Ground Response and Mining‐Induced Stress in Longwall Panel of a Kilometer‐Deep Coal Mine

Abstract

In order to improve ground control of the longwall mining, ground response and mining-induced stress in the longwall panel of a kilometer-deep coal mine are investigated in this study. Field measurements on abutment stress, roof displacement, and fracture development indicate that the region influenced by the longwall mining reaches 150 m ahead of the longwall face. Failure scope of the coal seam, where mining-induced fractures are well developed, ranges from 10 to 13 m inward the face line. Vertical stress concentration coefficient reaches 2.2. Based on the field measurements, a numerical model is moreover developed and utilized to examine the response of the principal stress to the longwall mining. The concentration coefficient, peak point location, and influence scope of the principal stress gradually become stable with an increase in face advancement. Regarding the major principal stress, the concentration coefficient and influence scope are 2.4 and 152 m, respectively, and the peak point locates 13 m inward the face line, which are consistent with the field measurements. With respect to the minor principal stress, the referred coefficient and scope are 1.5 and 172 m, respectively, and its peak point location is 21 m ahead of the face line. The major principal stress in the coal seam rotates from vertical to horizontal direction in the vertical plane parallel with face advance direction. The maximum rotation angle reaches 20°. The minor principal stress first rotates into the referred vertical plane and then it rotates from horizontal to vertical direction at the same speed with the major principal stress in the same plane. Rotation angle of the principal stress in roof strata is greatly enlarged, the rotation trace of which is influenced by the longwall mining and vertical distance above the seam. Based on the relation between rotation trace of the principal stress and face advance direction, the influence of stress rotation on the stability of roof structure is discussed.

Research Development and Critical Problems Existing in Strata Movement and Its Control

“…The movement of the strata causes a concentration of advanced mining stress while also causing the mining stress to deviate from its original direction, called mining stress rotation. The rotation trajectory of the mining stress is controlled by the workface advance direction, and eventually rotates to a vertical plane parallel to the direction of the advance, tilted toward the mining void area in that direction and tending to tilt toward the roadway space, as shown in Figure 5 [41,[50][51][52][53].…”

Evolution Mechanism and Control of Floor Heave in the Deep Roadway with Retained Bottom Coal

“…With the development of deeper coal resources in recent years [1][2][3], the buried depth of roadways has been increasing. Deep roadways account for 30% of the roadways excavated every year in China, of which 70% need to be repaired due to large deformations, greatly increasing production costs [4].…”