Analysis Of Characteristics Of Rock Dynamic Damage And Application Of Safty Control In Foundation Pit Excavation By Blasting

Based on laboratory test, field test and numerical simulation, the rock damage by blasting and the problems of security control is studied. Though the Indoor physical and mechanical tests of rock samples, the macro-and micro-mechanics parameter are obtained. By using the particle flow software PFC2D, the numerical specimens is established with the parallel bonded model which allows the normal force, shear force and moment transferring between particle and particle. By studying the influence of micromechanical properties of particles to the macroscopic mechanical properties of the specimen, some conclusions can be draw as follow:the greater the bonding modulus particle has the larger macro-elastic modulus the specimen will has, but the bonding modulus of particles has no influence on the peak strenth of the specimen; the greater the bonding strenth particle has the larger peak strenth the specimen will has, but the bonding strenth of particles has no influence on the elastic modulus of the specimen; the elastic modulus and the peak strength of the specimen will all be increased by increasing the bonding radius of particle.The stress strain curves of the unconfined compression test of the specimen is obtained. By analysis of the changing of the stress, strain, tangent modulus, kinetic energy of the specimen though whole loading process of the test, it can be found that there is a steep drop demarcation point lies in the tangent modulus curve and the point is also the increasing demarcation point of kinetic energy curve. These phenomenon shows that the microcracks in specimens start to gather and particles have started to slip, the damage threshold of D=0.18 can be determined.The numerical specimens with joint is established by weakening the strength of contact points of particles. By analysing the differences of the test between the specimen with joints and with no joints under different loading rate, it can be found that with the increasing of the weakening contact points the mechanical properties of the specimen will degradate, it also shows that with the increasing of loading rate the sensitivity of the peak strength of the specimen gradually is weakened.The blast load is simulated by the dynamic finite element software of ANSYS AUTODYN, and the results is reliable by comparing with the empirical formula.The rock mass with or without joints is established by using the software UDEC. The damage range of the non-jointed rock by blasting agree well with the results got from the field test.All above prove it feasible to study damage zone of rock by using UDEC, and then damage zone of jointed rock is also studied by UDEC.Finally,based on a engineering project the safty control and the measurement of the damage range of the rock foundation excavated by blasting are studied and a quality control procedures for the similar engineering problems is eatablished.