Soft Coal Roadway Research Articles

Study on the Truss Support Technology for Coal Side in a Soft Broken Coal Roadway Under High Stress

The coal side deformation and sliding can not be effectively controlled by use of the traditional bolt or cable support in the high stress crushed surrounding rock and large section roadway. For solving this problem, the new prestressed truss support technology is put forward, and its supporting principles of roof and two walls are stated. The mechanical model of cable-channel steel truss is established, and then the tensile strength of the cable and the maximum deflection of the channel steel are derived. By way of field investigation, mechanics theory analysis and actual production condition, the scheme is defined and applied in the replacement roadway. Measurement results of surrounding rock behavior show that the coal side displacement is no more than 254mm and the roof convergence is less than 172mm. Apparent economic and technical profits have been achieved.

Optimization on Gateway Section of Soft Coal Seam and Hard Roof and Supporting Technology

Support invalidity of a roadway have a largely influence on production safety of coal mines, especially the soft coal roadway, which deforms heavily. To solve this problem, it began from the gateway section optimization, based on the actual geological condition of Chang-gouyu Mine. The computational model was established up to optimize tunnel shapes using FLAC3D. The scopes of plastic zone, stress field, displacement field were compared and analysed for different shapes of roadway. The irregular trapezoid section is adopted, then the bolt support parameters were designed and field application was done. By using the irregular trapezoid, the stress distribution around the roadway is improved and the deformation and plastic zone is decreased. Under the geological conditions of the soft coal seam and hard roof strata, the stability of roadway was effectively controlled by using optimized trapeziform cross-section and bolting support.

The invalidation mechanism of bolt-mesh support in soft coal roadway

The bolting is easy to go out of force in soft coal roadway. Based on the field measured data, the reason of bolt pre-stressed hysteresis descending in soft coal roadway was analyzed in detail by theoretical analysis and field measurement. Closely encircling the changing law of anchorage force during the bolt bearing course, the reason of the low initial anchorage force in soft coal roadway, the effect of surrounding rock deformation on bolt anchorage force and the circulating hysteresis descending of anchorage force as well as the impact of the structure stability on bearing structure of the bolt-mesh support were analyzed. The analyzed results show there exists a great amount of bolt pre-stress hysteresis descending in soft coal roadway because of remarkable difference between bolt and soft coal deformable capability. Thus, many comprehensive measures should be taken to effectively control the initial loose deformation of non-anchorage rocks between two bolts, to achieve higher initial anchorage force and to prevent anchorage force losing during bolt bearing course. At the same time along with increasing the bolting strength, the structure compensating measures should be taken to ensure the structure stability of the bolt-mesh support and to realize the high-strength stable bolting.