岩石试样的加载卸载过程及杨氏模量

利用伺服试验机对岩样进行常规三轴的加载、卸载试验 ,研究岩样变形特性与应力状态的关系。岩石内部存在裂隙 ,加载过程中裂隙会闭合、滑移 ,逐步产生摩擦力 ,其最大值受到轴向应力和围压的显著影响 ,但具体数值、是否达到最大摩擦力由局部应力状态决定。卸载时摩擦力的作用方向会发生改变 ,并抑制裂隙面之间滑移变形的恢复 ,使岩样内部产生残余变形。围压对杨氏模量的影响与岩石内部的损伤状态有关 ,但岩石的损伤特征不能从岩样轴向压缩的加载或卸载杨氏模量直接反映。

Loading or unloading process in axial direction and Young’s modulus of rock specimen

The stress path of failure of rock mass is very complicated,which is different to the loading path of specimen in laboratory.In this paper,experiments of loading and unloading in axial direction of specimens were carried out in servo_controlled testing machine to study the deformation property of rock.There are fissures and cracks in specimen,which will close,slip and produce friction gradually in loading process.The maximum value of friction between fissures in specimen is influenced greatly by the axial stress and confining pressure,but the actual value is related to the local stress condition.In unloading process the direction of friction will convert to prevent restoration of shear deformation between the fissures,which results in the residual deformation in the specimen.The effect of confining pressure on Young's modulus is related to the damage state of rock,but can not be shown by Young's modulus directly.