压实黏土梁弯曲开裂性状试验研究

裂缝的存在显著降低黏土层的防渗性能。研制了土梁弯曲试验装置,研究了不同含水率压实黏土梁张拉开裂性状,分析了裂纹扩展过程,并采用PIV技术揭示了裂纹尖端的应变局部化现象,获得了不同含水率下压实黏土的开裂应变。试验结果表明:三点弯梁拉伸区可能出现多个应变局部化区域,其中靠近跨中的一个发展为宏观裂纹;裂纹宽度随中点挠度近似呈线性增长,且受含水率影响较小;含水率对土梁开裂特性和开裂应变影响很大,随着含水率由32.6%增至37.0%,土梁断裂挠度显著增加,裂纹尖端的应变局部化区域变大,开裂应变从2.4%增大至4.1%,跨中荷载挠度曲线呈现由跳回型向跳过型变化,荷载峰值明显降低,土梁由脆性断裂逐渐转变为延性断裂。

Experimental study on characteristics of bending cracks of compacted soil beams

The waterproofing properties of compacted clay barrier at landfill site will be significantly weakened by cracks. To reveal the characteristics of bending cracks of compacted soil beams with different water contents, a bending test apparatus is developed. Then the process of crack propagation is investigated. The strain localization near the crack tip is analyzed using PIV technology, and cracking strain of compacted soil beams with different water contents is obtained. The experimental results show that many strain localization regions are observed in the tensile zone of the beam, and the strain localization region near the mid-span becomes the macroscopic crack. The crack width increases linearly with the growth of mid-span displacement, which is independent of the water content. However, the water content has great influence on the cracking characteristics and strain of the beam. As the water content increases from 32.6% to 37.0%, the crack deflection of the beam increases markedly, the area of strain localization near the crack tip expands, and cracking strain increases from 2.4% to 4.1%. Additionally, as the water content increases, the pattern of load versus the mid-span displacement changes from “snap back” to “skip through”, and the peak load decreases noticeably. It is indicated that the crack pattern of compacted soil beams changes from brittle fracture to ductile one.