预制裂隙类岩石材料的分步卸载试验研究  

Experimental Study on Stepped Unloading of Rock-like Materials with Pre-existing Fissure

作　　者：余明坤[1] 许国伟[1] 唐国栋 范文臣[2] Yu Mingkun;Xu Guowei;Tang Guodong;Fan Wenchen(Yunnan Academy of Architectural Sciences,Kunming 650223,P.R.China;School of Safety and Resources Engineering,Central South University,Changsha 410083,P.R.China)

机构地区：[1]云南省建筑科学研究院,昆明650223 [2]中南大学资源安全与工程学院,长沙410083

出　　处：《地下空间与工程学报》2020年第6期1672-1681,共10页Chinese Journal of Underground Space and Engineering

基　　金：国家自然科学基金(11772358)。

摘　　要：采用聚乳酸(PLA)树脂材料预先充填开挖卸载区域、预埋云母片的方法制作类岩石裂隙试件,利用聚乳酸的热熔特性进行了分步开挖卸载试验研究。结合微裂纹扩展过程、发育形态、破坏面受力特征以及卸载破坏的应力应变关系,分析了预制裂隙在分步卸载下的起裂、扩展及贯通破坏机制。研究结果表明,靠近开挖断面的预制裂隙尖端最初起裂有拉伸裂纹和剪切裂纹,且极易与开挖断面贯通,而远离开挖断面的尖端最初起裂均为拉伸型翼裂纹。法向应力较低时,裂纹扩展所需的卸载步较多,更易引起裂隙尖端拉伸裂纹的扩展;法向应力较高时,裂纹扩展所需的卸载步较少,更易引起剪切裂纹的萌生与扩展。翼裂纹拉伸贯通与次生倾斜裂纹拉剪复合贯通的速率较慢,表现出明显的塑性屈服特性,而次生共面裂纹的剪切贯通速率较快。Rock-like fissure specimens is made by pre filling the unloading area with material of polylactic acid(PLA)resin and pre embedding mica slice,and the step excavation unloading test is carried out using the hot-melt properties of polylactic acid.Based on the expanding process and development form of micro-crack,the stress characteristics of failure surface and the stress-strain relationship of unloading failure test,analysis of the track,expansion and failure mechanism of pre-existing fissures under step-by-step unloading.The results show that the initial crack at the tip of pre-existing fissures near the excavation section is tensile crack or shear crack,and it is very easy to connect with the excavation section.The initial crack at the tip of pre-existing fissures away from the excavation section is only tensile wing crack.When the normal stress is low,crack expansion requires more unloading steps,so to cause the expansion of tensile crack at the tip of pre-existing fissures more easily;when the normal stress is high,the unloading steps needs less,so to cause the initiation and expansion of the shear crack more easily.The tensile failure of wing cracks and mixed tensile-shear failure of secondary inclined cracks is slow with obvious plastic yield characteristics,and the shear failure of secondary coplanar cracks is rapid.

关 键 词：岩石力学 预制裂隙 卸载 分步开挖 裂纹扩展 贯通破坏 

分 类 号：TU45[建筑科学—岩土工程]