Research On Construction Optimization And Numerical Simulation Of Blasting Vibration In Deeply Buried Central Ditch Of Tunnel In Alpine Region

Most of the climate in Xinjiang's high latitudes is cold or severe.When constructing tunnels in high-altitude regions,due to the influence of temperature,consideration will be given to setting up deep-buried central ditches.As a new technology,the setting of the deep buried central trench is not widely studied at home and abroad.Therefore,it is necessary to study the blasting excavation scheme of the deep buried central trench and the blasting vibration response.Based on the above reasons,this article takes the Alataoshan Tunnel of the Lanzhou-Xinjiang Railway Second-line Bozhou Branch Line Project as the engineering background,and uses the dynamic finite element software LS-DYNA and large-scale finite element software MIDAS-GTS to carry out the excavation and blasting scheme of the trench and the vibration response.Numerical simulation research in order to obtain the optimal blasting plan,and provide reference and guidance for similar projects in the future.The main research contents are as follows:(1)The inverse analysis of the physical and mechanical parameters of the surrounding rock is performed through the measured displacement values of the tunnel site and the mechanical properties of the surrounding rock.The elastic modulus,Poisson's ratio,cohesion,internal friction angle,gravity,bulk modulus,The specific values of a series of basic parameters such as the shear modulus are used as the basis of the finite element calculation.(2)According to the design scheme of the deep buried central trench,the LS-DYNA dynamic finite element software that simulates the blasting effect in the near area of the rock mass is used.The coefficients,charge length,and other working conditions under different micro-difference times were numerically calculated.The blasting funnel and the typical unit near the free surface under the minimum resistance line of 60 cm were compared for each working condition,in order to obtain Optimal operating conditions for the best number of initiation stages and the best time difference.(3)During the numerical simulation of the blasting excavation in the deep buried central trench,the monitoring and analysis of typical units in the blasting smashing circle and the vicinity of the smashing circle were performed,and the formation of weathered rocks in the tunnel site was obtained under the condition of good penetration between the blast holes The critical values of the crack zone and the blast crushed zone are compressive stress 2.49 MPa,tensile stress 1.16 MPa,shear stress 3.19 MPa,Mises yield stress 6.18 MPa,and vibration speed 0.59 m/s.(4)Using MIDAS-GTS software,the corresponding numerical simulation calculations of two-stage initiation and six-stage initiation under the differential time of 20?s were made and compared.The results show that the six-stage initiation under the cumulative effects of blasting vibration stress and velocity values are less than the two-stage initiation corresponding values,and the optimal engineering conditions for the six-stage initiation are 20?s.Taking the maximum principal stress of 0.85 MPa as the initial critical failure value of the lining concrete,the corresponding vibration speed threshold is 1.50cm/s.It is proposed that the inverted arch and the second liner should be 9m~12m away from the cross section of the ditch.It is obtained that the construction of the central ditch has basically no effect on the total construction period.