结构面应力松弛特性及其与蠕变和长期强度的关联性研究

Rheological properties study of rock mass engineering mainly includes two aspects which are creep and stress relaxation, however, current study, which mostly focuses on creep studying, take creep and stress relaxation as two relatively independent propositions. This study would like to reveal the correlation mechanism of creep and stress relaxation and mechanism of stress relaxation affecting on long-term strength. Based on shear relaxation test using artificial sample with discontinuities, this study is intending to study the shear stress relaxation regularities of discontinuities under different conditions, establish and verify a uniform constitutive relation of stress relaxation and creep from the perspective of different energy-consumption characteristics, propose a new determining method for long-term strength considering the effect of stress relaxation and an evaluation method on long-term strength, finally verify the above results in numerical simulation and further study the long-term effect of stress relaxation on discontinuities. This study would provide basis and method for long-term stability problem of rock mass engineering, which has great value in improving the rheological theory and engineering application.

岩体工程的流变特性主要包括：蠕变和应力松弛。过往研究主要从蠕变角度，且将蠕变和应力松弛作为相对独立的两个命题，但已有研究揭示了两者的关联性，本研究拟阐明应力松弛与蠕变的关联机制、及应力松弛对长期强度特性的影响机制。通过人工结构面剪切应力松弛试验，系统研究不同条件下结构面的剪切应力松弛特性；基于蠕变和应力松弛有关能量耗散特征的差异性，建立两者统一的流变本构关系；提出考虑应力松弛影响机制的长期强度确定方法及长期强度评价方法；最后对研究成果进行数值验证，进一步揭示应力松弛对结构面长期力学特性的影响。本研究为岩体工程长期稳定性评价提供依据和方法，对完善流变力学理论和工程应用均具有重要价值。

结构面的存在是造成岩体工程性质不连续、各向异性和不均一的根源，其流变力学特性是岩体流变力学一个极为重要的基础理论研究课题，同时又成为岩体工程实践中必须解决的应用课题。本课题以人工结构面试件（Barton标准剖面线结构面）为研究对象，开展了一系列剪切应力松弛试验。在此基础上，将应力松弛划分为快速应力松弛阶段、减速应力松弛阶段及应力稳定阶段；提出了应力松弛的诱发因素为：结构面磨损及微裂隙萌生和发展、粘弹性变形等，相应地定义了裂隙松弛和蠕变松弛，系统揭示了不同粗糙度系数、不同应力水平等条件下的结构面瞬时力学特性和结构面应力松弛特性，从剪切应力松弛试验过程中的法向变形演化等角度阐释了结构面应力松弛与蠕变特性之间的关联机制；从结构面应力松弛机制出发，建立了应力松弛的本构关系（H-K//B），并对其在粗糙度系数、应力水平、等应力循环加载等条件下的参数演化规律进行了学习，本构拟合与试验结果吻合较好；提出了抗应力松弛能力、松弛循环模量、蠕变松弛、裂隙松弛等概念，阐明了等应力循环加载过程中结构面的应力松弛特性，系统分析了结构面应力松弛特性与长期强度之间的关联机制，并提出了等应力循环加载应力松弛试验确定结构面长期强度的方法。该课题的研究成果可为岩石工程时效变形、时效应力演化及长期稳定性评价提供理论支撑和方法依据。