地下洞室高应力软岩卸荷扩容时效孕灾机制与长期稳定性研究

The excavation unloading of high stressed soft rock in underground cavern at great depth leads to time-dependent dilatancy disasters and then brings about long-term stability issue of surrounding rock. By performing a series of tests covering multi-scale approaches, including loading-unloading rheological test of high stressed soft rock under different stress paths, acoustic emission test, acoustic monitoring, CT scanning, SEM scanning test, meso-mechanical numerical test and in situ measurement information interpretation approach, this project plans to reveal the mechanical characteristics and time-dependent disaster inducing laws for high stressed soft rock subjected to unloading dilatancy effects, to identify the macro-micro time-dependent evolution mechanism, disaster inducing condition, their factors and relationships for unloading dilatancy behavior of high stressed soft rock, to propose mechanical model reflecting the key features of high stressed soft rock under complex stress path and dilatancy effect, to develop numerical simulation method describing the evolution process of time-dependent dilatancy behavior, to preliminarily constitute the theory for time-dependent disaster inducing analysis and the evaluation method for long-term stability of surrounding rock considering the excavation unloading effect of high stressed soft rock. The anticipated outcome may promote the development of rock mechanics at great depth and provide theoretical reference and application experience for disaster control, long-term performance prediction and safety assessment of high stressed soft rock in underground engineering projects at great depth.

针对地下洞室高应力软岩开挖卸荷诱导的扩容时效灾变现象及由此带来的围岩长期稳定性问题，通过开展一系列的不同应力路径下高应力软岩加卸载流变试验、声发射和声波监测、CT扫描和SEM扫描试验、细观力学数值试验以及高应力软岩洞室现场量测信息解译等多尺度多手段研究，揭示高应力软岩的卸荷扩容力学特征与时效损伤演化规律，识别高应力软岩卸荷扩容的宏细观时效演化机制、孕灾条件、影响因素及其相关关系，提出反映扩容时效孕灾条件和本质特征的力学模型，发展描述高应力软岩卸荷扩容时效孕灾演化过程的数值模拟方法，初步形成地下工程高应力软岩卸荷扩容的时效灾变分析理论与围岩长期稳定性评价方法，为丰富并推动深部岩石力学理论发展，以及为地下工程高应力软岩的灾变控制、长期稳定性预测与安全评价等提供理论依据和应用基础。

本项目针对地下洞室高应力软岩开挖卸荷诱导的扩容时效灾变现象及由此带来的围岩长期稳定性问题，采用室内试验、现场量测、数值分析、理论研究等方法，获得了围压、应力强度比、主应力差等对岩石卸荷扩容时效变形破裂演化特征及其影响规律，解译了岩石渐进性时效破裂演化导致的围岩向临空面的扩容效应，从宏细观上揭示了岩石卸荷时效扩容的围压抑制效应以及主应力差的诱导效应；建立了考虑弯扭贡献效应并耦合Weibull分布且带拉伸截止限的的摩尔库伦细观颗粒粘结时效破裂准则，提出了非均质岩石时效破裂细观力学模型及其数值模拟方法，实现对岩石细观层面上时效变形破裂演化及扩容孕育过程的模拟；建立了适用于加卸载全过程的广义岩体蠕变本构模型，研发了围岩裂纹扩展的时效演化XFEM数值计算方法；发展了描述高应力软岩卸荷扩容时效孕灾演化过程的宏细观数值模拟方法以及相应的模拟系统，初步形成地下工程高应力软岩卸荷扩容的时效灾变分析理论与围岩长期稳定性评价方法，在锦屏水电站地下洞室群、丹巴深埋长引水隧洞、引汉济渭秦岭深埋隧洞等地下洞室工程中进行了应用，进一步丰富了深部岩石力学理论，为地下工程围岩灾变控制、长期稳定性预测与安全评价等提供了理论依据和应用基础。