Micro-cracks are known to greatly affect the mechanical properties of granite and subcritical crack growth (SCG) is considered to be the main mechanism of brittle creep in rocks, including granite. Here, we provide new uniaxial compressive strength and creep experiments for Lanhélin granite, and a new multi-crack numerical model to explain the experimental observations. We first thermally-stressed our granite samples to create thermal micro-cracks. Uniaxial compressive strength experiments were then used to find the uniaxial compression strength of the thermally-cracked granite, a pre-requisite for brittle creep experiments. We introduced a new model that combines SCG theory and the numerical manifold method (NMM) to link the local damage caused by micro-crack propagation and the macroscopic creep deformation observed in the granite samples. We also investigated the influence of virtual micro-crack length, confining pressure, and differential stress on brittle creep behavior. According to our model, we can numerically simulate the entire creep process, from the small deformation caused by micro-cracks to the large displacement characteristic of brittle creep. The fact that the numerical simulations are in good agreement with experimental results shows that the NMM combined with the SCG theory is a suitable method for modeling the creep behavior of rocks.

众所周知，微裂纹会极大地影响花岗岩的力学性能，亚临界裂纹增长（SCG）被认为是包括花岗岩在内的岩石中脆性蠕变的主要机理。在此，我们为Lanhélin花岗岩提供了新的单轴抗压强度和蠕变实验，并提供了新的多裂纹数值模型来解释实验观察结果。我们首先对花岗岩样品进行热应力处理以产生热微裂纹。然后使用单轴抗压强度实验来找到热裂花岗岩的单轴抗压强度，这是脆性蠕变实验的先决条件。我们引入了一个新模型，该模型结合了SCG理论和数值流形方法（NMM），将由微裂纹扩展和花岗岩样品中观察到的宏观蠕变引起的局部损伤联系起来。我们还研究了虚拟微裂纹长度，围压和微分应力对脆性蠕变行为的影响。根据我们的模型，我们可以数值模拟整个蠕变过程，从微裂纹引起的小变形到脆性蠕变的大位移特性。数值模拟与实验结果吻合的事实表明，将NMM与SCG理论相结合是模拟岩石蠕变行为的合适方法。