Research Article Shaped Charge Hydraulic Blasting: An Environmental, Safe, and Economical Method of Directional Roof Cutting Quan Zhang , 1 Jiong Wang , 2 Shan Guo, 2 Weili Gong, 2 Longfei Feng, 3 Haosen Wang, 2 Can Ming, 2 and Zimin Ma 4 1 School of Mines, China University of Mining and Technology, Xuzhou, Jiangsu 221116, China 2 State Key Laboratory of Geomechanics & Deep Underground Engineering, China University of Mining and Technology, Beijing 100083, China 3 Center of Mine Disaster Control and Environment Management Technology, Xi’an Research Institute of China Coal Technology & Engineering Group Corp, Xi’an, Shanxi 710054, China 4 School of Resources and Environmental Engineering, Shandong University of Technology, Zibo, Shandong 255049, China Correspondence should be addressed to Quan Zhang; zhangquan@cumt.edu.cn and Jiong Wang; wangjiong0216@163.com Received 17 January 2021; Revised 14 February 2021; Accepted 28 February 2021; Published 13 March 2021 Academic Editor: Feng Xiong Copyright © 2021 Quan Zhang et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Shaped charge blasting (SCB)—a directional fracture blasting technology—has the disadvantages of low safety, harmful gas, and dust emissions. This study proposes a new type of directional rock-breaking technology called shaped charge hydraulic blasting (SCHB) that uses water as the blasting medium instead of air. To verify the effectiveness of the new method, we performed a theoretical analysis. Twelve groups of on-site directional roof-cutting tests were carried out on SCB and SCHB for comparison in a coal mine. The results showed that, although both blasting methods achieved the goal of directional roof cutting for noncoal pillar mining, SCHB had greater blasting power and produced 8% higher crack rate than SCB for the same charge amount. SCHB required 12.5% less charge than SCB when the crack rate was basically the same. SCHB effectively reduced the concentration of CO. The maximum concentration of CO was reduced by 22–62% compared with SCB. The maximum concentration decreased parabolically with the monitoring distance. In addition, water can absorb high temperature and inhibit sparks from blasting, so SCHB can prevent gas explosions. Therefore, SCHB is an environmental, safe, and economical method of directional roof cutting, which has wide applications in mining and geotechnical engineering. 1. Introduction Noncoal pillar mining does not need to manually or mechan- ically dig into the roadway. It automatically forms a roadway when coal is mined from the previous working face by roof cutting. It is known as the “the third mining science innova- tion” in China [1]. Directional roof cutting is one of the core technologies of this novel coal mining method. The principle of this method is shown in Figure 1. Directional rock-breaking methods include soundless chemical demolition agents, water jets, directional hydraulic fracturing, slot hydraulic blasting, and shaped charge blasting (SCB). Soundless chemical demolition agents have been tested in the laboratory, and they can break the rock direc- tionally [2, 3]. However, the demolition agents have the disadvantages of long reaction time [4], low power, and being easily affected by external temperature [5]. Therefore, it is not applied in directional roof cutting. The water jet can be pre- cisely oriented to cut the roof, but it is difficult and time- consuming to fix the nozzle with this method. Directional hydraulic fracturing involves creating a groove in the bore- hole and then performing hydraulic fracturing [6–8]. To a certain extent, it can be oriented to precrack the roof, but the technology has a limited range of crack orientation exten- sion. After the crack has spread along the prefabricated slot for a distance, the direction of crack propagation is controlled by the magnitude and direction of the in situ stresses. Slot hydraulic blasting uses a water jet to cut a slot of a certain Hindawi Geofluids Volume 2021, Article ID 5511081, 20 pages https://doi.org/10.1155/2021/5511081