Structural characteristics of strata overlying of a fully mechanized longwall face: a case study

Layered rocks exhibit notable transverse isotropy and have a significant impact on the deformation and failure characteristics of underground structures. To a large extent, the mechanical properties of layered rocks are related to the structure and stress state of their bedding planes. To obtain an in‐depth understanding of the deformation and yield characteristics of layered rocks, a mechanical model for layered rocks incorporating planes of weakness and volumetric stress is proposed by improving the strain‐hardening/softening ubiquitous‐joint model based on continuum mechanics methods. In this mechanical model, elastoplastic equations for the matrix and bedding planes of layered rocks are established. The evolution of the mechanical parameters of the matrix and bedding planes of layered rocks with the internal variable is determined. In addition, the sensitivity of the model parameters is analyzed, and a method for determining the parameters is provided to reduce the complexity in obtaining these parameters. The numerical calculation results for the laboratory tests on layered sandstone specimens under various stress levels agree relatively well with the test results, thereby validating the effectiveness of the improved model. The methods and results of this study provide a significant reference for the analysis of the deformation and failure of other layered rocks.

Section: Discussionmentioning

confidence: 99%

Section: Parameter Sensitivitymentioning

confidence: 99%

Anisotropic modeling of layered rocks incorporating planes of weakness and volumetric stress

Tan

Zhou

et al. 2019

“…This interaction can be interpreted using the bearing beam analogue, which has been generally accepted as a simplified tool for the analysis of overburden load transfer during underground space development. [40][41][42] Gao et al 43 stated that the strata located in the lower portion of the continuous deformation zone can be considered a bearing beam. This bearing beam complements the "stress arch" developed in the roof above the unmined coal, forming an entire compressive stress arch around the goaf.…”

Section: The Effect Of the Extracted Coal Panel On The Energy Distrmentioning

confidence: 99%

A numerical study of the mining‐induced energy redistribution in a coal seam adjacent to an extracted coal panel during longwall face mining: A case study

Wang

Qiu

Ning

et al. 2019

Mining of the coal seam adjacent to the extracted coal panel is widely practiced in China to improve coal resource recovery rates, but the energy change associated with longwall mining may present a new risk to ground stability and gateroad failure. To understand the energy change effectively, a meticulously validated numerical model, built using FLAC3D software, incorporating a double‐yield model for the gob materials and a strain‐softening model for the coal/rock masses, was developed to investigate the energy redistribution in coal seams and barrier pillars during the process of mining the coal seam adjacent to the extracted coal panel. The model results showed that the closer the region was to the LW 5301 gob, the higher the location and magnitude of the peak strain energy density. Consequently, the risk of rockburst in coal seams was greater than that in barrier pillars. Along the coal seam strike, with increasing advancing distance from the setup room, the magnitude of the peak strain energy density gradually increased to 1.88‐2.78 times the premining energy level. In addition, along the coal seam dip, the maximum distance from the peak strain energy density to the edge of the coal seam was approximately 16‐28 m, which is greater than that in the barrier pillar. The proposed numerical simulation procedure and calibrated method could be a viable alternative approach to evaluate longwall mining‐induced energy changes.

“…The production of thick coal seam accounts for about 50% of China's total annual coal production. Therefore, it is important to exploit thick coal seam resources, especially ultra‐thick mining, for the development of China's coal industry . Due to the high‐strength mining of the ultra‐thick coal seam, the ventilation and transportation requirements are very strict for the main roadway.…”

Section: Introductionmentioning

confidence: 99%

“…Therefore, it is important to exploit thick coal seam resources, especially ultra-thick mining, for the development of China's coal industry. 5,6 Due to the high-strength mining of the ultra-thick coal seam, the ventilation and transportation requirements are very strict for the main roadway. Thus, the section area of those roadways should be generally more than 15 m 23,7 .…”

Section: Introductionmentioning

confidence: 99%

Failure mechanism of the large‐section roadway under mined zones in the ultra‐thick coal seam and its control technology

Tai

Xia

Meng

et al. 2019

Aiming at serious deformation and failure of large‐section coal roadway under mined zones in ultra‐thick coal seam, its deformation and failure characteristics are analyzed based on the field measurement. This paper reveals the mechanism of roadway roof separation, roof leakage, and right rib extrusion. Based on the mechanism, two kinds of secondary support schemes are proposed, that is, “grouting + I‐steel support + bolt” (scheme I) and “grouting + U steel support + anchor + anchor cable” (scheme II). The industrial experiment is carried out at 1070 auxiliary transportation roadway in Tashan Coal Mine. The measured results show that the roadway roof separations of the secondary support scheme I and II are only 1/11 and 1/46 of the original support scheme, respectively, while the lateral displacements of the roadway are only 1/7 and 1/44 of the original support scheme. It could be seen that the deformation and failure of the roadway surrounding rock have been well controlled.