岩石裂纹附近的变形局部化与破坏——激光全息干涉法的应用

本文介绍了应用激光全息干涉法观测单轴压缩条件下裂纹附近的离面位移场和岩石的变形破坏过程。着重指出了裂纹构造活动与微裂隙丛集发育的变形局部化前兆在这种破坏过程中的相互关联,并就其所反映的震源物理本质进行了讨论。

CRACK RUPTURE AND LOCALIZATION OF DEFORMATION IN MARBLE——APPLICATION OF LASER HOLOGRAPHIC INTERFEROMETRY

Laser holographic interferometry technique is used for measuring the strain displacement field in the uni-axial compression testing of marble. The localization of deformation caused, by the augmentation of microcracks can be revealed by the hologram.Rock sample used is made of thin marble plate （105×80×6 mm） with a prefabricated tensile crack. The asperity surfaces of the crack is in contact to each other. Such a crack may be thought of as a seismic fault in an experimental simulation. The rock sample is stressed to failure under uni-axia] compression in a servo-controlled testing machine. The sample may be considered as under plane-stress state.The experiment shows:1. As the compressive stress is raised, the microfractures in the sample occur more and more frequently and with stronger intensity. The region of localization of deformation, in which the augmenting microcracks is concentrated and coalesced, is first formed from top. corner of the sample without macro-crak and it developed along the shear belt and resulted in final rupture.2. The asperities on the crack surfaces are sheared off during the slip motion. When the angle between the crack and the compressive axis is small （θ≈30°）, and the length of crack is relatively long （l≥45 mm）, the final rupture of the rock sample always happened along the shear belt where the crack is located.3. When the stress concentration comes about on the shear belt which conjugates the prefabricated crack, the interaction of these two causes the formation of X-type rupture in the rock sample.4. The crack system consisting of two cracks in the rock sample are also being tested. The state of deformation are also revealed by hologram. For two parallel cracks, the region in between the cracks could be a place of large "earthquake", it depends on the relative positions and relative slip motions of the two cracks.