麦秸秆加筋土的强度特性及细观结构分析

为了分析麦秸秆加筋对土体抗剪强度的影响,开展了4种加筋率(0.1%,0.2%,0.3%,0.4%)和3种加筋长度(5,10,15 mm)下的三轴剪切试验.通过CT(计算机断层扫描)扫描图像,对比分析了加筋土和素土在加载过程中的细观结构变化.结果表明:麦秸秆加筋黏性土的抗剪强度和抗变形能力较素土都有显著提高,其中筋材长度为10 mm时加筋效果较好.所研究加筋条件下,土体黏聚力较素土黏聚力增大0.1～2.3倍,内摩擦角变化在±2°范围内.与素土相比,加筋土在剪切过程中无明显的宏观剪切破坏,均为鼓胀破坏.围压较小时,加筋作用明显,对土体的刚度影响较大,随着围压的增大,影响逐渐变小.CT扫描结果显示,麦秸秆加筋能够限制土体变形和裂纹扩展.因此,麦秸秆适宜作为黏性土的加筋材料.

Strength Characteristics and Mesostructure of Wheat Straw Reinforced Soil

This study presents results of an laboratory triaxial experimental program with respect to study the effect of wheat straw reinforcement on the shear strength of soil. Three axis shear tests were carried out under four reinforcement rates (0.1%, 0.2%, 0.3%, 0.4%) and three reinforced lengths (5, 10, 15 mm). The mesostructure changes of reinforced soil and plain soil during loading are compared and analyzed by using computed tomography(CT) scan image. The results show that: the shear strength and deformation resistance of wheat straw reinforced soil are significantly improved than plain soil, and the reinforcement effect is better when the wheat straw length is 10mm.In this condition, the cohesive forces of reinforced soil are 1.1 to 3.3 times that of unreinforced soil, the internal friction angle changes in the range of ±2 degrees. Compared with plain soil, the macroscopic shear failure of reinforced soil during shearing is not obvious, and all of them are bulging failure. When the confining pressure is small, the effect of reinforcement is significant, and the effect on the stiffness of soil is fine. With the increase of confining pressure, the effect becomes weaker. CT scanning results show that wheat straw reinforcement can restrict soil deformation and crack growth. It is concluded from this study that wheat straws are a suitable reinforced material for cohesive soil.