断层错动引起地下隧道结构破坏的超重力离心试验与数值模拟研究

The active faults are widely distributed in China. With the increasing tension of urban land resource and the restriction of subway line direction, linear underground structures, including metro tunnels, inevitably step over active faults. Fault movements usually induce the ruptures of overlying soil and destroy underground tunnels. The strong soil-structure interaction brings about coupling of the overburden rupturing and underground structure damage. This project will firstly conduct soil rupture modes and corresponding forming conditions, as well as the soften behavior of soil rupture zone and soil-structure interface under fault slipping through laboratory experiments, and then propose soil rupturing criterion, mechanical models of soil rupture zone and soil-structure interface. On this basis, theories and methods for simulating the progressive rupturing of soil, progressive damaging of soil-structure interface and progressive failure of underground structure will be established. Secondly, by adopting both high gravity centrifuge tests and numerical simulations, the overall process of overlying soil rupture and underground tunnel structure damage induced by fault slip will be reproduced. The mechanism of soil-structure interaction and its influence on the coupling of overlying soil rupture propagation and underground tunnel structure damage process will be revealed. Typical failure modes of underground tunnels will also be identified and corresponding influence factors, such as parameters of soil and tunnel will be studied. Finally, practical assessment method for underground tunnel disaster, reasonable crossover ways as well as corresponding engineering countermeasures will be presented, which should provide technical supports for further improving of relevant specifications.

我国活断层分布广泛，受用地和走向限制，城市地铁隧道等线形地下结构不可避免地跨越活断层。断层错动引起上覆土层破裂，导致地下隧道结构破坏。土与结构间强烈的相互作用造成上覆土层破裂与地下隧道结构破坏过程耦合。本项目首先通过室内试验研究断层错动作用下土体破裂形式与产生条件、破裂带软化与土结接触面损伤特性，建立土体破裂准则及破裂带与土结接触面力学模型。在此基础上，提出模拟断层错动作用下土层破裂渐进扩展、土结接触面渐进损伤和地下结构渐进破坏的分析理论和方法。其次，结合超重力离心模型试验和数值模拟，再现断层错动作用下上覆土层破裂、地下隧道结构破坏的全过程，揭示土结相互作用机理及其对上覆土层破裂扩展和地下隧道结构破坏耦合的影响机制，研究土层、隧道与跨越方式等参数对地下隧道结构破坏模式的影响规律。最后，针对不同破坏模式，提出实用的地下隧道灾害评估方法、合理的跨越方式及岩土工程处置对策，为完善规范提供支撑。

剧烈的断层错动将引发强烈地震，并导致上覆土层破裂，形成破裂带，严重破坏破裂带影响区内的建、构筑物。研究断层作用下上覆土层破裂产生扩展过程，揭示破裂带与土层中隧道等建构筑物耦合作用机理显得尤为必要。本研究首先研制常重力条件下的断层错动试验装置，可实现正、逆断层、多种错动角度等条件的模拟，同时配套相应的试验监测系统，实现对试验结果的实时记录；采用研制的断层错动试验装置开展不同断层倾角、地表倾角、埋深条件下的断层错动试验，从而深入研究断层错动对上覆土层及隧道的影响及土中破裂带的形成及扩展机理；对传统数值模拟方法在应用于非连续变形问题时所存在的问题进行探索，提出适用的数值模拟方法及对常规方法改进；采用改进的数值模拟方法对断层错动引发上覆土层破裂的过程及对土层中隧道结构的影响进行研究，与模型试验结果的对比分析进一步加深了对断层错动过程的认识。