Results in Engineering (Dec 2024)
Model experimental study on high-pressure gas expansion directional rock-cracking based on directional expansion pipe
Abstract
The directional control of fracture surface is an effective technical measure to control the tunnel excavation forming. In order to make the expansion pipe produce the effect of directional rock-cracking, a high-pressure gas expansion directional rock-cracking technology based on directional expansion pipe is developed. There are two V-shaped bulges on both sides of the directional expansion pipe, which can form an imitation notching directional rock-cracking charging structure during charging and plugging. The structure guides the high-temperature and high-pressure gas to instantly produce a single directional fracture surface. The theoretical analysis, physical model tests as well as model damage detections are conducted to obtain application effect of this technology in directional rock-cracking and contour forming control. The results show that directional expansion pipe can effectively control the extension direction of the fracture surface, so that the adjacent rock-cracking holes are connected to each other to form a continuous fracture surface with obvious direction. Compared with conventional expansion pipes, the area of over-excavation and under-excavation generated by directional expansion pipes is reduced by 90%. And with the use of directional expansion pipes combined with the control holes, the area of over-excavation and under-excavation can be further reduced by 25%. The damage distribution around the directional fracture surface is characterized by ''high in the middle and low on both sides''. The damage values of the damaged core area in the middle can reach 0.46–0.71, while the damage values of the areas without fracture on both sides are between 0.01 and 0.16.
