上软下硬地层隧道渐进破坏机理与设计方法研究

Tunnel section is located in upper-soft lower-hard strata and structural plane between hard and soft strata, easy to cause surface subsidence, instability of surrounding rock and supporting damage, etc. Currently lack this kind of design method of tunnel, theoretical research seriously lagging behind the need of engineering practice, progressive failure mechanism and design method is theoretical basis of this kind of tunnel design, construction and operation safety. This project will use the comprehensive research techniques of combination of theory and practice, combined closely with upper-soft lower-hard strata characteristics, construction process and effect of the excavation, elaborating the progressive failure mechanism of the tunnel surrounding rock and the tunnel support progressive failure mechanism under interaction between surrounding rock and supporting, revealing the tunnel damage internal cause and mechanism, and on this basis, to put forward based on the common effect of geological and engineering factors quantitative classification indexes of surrounding rock, standards and methods, to put forward the quantitative failure evaluation indexes, standards and methods of surrounding rock and tunnel support under the interaction between surrounding rock and supporting, and tunnel support design parameters are put forward based on the combination of experience and theoretical analysis, to establish semi-quantitative engineering analogy design method for upper-soft lower-hard strata tunnel. For upper-soft lower-hard strata tunnel design, construction, maintenance, and disaster prevention and control to provide theoretical foundation and scientific method, to enrich and develop the theory on tunnel engineering in China has very important scientific significance and practical significance.

隧道断面位于上部为软弱地层、下部为坚硬地层和软硬分界结构面构成的复杂组合地层中，容易引发地表塌陷、围岩失稳和支护破坏等工程灾害，目前缺乏这类隧道的设计方法，理论研究严重滞后于工程实践需要，渐进破坏机理与设计方法是这类隧道设计、施工与运营安全的理论基础。本项目将运用理论与实践相结合的综合研究手段，紧密结合上软下硬地层特点、施工过程和开挖空间效应，精细化研究隧道围岩渐进破坏机理以及围岩与支护相互作用下隧道支护渐进破坏机理，揭示隧道破坏内在诱因和发生机制，在此基础上，研究提出地质因素和工程因素共同影响下隧道围岩量化分级方法，提出隧道围岩及围岩与支护相互作用下隧道支护破坏量化评价方法，提出经验和理论分析相结合的隧道支护设计参数，建立上软下硬地层隧道半定量设计方法。为上软下硬地层隧道的设计、施工、维护和灾害防治提供理论基础和科学方法，对丰富和发展我国隧道工程理论体系具有十分重要的科学意义和现实意义。

近些年上软下硬隧道工程实例越来越多，我国缺乏针对上软下硬地层隧道的设计方法，根源在于缺乏上软下硬地层隧道破坏机理及评价的专门研究。为了探讨上软下硬地层隧道在设计、施工和管理中的关键科学问题及应用前景，本项目针对上软下硬地层隧道破坏机理和设计方法开展了系统研究。首先，通过对上软下硬地层隧道破坏因素及影响的研究，实现了对破坏因素的辨识、估计和评价；然后，通过对上软下硬地层隧道渐进破坏机理的精细化研究，揭示了隧道围岩稳定演化趋势，提出了上软下硬复合地层隧道的破坏模式和破坏形态；在此基础之上，通过对上软下硬地层隧道围岩量化分级方法的研究，形成了上软下硬复合地层隧道围岩量化分级的指标、标准和方法；其次，通过对隧道破坏量化评价方法的研究，以突变理论和隧道极限状态为基础，建立了内在基于安全系数和外在基于变形的统一破坏定量评价判据；最后，通过对上软下硬地层隧道半定量设计方法的研究，结合隧道破坏量化评价方法，提出了隧道支护结构的半定量设计参数，建立了适合上软下硬复合地层隧道的半定量设计方法。相关研究内容和成果对丰富和发展我国隧道工程设计、施工和安全管理理论具有十分重要的科学意义和现实意义。