纤维加筋土中单根纤维的拉拔试验及临界加筋长度的确定

纤维加筋土物理力学性质主要受纤维与土界面之间作用力大小的控制,了解界面的微观力学行为对研究纤维加筋土的机制及工程应用具有重要意义.首先,利用自行设计的纤维拉拔试验装置,对不同含水率和不同干密度的土样进行了单根纤维的拉拔试验,测试并计算了单根纤维与土接触面之间的剪切强度和残余剪切强度,分析了含水率和干密度大小对它的影响.结果表明,设计的试验装置和试验方法能较好地进行单根纤维的拉拔试验,具有较高的准确性和精度.获得了纤维加筋土中界面剪切强度和残余强度与土样含水率和干密度之间的定量关系;分析拉力-位移曲线表明,加筋土中纤维的拉拔特性取决于筋土界面的力学行为,曲线的形状受含水率和干密度的影响不明显.最后,利用测得的筋土界面强度导出了纤维加筋的临界长度.

Single fiber pull-out test and the determination of critical fiber reinforcement length for fiber reinforced soil

The interfacial interaction between the fiber and soil matrix is a key parameter in controlling the strength behavior, physico-mechanical properties of fiber reinforced soil (FRS). Therefore characterization and analysis of the micromechanical behavior such as the interfacial shear strength ?f is significant for investigating the mechanism of FRS and particular application to engineering. In order to assess and investigate the ?f and interfacial residual shear strength ?r of PP-fiber (polypropylene fiber) reinforced soil, the single fiber pull-out tests are carried out on the soil samples with different water contents and soil dry densities by using the tester designed by ourselves. The influence of water content and dry density on the ?f and ?r is analyzed. This investigation proves that the designed tester can be applied to single fiber pull-out test effectively; and the test results are exact. It is found that the ?f and τr of samples are decreased with the increase of water content, while increased with an increase in soil dry density. The behavior of the force-displacement curves in the pull-out test depends ultimately on the intrinsic characteristics of the interface; and the shape is not significantly influenced by the water content and dry density. Finally, the critical fiber length is assessed by the obtained interfacial shear strength of fiber/soil.