脆性岩石细观裂纹扩展与变形、强度时间演化关系研究

Brittle behavior is obvious for the surround rock in the deep tunnel, the rock behaving brittle characteristics is called as brittle rock. Brittle rock is the important part in the surrounding rock of deep underground engineering. The deformation and strength of brittle rocks has great significance for evaluating the strength, safety and stability of surrounding rock in the deep underground engineering. Microcrack has great influence on the deformation and strength of brittle rocks. Theoretical relations of microcrack growth, and steady-state, accelerated creeping deformations (axial, lateral and volumetric strains) are hardly studied under static compressive loadings. Furthermore, relation of microcrack growth and evolution of shear strength during creep is rarely studied. The problems to be solved are: 1) Correlation of microcrack growth and axial, lateral and volumetric strains during creep, 2) Relation of microcrack growth and evolution of shear strength during creep, 3) Effect of loading and unloading path on evolution of deformation and shear strength caused by microcrack growth during creep. In this study, based on fracture and damage mechanical theories with combination of experimental results, these problems will be studied. The studies have an important theoretical meaning for understanding the deformation and failure of brittle rocks, and have a significant application value for safety of design, construction and supporting on the deep underground engineering.

深部隧道围岩的脆性行为非常常见，姑且称具有这种脆性行为的岩石为脆性岩石。脆性岩石是深部地下工程围岩的常见类型，其变形及强度问题对评价深部地下工程围岩强度、安全性和稳定性有着重要意义。脆性岩石内部细观裂纹对岩石变形及强度有着重要影响。在静力压缩蠕变作用下，岩石内部裂纹扩展与稳态、加速蠕变变形（轴向、横向及体积应变）演化关系模型研究欠缺；同时，岩石内部裂纹扩展与剪切强度演化关系模型研究几乎没有。本项目将解决脆性岩石压缩蠕变过程中的以下问题：1）岩石内部裂纹扩展与岩石轴向、横向及体积变形演化之间的相互关系；2）岩石内部裂纹扩展与岩石剪切强度时间演化之间的关系；3）加、卸载路径改变对裂纹扩展作用岩石变形、强度演化影响。本项目将基于固体断裂、损伤力学理论，并结合试验研究上述问题。这些问题的解决，对于认识脆性岩石变形与破坏具有重要的理论意义；对深部地下工程设计、施工和支护的安全有着重要的工程应用价值。

随着我国综合国力不断提升，深部地下工程的建设需求不断增加。脆性岩石是深部地下工程围岩主要组成，此外脆性岩石内部存在大量细观裂纹，细观裂纹的变化对于岩石宏观力学特性有着重要影响，此前，对于脆性岩石细观裂纹扩展与宏观变形、强度时间演化关系的研究一直是一个难点问题。本研究基于脆性固体材料断裂、损伤力学理论，建立了脆性岩石静态、准静态及动态压缩荷载作用脆性岩石细观裂纹与宏观力学特性之间的宏细观力学模型。1）提出了准静态压缩荷载作用下，脆性岩石细观裂纹扩展与宏观轴向、横向及体积应变之间的宏细观力学关系模型，研究了粘聚力、内摩擦角及剪切强度随裂纹扩展或变形演化关系，探讨了裂纹成核机理及高渗透压宏细观力学机理。2）提出了静态压缩荷载蠕变作用下，脆性岩石细观裂纹扩展、轴向应变、横向应变、体积应变、内摩擦角、粘聚力及剪切强度的时间演化宏细观力学模型，研究了加卸载路径对岩石变形及剪切强度演化影响，并探究了蠕变裂纹恢复及成核宏细观机理及高渗透压蠕变宏细观机理。3）提出了动态轴向压缩荷载作用下，裂纹扩展导致脆性岩石应力应变关系的宏细观模型，研究了裂纹速率及应变率对岩石动压缩强度、动弹性模量、动内摩擦角、动粘聚力及动剪切强度的影响。并在以上研究基础上讨论了裂纹尺寸、角度及裂纹摩擦系数对脆性岩石静态、准静态及动态力学特性影响。以上研究结果对于深部地下工程施工阶段围岩微震、岩爆及长期运营过程中围岩变形稳定性评价具有重要意义，此外该结果对于地壳地质灾害机理评价也具有重要参考价值。