Rock cavern stability has a close relationship with the uncertain geological parameters, such as the in situ stress, the joint configurations, and the joint mechanical properties. Therefore, the stability of the rock cavern should be studied with variable geological conditions. In this paper, the coupled hydro-mechanical model, which is under the framework of the discontinuous deformation analysis, is developed to study the underground cavern stability when considering the hydraulic pressure after excavation. Variable geological conditions are taken into account to study their impacts on the seepage rate and the cavern stability, including the in situ stress ratio, joint spacing, and joint dip angle. In addition, the two cases with static hydraulic pressure and without hydraulic pressure are also considered for the comparison. The numerical simulations demonstrate that the coupled approach can capture the cavern behavior better than the other two approaches without the coupling effects.
It is well-established that pore pressure built up in discontinuities has a profound effect on the mechanical behaviors of the jointed rock masses. The discontinuous deformation analysis (DDA) is a discontinuum theory which can account for the interactions between pore pressure and rock mechanics. It is also a numerical method or computer program commonly applied to hydro-geomechanical modeling.Research and development of DDA hydro-mechanical model has been thriving over the last two decades. The main objective of this research study is to further contribute to those efforts. Specifically, the following works have been conducted to achieve this objective: (i) a seepage analysis extension is proposed to the DDA method for the modeling of seepage flow within jointed rock masses; (ii) to improve the computational efficiency of the extension in simulating quasi-static hydromechanical problems, a new solution scheme featuring a constant hydraulic aperture is introduced; (iii) a stochastic flow modeling extension is proposed to the DDA method for the simulation of heterogeneous hydraulic conductivity and aperture fields; (iv) a hydraulic crack initiation-propagation extension complete with a coupled hydro-mechanical analysis algorithm is introduced to the hybrid DDA-FEM model for the simulation of hydraulic fracturing problems. To investigate the reliability, efficiency and limitation of the proposed DDA extensions, a series of numerical examples are presented and discussed. The capability of the new DDA extensions in modeling realistic engineering problems are also verified through meaningful case studies.
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