干湿交替对砂岩断裂特性影响试验研究

An Experimental Study on Fracture Characteristic of Sandstone Subjected to Cyclic Wetting and Dryings

董世明 淦志强 华文

DONGShiming GANZhiqiang HUAWen

深地科学与工程教育部重点实验室·四川大学, 四川 成都 610065 破坏力学与工程防灾减灾四川省重点实验室·四川大学, 四川 成都 610065

MOE Key Laboratory of Deep Underground Science and Engineering, Sichuan University, Chengdu, Sichuan 610065, China Key Laboratory of Failure Mechanics and Engineering Disaster Prevention and Mitigation of Sichuan Province, Sichuan University, Chengdu, Sichuan 610065, China

周期性的水岩相互作用对岩石的物理力学性能有较大的影响，被认为是影响岩土工程安全稳定性的重要因素之一。以典型的均质青砂岩为试验对象，利用中心裂纹圆盘试件开展了砂岩I~II复合型断裂试验，研究了干湿交替作用对砂岩I~II复合型断裂特性的影响；通过观测干湿交替后砂岩微观结构的变化特征，探讨了干湿交替作用的劣化机理；并结合复合型断裂则对试验结果进行了有效评估。研究表明，砂岩的纯I型，纯II型以及I~II复合型断裂韧度均随着干湿交替次数的增加而逐渐减小；其劣化趋势基本一致，但劣化程度略有不同。当加载角较大或II型分量主导时，干湿交替作用对砂岩断裂韧度的劣化影响更为显著。考虑了应力影响的广义最大周向应变准则和广义最大周向应力准则都能对试验结果进行很好的预测。在纯II型时，基于广义最大周向应变准则的理论预测值比基于广义最大周向应力准则的理论值更接近试验值。

Periodic water-rock interaction has a great influence on the physical and mechanical properties of rock materials, which has been recognized as one of the important factors affecting the safety and stability of geotechnical engineering structures. In this study, we conducted a series of fracture tests with central cracked Brizilian disk specimens on a typical sandstone after undergiong wetting-drying cycles to investigate the influence of cyclic wetting-drying on the mixed mode I~II fracture resistance and crack propagation. Meanwhile, the degradation mechanism of cyclic wetting and drying was discussed by observing the changing characteristics of the microstructure of sandstone after undergoing cyclic wetting and drying. Finally, the experimental results were compared with the theoretical values based on the fracture criteria. The results show that the pure mode I, pure mode II and mixed mode fracture toughness of sandstone decrease with increasing number of wetting-drying cycles. The deterioration trend of fracture toughness is similar, but the degradation degree is slightly different. The degradation effect of wetting-drying cycles is more significant for a large loading angle or a mode II dominant loading condition. In addition, there is a good agreement between the experimental results and the theoretical values based on the generalized maximum tangential strain and generalized maximum tangential stress criteria, which takes into account the T-stress near the crack tip. Moreover, the criterion provide a better prediction for pure mode II when compared with the criterion.

10.11885/j.issn.1674-5086.2020.09.30.03