Evaluation of the Effect of Fault on the Stability of Underground Workings of Coal Mine through DEM and Statistical Analysis

Abstract

The rock mass around an excavation is generally traversed by different geological discontinuities such as faults, folds, slips, joints, etc. Fault is one of the major geological discontinuities which creates lot of difficulties during underground winning of coal. Entire stress regime and ground conditions in the formation are altered in and around the faults. Faults also impose detrimental effects by introducing impurities, including clay and various forms of mineral matter into the coal seams; opening of pathways for the influx of water and gas into the underground workings; displacing the coal seams upward/downwards making the coal seams difficult or sometimes impractical to mine. Appropriate evaluation of the effect of the fault on the stability of the underground workings is a requisite for safe design of the underground mining structures. In this paper, a study has been carried out to assess the effect of the fault on the stability of underground coal mines by numerical simulation with distinct element method (DEM). On the calibrated DEM model, parametric study has been performed by varying the selected parameters, the dip and the friction angles of the fault. The analysis of variance (ANOVA) shows that both the factors have statistically significant effect on the strength of the coal pillar. Similarly, the displacement of the immediate roof and the height of the disturbed strata are evaluated by the DEM modelling and statistical analysis when the fault passes through the middle of the gallery. The results of ANOVA for both cases indicate that the both factors have significant effect on the displacement of the immediate roof and the height of the disturbed strata. It is obtained from the study that the low angle fault causes high instability in the immediate roof. The paper has been supplemented with the field observations where instability in underground roadways of a coal mine in India is caused by the fault. It was observed in VK-7 incline mine of Singareni Collieries Company Limited, India that there was sudden failure of immediate roof of a roadway where a low angle fault crosses the middle of the roadway. The findings of the paper help to understand the behaviour of the coal pillar and the surrounding rock mass in the presence of the fault. The study would also help to take appropriate decisions about the unstable regions of the working safeguarding safety in underground coal mines.

Constitutive model of rock triaxial damage based on the rock strength statistics

“…The rock is a natural underground engineering material and formed under the natural environment, resulting in complex internal structures and some internal defects (Cai et al, 2018;Das et al, 2018; Figure 8. The peak point stress under different stress.…”

Quantitative Evaluation for the Threat Degree of a Thermal Reservoir to Deep Coal Mining

“…According to a certain scale, the study area is into several square blocks, and the blocks containing faults are counted and numbered. For block i, first divide it according to the Minquan County 6 Geofluids magnification of scale r = 1/2, and count the number of block segments containing fault trajectories N ð1/2Þ; further, divide it according to the scale r = 1/4, 1/8, 1/16 ⋯ , and count the number of blocks N ðrÞ containing fault trajectories. Then, the fitting straight line equation of lg ðrÞ and lg NðrÞ can be constructed, and the slope of the line is the fault fractal dimension D of block i.…”

“…Many scholars have carried out a series of research works on the problem of coal seam roof disasters. The theories and methods formed mainly include the "upper three zones" theory [1][2][3], the "key layer" theory [4], the "three maps-double prediction method" [5], the mathematical comprehensive evaluation method [6], and the numerical simulation method [7]. Among them, the "upper three zones" theory is the most widely used, and the corresponding empirical formula calculation guides the prediction, evaluation, and prevention of a coal seam roof water inrush [8,9].…”

Discrete Element Simulation of Fracture Evolution around a Borehole for Gas Extraction in Coal Seams

“…In recent years, numerical simulation often has been used in the study and analysis of fracture propagation in rock materials, such as in scanning electron microscopy (SEM), atomic force microscopy (AFM), , extended finite element method (X-FEM), boundary element method (BEM), , and cellular automata (CA) . Discontinuous medium methods, such as DEM (discrete element method), , rock failure process analysis system (RFPA), , and universal distinct element code (UDEC), have also been used. , In these numerical methods, DEM is often used to simulate the mechanical behavior of some rock materials. On the basis of the principle of DEM, PFC 2D (particle flow code) has been greatly developed.…”