Mechanism and salvage of sand-water mixture inrush induced by roof falling in deep coal roadway

A serious sand-water mixture inrush occurred during the construction of a return air subinclined roadway buried 880 m underground in the Wanfu Coal Mine, Shandong province, China. The maximum flow rate of sand-water mixture reached 14 580 m3/h with a total mixture volume of 22 000 m3. The roadway network with a total length of 2 400 m was flooded, causing a casualty and significant economic losses. That is the deepest sand-water mixture inrush disaster known until now. This work analyzes the mechanism of the disaster, proposes i-deas for the prevention and control of the secondary disaster, and discusses the specific salvage plan that was conceived and implemented. Through monitoring of the water level of the main aquifer, sampling, and testing of silted water and sand, and the analysis of geological conditions, it was quickly determined that the main reason of the disaster was the sustained roof fall of the subinclined roadway, and the Neogene bottom sand aquifer with a burial depth of about 750 m and a water pressure of over 7 MPa was forced to connect. In the salvage, the possibility of secondary disasters was analyzed, a safety retaining bulkhead was constructed with underground grouting to effectively prevent secondary disasters of water and sand inrush again and to ensure the safety of underground salvage personnel. Directional drilling and mass grouting in the ground were used to block the pathway of sand-water mixture inrush and reinforce the sand auifer. This study can better the understanding of the importance of geological work in disaster prevention and control of deep underground engineering, which also provides a reference for the disaster prevention and control of sand-water mixture inrush with high potential energy. © 2024 China University of Mining and Technology. All rights reserved.