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Study on Gas Occurrence Characteristics and Prevention Technology for
Tunnels in Natural Gas-bearing Sandstone Formation
(1. The Second Engineering Co., Ltd. of China Railway 18th Bureau Group, Fengrun 064000; 2. School of Geoscience and Technology,Southwest Petroleum University, Chengdu 610500)
Abstract In order to solve the technical problems that gas emission and gas pressure is difficult to be predicted
quantitatively, and the spark induced by cutting surrounding rock may ignite gas during the milling excavation of horizontal natural gas-bearing sandstone formation in hydraulic tunnels, based on the analysis of geological identification and the characteristics of occurrence and migration of natural gas-bearing sandstone formations in Muzhuzhai tunnel of Tingzikou water diversion project, comprehensive prevention and control technologies such as comprehensive detection, directional drilling and discharge, and gas risk control, etc.are proposed. The research shows that: (1)the gas concentration in the borehole is as high as 80%, the gas pressure is 0.62 MPa, and the gas emission in the borehole is about 30 L/min. It shows that there is pressurized gas in the natural gas-bearing sandstone formation,and abnormal emission is easy to occur after the fracture is connected. (2) Within the discharge range of 35 m in front of the tunnel face and 15 m on the side wall of the tunnel, Ф89 mm gas discharge boreholes shall be arranged in the natural gas-bearing sandstone formation according to the effective emission radius of 3.2 m and the spacing
between the holes at the bottom of 4.5 m. After discharge, the residual gas pressure is less than 0.15 MPa, the gas emission at the working face is 0.24 m3/min, with the gas emission reaching the expected goal. (3) During the gas discharge operation, through the environmental safety monitoring at the working face, the review and determination of ventilation capacity, and the grouting and sealing of the discharge holes after the completion of gas discharge, the safety operation of drilling and gas discharge is realized.
Abstract：
In order to solve the technical problems that gas emission and gas pressure is difficult to be predicted
quantitatively, and the spark induced by cutting surrounding rock may ignite gas during the milling excavation of horizontal natural gas-bearing sandstone formation in hydraulic tunnels, based on the analysis of geological identification and the characteristics of occurrence and migration of natural gas-bearing sandstone formations in Muzhuzhai tunnel of Tingzikou water diversion project, comprehensive prevention and control technologies such as comprehensive detection, directional drilling and discharge, and gas risk control, etc.are proposed. The research shows that: (1)the gas concentration in the borehole is as high as 80%, the gas pressure is 0.62 MPa, and the gas emission in the borehole is about 30 L/min. It shows that there is pressurized gas in the natural gas-bearing sandstone formation,and abnormal emission is easy to occur after the fracture is connected. (2) Within the discharge range of 35 m in front of the tunnel face and 15 m on the side wall of the tunnel, Ф89 mm gas discharge boreholes shall be arranged in the natural gas-bearing sandstone formation according to the effective emission radius of 3.2 m and the spacing
between the holes at the bottom of 4.5 m. After discharge, the residual gas pressure is less than 0.15 MPa, the gas emission at the working face is 0.24 m3/min, with the gas emission reaching the expected goal. (3) During the gas discharge operation, through the environmental safety monitoring at the working face, the review and determination of ventilation capacity, and the grouting and sealing of the discharge holes after the completion of gas discharge, the safety operation of drilling and gas discharge is realized.
HAO Junsuo1 ZHANG Xiangbing1 WANG Shiguang1 CHU Xiaojin1 SU Peidong2
.Study on Gas Occurrence Characteristics and Prevention Technology for
Tunnels in Natural Gas-bearing Sandstone Formation[J] MODERN TUNNELLING TECHNOLOGY, 2025,V62(2): 241-253
2025, Vol. 62 