深部岩体力学研究与探索

RESEARCH AND DEVELOPMENT OF ROCK MECHANICS IN DEEP GROUND ENGINEERING

当今世界经济的迅速发展,地球浅部矿物资源逐渐枯竭,资源开发不断走向地球深部。目前煤炭开采深度已达1 500 m,地热开采深度超过3 000 m,有色金属矿开采深度超过4 350 m,油气资源开采深度达7 500 m,深部资源开采已成为常态。但是深部资源开发中常伴随着重大灾害事故,难以有效预测与防治,一方面说明深部岩体可能存在着完全异于浅部的力学本构行为,另一方面说明目前岩石力学理论发展已滞后于人类岩土工程实践活动,难以进行有效、科学指导,亟待探索和开拓。目前人们对超深部的岩石性质和行为还缺乏了解,一些基本概念和基本理论还尚未建立。深部是什么?多深算进入深部?浅部和深部有什么本质不同?经典力学理论能否描述超深部岩体力学行为?如何揭示深部岩体开发扰动影响下那"看不见,摸不到"的黑箱力学过程?深部环境(如地震地质环境、化学环境、热力学环境和微生物环境)如何对能源开发与存储、CO2与核废料地质处置等重大工程发生在岩石中的微观过程共同产生影响等等,这些重大的、基础性岩石力学科学问题亟待人们做出回答。从煤炭开采中的岩石力学问题研究入手,对以上深部岩体力学的一些共性的概念性和基础性问题进行探讨。指出深部静水压力是深部岩体应力状态的典型基本特征。深部不是深度,而是一种力学状态。发展有别于传统岩体力学的基于应力空间路径的采动岩体力学。提出将CT技术、3D打印技术和分形重构方法及应力冻结技术相结合的深部岩体力学的可视化研究手段,再现深部岩体在开发扰动下应力变化、裂隙演化、体积破裂、塑性失稳以及微观渗流等的力学行为和过程。这些工作将为深部岩体力学研究带来方法上的进步。

Rapid development of world economy has been gradually exhausting the shallow mineral resources. More and more attentions have been paid to the mineral exploitation in deeper subsurface of the earth. For examples,current coal mining has reached 1 500 m in depth; geothermal exploitation has reached over 3 000 m,the depth for ferrous metal mining over 4 350 m and for oil and gas development 7 500 m. Therefore,deep miningis an on-going mining industry. However,more and more engineering accidents or hazards have occurred in deep mining. These accidents or hazards are difficult to be predicted with the current theories or experiences because the mechanical behaviors in deeper ground have not been well understood. On the other hand,current research and development in rock mechanics cannot solve the practical problems in deep ground engineering. A novel research and development scheme should be specially designed for deep ground engineering. Particularly,fundamental concepts and basic theory of rock mechanics should be revisited for deep ground engineering. For examples,what is the deep ground engineering?Is it measurable by the depth of ground?What is the essential difference of the mechanical properties of rock in shallower and deeper subsurface?Can the classical rock mechanics be applied to describe the mechanical behaviors of rocks in deep ground?How can the black box of rock mechanics in deep ground be revealed during the mining induced disturbance ? How does engineering activity such as the development and storage of energy,CO2 sequestration and nuclear waste disposal in deep environments(such as earthquake,geology,geochemistry,geothermal environment as well as microbial environment) affect the micro-scale variation of rock ? These are the fundamental questions in rock mechanics for deep ground engineering. This paper revisits these fundamental concepts by taking the rock mechanics in coal mining as an example. Our results showed that hydrostatic pressure was a typical stress state in deep ground engineering. Deep ground was defined by its stress state instead of its depth. Based on this concept of stress state,we proposed a framework of rock mechanics for mining process in terms of stress paths. Such a framework is different from the classical rock mechanics. Furthermore,a visualization technology was then developed for the investigation of rock mechanics in deep ground. This technology combined the CT scanning,the 3D printing,the reconstruction technology with fractal analysis and the stress freezing technology. This visualization technology provided transparent observation of the disturbance of stress during mining,the development of fractures,the volumetric breaking,the plastic instability and the micro-seepage.