Discrete element modeling of progressive failure in a wide coal roadway from water-rich roofs

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.

“…K and G are, respectively, bulk modulus and shear modulus of rock. The formulas for K and G are as follows:

K = \frac{E}{3 (1 - 2 μ)}

G = \frac{E}{2 (1 + μ)}

E and μ are the modulus of elasticity and Poisson's ratio in the rock, respectively.…”

Section: The Deformation and Failure Mechanismmentioning

confidence: 99%

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

“…The stratigraphic column of LW15104 is shown in Figure 9. 37 Therefore, several numerical simulation experiments have been solved to study the quantitative relationship between working face mining speed and calculation steps for model after each advancing a certain distance. Finally, the working face advancing speed can be represented as calculation steps for the model after each advance of a certain distance in UDEC numerical calculations, namely, the faster the working face advanced, the fewer corresponding calculation steps for model after each advance over a certain distance.…”

Section: Determination Of Simulation Parametersmentioning

confidence: 99%

Determination of working resistance based on movement type of the first subordinate key stratum in a fully mechanized face with large mining height

Zou

2019

The increase in extraction height will increase the mining‐induced overlying strata failure height. In this scenario, the strata pressure behavior is strong in a fully mechanized face with large mining height (FMFLMH), which frequently causes coal wall falls, roof falls, and hydraulic support failure accidents (e.g., support closure and hydraulic column damage). The key to solving these issues is to determine support's working resistance of the FMFLMH. In this paper, comprehensive theoretical analysis, numerical simulation, and field observation were applied to determine the support's working resistance in the FMFLMH based on movement type of the first subordinate key stratum (SKS 1). First, six kinds of movement types of SKS 1 in the FMFLMH are found and defined by theoretical analysis and numerical simulation, which are the direct caving movement type of cantilever structure (direct caving), the double‐sided rotation movement type of cantilever structure (double‐side rotation), the quadratic rotation movement type of cantilever structure (quadratic rotation), the alternative movement type of cantilever structure hinged structure (alternate hinged), the voussoir beam structure movement type (voussoir), and the short voussoir beam structure movement type (short voussoir), respectively. Besides, based on this, the support load calculation model of each movement type was established, and a formula for the support working resistance of each movement type was obtained. Finally, the correctness of the formulae for the support working resistance under six types of movement of SKS 1 were verified using measurement data from four FMFLMHs in China. These research results have important guiding significance for reasonable selection of support and ensuring safe mining of the FMFLMH.

“…5,6 To date, many scholars have carried out extensive research on burnt rocks. Under the influence of roadway excavation, the surrounding rock instability problem such as severe deformation of surrounding rock, failure of supporting structure, and increase of roofing probability is very prominent, and it has become an important problem hindering safety and efficient production of mines.…”

Section: Introductionmentioning

confidence: 99%

The effect of burnt rock on inclined shaft in shallow coal seam and its control technology

Yuan

Liu

Zhu

et al. 2019

Burnt rock is a geo‐material widely existed in many countries. After the rock mass is burned, the fracture is developed, the structure is destroyed, the integrity and strength are reduced, and a good water storage space is formed in suitable hydration conditions. In this paper, the roof fall characteristics and failure mechanism of inclined shaft in shallow water‐rich burnt rock area (SWRBRA) are analyzed using theoretical analysis, numerical simulation, and field measurement. It is revealed that the main factors causing the instability of surrounding rock on inclined shaft in SWRBRA are the deterioration of structure and integrity after rock mass is burnt, the weakening of surrounding rock strength under the action of fissure water, and the lagging support method. Therefore, the key measure to control the stability of surrounding rock in SWRBRA is to block cracks to eliminate the weakening effect of water and advance reinforcement to improve the surrounding rock strength. Through the comprehensive technologies such as rear roadway reinforcement, filling, and rebuilding artificial false roof and pipe shed advanced support, the effective restoration of the roof fall area in SWRBRA is realized. The surrounding rock fractures were closed, the strength of surrounding rock is improved by means of grouting reinforcement, and the stability control of surrounding rock of inclined shaft in SWRBRA is achieved.