梯级等幅周期循环荷载作用下双裂隙黄砂岩力学特性试验研究  

Experimental investigation on mechanical properties of yellow sandstone samples containing two coplanar fissures under multistage constant-amplitude-cyclic loading

作　　者：李克升 刘传孝[2] LI Kesheng;LIU Chuanxiao(State Key Laboratory for Geomechanics and Deep Underground Engineering,China University of Mining and Technology,Xuzhou,Jiangsu 221116,China;College of Water Conservancy and Civil Engineering,Shandong Agricultural University,Tai¢an,Shandong 271018,China)

机构地区：[1]中国矿业大学深部岩土力学与地下工程国家重点实验室,江苏徐州221116 [2]山东农业大学水利土木工程学院,山东泰安271018

出　　处：《岩石力学与工程学报》2023年第8期1945-1958,共14页Chinese Journal of Rock Mechanics and Engineering

基　　金：国家自然科学基金资助项目(51574156);山东省重点研发计划(2018GNC110023)。

摘　　要：为研究不同动态加载频率下含预制共面双裂隙黄砂岩的力学性质和破坏特征,通过梯级等幅循环加卸载试验,借助声发射和高倍扫描电镜等设备,详细分析岩石的力学性质和变形特征,探讨整个加载过程中声发射参数的演化规律,并基于试样破坏断口处的微观构造,阐述动态加载频率对其疲劳损伤机制的影响。研究结果表明:(1)随着频率增加,试样的峰值强度、疲劳寿命和轴向应变均呈现增长趋势;(2)试样疲劳应变曲线随时间增加呈现周期性的梯级波动增长,且在岩样破坏前出现突增现象;(3)随着频率增加,声发射累计振铃计数呈二次函数增长,在高频条件下,试样破坏前监测到较高的振铃计数;(4)试样宏观破坏模式受预制裂隙和加载频率共同影响,裂纹萌生于预制裂隙尖端并逐渐向两端扩展,裂纹数目随频率增加而增长,在低频条件下,萌生于预制裂隙内尖端的翼裂纹更易汇合导致岩桥贯通;(5)随着频率增加,试样破坏断口的微观构造特征由沿晶断裂为主演化为沿晶断裂、穿晶断裂和解理断裂共存,最终向穿晶断裂为主的方向发展。This work aims to elaborate the mechanical properties and damage characteristics of yellow sandstone samples containing two coplanar fissures under diverse dynamic loading frequencies.To this end,multistage constant-amplitude-cyclic loading experiments were conducted on fissured sandstone,and the fatigue mechanical properties and deformation of the rock,the evolution of acoustic emission(AE)parameters during the loading process,the microstructural characteristics of the fractured surface of specimens,as well as the role of loading frequency on fatigue damage mechanism,were analyzed.The results show that:(1)The peak strength,the fatigue life,and axial strain of the specimens increase with growing frequency.(2)The strain of the specimen increases in a stepwise manner with longer time,and at the last fatigue stage,the specimen deformation rises dramatically until the specimen fails.(3)The accumulative AE ringing counts of the samples show a quadratic function increase with higher loading frequency,and the samples under high loading frequency capture more ringing counts before failure compared to those under low loading frequency.(4)The ultimate failure mode of the specimen is related to both the pre-existing flaws and the loading frequency,that is,the samples under low loading frequency conditions perform few cracks and unclear propagation path,and it is clearly observed that the cracks coalescence directly between the two inner tips of the pre-existing flaws.Samples under high frequency conditions exhibit complex failure mode,i.e.,wing cracks appear at pre-existing fissures tip,and the outer wing cracks respectively extend to the specimen ends,while the inner wing cracks gradually extend after indirect coalescence.(5)As the dynamic loading frequency climbs,the microscopic features of the fractured surface of the specimen evolves from dominant intergranular fracture,to the coexistence of intergranular fracture,transgranular fracture,and cleavage fracture,and to dominant transgranular fracture.

关 键 词：岩石力学 共面双裂隙 梯级等幅疲劳加载 加载频率 声发射 微观损伤机制 

分 类 号：TU45[建筑科学—岩土工程]