Accident Analysis in Relation to Main Roof Structure When Longwall Face Advances toward a Roadway: A Case Study

Practices show that hydraulic supports crushing accidents or roadway supports failure often take place when a longwall face advances toward an abandoned roadway or a predriven equipment recovery room. Therefore, a 2D similar simulation experiment is conducted to reveal the loading mechanism. The result shows that when the workface advances close to roadways, the main roof breaks ahead of the workface and leads to instability of higher strata. These two changes induce a sharp increase of the load on supports and lead to an accident. Thus, more attention should be paid to the advanced fracture. Therefore, mechanical analysis is used to explain the advanced fracture. Results show that the failure of coal pillar being excavated induces a sharp increase in the main roof’s hanging length. Once the hanging length reaches the limit, the advanced fracture takes place. Therefore, the stability of the coal pillar and the hanging length of roof strata are two key factors that may induce an accident. To prevent the a similar supports crushing accident, the partial backfilled technology which partly backfills the abandoned roadway in height and length to maintain the stability of the coal pillar is put forward and put into practice. The field test shows a good effect.

Study on Failure Characteristic Simulation of Seam Floor for Coal Mining above Confined Aquifer Based on Fluid-Solid Coupling Theory

Water inrush is one of the main types of coal mine water disaster. Based on fluid-solid coupling theory, the confined water inrush numerical model is performed using FLAC3D program and similar simulation experiment, and the floor damage field and confined water vector field are simulated. The results show that, in the coupling action of mining stress and pressure of confined water, the mining floor was divided into four zones, namely the mining damage zone, effective confining protection zone, confined water soil-fluid coupling lifting zone, original confined water lifting zone. Confined water-conductive zone with the periodic roof pressure fluctuate, at each pressure and flowing zone height reaches the maximum, rise with height remained unchanged, the distribution shape of a "wave", water inrush is the results of effective connectivity of mining damage zone and Confined water-conductive zone, plate thickness of water-resisting layer exists or not, waterproof performance and the pressure of confined water inrush size is the key

The Deformation and Failure Characteristics Research of the Roof Rocks in Anchorage Areas

Aiming at the problems that local roof falls during the roadway driving, similar simulation experiment and numerical analysis experiment is designed to compare and analysis the deformation and failure characteristics in anchorage areas for different supporting forms. The results show that: if the A3 round steelanchoris used to support in the experiment, the rocks loaded 240kg began to appear local caving, the roof loaded 360kg appear fully caving, the ultimate bearing capacity of the roof support structure is achieved, the falling height is 2.4m above the roof. As the distance beyond the bolt anchorage range, the stability of the roof is hardly to maintain. When we choose deformed steel bar bolt, the bearing capacity of supporting structure reach to 624 kg, 73% is increased compared to A3 round steel anchor, and the capacity is greater than the actual load in the overburden; the deformed steel bar bolt make the roof form a complete anchorage structure, increase the bearing capacity of the roof structure.

Experimental Investigating of Latex Cement as Similar Material Simulating Soft Rock Creep

This paper takes styrene-butadiene latex with 37% solid contents, the portland cement of number 45r and fine sands with 0.2mm diameter to prepared similar material, the mass ratio of cement and fine sand is fixed, different ratio of the specimens are prepared by adjusting the latex ratio. The MATLAB fitting and ANSYS simulation calculation are used to compare to the date of soft rock. The analysis shows that the latex cement can be used for deep soft rock rheology theory and polymer materials similar simulation experiment.

Research on the Height of Caving Zone and Roof Classification of Mining Whole Height at One Times in Thick Coal Seam

Research on the division of the overlying rock roof of stope has great significance. The existing classification method is based on the determination of existing mining height and loose coefficient , and such studies have been proved exist some limitations in the applications of thick coal seam full coal mining. Theoretical analysis and similarity simulation experiments show that during the mining all height at one times in thick coal seam, as the recovery room increase ,the thickness of immediate roof of the overlying strata which fall with the mining increased signifi-cantly, and the structure of the overlying critical layer to stabilize that is the layer of hypogyny basic roof gradually increased. Through theoretical analysis and summarizing similar simulation experiment phenomenon, based on the definition and characteristics of the immediate roof and main roof, with elastic thin mechanics and the key strata theory as the research foundation, doing scientific classification of mining face's roof in all height at one times in thick coal seam, and combined impact of all factors, which influence the breakage and caving of Basic Roof, to estab-lish a scientific judgment in the length of work face and the pressure of basic roof for practical production relations, provide certain theoretical basis.