Simulation Studies Of Rock Blasting Process Under Initial Stress

Because of the decrease of shallow resources and the need of some engineering, both the resources exploitation and the tunnel excavation go into the deep underground. Deep rock mass is often in a high stress environment, when blasting, rock will rupture under the combined action of blasting loadings and initial stress, this process is very complex and can’t be analyzed with the theory of shallow rock blasting, so it is necessary to analyze the rock blasting process under initial stress.In this paper, the numerical simulation study of rock blasting process under initial stress is carried out by using the finite-element software LS-DYNA and ABAQUS, following work has been completed:(1) The rock blasting process is analyzed theoretically, combing with rock blasting process, the effect of rock strain rate under blasting dynamic loading, kinetic process of rock blasting and superposition of blasting loading and initial stress are analyzed.(2) Numerical simulation of rock blasting process under initial stress which is in spherical charge is carried out by using LS-DYNA, blasting under different resistance line is compared on funnel size, the results indicate that:blasting funnel of different resistance line is very variable, in these calculation models, the blasting funnel of resistance line W=20mm is maximum, the initial stress does not affect the propagation of stress wave in the spherical charge, but it would restrain the formation of blasting funnel which is perpendicular to the initial stress direction; Numerical simulation of rock blasting process under initial stress which is in column charge is carried out, the results indicate that:the initial stress does not affect the propagation and attenuation of blasting stress wave in the column charge, but it would restrain the formation of crack which is perpendicular to the initial stress direction; Numerical simulation of blasting process under unloading initial stress is carried out, the results indicate that:unloading stress wave can improve the distribution of stress field in the rock and promote the formation of blasting crack.(3) Numerical simulation of row-hole blasting process and pre-splitting blasting process under initial stress is carried out by using LS-DYNA, the results indicate that:While the distance of each hole is appropriate, the crack between different holes would link up, when the row-hole is parallel to the initial stress, blasting effect of row-hole is best, and when the row-hole is perpendicular to the initial stress, blasting effect is worst, in the pre-splitting blasting, when pre-splitting hole and blasting hole are parallel to the initial stress, pre-splitting hole would induce the formation of crack between two basting holes; Numerical simulation of rock blasting process with joints under initial stress is carried out, the results indicate that:the joints have transmission and reflection effects to blasting stress wave, and the rock would form reflected tensile crack, but the through joints would prevent crack from further extendng, when the angle between the line of partial joint tip, blasting hole and partial joint is small, partial joint tip would induce crack growth; Numerical simulation of rock blasting process which has a hollow area under initial stress is carried out, the results indicate that:the hollow area provides free surface to blasting, and it can improve the stress distribution of rock and blasting effects.(4) Numerical simulation of crack growth process driving by blasting gas is carried out by using ABAQUS, the results indicate that:with the growth of crack, blasting gas pressure decreases and the rate of crack growth decreases, when the blasting gas pressure reaches the critical pressure, crack stop growing; Numerical simulation of crack growth process driving by blasting gas under initial stress is carried out, the results indicate that:the initial stress would inhibit the growth of crack which is perpendicular to the initial stress direction, when the direction of initial crack is same as the direction of initial stress or initial stress resultant, crack would grow along the original direction, otherwise, the crack grows to deflect the direction of bigger initial stress.