中文摘要：

首先以大庆油田薄差油藏的砂泥岩储层力学参数为基础,根据相似原理,制备了砂泥岩相似材料试件。然后通过三点弯曲实验构建了Ⅰ型裂缝扩展,并采用数字散斑相关方法,获得了裂缝扩展过程中试件表面散斑场的变化规律。由此给出了界面位置处裂尖的应力奇异性阶数及应力强度因子,了解了材料强度差异对裂缝在界面扩展特性的影响。分析表明,当垂直裂缝从高强度材料一侧扩展时,界面的应力奇异性阶数大,界面的应力集中效应高,KⅡ/KⅠ比值小,裂缝拐折程度小,反之亦然。

英文摘要：

Taking sandstone and shale reservoir mechanical parameters of thin and poor oil deposit from Daqing oil field as design basis, according to similarity principle, specimens similar to practical sandstone and shale were prepared first. Type I crack extension was established by three-point bending experiment. Digital speckle correlation method was adopted to obtain the evolution of specimen surface speckle field in crack extension process. Thus, stress singularity order of crack tip and stress intensity factor in the bedding interface position are given. Then the influence of material strength difference on crack extension characteristics in bedding interface is understood. Analysis shows that when vertical cracks extend from material＇s high strength side, the interface stress singularity order is large, and the interface stress concentration effect is high. Meanwhile, ratio of KⅡ/KⅠ is small and crack inflection degree is also small, and vice versa.