中文摘要：

节理岩体在加载与卸荷条件下,力学特性显著不同,现阶段对于节理岩体卸荷条件下的损伤特性研究较少,且未考虑不同卸荷程度对节理岩体力学特性的影响,基于此,本文开展含不同倾角预制节理岩体在不同程度卸荷损伤后重复加载试验,综合分析卸荷程度、节理倾角及围压对岩体变形特性的影响规律。研究结果表明：（1）岩样的峰值强度随着卸荷量的增加有不同程度的降低,卸荷程度较低时,对岩样极限强度影响较小,随着卸荷量逐渐增大,岩样极限强度降低程度增大。（2）围压较低时,岩样脆性跌落特征明显,随着围压的增高,岩样破坏后达到残余强度的变形开始增加,不同卸荷量造成的差异开始逐渐减小。（3）节理及卸荷量对岩样泊松比均有较大影响,节理岩样泊松比大于完整岩样,节理倾角为45°时,岩样泊松比最大;岩样泊松比随卸荷程度增加而增大,卸荷程度越高,泊松比增大速度越快。（4）节理岩体弹性模量与加载围压的大小、节理倾角以及卸荷损伤程度均有关系。随着围压的升高,岩样弹性模量逐渐增大,其增长速度随围压增大而逐渐降低;卸荷程度越高,岩样弹性模量降低程度越大,对于含不同倾角节理的岩体,影响程度又不一样,其中含45°,60°倾角节理所受影响最大。

英文摘要：

The mechanical properties of jointed rock mass are significantly different under loading and unloading conditions. However,the current research on the damage characteristics of jointed rock mass under unloading conditions is relatively less,especially the influence of different unloading degree on mechanical properties of jointed rock mass is not considered. In order to understand the influence of unloading degree,joint dip angle and confining pressure on the deformation characteristics of rock mass,the repeated loading tests are performed in laboratory. The results show that with the increment of unloading value,the peak strength decreases. It has little effect on the rock mass ultimate strength when unloading degree is low. With the increase of unloading value,the reduction of the rock ultimate strength increases. The characteristics of brittle stress drop is obvious under the low confining pressure condition,whereas with the increase of confining pressure,the rock mass deformation from failure to residual strength increases and the influence of unloading degree on rock mass mechanical properties decreases gradually. The joint dip angle and unloading degree have great effect on the Poisson＇s ratio. The Poisson＇s ratio of jointed rock specimen is bigger than that of intact rock specimen,and it reaches a maximum value when the joint dip angle is 45°. The Poisson＇s ratio increases with the unloading degree,and the unloading degree is higher,the increase rate of Poisson＇s ratio is faster. The confining pressure,joint dip angle and the unloading damage degree are associated with the elastic modulus of jointed rock mass. With the increase of confining pressure,the value of elastic modulus increases but the increase rate decreases. The reduction degree of elastic modulus increases with the increase of unloading degree. Moreover,the impact of unloading degree on elastic modulus is different for rock specimens with different joint dip angles,in which the rock specimens with 45°and 60° joint dip angles are mos