不同加、卸荷速率下软硬互层岩体组构效应的水-力耦合特征

How to reveal and evaluate the hydro-mechanics coupling characteristic of the fabric effect on alternatively distributed soft and hard rockmass (ADSHRM) under anisotropic stress field and pore water pressure stress field is a objective needs and fundmantal research topic for the safety construction of deep engineering rock mass. This study will conduct a series of ture triaxial stress path and direct shear tests under consolidated undrained condition at different loading and unloading rates combining with pore water pressure,AE and SEM testing to reveal the fabric effect which hard host rock and weak intercalated layer present while bearing loads together from macroscopic and mesoscopic levels.The effect of weak intercalated layer/host rock interface morphology, the thickness, dip, and particle breakage of weak intercalated layer on the rate-dependent strength of ADSHRM，will be explored based on the testing results. A strength criterion depicting different failure modes and a hardening rule describing the influence of dirfferent stress paths will be established.After embedding the strength criterion and hardening rule in the FLAC3D,the anisotropic rate-dependent constitutive model which discribes the hydro-mechanics coupling characteristic of the fabric effect of ADSHRM will be implemented and applied to model the excavation of a large complex underground powerhouse at Baihetan plant affected by many weak intercalated layers.It is now expected to provide a theoretical reason for the excavation methods without blasting and construction parameters of the large complex underground engineering affected by weak intercalated layers.

如何揭示软硬互层岩体组构效应在各向异性应力场与孔隙水压应力场叠加条件下水-力耦合特征的率相关性并予以量化评价，一直是深部岩体工程安全建设的一个客观需求和基础研究课题。本项目基于不同加、卸荷速率和固结不排水条件下的真三轴应力路径及直剪试验，并结合同步孔隙水压力、声发射测试及破坏面电镜扫描，从宏、细观层面揭示坚硬母岩和软弱夹层共同受载时的组构效应，探究不同加、卸荷速率下软弱夹层孔隙水压力、厚度、产状、粒组及其与母岩界面形貌等组构要素对软硬互层岩体强度的影响；建立描述软硬互层岩体多种破坏模式的率相关复合强度准则及硬化法则并嵌入通用数值计算程序，实现描述不同加、卸荷速率下组构效应水-力耦合特征的率相关各向异性模型；将该模型应用于受软弱夹层影响的白鹤滩水电站地下厂房开挖过程的模拟并检验其适用性。本项目有望为受软弱夹层影响的大型复杂地下工程开挖方式（非钻爆法）和施工参数的选择提供理论依据。

针对开挖卸荷条件下软硬互层岩体变形破坏机理认识不清、评价准则缺乏坚实的理论基础以致造成无法有效评价该工程岩体稳定性的瓶颈问题，严格按照计划书拟定的由室内试验→现场调查→理论建模→工程应用的总体研究思路开展工作。针对复杂应力条件下软硬互层岩体破坏的力学机制、模型、准则及工程应用等关键问题，在试验研究、机理分析、力学模型建立和围岩安全性评价指标方面进行了深入系统地研究，总体上达到了预期目标。研究取得了四个代表性成果: (1) 基于室内软弱夹层加卸载试验和理论分析，结合电镜扫描和压汞实验结果，揭示了软弱夹层不同先期固结压力下、加卸载作用下的剪切、拉伸破坏特性、规律与颗粒破碎机制；(2) 基于软硬互层岩体复合体（上下母岩+软弱夹层）的室内三轴加、卸载试验，揭示了软硬互层岩体在加、卸载条件下的变形破坏全过程及应力响应行为；(3) 考虑横观各向同性弹性参数的裂化对围岩力学响应的影响，提出了各向同性及横观各向同性岩体弹塑性耦合模型的弹模裂化极限取值统一限定条件，建立了软硬互层岩体的横观各向同性弹塑性耦合等效模型，在该模型中既可以考虑层状岩体强度在峰后随塑性应变增大而减小的现象，也能考虑其弹性模量在峰后随塑性应变增大而不断劣化的现象；(4) 基于上述软硬互层岩体的横观各向同性弹塑性耦合等效模型，分别建立了基于刚度劣化的围岩松动圈评价指标和基于强度弱化的围岩损伤评价指标，用于融合现场松动圈测试结果和局部破坏信息的围岩松动圈识别和破坏程度评价。