剪切荷载作用下砂岩细观开裂扩展演化特征研究

 利用自主研发的煤岩细观剪切试验装置，对砂岩在剪切荷载作用下微裂纹的开裂扩展过程及其破坏后细观裂纹的分布特征进行试验研究，同时借助图像处理技术，探讨砂岩在剪切荷载作用下微裂纹的时空演化规律。研究结果表明：在剪切荷载作用下，砂岩试件外观损伤在加载过程中的大部分阶段不明显，而砂岩的开裂扩展在相对较短的时间内完成，且开裂扩展过程中产生的变形较小，其明显的开裂扩展过程多发生在峰值应力后的破坏阶段，且总体上是自下往上发展的；砂岩断裂破坏过程中既有绕晶破裂，也有穿晶破裂产生，但其开裂扩展主要产生于颗粒边界和胶结物中，这主要是该破裂方式需要消耗的能量较少；由于受砂岩表面矿物颗粒的排列组合方式、胶结程度等因素的影响，细观裂纹的开裂扩展方向具有一定的不规则性，与预定的剪切面方向有一定程度的偏差。

STUDY OF EVOLUTION LAW OF MICROFRACTURING PROGRESS OF SANDSTONE UNDER SHEAR LOADING

Experimental study is made on microfracturing progress of microcrack of sandstone and its distribution characteristics after failure under shear loading condition by independent developmental coal or rock microscopic shear testing device. Simultaneously，temporal and spatial evolution law of microcrack of sandstone under the shear loading is also researched by image processing technology. The results show that damage of sandstone specimen in external appearance is unconspicuous in most part of the loading process，and microfracturing progress of sandstone is finished in a relatively short time. Deformation of sandstone is also small during the fracturing progress. The conspicuous microfracturing progress is in the damage stage after peak stress and in general the fracture is extended upward from the bottom of the specimen. Furthermore，in the process of rupture failure of sandstone，it is produced both intergranular fracture and transgranular fracture，however，the main microfracturing progress is produced in grain boundary and cement；this is mainly low consume energy in the failure mode. Because the fracturing progress of microcrack is influenced by permutation and combination mode and cementation degree of mineral particles in sandstone surface；the spreading direction of microcrack has irregularity，which has bias in some degree compared with predetermined shear plane.