Mechanism of energy adjustment and balance of rock masses near a deep circular tunnel

During the excavation of deep tunnels, the adjustment and balance of energy have a significant influence on the mechanical behavior of the surrounding rock masses. Understanding the energy changes in the surrounding rocks will facilitate the prevention of geotechnical disasters and the optimization of supporting schemes. The deformation and failure modes of the surrounding rock masses around a deep-level circular tunnel are analyzed by considering the stress conditions and deformation compatibility. The mechanism of energy adjustment and laws of energy transmission and transformation in the surrounding rock masses under quasi-static unloading condition are investigated. The energy balance in the surrounding rock masses is proved rigorously from the mathematical viewpoint, and the physical interpretations for each energy component are given. The results indicate that the input external energy from far region is transferred to near region in the form of work done by radial stress. The input external energy can be divided into three parts: the potential energy stored in the rock masses, the energy dissipated by plastic deformation and the work done by pressure of rock masses that will transfer into potential energy in supporting (or kinetic energy of the surrounding rock). The adjustment process of the whole energy accords with conservation of energy.