Key Takeaways & Executive Findings
- •• A novel SICMUR framework is proposed where the coal seam itself serves as the reservoir floor, challenging conventional CMUR designs. • Triaxial tests show a 3.5 MPa strength increase per 100 m depth and a 58-fold post-peak permeability surge at 300 m vs. 100 m, highlighting depth-dependent behavior. • Similar simulations reveal significant mining-induced stress redistribution and deformation, with a minimum 40 m safety distance required between reservoirs and lower coal seams. • Critical construction parameters for Wudong mine SICMUR include collapse zone heights of 9.9–12.31 m and water-conducting fracture zone heights of 31.96–37.40 m.
Abstract
Coal mine underground reservoir (CMUR) technology mitigates water scarcity in China’s coal-rich western regions but lacks tailored solutions for steeply inclined coal seams. This study develops a novel framework of steeply inclined coal mine underground reservoirs (SICMUR), which is a paradigm shift from conventional CMUR that the coal seam itself serves as the reservoir floor, challenging conventional designs due to depth-dependent permeability and mechanical constraints. Triaxial mechanical-seepage tests on Xinjiang Wudong coal samples (100, 200, 300 m depths) revealed a 3.5 MPa triaxial strength increase per 100 m depth and a 58-fold post-peak permeability surge at 300 versus 100 m. Similar model simulations revealed mining-induced stress redistribution and significant deformation effects, particularly subsidence and water-conducting fractures during lower coal seam mining. Results indicate a minimum 40 m safety distance between reservoirs and lower coal seams. Critical construction parameters were investigated for Wudong mine SICMUR as collapse zone heights (9.9–12.31 m) and water-conducting fracture zone heights (31.96–37.40 m). This work systematically bridges SICMUR concepts to field implementation, offering a framework for water preservation in steeply inclined mining while addressing safety concerns, providing a new approach for water reservation in steeply inclined coal mining.
1. Introduction
Xinjiang holds an estimated 2.19 trillion tons of recoverable coal reserves, accounting for over 40% of China’s total estimated reserves. In Xinjiang, the coal seams in mining present several geological challenges. They are typically shallow (with coalbed methane resources below 2000 m amounting to 7.5 trillion m3, about one-quarter of the national total [1]), thick (average cumulative coal-bearing strata in northern Xinjiang exceed 20–40 m [1,2]), and steeply inclined (these seams account for over 30% of the world’s steeply inclined coal seam reserves [3]). Given the shallow depth and large thickness of the seams, as well as the scarcity of water resources, underground mining poses severe challenges to ecological protection. Balancing coal extraction with water conservation is crucial for achieving sustainable green mining practices throughout the Xinjiang coal mining lifecycle.
The current technologies for protecting water resources in coal mining primarily encompass two categories: Water-preserving coal mining methods and underground water reservoir systems in coal mines. Water-preserving coal mining technologies have evolved significantly since the 1950s when Soviet scholar A.H. PiuH first applied continuum mechanics theory to model overburden subsidence [4]. UK researchers Berry and Sales [5] later extended this work in the 1960s by exploring displacement in planar and three-dimensional rock strata. By the 1980s, Polish researchers, including Knothe and Litwiniszyn [6], achieved 20%–30% subsidence reduction using backfill materials and grouting techniques. In China, researchers have also contributed to this field, but the unique challenges of steeply inclined seams require innovative solutions.
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Ersheng Zha, Hongfei Duan, Mingbo Chi, Jiulin Fan, Jianjun Hu, Baoyang Wu, Cong Yu, Jiancheng Tong (2025). Depth-dependent mechanical-seepage behavior and safety mining distance of the steeply inclined coal mine underground reservoir. SinoTechIntel Verified Research. https://doi.org/10.1016/j.ijmst.2025.07.006
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Frequently Asked Questions
What is a steeply inclined coal mine underground reservoir (SICMUR)?
SICMUR is a novel framework for water storage in steeply inclined coal seams, where the coal seam itself serves as the reservoir floor, differing from conventional CMUR designs.
How does depth affect the mechanical and seepage properties of coal in SICMUR?
Triaxial tests on coal samples from 100, 200, and 300 m depths showed a 3.5 MPa increase in triaxial strength per 100 m depth and a 58-fold increase in post-peak permeability at 300 m compared to 100 m.
What is the recommended safety mining distance for SICMUR?
The study indicates a minimum safety distance of 40 m between the reservoir and lower coal seams to prevent water-conducting fractures from compromising the reservoir.
What are the critical construction parameters for SICMUR at Wudong mine?
The collapse zone height ranges from 9.9 to 12.31 m, and the water-conducting fracture zone height ranges from 31.96 to 37.40 m, which are essential for designing safe reservoir dimensions.
How does SICMUR contribute to water preservation in coal mining?
SICMUR provides a framework for storing water in steeply inclined coal mines, mitigating water scarcity in arid regions while addressing safety concerns, thus promoting sustainable green mining.
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