Key Takeaways & Executive Findings
- •• Weathering and oxidation significantly degrade the strength and increase plastic deformation of coal-rock masses, compromising structural stability. • Mining-induced stress redistribution creates concentration zones ahead of the coal wall and at face ends, leading to roof and rib failures. • Overlying strata exhibit four distinct deformation-failure stages: bed separation, immediate roof fracture, main roof fracture, and high-level strata collapse. • The findings provide a scientific basis for safe and efficient mining in weathered and oxidized zones, guiding support design and roof management.
Abstract
Affected by the depositional environment, coal seams in the weathered and oxidized zone and their overlying strata are characterized by developed fractures and poor self-stability, leading to difficulties in roadway and working face roof management. This paper analyzes the failure characteristics of coal-rock masses in this zone. Combined with model tests and numerical simulation methods, it investigates the stress distribution status, deformation-failure characteristics, and movement-fracture laws of the overlying strata in a fully mechanized top-coal caving working face. The results indicate: (1) Weathering and oxidation significantly degrade strength and increase plastic deformation in coal-rock masses; (2) Under mining-induced disturbance, overlying strata stress is released from the in-situ state and sharply reduced, forming stress concentration zones ahead of the coal wall and at face ends; (3) During mining, fractures propagating upwards from the coal wall trigger rib spalling and top-coal collapse, forming combined cantilever and articulated rock beam structures. The overlying strata sequentially undergo four deformation-failure stages: "bed separation, immediate roof fracture, main roof fracture, and high-level strata collapse". The research findings can provide a basis for the safe mining of fully mechanized top-coal caving faces in weathered and oxidized coal.
1. Introduction
Under the influence of wind oxidation, coal-rock masses in wind oxidation zones exhibit well-developed joints and fractures, with rocks displaying loose and fragmented characteristics and containing clay minerals prone to water-induced softening and expansion. These unique geological conditions significantly reduce the structural stability of rock masses and cause systematic degradation of mechanical parameters, such as shear strength and cohesion.
Under such geological conditions, overburden migration demonstrates dynamic behaviors markedly distinct from those in conventional mining areas. Notably, as a typical geohazard, jointing of the overlying strata shows a marked tendency to intensify within wind oxidation zones, characterized by significantly enhanced fracturing activities and continuously expanding migration ranges [1−3]. These geomechanical responses severely compromise coal mine safety and extraction efficiency while posing multifaceted threats to the ecological environment of mining areas [4−6].
In response, numerous scholars have dedicated efforts to investigating the anomalous properties of coal-rock in wind oxidation zones, aiming to provide scientific foundations for managing such strata. Current research on the migration mechanisms of overburden in wind oxidation zones has achieved preliminary progress. ZHU et al [7] focused on the 13116 working face in the wind oxidation zone of Gubei coal mine, analyzing rock weathering-oxidation characteristics. They proposed a power-law ultrafine cement grouting reinforcement technology incorporating time-dependent rheological parameters, achieving favorable engineering outcomes. TIAN et al [8] employed scanning electron microscopy (SEM) and X-ray diffraction (XRD) to examine the microstructural morphology and material composition of coal-rock masses in wind oxidation zones. Their study revealed anomalous evolution characteristics under weathering-oxidation conditions, leading to the development of a coupled support technology for roadways that significantly improved surrounding rock control. ZHAO et al [9], KHORASANIPOUR et al [10], and ZHOU et al [11] collected rock samples from diverse strata within wind oxidation zones through field investigations. Their work systematically characterized the physico-mechanical properties of weathered-oxidized rock masses, complemented by SEM and XRD analyses of microscopic textures and mineral assemblages across rock types.
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TIAN Mao-lin, YANG Cheng, CHEN Shao-jie, YIN Da-wei, ZHOU Yuan, ZHANG An-fu, WANG Jia-bao (2026). Research on movement and fracture laws of overlying strata in fully mechanized top-coal caving faces within shallow-buried weathered and oxidized zones. Journal of Central South University. https://doi.org/10.1007/s11771-026-6295-1
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Frequently Asked Questions
What are the main characteristics of coal-rock masses in weathered and oxidized zones?
Coal-rock masses in these zones exhibit well-developed joints and fractures, loose and fragmented rock structures, and contain clay minerals that are prone to water-induced softening and expansion. These features significantly reduce structural stability and degrade mechanical parameters such as shear strength and cohesion.
How does mining affect stress distribution in overlying strata of weathered and oxidized zones?
Mining-induced disturbance causes stress release from the in-situ state, leading to sharp reductions and the formation of stress concentration zones ahead of the coal wall and at face ends. This stress redistribution contributes to roof and rib failures.
What are the four deformation-failure stages of overlying strata in fully mechanized top-coal caving faces?
The overlying strata sequentially undergo four stages: bed separation, immediate roof fracture, main roof fracture, and high-level strata collapse. These stages describe the progressive failure process under mining conditions.
What methods were used in this study to investigate overburden movement and fracture laws?
The study combined model tests (similarity simulations) and numerical simulation methods to analyze stress distribution, deformation-failure characteristics, and movement-fracture laws of overlying strata in a fully mechanized top-coal caving working face.
What is the practical significance of this research for coal mining?
The findings provide a scientific basis for safe mining in weathered and oxidized zones, helping to guide support design, roof management, and the prevention of geohazards such as rib spalling and top-coal collapse, thereby improving extraction efficiency and safety.
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