外文翻译--关于倾角煤层挖掘巷道的锚杆支护的研究(编辑修改稿)

外文翻译--关于倾角煤层挖掘巷道的锚杆支护的研究(编辑修改稿)内容摘要：

nimum thickness  can be derived and then the total length of a bolt can be easily determined as follows: 12l l l    (1) Where , 1l is the length of bolted end。 2l is the length of outer part. Bolt spacing a can be derived by the criteria that no slip occurs along bedding planes. Besides the abovementioned conditions, the safety of the bined beam must be checked to prevent it from longitudinal instability. When all the conditions are satisfied, roof bolt parameters can ready be determined. As for sidewall bolts, their length and spacing can be derived by soil bracing theory in soil mechanics. It should be noticed when roof is posed of weak and loose strata, some bracing measures must be taken to protect the integrity of the fragile roof. 4. Bolting of the gateway and its assessment Support assessment by discrete element method We consider two case in order to pare , first case: only the roof is bolted。 second case: both roof and sidewall are bolted. Having been bolted in the first case, the roof has a obvious higher stiffness and strength, in the initial stage, only slight deflection occurs. However, with the sidewall coal failing and caving, the free span of the roof increases, the roof gradually enters unstable stage, subsiding and bedding separating as shown in . Compared with the unsupported gateway, the gateway with roof bolted can keep stability for much longer time even it destabilizes finally. In the second case, the sidewall coal deformation and failure are strictly controlled by the sidewall bolts, the sidewalls are stable. Roof deflects only a small amount. Displacement can be hardly seen in the block diagram(). The overall surrounding strata are in stable conditions. Even influenced by mining activity the gateway only fails locally, the roof is, however rather stable. It is, thus important to adopt a prehensive bolt support pattern including the sidewalls. Bolting scheme and its implementation Based on the inclined bined beam theory, gateway loosed zone measurement and discrete element analysis, four bolts long are installed in the roof. At the outer end of each bolt, a testing device is installed(  5patent of National Bureau of China) to ensure that at least 20kN pretension is exerted. Bolt spacing is , array pitch is . Due to rather developed joints, steel bends are used together with roof bolt to ensure support effectiveness and prevent local roof caving. The steel plate is thick, long and wide. The coal sidewall is reinforced by timber bolt with spacing , timer bolt for upper sidewall is long and for the lower sidewall. The timber bolt is installed with no less pretension. In the influence zone of front abutment pressure, strengthened supports are added. Metal frictional prop with timber cap is set as temporary reinforcement. The reinforcement distance is 25m ahead of the working face. The reinforced props are arranged in the center line of the gateway. More attentions should be paid to gateway excavation procedure. The roof bolts should be installed as soon as possible after the roof is exposed, then the sidewall bolt. The maximum delayed time should be less than 6 hours, which can make the roof deform exceedingly and integrity worsening. After each construction cycle, the bolts near the driving face should be refastened to assure their anchorage force. Measurement of gateway closure In order to assess the effectiveness of the support scheme, the gateway closure is monitored during its driving and working face retreating. The closure of roof vs floor, sidewalls and roof subsiding velocity are shown in . It can be seen that when the working face is far away from the monitoring area, the deformation of t。