Study On Treatment Of Boulder Blasting In Shield Construction Tunnel

In the process of subway construction by shield tunneling method,boulder or groups of boulder are often encountered in the stratum traversed by shield tunneling machine.When shield tunneling machine encounters boulder,it will cause serious problems such as tunneling difficulty,construction period out of control and construction cost increase.Therefore,"finding and dealing with boulder" has become an urgent problem to be solved in the process of subway construction.In this paper,the method of detecting underground boulder is studied and the feasibility of detecting underground boulder by geological radar is verified by an example.The single and double hole two-dimensional blasting model is established to analyze the crushing effect of rock mass,and the feasibility of the blasting simulation is verified by the numerical simulation results.Based on the analysis of the strength and size of the boulder,the numerical test of underground boulder blasting in shield section of subway is carried out.Using Visual basic integrated development environment,the program code is written to develop the design platform of underground boulder blasting,and the calculation platform is visualized and applied to practical engineering.The main research results are as follows:(1)Through the example,the geological radar detection results are consistent with the drilling verification results,verify the feasibility of geological radar to detect underground boulder.(2)According to the material model selected in this paper,a single hole air uncoupled charge blasting model and a double hole air uncoupled charge blasting model are established to simulate the crack propagation process of boulder mass under the action of explosion shock wave,and the feasibility of boulder blasting simulation is verified by the numerical simulation results.(3)The finite element software ANSYS/LS-DYNA is used to simulate the blasting of the boulder in the shield section of the subway tunnel,and the blasting parameters and the minimum safe distance under different strength and size of the boulder are obtained.The blasting parameters and the minimum safe distance under each working condition are summarized to provide data support for the Visual basic development platform.The relationship between the strength and size of boulder and the powder factor and minimum safe distance is studied by single and two-factor analysis,and the curve fitting analysis was carried out.The three-dimensional surface fitting was carried out on the results of two-factor analysis,and the fitting equation was obtained.(4)Using Visual basic integrated development environment,the design platform of underground boulder blasting is developed and visualized.Then combined with the engineering example,the use of blasting design platform for parameters are calculated.