摘要
对含预制缺陷的大理岩平板施加单轴压缩,在扫描电镜下即时观察并记录了试件表面微破裂的发育及演化过程;根据记录资料,研究了裂纹密度分布和几何形状及其与材料本身颗粒大小和应力水平之间的关系,并拟合了经验关系式。试件分为带圆孔(直径5mm)和带割缝(与外载方向成45°,贯穿试件厚度)两种。整体尺寸均为20×10×2.5mm。实验表明,在室温下,大理岩材料受准静态单轴压缩时,微裂纹多发育在颗粒边界上,虽然从宏观上看,从割缝逐渐生长出来的新生裂纹似乎是沿一条圆滑的路径扩展而逐渐转向与外力方向平行。但是从微观上看,微裂纹的扩展和连通始终是沿颗粒边界曲折前进的。裂纹的密度先是随应力而提高。然后逐渐趋于稳定;裂纹在某个带上集中而形成主破裂时,其周围的部分裂纹会闭合;同时还观察到,卸载时裂纹闭合且宏观断裂的宽度变窄。这一现象在录象记录中表现得尤为明显。
Uniaxial compression tests of marble plates containing a prefabricated flaw were conducted under direct SEM observation. Subsequently, the relation among the distribution and geometry of cracks, the stress level and grain size was analysed. Experimental results indicated that when the spectimen was loaded by quasi-static uniaxial compression at room temperature, microcracks mostly devcloped along grain boundaries. Macroscopically, it was observed that the crack which initiated from the flaw turned gradually and smoothly to the loading direction, but the coelcscence of microcracks actually took place along a zigazag path following grain boundaries. The density of microcracks first increased rapidly and then gradually with the increase of loading. When microcracks clustered in a certain narrow belt to form a macroscopic fracture, some microcracks in the vicinity of the potential main fracture closed partially or even completely. This phenomenon can be more clearly seen in video records of the experimental process.
出处
《岩石力学与工程学报》
EI
CAS
CSCD
1992年第3期284-294,共11页
Chinese Journal of Rock Mechanics and Engineering
基金
国家自然基金
关键词
岩石
微破裂
发育
扫描电镜
观测
microfracturing of rock, real-time SEM obscrrvation
