岩石节理分级剪切加载-蠕变-卸载的能量与变形特征

Energy and deformation characteristics of rock joints under multi-stage shear loading-creep-unloading conditions

为分析岩石节理在剪切加载-蠕变-卸载下的能量演化与变形特征,利用GCTS(RDS-200型)岩石剪切测试系统对人工劈裂岩石节理进行分级剪切加载-蠕变-卸载试验。结果表明:在法向应力小于6.5 MPa和大于7.8 MPa时,滞回环面积与循环级数分别符合线性和指数关系;总变形能和弹性变形能与法向应力呈正相关,与循环级数呈指数关系;塑性变形能与循环级数和法向载荷呈正相关。各级剪切应力加载终止时的剪切位移外包络线与直剪应力-位移曲线变化趋势相同,具有加速上升段、匀速上升段和匀速下降段;累积剪切塑性变形随循环级数增加而增大,但增大速率逐渐变慢;各级剪切加、卸载曲线均能以剪切滑移点为界分为两个阶段;剪切失稳前,加、卸载阶段的法向位移-剪切应力曲线出现在上一循环前方,循环剪切加载和(或)蠕变结束时的累积法向变形出现从增加到减小的现象。

This study aims to investigate the energy and deformation characteristics of rock joints under multi-stage shear loading-creep-unloading conditions. The experiments were conducted on jointed marble specimens using a GCTS（RDS-200） servo-controlled testing machine. The results showed that the area of the hysteresis loop had linear or exponential relationships with cycling numbers, when the normal stress was lower than 6.5 MPa or higher than 7.8 MPa, respectively. The total deformation energy and the elastic deformation energy were positively related to the normal stress and exponentially related to the cyclic number, respectively. However, the plastic deformation energy was positively correlated with cycle number and normal load. At the ends of different levels of shear stress loading, the outer envelope of the shear displacement curve had the same trend as the direct shear displacement-shear stress curve. It could be divided into three stages： accelerated growth, linearly increasing segment and linearly decreasing segment. The accumulated plastic displacement increased with increasing loading cycles, but the increasing rates decreased gradually. Each shear loading or shear unloading curve can be divided into two stages according to the shear sliding point. Before the shear failure of rock joint, the normal displacement-shear curve became lower than the later ones under shear loading and unloading conditions. The accumulated normal displacement changed from increasing to decreasing at the ends of cyclic shear loading and creeping at each stress level.