Experimental study on characteristics of rock fracturing by high-pressure foam
摘要
In view of the shortcomings of the drilling and blasting method and the mechanical method in rock breaking engineering, based on the high viscosity and compressibility of foam, the rock-fracturing technology by high-pressure foam is proposed. Firstly, the rock fracturing devices by high-pressure foam are designed, the process of high-pressure foam instantaneous release to boreholes is theoretically analyzed, and then the testing devices for rock fracturing force by high-pressure foam are built and the relevant experiments are carried out. By using the developed experimental system of rock fracturing by high-pressure foam, the foam-fracturing characteristics with different air volume fractions are investigated, and the mechanism of high-pressure foam fracturing is revealed. The results show that when it is released, the high-pressure foam can produce a higher fracturing force than the initial foam pressure, but the fracturing force increases and then decreases with the increase of the air volume fraction of foam. The high-pressure foam fracturing goes through four stages of crack initiation, crack expansion, crack separation and end of cracking. The rock-breaking weight increases and then decreases with the increase of air volume fraction. When the air volume fraction is 60%, the rock-breaking form is blasting crater, which is mainly caused by the tensile stress generated by the compressive stress waves reflected on the rock upper surface. When the air volume fraction is 70%~90%, the rock-breaking form is stripped large stones, which is mainly caused by the effects of the stress concentration at the bottom of boreholes.