Abstract
The fully mechanized mining with large mining height is the main method for high yield and efficient coal mining in China. The key stratum structure (KSS) is the basis of revealing the mechanism of roof weighting and determination of support working resistance of the longwall face with large mining height (LFLMH) in the shallow coal seam. The height of the caving zone at LFLMH is large, the thick immediate roof forms the “short cantilever beam” structure commonly, and the hinge layer of the overlying key stratum will move upward to the higher position. The “high position oblique step voussoir beam” structure of single-key stratum (SKS) and “oblique step voussoir beam and voussoir beam” structure of double-key stratum (DKS) in the shallow coal seam were proposed with physical simulation and Universal Distinct Element Code (UDEC). The analysis of the KSS and numerical simulation reveals the mechanism of strong roof weighting at the SKS longwall face and large-small alternate periodic weighting at the DKS longwall. It is concluded that the large static load caused by the “equivalent immediate roof (EIR)” is the basic load, and the instability load of the KSS is the additional dynamic load of support. Besides, the calculation methods of the reasonable support working resistance at LFLMH were obtained and verified with engineering applications.
Highlights
Numerical Simulation of the key stratum structure (KSS)E No 15201 longwall face with large mining height (LFLMH) (LW15201) at Zhangjiamao coal mine and the No 22303 LFLMH (LW22303) at Bulianta coal mine are taken as the background to study the overlying strata structure and mechanism of roof weighting at LFLMH in the shallow coal seam
Ju and Xu have analyzed the structural characteristics of key stratum and strata behavior of the longwall face with super large mining height [18] and proposed the “cantilever beam and voussoir beam” structure, which leads to the alternating roof pressure [19]
High position oblique step voussoir beam structure; R1 is the force on the equivalent immediate roof (EIR) from the block M, kN; R2 is the weight of the “short cantilever beam,” kN; R3 is the weight of caving EIR, kN; Pm is the support load, kN; A, B, and C are the hinge point of the key blocks
Summary
E No 15201 LFLMH (LW15201) at Zhangjiamao coal mine and the No 22303 LFLMH (LW22303) at Bulianta coal mine are taken as the background to study the overlying strata structure and mechanism of roof weighting at LFLMH in the shallow coal seam. E UDEC numerical models were established with the Mohr–Coulomb failure criterion to study the overlying strata structure during the advance of the longwall face. Mohammad et al [35] have suggested that the stiffness of the numerical model should be equal to 0.47 times the average stiffness value of the laboratory tests. Erefore, the elastic modulus and tensile strength of coal and rocks are equal to Physical simulation experiment of roof structure of large mining height in the shallow coal seam (1 : 50) Cai et al [36] have suggested that the elastic modulus of coal and rocks should be 0.1 to 0.25 times that of the laboratory tests, while Poisson’s ratio of coal and rocks is assumed to be 1.2 to 1.4 times that of the laboratory tests. erefore, the elastic modulus and tensile strength of coal and rocks are equal to Physical simulation experiment of roof structure of large mining height in the shallow coal seam (1 : 50)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
