摘要
Traditional soil additives like Portland cement and lime are prone to cause the brittle fracture behavior of soil,and possibly,environmental impacts.This study explores the potential use of polyurethane organic polymer and sisal fiber in improving the mechanical performance of sand.The effects of polymer content,fiber content,and dry density on the unconfined compressive strength(UCS)and direct tensile strength(DTS)of the polymer-fiber-sand composite were evaluated.The results showed significant increase in UCS and DTS of the reinforced sand with the increase of polymer content,fiber content,and dry density.At high dry density condition,a single peaked stress−strain curve is often observed.Higher polymer content is beneficial to increasing the peak stress,while higher fiber content contributes more to the post-peak stress.The combined use of polymers and fibers in soil reinforcement effectively prevents the propagation and development of cracks under the stress.Scanning electron microscopy(SEM)test was also performed to investigate the micro-structural changes and inter-particle relations.It was found through SEM images that the surface coating,bonding,and filling effects conferred by polymer matrix greatly enhance the interfacial interactions,and hence provide a cohesive environment where the strength of fibers could be readily mobilized.
本研究采用聚氨酯型固化剂和剑麻纤维对砂土进行改良,针对不同固化剂含量(1%,2%,3%和4%与干砂的质量比)、纤维含量(0%,0.2%,0.4%,0.6%和0.8%与干砂的质量比)和干密度(1.45,1.50,1.55和1.60 g/cm^(3))的改良砂土进行无侧限抗压强度试验和抗拉试验研究,并结合扫描电镜图像对其微观机理进行进一步的分析。试验结果表明:改良砂土的抗压和抗拉强度均得到了显著提高;砂土的抗压强度与抗拉强度随固化剂含量增大而增大;纤维的加入提高了改良土体的残余强度;改良土体的破坏应变随着干密度的增大而减小;固化剂与纤维的联合作用抑制破坏过程中裂纹的发展。为通过扫描电镜图像发现,聚氨酯在土颗粒之间产生的联结增强了界面间的作用,为纤维产生拉筋作用提供了黏结环境。
基金
Project(41877212)supported by the National Natural Science Foundation of China
Project(2017010)supported by the Water Conservancy Science and Technology Project of Jiangsu Province,China
Project(B200202013)supported by the Fundamental Research Funds for the Central Universities,China。
