关键块体概率分析在复杂构造条件下大型地下工程开挖中的应用

锦屏一级水电站泄洪洞位于雅砻江右岸埋深大于100m的大理岩中,构造条件复杂,确定隧洞开挖面是否可能产生关键块体对工程安全具有重要意义。本文在对泄洪洞中导洞地质调查和研究基础上,将随机概率模型引入关键块体理论,分析关键块体的生成概率、体积大小与安全系数,得出关键块体形成概率服从负指数分布,主要取决于J②、J④组裂隙迹长的分布情况； 关键块体的体积与主要结构面迹长成正比,最终收敛于结构面对关键块体完全切割时的关键块体体积； 关键块体的安全系数随主要结构面迹长的增加而降低,但是同样收敛于结构面对关键块体的完全切割情况。为设计有效的加固方案提供了依据,具有积极的工程应用价值。

PROBABILITY ANALYSIS OF KEY ROCK BLOCKS AT COMPLEX GEOLOGICAL STRUCTURES DURING EXCAVATION OF LARGE SCALE StationUNDERGROUND CHAMBER

Flood discharging tunnel at Jinping First Stage Hydropower Station situates in marbles on right bank of Yalong River where complex geological structures condition appears and the cover depth is more than 100 m. It is clear whether there are key rock blocks on the excavation planes during excavation will sufficiently affect engineering safety. This paper bases on geological conditions in one part of central drift in the flood discharging tunnel,and draws stochastic probability into key block theory. It studies the generation probability,volume and safety factors of these potential key blocks and obtains the following conclusions. The generation probability of key blocks shows an exponential distribution,on the condition that faults are extended freely. The probability will mainly determined by the length distribution of two joint sets. The relationship between volume of key blocks and trace length of main structural planes is direct ratio. But as trace length increases,the volume of blocks will approach to the maximum value which indicates the complete cut state. The safety factors of key blocks decrease with the growth of the main structural plane trace length. It has a minimum value which shows the complete cut state. These are useful to offer effective reinforcement design and have important engineering values.