Simulating excavation damaged zone around a circular opening under hydromechanical conditions

Abstract

The excavation damaged zone (EDZ) is a zone in which hydromechanical and geochemical modifications induce significant changes in flow and transport properties [1]. It is also sometimes referred to as the ‘‘disturbed rock zone’’ (DRZ) [2,3]. Microfracturing, a redistribution of in-situ stresses and rearrangement of rock structures will occur in this zone, resulting in drastic changes of permeability to flow, mainly through the fractures and cracks induced by excavation [4–6]. The creation of an EDZ is expected around all man-made openings in civil engineering (e.g. transportation tunnels and hydroelectric powerhouse), in underground mining (e.g. main shafts, horizontal tunnels, ventilation shafts, drifts and stopes), and in petroleum engineering (e.g. deep borehole). The EDZ phenomenon is of great interest in the field of radioactive waste management as it may provide a pathway for groundwater flow and potentially radionuclide transport around an underground repository for radioactive waste. The hydromechanical behaviors in the EDZ are also key issue that should be addressed in order to operate the underground mining, especially in countries such as China where a number of coal deposits are located above karst aquifers that contain large volumes of water. It is deemed that there are mainly three processes, which are stress redistribution, damage by the excavation process and weathering or interaction between rock and groundwater, may contribute to formation of the EDZ around an