【作者】 陶剑；

【导师】 杨兴国； 鲁功达；

【作者基本信息】 四川大学 ， 水工结构工程， 2023， 博士

【摘要】 为全面推进我国西部大开发的重大战略任务实施,一批如川藏铁路、西电东送以及雅鲁藏布江下游水电开发等大型水电与交通工程建设正相继朝着地形地质条件复杂的高山峡谷地区拓展。西部艰险山区的交通巷道和水电洞群通常埋深较大,同时在强烈的内外动力地质作用下将普遍面临高地应力和高地温的不良地质问题。其中,高地应力环境将可能诱发岩爆和大变形等围岩失稳灾变问题,而高地温现象则将显著劣化衬砌结构强度并造成劳动工作效率降低,进而对地下工程的施工进展和运营安全构成严峻挑战。在深埋高温地下硐室的建设过程中,钻爆开挖产生的初始动力损伤将造成岩体力学性质劣化并诱发卸荷路径下的围岩时效变形,同时为了减轻高温热害而采取的人工降温措施则将导致围岩温度-应力调整进而加剧蠕变发展。然而,现有的地下工程设计方法通常未考虑岩体的动力开挖卸荷效应,同时常规的时效变形本构理论也尚未充分认识降温扰动作用对围岩蠕变发展的复杂影响。因此,研究开挖卸荷与冷却降温作用下的围岩时效变形机理,对提升极端地质环境条件下的地下工程建设运营安全,进而促进艰险山区的基础设施建设以及深部资源的开发利用具有重要的理论与工程指导意义。本文综合采用理论分析、模型概化、本构开发以及数值仿真等技术手段,系统研究了不同地质环境、开挖方式以及降温工况组合条件下的围岩蠕变演化规律,取得了如下创新性成果:(1)根据弹性动力学理论揭示了地应力对岩石爆炸屈服破坏模式的决定性作用,同时结合数值模拟方法分析了爆破粉碎区和爆生裂纹随原岩应力的演化规律,进而阐明了静态应力与动态荷载的组合作用力学机制与爆炸破岩机理。在此基础上,通过考虑地应力瞬态释放与人工降温扰动作用,建立了针对爆破-卸荷-降温全过程的深部岩体开挖响应理论模型,并采用应力轨迹分段表征方法实现了各开挖子过程的解耦分析,最终阐释了不同开挖方式与地质条件下的围岩热力响应机理。(2)在边界面理论框架下将亚临界裂纹扩展的微观机制推广至岩石蠕变力学行为的宏观表征,进而建立了可实现流程化参数标定的粘塑性边界面损伤(BS-VPD)本构模型,有效捕捉了岩石减速、匀速以及加速三阶段的蠕变响应特征。通过初始损伤映射技术提出并验证了动力开挖卸荷条件下的围岩时效变形模拟方法,进而计算分析了不同地质环境与开挖工况下的围岩蠕变发展演化规律,最终揭示了动力开挖卸荷过程对围岩时效变形的控制性作用。(3)建立了深埋高温硐室降温过程的热力耦合解析模型,进而基于点安全系数法揭示了冷却降温作用下的高温隧洞稳定状态演化规律。同时,在不可逆热力学框架下将所提出的BS-VPD模型进一步推广至非等温条件,进而建立了热力耦合的岩石时效变形本构模型(BS-TVPD)并嵌入地下硐室冷却降温的数值计算程序。通过模拟分析不同地质环境与降温扰动工况下的围岩蠕变发展演化规律,最终阐明了人工降温条件下的围岩时效变形机理。(4)基于BS-VPD/TVPD模型开展了典型高应力与高地温环境的地下工程围岩时效变形研究,结合理论分析与原位监测等技术手段阐释了不同开挖卸荷与冷却降温工况下的围岩蠕变时空发展演化规律,研究成果可为优化深埋硐室的施工开挖设计以及人工降温方案,进而保障地下工程的长期安全稳定运行提供重要的理论指导与技术支撑。更多还原

【Abstract】 To comprehensively promote the implementation of China′s major strategic task of western development,a multitude of hydropower and traffic projects are shifting progressively towards the high-relief terrains of complex geology.Typical examples include the Sichuan-Tibet Railway,West-East Electricity Transmission,and hydropower development in the lower Yarlung Tsangpo.The underground excavations developed in these mountainous areas are typically buried at hostile depths and subject to intense tectonic actions,leading to challenging geological conditions of high in-situ stress and elevated temperature.Such a primordial geopressure environment may induce rockburst and large deformation of the surrounding rockmass,while the unfavorable geothermal settings could cause significant degradation of the lining structure and reduce substantially the efficiency of production.Therefore,how to ensure effectively the safe construction and long-term operation of subsurface excavations in hostile geological environments has constituted a critical concern for rock mechanics practitioners.The dynamic excavation of underground structures within prestressed geothermal deposits usually induces initial damage due to the coupling of blast loading and transient unloading,resulting in mechanical deterioration of the rockmass and hence inducing time-dependent deformation during the secondary stress adjustment.On the other hand,the implementation of active cooling protocols intended to create a decent working environment may lead to further modification of the stress and temperature around the excavation,thereby exacerbating rock creeping.Nevertheless,existing design for subsurface construction has normally neglected the effect of transient unloading during dynamic excavation,while the traditional theory of creep characterization has yet to comprehend comprehensively the intricate influence of cooling disturbance on time-dependent rock deformation.Therefore,a rational understanding and description of the time-dependent rock deformation induced by dynamic excavation and active cooling are of indispensable theoretical and practical significance for ensuring the safe construction and operation of underground projects in extreme geological conditions.In this study,we have conducted a systematic investigation of the time-dependent rock deformation under different geological environments,excavation strategies,and cooling protocols by integrating comprehensive techniques.The innovative findings obtained are summarized below:(1)The elastodynamic theory is employed to reveal the critical control of ground pressure on rock yielding under explosive impact,and the numerical method is adopted to analyze the evolution of blast-induced crushed zone and rock fracture in different in-situ stress fields.Consequently,the underlying mechanisms for the joint action of static stress and dynamic loading are thoroughly elucidated.On this basis,a theoretical framework is developed to investigate the response of deep rock excavation during the successive blast loading,transient unloading,and air-cooling sequence.The sub-loading processes are then decoupled and analyzed respectively using a stress projection technique,and the thermal-mechanical rock behaviour under various geological conditions and excavation schemes are finally scrutinized.(2)By upscaling the microscopic subcritical cracking towards macroscopic creep characterization based on the bounding surface concept,a viscoplastic bounding surface damage(BS-VPD)model is established to capture the trimodal creep behaviour across primary,secondary,and tertiary regimes.Subsequently,we have proposed a novel numerical approach for characterizing the time-dependent deformation of the dynamically-disturbed excavation based on mapping of initial damage.The creep development of the surrounding rockmass under different geological environments and excavation conditions is then analyzed carefully,revealing eventually the significant influence of initial dynamic excavation on the resulting time-dependent rock deformation.(3)The spatiotemporal evolution of the local factor of safety(LFS)during rock cooling is examined analytically in this study,and the thermal-mechanical excavation stability subject to practical cooling perturbations is then clarified quantitatively.Meanwhile,by further extending the proposed BS-VPD model into the non-isothermal regime within the irreversible thermodynamic framework,a new BS-TVPD model is developed and then embedded into the numerical procedure designed for characterizing tunnel cooling.The established framework is utilized to explore the creep development of the surrounding rockmass under different geological conditions and cooling protocols,thereby revealing the underlying mechanism of time-dependent rock deformation subject to active cooling treatment.(4)Based on the proposed BS-VPD/TVPD models,we have conducted a numerical investigation on the time-dependent rock deformation of typical underground projects operated in extreme geopressure and geothermal environments.The spatiotemporal rock creeping under different excavation and cooling conditions is then explained by further integrating theoretical analysis and in-situ monitoring.The novel insights obtained in our study could provide important theoretical guidance and technical assistance for optimizing the excavation design and cooling scheme of subsurface excavations,thereby ensuring the long-term stability of underground projects developed in harsh geological environments.更多还原