Developments And Applications Of The DDA Method For Modeling Blasting-induced Rock Failures

Discontinuous Deformation Analysis (DDA) is the method that computes the static and dynamic behavior of discontinuous block systems. DDA method to deal with rock blasting problems is studied in this research. Firstly, this paper reviews the numerical simulation method of blasting rock breaking and combed the basic principle of DDA method. And then perfected the basic functions of the main program of DDA.Secondly,the DDA sub block cracking algorithm based on sub block element stress level is verified. And then simulated the explosion stress wave effect on the rock breaking. The DDA method for the rock burst of gas pressure under the condition of multi hole is studied,and then compiled and verified the main program;Finally, the paper simulates the action of drilling and blasting combined blasting stress wave and blasting gas pressure, and study drilling and blasting broken rock mechanism and its influencing factors.The specific research contents and results are summarized as follows:(1) The related problems of the static and dynamic conditions are simulated and analyzed by the improved DDA cracking algorithm. The main purpose is to verify the accuracy of the improved DDA algorithm. Under the condition of static condition, it is mainly to simulate and analyze the square piece with a preset crack in the rock specimen. The simulation and analysis of the Hopkinson's rod layer crack is mainly carried out under the condition of the dynamic condition.(2) The effect of the explosion-induced stress waves in drilling blasting of rock is numerically simulated by the DDA. The uniform triangular shock loads are applied on the borehole walls to simulate the effect of explosion-induced stress waves. Two examples, a single-borehole model and two-borehole model, are carried out. The simulation results show that the blasting-induced rock failures under the effect of explosion-induced stress waves are well reproduced by the DDA. And in two-borehole drilling blasting of rock example, the effect of the explosion-induced stress waves on the process of drilling blasting of rock and rock failures in it under the conditions of the simultaneous loading and delay loading are compared and analyzed.(3) The DDA algorithm to simulate drilling blasting of rock under the effect explosion gas pressure in multi-borehole conditions are studied, and the corresponding DDA computer program is realized. The permeability loading of explosion gas on rock cracks and the re-distribution of gas pressure in adjacent blasting chambers are taken into account as the key to realizing the simulation. After the implementation of modeling the effect of explosion gas pressure, the numerical models of single-borehole, two-borehole as well as multi-borehole are established to verify the single effect of the explosion gas pressure. As the result shows, during the drilling blasting of rock, the process of borehole expansion, rock mass failure, borehole propagation, explosion gas leaking and rock casting can be numerically reproduced well by this developed method.(4) On the basis of previous work, by loading the explosion-induced stress waves and the explosion gas pressure simultaneously, the process of rock failures in drilling blasting are simulated under different conditions. The influences of the energy proportion of explosion-induced stress wave and explosion gas pressure, the rock mass characteristics, the ground stress levels and the minimum resistance line are investigated. The mechanism of rock failures in drilling blasting is studied and the effects of above mentioned factors on rock failures are analyzed.