【摘要】 本文介绍了以激光全息干涉法观测单轴压缩下,大理岩岩样表面的变形位移场。全息干涉图可以反映出由于岩石内部微裂隙丛集激增所导致的变形局部化,实验采用板状大理岩试件,在中心处预制了不同角度的裂缝,实验在 MTS 伺服压机中加载直至宏观破坏,观测了裂隙的发展过程。实验表明:当裂缝角θ小于45°时,先在裂缝尖端处的张应力集中部位出现新裂纹,它的起裂角(与原裂缝的交角)β≈90°,裂纹弯向压力方向并趋于稳定。当θ>45°时,在上述张裂纹稳定后,在裂缝尖端附近再次发生张裂,其起裂角β≈60°,同样弯向压力方向后稳定。在这些前期张破裂稳定后,在张裂的相反方向,也即裂缝的共轭方向上,出现内部微裂隙的丛集,并随后发生宏观的剪破坏,我们认为此逆向剪切破坏与大理岩的多晶组构有关,与应变弱化过程中变形和应力的调整有关。更多还原

【Abstract】 Laser holographic interferoinetry technique is used for measuring the strain displacement field in the uni-axial compression testing of marble samples. The localization of deformation caused by the augmentation of microcracks can be revealed by the hologram.The rock sample used is a thin marble plate (105×80×6 mm) with a alot 25mm long, and less than 1 mm wide. It is stressed to failure under uni-axial compression in a servo-controlled testing machine. The sample is thought to be in a plane-stress state.The experiment shows:1. The strength of the rock sample is related to the angle 9 between the slot and the compression axis, when 0=45°, it is lowest, in agreement with the theory of fracture mechanics).2. When θ is less than 45°, crack starts to grow from points initially under tensile stress near the slot tip. The crack extensions initially make an angle β≈90° with the slot and gradually bend towards the axial direction and then become stable.3. When angle θ is larger than 45°, secondary crack growth can happen near the ends of the slot after the primary cracks. These secondary cracks initially make an angle β≈60° with the slot. They also bend towards the axial direction and then become stable.4. For the θ tested, especially when less than 45°, at the peak or over the peak loading, with the primary and secondary cracks already stabilized, there appears to have mierofractures springing up around slot tips, and developing into shear fractures in the direction conjugate to the slot and opposite to those of the two previous tensile cracks. These shear fractures seem to be the result of strain softening during the adjustment of stress and deformation near the crack tips under increasing axial loading.更多还原