损伤岩石试样的力学特性与纵波速度关系研究

STUDY ON RELATION BETWEEN MECHANICAL PROPERTIES AND LONGITUDINAL WAVE VELOCITIES FOR DAMAGED ROCK SAMPLES

讨论大理岩试样围压下压缩和砂岩试样经历不同温度烘烤后的力学特性与纵波速度的关系。岩石不是线弹性材料,纵波速度、杨氏模量和强度是岩石试样力学性质的不同宏观表现。大理岩块曾经历地质应力,局部的低强度材料可使其附近材料承受较小荷载,晶粒之间维持相对较好的接触状态,因而试样初始纵波速度和强度呈负相关性。围压下压缩时大理岩试样承载能力随着变形增大可以大致保持恒定,但内部材料产生损伤弱化,损伤特性与围压、轴向变形有关。损伤大理岩试样的纵波速度和单轴强度、杨氏模量之间具有相关性,但例外现象大量存在。粗砂岩主要由矿物颗粒和胶结物构成,试样烘烤后胶结物发生变化而刚度降低,因而纵波速度和初始切线模量随温度增加而降低;但岩石的热变形可以改善颗粒间接触状态,降温之后因摩擦作用等并不会消失,因而在500℃之内平均模量随温度增加变化不大,强度却有增大趋势;其后平均模量和强度才开始降低。

The longitudinal wave velocity was used to review the mechanical properties of marble specimens which were compressed under confining pressure and coarse sandstone specimens which were heated to various temperatures. Rock is not a kind of linear elastic material. The longitudinal wave velocity, Young＇s modulus and strength are different macroscopical behaviors of rock mechanical properties. There is a clear inverse correlation between strength and longitudinal wave velocity of specimens. It can be explained as that marble has been compressed by geostresses and the lower strength in a local place would result in the lower stress on the material neighborhood and better contact among crystals. Marble specimen was damaged continuously during compression under confining pressure while the bearing capacity keeps constant. The damage in specimen changes with confining pressure and axial deformation. The longitudinal wave velocity, uniaxial strength and Young＇s modulus of damage specimens only have a positive statistic correlation roughly, but there are some exceptions. Sandstone is made of mineral particles and cement. The cement will be weakened after heated, which results in the decrease of longitudinal wave velocity and initial modulus. But thermal deformation may improve the contact state of mineral particles departed by fissure, so the average modulus is nearly the same and strength becomes higher before temperature increases to 500 ℃, after that the average modulus and strength decrease with temperature.