Abstract: Model tests and discrete element simulation are conducted to study the effects of water velocity on temperature and stress in
a physical rock mass model with sparse non-orthogonal sand-filled fractures，and the differences in temperatures and thermal stresses
between the tests and the discrete element simulations are analyzed and attributed to mismatches between the test setups and the
discrete model setups. The granite rocks in Beishan area in Gansu Province are studied. Results show that the filled sand fractures
strengthen thermal conductivity of fractures media, and both temperature and thermal stress of rock mass without filling are lower than
those with filling sand. Both the tests and discrete element simulations indicate that the rock mass temperature and stress decrease with
increasing fracture water velocity, but the time required for the system to reach the steady state becomes shorter. The model test shows
that oblique fracture water flow controls the temperature field. Because the existing 3DEC software does not take into account the
changes of thermal property parameters of water with temperatures, thus generating natural convection heat transfer, oblique fracture
water flow and vertical fracture water flow near the heat source control the temperature field.

Key words: non-orthogonal sand-filled fractured rocks, water flow and heat transfer, thermal stress, physical modeling, discrete
element simulation