NUMERICAL STUDY ON CRACK PROPAGATION AND STRESS WAVE PROPAGATION DURING BLASTING OF JOINTED ROCK MASS

There are a large number of naturally formed joints in natural rock mass, which lead to changes in the mechanical properties, vibration, permeability, energy transfer and other properties of rock mass. The propagation and attenuation of blast stress waves in the rock mass with joints also change, which affects the effect and safety of engineering blasting. The explosion crack propagation and explosion stress wave propagation law of the jointed rock mass are studied, and the effective stress and vibration velocity of the rock mass on both sides of the joint are obtained by establishing the explosion numerical model of the jointed rock mass. The transmission and reflection coefficient and the transmission and reflection energy ratio of the joint are calculated by using the stress wave wave theory and energy density theory. On this basis, the effects of joint geometric parameters (joint filler thickness D, normal distance R from blast source to joint, vertical distance H from blast source to joint, joint inclination \theta ) on the expansion of blast cracks at different positions of the joint were studied. And the relationship between the above-mentioned joint geometric parameters and the joint's transmission and reflection coefficient and transmission and reflection energy ratio. The results show that when the joint is located in the crack area and the ratio H/R of the vertical distance H from the blast source to the joint to the normal distance R is equal to 1, the reflection coefficient and reflected energy ratio of the joint are at the maximum value, and shear stress becomes the main factor affecting the damage of joint surface within this range. The fracture area of the rock mass near the explosion side of the joint is positively correlated with the thickness D of the joint filler. The fractured area of the rock mass near the blast side of the joint is negatively correlated with the normal distance R from the blast source to the joint and the vertical distance H from the blast source to the joint. When the joint is located in the crack area, the joint has the greatest impact on the blasting effect of the rock mass.