岩石Ⅰ/Ⅱ复合断裂韧度测试的单边切槽深梁试件:数值分析与标定  

Single edge notched deep beam specimen to test Ⅰ/Ⅱ mixed-mode fracture toughness of rocks:numerical analysis and calibration

作　　者：罗毅[1,2] 任利[1,2] 谢凌志[1,2] 李存宝[1,2] 王俊[1,2] 高超[2] 

机构地区：[1]四川大学建筑与环境学院,四川成都610065 [2]四川大学能源工程安全与灾害力学教育部重点实验室,四川成都610065

出　　处：《岩石力学与工程学报》2016年第A02期3633-3643,共11页Chinese Journal of Rock Mechanics and Engineering

基　　金：四川省科技厅科技支撑项目(2012FZ0124);四川省应用基础研究计划(2015JY0280)~~

摘　　要：提出一种用于岩石材料I/II复合断裂韧度测试的新试件——单边切槽深梁(SENDB)试件,使用有限元法对新试件I(II)型无量纲应力强度因子YI(YII)及无量纲T应力T*进行系统研究和数值标定。研究结果证实SENDB试件可方便地通过调整裂纹倾角?、裂缝长度a和支座间距2S实现从纯I型到纯II型任意I/II复合度荷载作用下的岩石断裂韧度测试。与现有弯曲类试件对比分析表明:(1)SENDB试件与经典的单边切槽梁(SENB)试件在几何尺寸和岩石复合断裂韧度测试方法上存在显著差异,SENDB试件是通过调整裂缝倾角实现复合加载,而SENB则是通过移动裂缝位置(无法实现纯II型加载)或四点弯曲试验(加载装置复杂)实现复合加载;(2)因可方便地加工系列尺寸(包括大尺寸)的试件,新构形相比圆盘类试件在尺寸效应研究方面略有优势;(3)与国外学者新近提出的ECT试件相比,SENDB试件可选择的量纲一的裂缝长度和量纲一的支座间距范围要更宽泛;(4)为了实现从纯I型到纯II型整个区间的复合断裂测试,对SENDB,SCB和ECT三种试件,均应使用较小的支座间距或较长的裂缝。A new specimen,namely the single edge notched deep beam（SENDB） specimen,which could test the mixed-mode fracture toughness of rock materials was proposed. The finite element method（FEM） was used to analyze and calibrate the mode I and mode II dimensionless stress intensity factors（i.e. YI and YII） and the dimensionless T-stress（i.e. T＊） of the new specimen. Numerical results demonstrated that the SENDB specimen indeed could test the mixed-mode fracture toughness of rocks in a full range of mode mixities from pure mode I to pure mode II by different combinations of the crack inclined angle a,the crack length a and the half distance S between the two bottom supports. The dimensions of the new specimen significantly differed with the ones of the classic single edged notched beam（SENB） specimen,and the mixed-mode loadings can be introduced by an inclined crack in a SENDB specimen while for a SENB specimen mixed-mode loadings are introduced with asymmetry three points bend test（which can not introduce pure mode II loading） or four points bend test（which requires a complex loading fixture）. In the aspect of the investigation on scale effect,the SENDB specimen is more suitable than the disc-type specimens,especially for very large size. Compared to the edge crack triangular（ECT） specimen recently proposed by other researchers,the SENDB specimen can conduct mixed-mode fracture tests within a large range of dimensionless crack length and dimensionless span distance. To successfully conduct a pure mode II fracture test,a relative small span distance and a relative long crack are recommended for SENDB,SCB and ECT specimens.

关 键 词：岩石力学 断裂韧度 单边切槽深梁试样 三点弯曲试验 复合断裂 

分 类 号：TU45[建筑科学—岩土工程]