The granites are taken from Beishan area in Gansu province which is selected as a potential high-level radioactive waste disposal repository in China. The sparsely irregularly fractured rock model of 750 mm ×300 mm ×1 000 mm (width × thickness × height) consists of 18 granite rocks with vertical and oblique fractures with thermal sensors

pressure sensors and square strain rosettes installed in the interior

and a heater is placed on one side to study the influence of the heat source temperature and the crack velocity on the temperature and stress of the rock. The test results reveal that: vertical fracture water flow is mainly from the top inlet to the bottom outlet vertically

and oblique fracture water flow is mainly from the side inlet to outlet obliquely

with weak interchange flows at the intersections of the vertical and oblique fractures. Heat conduction and oblique fracture water flow control the temperature distributions in the model because a heater is put between the two oblique fracture intakes and oblique fracture length is less than the vertical fracture

while the vertical fracture water flow hinders heat conduction to the far side of the heat source. Heat transfer paths are mainly from left to right in the upper rock layer and from top to bottom in the middle rock layer and the low rock layer

due to the irregularities of heat conduction and water flow and heat transfer. The temperature gradients are smaller and thus contraction of rock is affected by tensile stress in the upper and lower rock layers

whereas the temperature gradients are larger and expansion of rock is affected by compressive stress in the middle rock layer. The major principal stress direction is being approximately orthogonal to the intersections of the oblique fracture planes and the vertical fracture planes

and the stress increment increases with the increasing of temperature gradients in the oblique planar direction. The higher the heat source temperature is

the lower the fracture water flow velocity is

the higher the rock temperature is

the greater the rock stress is

and the system requires longer time to reach steady state.