Abstract
In coal underground mining, situation of longwall face striding across (SAR) or passing through roadway (PTR) is very common, especially in an inclined coal seam mining. A roadway supporting design method, consisting of a model using to determine the minimal rock strata thickness and a segmental supporting scheme, is developed. In addition, to represent the mechanical behaviour of the caved material authentically, an elastic model was developed. The results showed that the elastic model has a good agreement with the caved material mechanical behaviours at a relatively lower stress condition. By using a FDEM method, a real case in Xutuan coal mine is studied. Compared with the process without backfill, the z-displacement of cross-cut roof decreased shapely after backfilling, with a maximum z-displacement, decreases from 0.76 m to 0.13 m and from 0.39 m to 0.064 m in PTR and SAR section, respectively. Therefore, the possibility of fall of ground (FOG) and crushing accidents can be reduced effectively with backfilling material of wood cribs. And the maximum subsidence (SAR section side) of face floor is 0.16 m, which is small enough to ensure normal production. The results of this study are likely to be useful as a reference for the safe and efficient mining of coal resources under similar conditions.
Highlights
IntroductionMany roadways are excavated in coal or rock strata at different depths
In underground coal mining, many roadways are excavated in coal or rock strata at different depths
Each of them plays a functional role in the coal mine production; a few are used for transportation while others are used for ventilation
Summary
Many roadways are excavated in coal or rock strata at different depths. As the mining activity proceeds, it is inevitable for the longwall face to stride across (SAR) or pass though roadways (PTR). E abutment pressure, together with the coal seam gravity, is transmitted to the face floor, which could increase the stress to severalfold above that of the primary rock and can affect the face floor and supporting structures. Us, maximal floor failure depth plays a vital role in SAR. Once the maximal floor failure depth exceeds its critical value, the roadway is destroyed and the supports of the longwall face fall down. Erefore, the maximal floor failure depth and roadway loosening zone affect SAR. Because of the inclination of the coal seam, it is inevitable to encounter a situation, in which both SAR and PTR appear simultaneously. Based on geological and mining condition of Xutuan coal mine, a FDEM numerical analysis is conducted by comparing the behaviour of the cross-cut rock mass with or without supporting
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