In this study, the stress change of a rock mass in front of the working face during underground excavation was simulated. The effect of loading and unloading rates on the mechanical characteristics, strain energy, and failure mode evolution of the sandstone were investigated. It was found that the loading rate of vertical stress had little effect on the varying trend of the volume strain, and the volume change of the sandstone was mainly caused by the compression in the vertical direction under low unloading rate. The true triaxial strengths of sandstones under various loading and unloading rates were well characterized by the linear Mogi criterion. For energy evolution, as the loading rate increased, the total absorption energy, elastic strain energy, and dissipation energy increased. Increasing the unloading rate resulted in gradual decrease in the strain energy. The failures of sandstones were more severe at high loading rate as the elastic strain energies were higher in these conditions. For a given loading rate, more cracks were formed by consuming less energy under high unloading rate. Furthermore, compared with the loading rate of vertical stress, the unloading rate of horizontal stress was the main reason for the change in rock failure mode. Based on the change law of the curve of elastic strain energy-strain, the crack damage stress thresholds of the sandstone under different loading and unloading rates were determined, which were found to positively and negatively correlate with the loading and unloading rate, respectively.

在这项研究中，模拟了地下开挖过程中工作面前方岩体的应力变化。研究了加载和卸载速率对砂岩力学特性，应变能和破坏模式演变的影响。发现垂直应力的加载速率对体积应变的变化趋势影响很小，砂岩的体积变化主要是由于低卸载速率下垂直方向的压缩所致。线性Mogi准则很好地表征了砂岩在各种加载和卸载速率下的真实三轴强度。对于能量演化，随着加载速率的增加，总吸收能，弹性应变能和耗散能都增加了。增加卸载速率导致应变能逐渐降低。在这些条件下，弹性应变能较高，因此在高加载速率下，砂岩的破坏更为严重。对于给定的加载速率，在高卸载速率下消耗更少的能量会形成更多的裂纹。此外，与垂直应力的加载速率相比，水平应力的卸载速率是导致岩石破坏模式改变的主要原因。根据弹性应变能-应变曲线的变化规律，确定了砂岩在不同加载和卸载速率下的裂纹损伤应力阈值，发现其与加载和卸载速率分别呈正相关和负相关。在这些条件下，弹性应变能较高，因此在高加载速率下，砂岩的破坏更为严重。对于给定的加载速率，在高卸载速率下消耗更少的能量会形成更多的裂纹。此外，与垂直应力的加载速率相比，水平应力的卸载速率是导致岩石破坏模式改变的主要原因。根据弹性应变能-应变曲线的变化规律，确定了砂岩在不同加载和卸载速率下的裂纹损伤应力阈值，发现其与加载和卸载速率分别呈正相关和负相关。在这些条件下，弹性应变能较高，因此在高加载速率下，砂岩的破坏更为严重。对于给定的加载速率，在高卸载速率下消耗更少的能量会形成更多的裂纹。此外，与垂直应力的加载速率相比，水平应力的卸载速率是导致岩石破坏模式改变的主要原因。根据弹性应变能-应变曲线的变化规律，确定了砂岩在不同加载和卸载速率下的裂纹损伤应力阈值，发现其与加载和卸载速率分别呈正相关和负相关。与垂直应力的加载速率相比，水平应力的卸载速率是导致岩石破坏模式发生变化的主要原因。根据弹性应变能-应变曲线的变化规律，确定了砂岩在不同加载和卸载速率下的裂纹损伤应力阈值，发现其与加载和卸载速率分别呈正相关和负相关。与垂直应力的加载速率相比，水平应力的卸载速率是导致岩石破坏模式发生变化的主要原因。根据弹性应变能-应变曲线的变化规律，确定了砂岩在不同加载和卸载速率下的裂纹损伤应力阈值，发现其与加载和卸载速率分别呈正相关和负相关。