高应力下大型硬岩地下洞室群稳定性设计优化的裂化–抑制法及其应用

Cracking-restraint design method for large underground caverns with hard rock under high geostress condition and its practical application

针对高应力下大型硬岩地下洞室群突出的围岩灾害性破坏问题,在多个深部/高应力地下洞室群开挖方案与支护参数优化研究及实践基础上,提出高应力下大型硬岩地下洞室群稳定性优化的裂化–抑制设计方法新理念及其基本原理、关键技术和实施流程。该方法认为高应力下地下洞室硬岩大变形与灾害性破坏本质上是其内部破裂发展和开裂的外在表现形式,为此建立以抑制硬岩内部破裂发展为关键切入点的理念,以硬岩的开裂测试分析、减裂开挖调整、止裂支护控制为三要素,提出:(1)通过系统地开展洞室群开挖方案优化分析,从开挖角度尽量减少和避免围岩开裂的规模、深度和程度技术体系;(2)通过支护参数、支护时机优化,从支护角度抑制围岩进一步裂化并强化松弛/开裂围岩的整体性从而抵抗地层压力,将围岩从被支护对象转换为承载结构,从而实现充分调动围岩自身承载性能来维护和再造围岩承载拱,达到工程安全、高效和经济的目标。拉西瓦水电站地下洞群开挖顺序优化、白鹤滩水电站地下厂房顶拱支护方案优化、中国锦屏深地实验室的围岩支护参数复核等工程实践表明了其合理性和实用性。

The stability of surrounding hard rock in large underground caverns always challenges its design and excavation under high geostress condition. A new cracking-restraint design method for caverns? stability optimization was proposed based on the summarization and practice of many underground caverns under high geostress condition. This method points out that the inner cracking of hard rock is the root factor for rock?s large deformation and failure. Taking the testing of rock mass break,excavation optimization for reducing the cracking scale and supporting reinforcement for restraining the cracking development as three basic factors and considering the way of restraining cracking of hard rock as the key issue ideology,optimization operations were synthetically carries out. A technical system for reducing or avoiding cracking scale,depth and degree of hard rock was proposed through improving the global excavation scheme. It is pointed out that,for the purpose of safety,efficiency and economy,rational selections of supporting parameters for rock bolts or cables and supporting time for surrounding rock help to restrain cracking of surrounding rock and to strengthen the integrality and the resistance of cracking surrounding rock,and make surrounding rock as a bearing structure for fully mobilizing its own bearing capacity to reinforce or build a load-bearing arch of surrounding rock. Applications in Laxiwa hydraulic station,Baihetan hydraulic station and Chinese Jinping deep laboratory indicate that the developed method is reasonable and useful.