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隧道围岩中的结构面将岩体切割成块体,块体在自然状态下的静力平衡因为隧道开挖而被打破,临空面的产生和动荷载的施加都可能导致块体的滑移,进而引起围岩失稳。以往应用块体理论寻找关键块体时,多只考虑纯重力的作用,而忽视了爆破振动、地震等动荷载对诱发失稳灾害的重要作用。将爆破振动荷载和地震荷载转化为等效静力,并通过数学计算求出使块体安全系数最低的动荷载方向,再利用关键块体理论矢量分析方法分析隧道围岩的稳定性。在长岗隧道中的应用表明,考虑动荷载作用下的块体安全系数明显小于只考虑重力作用时的安全系数,原本稳定的块体也可能在动荷载作用下变成关键块体导致围岩失稳,这与长岗隧道现场记录的破坏现象相符。
The rock mass is cut into blocks by the structural plane in the surrounding rock of the tunnel. The static balance of the block in the natural state is broken by excavation of the tunnel. The generation of the free surface and the application of dynamic load may cause the sliding of the block Move, and then cause the surrounding rock instability. In the past, when applying block theory to find key blocks, the effect of pure gravitation was more than that of pure gravitation, while the important role of dynamic loads such as blasting vibration and earthquake in inducing instable disasters was neglected. The blasting vibration load and seismic load are transformed into equivalent static force, and the dynamic load direction with the lowest block safety factor is obtained through mathematical calculation. The stability of surrounding rock of tunnel is analyzed by the key block theory vector analysis method. The application in Chang-Gang tunnel shows that the stability factor of block under considering dynamic load is obviously less than that of safety factor when only gravity is taken into consideration. The originally stable block may also become a key block under the action of dynamic load and lead to the surrounding rock Unstable, which is consistent with the damage recorded by the site of Changgang Tunnel.