Abstract: In order to study coupled groundwater flow and heat transfer in the near-field of high-level nuclear waste repositories, a meter-scale physical model with regular fractures has been constructed, using rock blocks taken from the preliminary potential Beishan site in China’s Gansu province, to conduct experiments of fracture water flow and heat transfer. As a preliminary theoretical study of the physical modeling, this paper presents a numerical modeling analysis of the fractured rock physical model using an equivalent continuum model. Under the prescribed conditions, the calculations reveal: heat conduction and fracture water flow turn quickly from uncorrelated in the early phase of heating to fully coupled at later times; while the standstill fracture water essentially behaves through heat storage and conduction, the fracture water flow can induce heat convection between water and the rock matrix as well as heat advection; if the fracture water flux is kept constant, then variation of the fracture aperture would exert little influence on the system; if the fracture water velocity is kept constant, then the effect of the variation of the fracture aperture would be significant; higher heat intensity would cause more convection heat transfer from fracture water flow and larger water pressure increase, and the latter effect would be much more significant when the temperature exceeds 100℃; the model system approaches to steady state after about 7 days of heating , with the amount of heat flushed out due to fracture flow equaling the effective heat input.

Key words: nuclear waste repository, fractured rock, groundwater flow, heat transfer, equivalent continuum model, numerical modeling