Mining-Induced Failure Criteria of Interactional Hard Roof Structures: A Case Study

Abstract

Due to the additional abutment stress, interactional hard roof structures (IHRS) affect the normal operation of the coal production system in underground mining. The movement of IHRS may result in security problems, such as the failure of supporting body, large deformation, and even roof caving for nearby openings. According to the physical configuration and loading conditions of IHRS in a simple two-dimensional physical model under the plane stress condition, mining-induced failure criteria were proposed and validated by the mechanical behavior of IHRS in a mechanical analysis model. The results indicate that IHRS, consisting of three interactional parts-the lower key structure, the middle soft interlayer, and the upper key structure-are governed by the additional abutment stress induced by the longwall mining working face. The fracture of the upper key structure in IHRS can be explained as follows: Due to the crushing failure, lower key structure, and middle soft interlayer yield, the action force between the upper and lower key structures vanishes, resulting in fracture of the upper key structure in IHRS. In a field case, when additional abutment stress reaches 7.37 MPa, the energy of 2.35 × 10 5 J is generated by the fracture of the upper key structure in IHRS. Under the same geological and engineering conditions, the energy generated by IHRS is much larger than that generated by a single hard roof. The mining-induced failure criteria are successfully applied in a field case. The in-situ mechanical behavior of the openings nearby IHRS under the mining abutment stress can be clearly explained by the proposed criteria.

Determination of the key parameters of high‐position hard roofs for vertical‐well stratified fracturing to release strong ground pressure behavior in extra‐thick coal seam mining

“…The excavation of a fully mechanized top-coal caving face in an extra-thick coal seam redistributes the stress around the stope, and the overlying strata movement will form large and small structures above the stope ( Figure 2). 34,35 After the HHRs in the large structure break, their weight and the follow-up rock load (q) are transmitted to the coal wall and the hydraulic support through the lower roof. The hydraulic support and the coal wall share the roof rock mass and transfer load (F L ) in the small structure of the stope.…”

“…Theoretically, smaller values of h c are preferable. However, considering the construction efficiency, engineering effort, and cost input, the reasonable HHR fracturing thickness can be obtained by simultaneous consideration of equations (34)(35)(36) once the relevant parameters have been determined.…”

Method of Entry Layout under Synergistic Effects of Abutment Stress and Dynamic Stress

“…e loading stress mainly consists of original stress, abutment stress, and dynamic stress [7][8][9]. e abutment stress is the loading effect of the overburden rocks' weight above the worked-out area on the rock around the workedout area, which always results in the increasing of the stress in the rock [10].…”

Study on Rule of Overburden Failure and Rock Burst Hazard under Repeated Mining in Fully Mechanized Top-Coal Caving Face with Hard Roof

“…Based on the theory of key strata and rock control, combined with the law of mechanical load and energy conservation in the system, the mechanism of rock burst induced by key strata of thick and hard roof is revealed [3]. By analyzing the failure mode of the hard roof in physical model, the interaction of hard roof structure is easy to induce the occur of rock burst [4]. Nine different types of rock burst through the statistics of the geostress in the rock burst mining area are summarized [5], which provided a reference for understanding the mechanism of rock burst.…”