关键词: 稀疏不规则裂隙岩体, 热源, 裂隙水流速, 三维水流-传热, 温度应力, 模型试验

Abstract: 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.

Key words: sparsely irregularly fractured rocks, heat source, fracture water velocity, 3D water flow and heat transfer, temperature and stress, model test