Cooperative load‐bearing characteristics of a pillar group and a gob pile in partially caved areas at shallow depth

Abstract

Stress concentration in partially caved goaf is the main cause of dynamic pressure accident in the lower seam mining. Aimed at the characteristics of caving in shallow partially caved goaf (PCG) and the specificity of interior load‐bearing structures, a classification criterion of goaf caving was proposed. The characteristics of cooperative load‐bearing in pillar group and gob pile were revealed by numerical calculation, physical simulation, and theoretical analysis. Taking intermittent mining as an example, combined with the deformation behaviors of the main roof and the loading characteristics of waster rock mass, the characteristics of the load‐bearing of gob piles were described in the form of a piecewise function. A FLAC3D model of intermittent mining is modeled to evaluate the stability of pillars, the long‐term stability and distribution laws of overlying loads were revealed through a refined model. The results show that the width of the caved zone bearing the load in the intermittent goaf is about 20 m, and the maximum load‐bearing capacity is 1.055 MPa. The maximum depth of the plastic region in one side of the pillar is 1.48 m, and the load on elastic zone is about 11.33 MPa. This study provides a method for the study of the caving characteristics and load uncertainty in PCG, and the results provide important theoretical values for the safe mining of lower coal seams.

Depressurizing boreholes for mitigating large deformation of the main entry

“…The applicability of the criterion to other roadways, whose instability is mainly attributed to the retreat of longwall panels, needs further investigation. This is because longwall-affected roadways may experience different failure mechanism, [43][44][45][46][47] comparing to the roadway failure caused by high in situ stress condition.…”

Influence of supercritical, liquid, and gaseous CO2 on fracture behavior in sandstone

“…Shanxi has the largest coal bed methane reserves, accounting for 91.5% of the national total. [20][21][22] Rock is damaged and destroyed to varying degrees under the influence of geological processes such as in situ stress, [23][24][25][26] temperature, 27,28 and hydrochemical corrosion. 29 For example, Ma et al 29 used the Forchheimer coefficient as an index to investigate the influencing mechanism of erosion on the nonlinear hydraulic properties of the broken red sandstones.…”

Evolution of mining‐induced stress in fully mechanized top‐coal caving under high horizontal stress

“…Furthermore, the magnitude and direction of the principal stresses around the stoping roadways caused by the traditional long‐wall mining and fully mechanized caving were analyzed by employing numerical simulation with finite difference . By using a numerical simulation, the mining‐induced stress field in fully mechanized caving of coal seams with different thicknesses was studied and main characteristics of stress evolution and danger zones were expounded . The range of influence and evolution of vertical stress were obtained through field measurement of vertical stress in the top‐coal in Tashan Coal Mine, Shanxi Province .…”