Ⅰ型加载模式下裂纹长度对压实黏土起裂机制的影响研究

Investigation of Crack Length on Crack Initiation Mechanism of Compacted Clay under Mode Ⅰ Loading

对含不同长度预制裂纹的压实黏土试样开展Ⅰ型断裂试验,结合数字图像相关方法从宏细观角度分析了Ⅰ型加载模式下土体的断裂机制,包括荷载-位移曲线、临界断裂韧度JIC、水平位移场等,结果表明:土体破坏模式与预制裂纹长度无关,荷载-位移曲线可分为压密阶段、线性变化阶段和破坏阶段;随着预制裂纹长度增大,试样临界断裂韧度JIC呈线性递减;随着荷载增大,预制裂纹尖端处的局部变形增大,水平位移等值线逐渐汇集。引入细观分析指标-水平应变密度D_(E),得出水平应变密度DE随着预制裂纹长度增大逐渐降低,与临界断裂韧度JIC呈线性相关。

Mode Ⅰ fracture tests are carried out on compacted clay specimens containing precast cracks of different lengths,and the fracture mechanism of the soil is analyzed from the macroscopic perspective by combining digital image correlation methods,including load-displace⁃ment curves,critical fracture toughness J_(IC) and horizontal displacement field.The results show that the soil damage mode is independent of the precast crack length,and the load-displacement curves can be divided into compression-density phase,linear change phase and dam⁃age phase.The load-displacement curves can be divided into compression-density phase,linear change phase and damage phase;with the increase in precast crack length,the critical fracture toughness J_(IC) of the specimen decreases linearly;with the increase in load,the local de⁃formation at the tip of the precast crack increases and the horizontal displacement contours gradually converge.The horizontal strain density D_(E),which is an index of fine view analysis,is introduced,and it is concluded that the horizontal strain density D_(E)decreases gradually with increasing precast crack length and is linearly correlated with the critical fracture toughness J_(IC).