatial distribution of damage variables and the evolution of damage location over time,the dynamic fracture and crack propagation process of rock mass under blasting load is studied.The factors influencing the breaking effect of the lone rock are studied separately.In order to study the dynamic crushing mechanism of rock mass,the numerical calculation model of single-hole blasting of circular rock mass was established,the crack distribution and crushing partition of rock mass under blasting load were studied,and the blasting crushing partition of rock mass was obtained by the unit consumption of explosive In order to study the influence of uncoupling medium and uncoupling coefficient on rock mass breaking effect,the numerical calculation model of air medium and water medium uncoupling charge was established respectively,and different uncoupling coefficients were set for calculation,and the uncoupling coefficient was obtained.The relationship with the crushing effect of the rock mass and the distribution characteristics of the cracks under different coupling media;for the engineering characteristics of large strength difference between the internal and external rock masses of the boulder blasting,to establish the impact of the strength difference between the rock and the surrounding rock on the crushing effect,establish The numerical calculation models of the boulder and surrounding rock with different degrees of strength difference between the inner and outer rocks are studied,and the damage and crack distribution characteristics at the interface between the inner and outer rocks are studied.Based on the analysis of single influencing factors,the immune clonal selection algorithm and the support vector regression algorithm are introduced to establish the optimization method of the design parameters of the hole network of the solitary stone deep hole blasting,and the damage area ratio is used as the effect evaluation index.The blast hole spacing and uncoupling coefficient are optimized,which provides a certain reference value for the application of the blasting engineering of the boulder.