Westerly花岗岩试样单轴压缩破坏瞬时微裂纹观察

 利用Nishiyama和Kusuda(1994)提出的荧光方法，对Westerly花岗岩试样单轴压缩破坏瞬时微裂纹进行详细的实验观察。应用这种方法，能同时有效、容易地确认微裂纹的产生方式，如长石颗粒间的解理裂纹、石英颗粒间的晶内裂纹和这些裂纹的宽区域分布。作为一个观察结果，确认拉长的相连裂纹对花岗岩破坏有直接影响，这些裂纹大致分为3类。据推测，这3类裂纹不能同时发展，每一类有不同的产生机制。单轴压缩下裂纹的产生机制是：首先，在平行于施加荷载方向产生许多微裂纹，长裂纹是通过延长和合并微裂纹诱发产生的；然后，通过进一步加载，产生断层面，各部分的裂纹被连接、扩展；最后，花岗岩试样发生破坏。

OBSERVATION OF MICROCRACKS PATTERNS IN WESTERLY GRANITE SPECIMENS STRESSED IMMEDIATELY BEFORE FAILURE BY UNIAXIAL COMPRESSIVE LOADING

Microcrack development patterns in Westerly granite specimens stressed immediately before their ultimate failure by uniaxial compressive loading are observed using the fluorescent method proposed by Nishiyama and Kusuda(1994). Applying this method,the microscopic crack growth patterns,such as cleavage cracks within feldspar grains and intracrystalline cracks in quartz grains,and the wide-area distributions of these cracks are simultaneously confirmed with accuracy and ease. As a result of the observations,the elongated contiguous cracks estimated to have a direct impact on the final failure of granite are identified;and these cracks are roughly classified into three types. It is inferred that these three types of cracks do not develop at the same time;and each type has a different mechanism of generation. The mechanism of crack development under uniaxial compression is suggested to occur as follows. Firstly,many microcracks running parallel to the loading direction are induced by loading. Next,long cracks are induced by the elongation and coalescence of these microcracks located near the sides of the specimen. Then,the sides move outward due to further loading,generating the fault plane. The cracks within the relatively less damaged remaining parts are linked and propagated;and finally,these cracks induce the failure of specimen.