黄麻与聚乙烯醇纤维增强水泥土的弯曲及早期抗裂性能

深层水泥土搅拌桩围护墙具有水泥基材料的特性,包括脆性破坏以及较低的拉伸强度和弯曲强度,且温度应力产生的干燥收缩可能会导致裂缝的产生并引起墙体渗漏和塌陷。本文研究了黄麻纤维和聚乙烯醇(PVA)纤维增强水泥土搅拌桩的弯曲性能和裂后性能,并对纤维改善水泥土早期干缩裂缝的效果进行了对比。结果表明,随着黄麻纤维和PVA纤维含量的增加,第一裂缝弯曲强度和峰值弯曲强度均逐渐增加。纤维对改善水泥土的裂后性能起着至关重要的作用,水泥土残余弯曲强度比、延性指数和韧性随纤维含量增加显著提高。黄麻纤维在韧性方面的表现略好于PVA纤维,在其他裂后指标上两种纤维差距较小。采用数字图像相关方法研究纤维对水泥土早期塑性收缩裂缝的影响,结果表明,水泥土中添加纤维可有效抑制干燥条件下收缩裂缝的形成和扩展,纤维的掺入有效减小了水泥土干缩裂缝的宽度和数量,且纤维含量越多效果越佳。

Flexural Performance and Early Desiccation Cracking Behavior of Cemented Soil Reinforced by Jute and PVA Fibers

Deep cemented soil mixing retaining wall has the characteristics of cement-based materials, including brittle failure, low tensile strength and flexural strength. The drying shrinkage due to temperature stress may lead to desiccation cracks, which may result in leakage and collapse. In this paper, the flexural performance and post-cracking performance of jute fiber and polyvinyl alcohol (PVA) fiber reinforced cemented soil were studied, as well as the effects of fibers on reducing desiccation cracks of cemented soil at early stage. The results show that with the increase of fiber content, the first crack flexural strength and peak flexural strength increase. In addition, the fiber has good results in improving the post-cracking performance of cemented soil. The residual flexural strength ratio, ductility index and toughness increase significantly with the increase of fiber content. The jute fiber is slightly better than PVA fiber in toughness, it is observed tiny difference between the two types of fibers with regard to other post-cracking index. Moreover, the digital image correlation method was used to study the effects of fibers on the early desiccation shrinkage cracks of cemented soil. The results indicate that the fiber significantly restrains the formation and propagation of desiccation cracks under dry conditions, reduces the width and quantity of cracks, and the effect is positively related to the fiber content.