Evolution law of surrounding rock stress field for ultra-deep shaft development blasting

With the increase of the construction depth for ultra-deep shaft development blasting, it is prone to occur problems such as reduced driving efficiency, frequent dynamic disasters, wellbore instability and fracture under the coupling effect of deep high stress and strong blasting disturbance. In this paper, the dynamic evolution process of surrounding rock stress field and the propagation law of explosion stress wave in the process of ultra-deep shaft development blasting were studied by combining theoretical analysis with physical model test. The theoretical analysis model of ultra-deep shaft blasting excavation was established based on elastic mechanics, and the stress distribution and failure mechanism of surrounding rock under the coupling effect of deep high stress and blasting load were explored. Based on the self-developed dynamic response test system of surrounding rock in ultra-deep shaft development blasting, the propagation and attenuation law of blasting stress wave in surrounding rock under the influence of different ground stress characteristics were tested and analyzed. The results show that the stress distribution law of surrounding rock in ultra-deep shaft development blasting is affected by the superposition effect of the static stress field under the action of in-situ ground stress and the dynamic stress field under the action of blasting load, there is an increasing effect for the radial stress and a weakening effect for the hoop stress in the surrounding rock. There are tensile phase and compressive phase in the blasting strain waves measured in the shaft model test, and the radial direction is dominated by compressive strain, and the hoop direction is dominated by tensile strain. The blasting stress wave in the surrounding rock attenuated in the form of power exponential function with the increase of the measuring point proportional distance in the horizontal and vertical directions. The attenuation rate of the radial explosion strain wave was greater than that of the hoop strain wave. In addition, due to the influence of the propagation direction for the stress wave, the attenuation index of the radial peak strain and the hoop peak strain in the vertical direction were greater than those in the horizontal direction. The dynamic evolution process of the surrounding rock stress field and the propagation law of the explosion stress wave were further studied by experimental results compared with the theoretical analysis and the field test results in the literature. The conclusion of this study can provide a theoretical basis for the stability analysis of surrounding rock and the parameters design of development blasting in ultra-deep shaft.