Mining and geological conditions deteriorate consecutively during underground coal extraction in Poland. Increasing depth of exploitation (nowadays: below 1,000 m), numerous tectonic discontinuities, unstable rock properties and multi-seam exploitation, leaving numerous edges and pillars, demand the use of various schemes of advanced support constructions. The main support applied in Polish underground coal mines in Upper Silesian Coal Basin is a steel yielding support, whereas roof bolting is applied only occasionally due to the occurrence of bedded roof with weak rocks. Nevertheless, in recent years bolts have been used in a wider range for standing support reinforcement. Experience in this subject clearly indicates that the stand-and-roof-bolting support has proved effective in difficult mining and geological conditions at great depths. Steel bolts with the length of approx. 2.5 m and load-bearing capacity of 120-M50 kN applied so far are replaced by cable or strand bolts with the length of 5*7 m and load-bearing capacity of 280*450 kN.The paper is an evaluation of a stand-and-roof-bolting support. The analysis was carried out on the basis of numerous underground research studies: convergence, support loading (with the help of dynamometers and instrumented bolts) and roof bed separation (with the use of telltales and endoscopic infrared cameras). The evaluation indicated that a suitable scheme of mining support largely improves the functionality of roadways. Additionally, the fracture zone surrounding the working decreases, which allows the rock mass to reach its maximum load-bearing capacity. An application of proper support schemes not only provides safety of work at the crossings of galleries and entries, but also it allows using the same gallery for the next longwall panel. Furthermore, there is an instance illustrating how a stand-and-roof-bolting support can transmit and accumulate the dynamic loading.
展开▼
