Abstract: To study the influence of thermal physical parameters of rock mass on seepage heat transfer results, based on discrete element 3DEC software, the heat-flow coupling numerical model of granite with parallel double fractures was established, and the model was verified by comparing with the analytical solution. Based on the numerical model, the distribution characteristics of the rock mass temperature field under different parameters were studied. Combined with the orthogonal experiment method, the sensitivity analysis of the parameters affecting the heat-fluid coupling was carried out. The results showed that the maximum error between the numerical solution and the analytical solution was 3.45%, which indicated that the model is accurate and reliable in studying the heat transfer problem of water flow in fractures. After the model runs for 24 h, the temperature of the inlet and outlet of the fracture is different under different schemes, which indicates that different parameters have different effects on the seepage heat transfer. Along the flow direction of fracture fluid, the sensitivity of model temperature to test parameters tends to decrease. The range values of specific heat capacity of rock mass, fluid velocity and fracture opening at the fracture inlet (point B) are 10.25, 13.80 and 13.25 respectively. The specific heat capacity of rock mass, fluid velocity and fracture opening were the main factors affecting the temperature of heat flow coupled model. The extreme difference values of rock mass heat conductivity and fluid rock heat transfer coefficient were 6.53 and 4.66, respectively. The rock mass heat conductivity and fluid rock heat transfer coefficient had little influence on the model temperature.

Key words: heat-flow coupling, orthogonal test method, sensitivity analysis, double fractured rock mass, numerical modeling