节理化进水口的超大直径岩塞施工期变形稳定分析

Deformation and Stability Analysis of Large Diameter Underwater Rock Plug with Substantial Joints during Construction

长甸电站水下岩塞为我国首例超大直径岩塞,其平均直径达12.3 m且地质条件较为复杂,是该电站改造工程的重大技术难题之一。针对长甸电站进水口边坡岩体节理发育的特点,采用3DEC方法建立了节理岩体模型,对施工期集渣坑、连接段开挖导致的岩塞局部拉应力和非连续变形特征进行了分析,进而,基于强度折减法对爆破前期岩塞体的潜在失稳模式和稳定性分区进行了评价。研究表明,节理对岩塞体的稳定特征影响突出,岩塞体的潜在失稳模式呈现由洞内浅层向深部追踪节理密集带Jm7发展的趋势,岩塞掌子面局部拉应力区的块体稳定性相对最差;而考虑结构面的不同连通率的岩塞体整体安全系数在2.2~5.1之间,满足安全性要求。针对节理化岩塞体采用的3DEC模拟能够良好地反映结构面的控制性作用,分析方法可以为类似工程提供参考。

The underwater rock plug( average 12.3 m in diameter) of Changdian plant is the first and largest rock plug in China. Its large scale and complex geological conditions are important technical issue of this project.Considering the large number of rock mass joints at water intake,three dimensional distinct element method( 3DEC)has been adopted to build up a model which contains various discontinuities. Based on the numerical simulation,the tensile stress distribution and the discontinuous deformation characteristics of the large-scale rock plug have been analyzed. Moreover,using the 3DEC strength reduction technique,the potential instability modes and stability zoning of the rock plug before blasting period have also been evaluated. Result shows that discontinuities have prominent effects on the stabilization of the rock plug. The potential failure zone starts from the excavating face,and developing deep along the joint band Jm7. Regardless of the safety factor of the local rock block in excavating face with tensile stress is relative low,the overall safety factor of the rock plug is 2.2 ~ 5.1,which satisfies the requirement of project.The 3DEC method,reflects the structure controlling effect by discontinuities,has been applied successfully to analysis the deformation and stability of the large-scale rock plug. The proposed analysis method could be a reference for other similar projects.