Development and verification of a micromechanics-based continuum theory for long-term deterioration of hard rock

本研究旨在建立一个基于细观力学的连续损伤模型来分析脆性岩石在压缩作用下的短期和长期行为。在这项研究中开发的模型提供的信息不仅宏观力学响应的岩石，如强度，但也微观信息，如裂纹长度和裂纹密度在非弹性变形。该模型涉及的参数较少，可以通过三轴压缩试验、蠕变试验和微裂纹的微观观察来确定。该模型来自拉伸微裂纹力学。据推测，局部拉应力，从而滑动上的凹凸导致微裂纹生长。通过对单个微裂纹分析的推广，并考虑到相邻微裂纹间的相互作用对裂纹扩展的直接影响，导出了脆性岩石压缩裂纹扩展模型，为了说明该模型的预测结果， ...更多信息 通过对稻田花岗岩短期力学试验的模拟，验证了该模型的有效性。将数值计算结果与三轴压缩试验结果和微观裂纹观测结果进行了比较。数值模拟得到的峰值应力与围压高于10 MPa的三轴压缩试验中观察到的峰值应力吻合较好，而且本模型能够再现实验室蠕变试验中常见的三个特征阶段。通过拟合干、湿两种条件下的蠕变应力比曲线与破坏时间的数值计算结果，确定了稻田花岗岩亚临界微裂纹扩展参数。扩展模型的使用不仅可以分析微裂纹长度的扩展，而且可以分析隧道周围开挖损伤区随时间的发展。少

The purpose of this study is to establish a micromechanics-based continuum damage model to analyze short- and long-term behavior of brittle rocks under compression. The model developed in this study provides information on not only the macroscopic mechanical responses of rock such as strength, but also microscopic information such as crack lengths and crack density during inelastic deformation. A small number of parameters are involved in this model and can be identified from the results of triaxial compression tests, creep tests and microscopic observation of microcracks. The model is derived from the mechanics of tensile microcracks. It is assumed that local tensile stress thereby sliding up on asperities causes microcracks growth. By generalizing the analysis of one single microcrack and also, including the effects of interaction among neighboring microcracks directly on cracks growth, the proposed model for brittle rocks under compression is derived.In order to illustrate the predi … More ctive capability of the proposed model, the model is applied to simulation of short-term mechanical tests of Inada granite. Numerical results are compared with experimental data from triaxial compression tests results and microscopic observations of microcracks. The peak stress obtained numerically is in good accordance with the one observed in triaxial compression tests under a confining pressure higher than 10 MPa.Furthermore, the present model is capable of reproducing the three characteristic stages of long-term behavior commonly observed in laboratory creep tests. The sub-critical microcrack growth parameters can be determined for Inada granite by fitting the numerical results of elapse time to failure versus the creep stress ratio curve with the experimental data under both dry and wet conditions. Use of the extended model makes it possible to analyze not only the extension of microcrack length, but also the development of the excavation damage zone around tunnels as a function of time. Less