In order to investigate the effects of fracture surface roughness and initial stress on thermal stresses generated in fractured rock masses, we conducted laboratory heating experiments on 100-mm cubic granite specimens that contained four different kinds of roughness in fractures (i.e., polished, sawcut, mated rough, and unmated rough) under different initial stresses. Thermal expansion in the vertical direction was mechanically restricted during heating, while the sample was free to expand in the horizontal direction where heating was applied through a pair of loading plates. Thermal stresses in intact rocks without discontinuities were also measured for comparison. Results revealed that the temperature distribution was nonuniform in the samples. Thermal stress was generated in the vertical direction, and it was higher in the intact rock than that in the rock masses that contained discontinuities. For the fractured rock masses, thermal stress was the highest in the polished fracture, followed by the sawcut fracture, and then the mated rough fracture, and it was the lowest in the unmated rough fracture. We found that the thermal stress has a linear correlation with the apparent equivalent Young’s modulus, which characterizes the total mechanical deformation of both the granite matrix and the fracture. We also confirmed that the thermal stress level was higher for a larger initial stress in the case with the mated rough fracture. One main reason that the thermal stress varied with fracture surface roughness, fracture wall offset, and initial stress was thought to be attributed to different magnitudes of fracture stiffness, which is dominated by fracture surface contact.

为了研究裂隙表面粗糙度和初始应力对裂隙岩体产生的热应力的影响，我们对含有四种不同裂隙粗糙度（即抛光、锯切、配合毛坯和未配合毛坯）在不同的初始应力下。垂直方向的热膨胀在加热过程中受到机械限制，而样品在水平方向自由膨胀，其中通过一对加载板进行加热。还测量了没有不连续性的完整岩石的热应力以进行比较。结果表明，样品中的温度分布不均匀。热应力产生于垂直方向，且完整岩石中的热应力高于含有不连续体的岩体。对于裂隙岩体来说，磨光裂隙中热应力最高，锯切裂隙次之，配合粗糙裂隙次之，未配合粗糙裂隙中热应力最低。我们发现热应力与表观等效杨氏模量具有线性相关性，它表征了花岗岩基体和裂缝的总机械变形。我们还证实，在配合粗糙断裂的情况下，初始应力越大，热应力水平越高。热应力随断裂表面粗糙度、断裂壁偏移和初始应力变化的主要原因被认为是由于不同大小的断裂刚度所致，而断裂刚度主要由断裂表面接触决定。