Influence Of Abutment Pressure Research Articles

Research on the Influence of Slurry Filling on the Stability of Floor Coal Pillars during Mining above the Room-and-Pillar Goaf: A Case Study

Room-and-pillar mining is a commonly used mining method in previous practice in northwest China mining area. Due to priority selection of high-quality resources, coal mines in northwest China generally have to face upward mining above goaf. Thus, the stability of a floor coal pillar influenced by mining activities plays an essential role in upward mining above goaf. The results indicated that a floor coal pillar kept stable before coal excavation in the no. 6107 working face in the Yuanbaowan coal mine; however, the plastic zone in the floor coal pillar expanded sharply and the elastic core zone reduced suddenly on the influence of abutment pressure. Finally, the floor coal pillar supported failure. Accordingly, the paper proposed a floor coal pillar reinforcing technique through a grout injection filling goaf area. As physically limited by a different-height filling body on the double sides, the plastic zone scope and horizontal displacement and loading capacity of the floor coal pillar were studied, working out that the critical height of the filling body should be about 6 m which can ensure safe mining when upward mining above goaf. Case practice indicated that the fractures induced by mining in the floor coal pillar, filling body, and floor can be restrained effectively when the filling body height is 6 m, which can ensure floor coal pillar stability and safe mining of the no. 6107 working face in the Yuanbaowan coal mine. The research can provide theoretical and technical guidance for upward mining above goaf and have a critical engineering practice value.

Investigation on the Influence of Abutment Pressure on the Stability of Rock Bolt Reinforced Roof Strata Through Physical and Numerical Modeling

In underground coal mining, high abutment loads caused by the extraction of coal can be a major contributor to many rock mechanic issues. In this paper, a large-scale physical modeling of a 2.6 × 2.0 × 1.0 m entry roof has been conducted to investigate the fundamentals of the fracture mechanics of entry roof strata subjected to high abutment loads. Two different types of roof, massive roof and laminated roof, are considered. Rock bolt system has been taken into consideration. A distinct element analyses based on the physical modeling conditions have been performed, and the results are compared with the physical results. The physical and numerical models suggest that under the condition of high abutment loads, the massive roof and the laminated roof fail in a similar pattern which is characterized as vertical tensile fracturing in the middle of the roof and inclined shear fracturing initiated at the roof and rib intersections and propagated deeper into the roof. Both the massive roof and the laminated roof collapse in a shear sliding mode shortly after shear fractures are observed from the roof surface. It is found that shear sliding is a combination of tensile cracking of intact rock and sliding on bedding planes and cross joints. Shear sliding occurs when the abutment load is much less than the compressive strength of roof.

Field investigation of using water injection through inseam gas drainage boreholes to control coal dust from the longwall face during the influence of abutment pressure

Coal dust is a primary contributor to underground coal-mining disasters and is also a major factor in adversely affecting the occupational health of mine workers. Pre-wetting the coal seam with water injection is widely considered as one of the effective means of mitigating coal dust generation during mining. Injecting water through inseam long boreholes parallel to the working face is a commonly used technique. However, for most fully-mechanised top-coal caving working faces, inseam gas drainage boreholes are drilled to extract gas from the gassy seam prior to mining. Therefore, there is neither enough time nor space at the working site for an elaborated water injection process. Based on the mining conditions at Panel 9801 of the Yangquan coalfield, this study designed a water injection system through the inseam gas drainage boreholes to control dust arising from the longwall face. Under the influence of abutment pressure, water injection through a set of inseam gas drainage boreholes was experimentally investigated to offset the conflict between water injection and gas drainage in terms of the time and space availability. The relations between the amount of injected water, the injection rate, the seam moisture content and the coal dust level at the working space were investigated. The effect of water injection for dust control at different distances ahead of working face was assessed. With the change of abutment pressure, the effect of water injection to inseam gas drainage and gas emission at working face was revealed and a space-time balance between gas drainage and dust control by water injection was established. The results indicate that under the influence of abutment pressure, water injection through inseam gas drainage boreholes wetted the seam and decreased the dust level at the working face. Water injection only has marginal influence on inseam borehole drainage and has a negligible impact on the gas level produced at the working face. Under the influence of abutment pressure, the optimum area for water injection through the inseam boreholes was the primary fracture opening zone and the secondary fracture development zone.

Reasonable Entry Layout of Lower Seam in Multi-Seam Mining Based on Numerical Simulation

Based on the geological conditions of 6# coal seam and 8# coal seam in Xieqiao Coal Mine, to determine reasonable entry layout of lower seam in multi-seam mining, alternate internal entry layout, alternate exterior entry layout and overlapping entry layout were put forward and simulated by FLAC3D. Then stress distribution and displacement characteristics of surrounding rock were analyzed in the three ways of entry layout, leading to the conclusion that alternate internal entry layout is a better choice for multi-seam mining, for which makes the entry located in stress reduce zone and reduces the influence of abutment pressure of upper coal seam mining to a certain extent,. And the mining practice of Xieqiao Coal Mine tested the results, which will offer a beneficial reference for entry layout with similar geological conditions in multi-seam mining.