聚丙烯纤维加筋砾质黏土的拉伸断裂特性研究

Tensile fracture properties of gravelly soil reinforced by polypropylene fiber

自主研发了一种用于土体拉伸试验的新型拉伸装置,针对不同砾石含量、不同纤维含量的砾质黏土开展了多组拉伸试验。由试验结果发现,砾质黏土的抗拉强度随着砾石含量的增大而降低,在砾质黏土中掺入聚丙烯纤维后,其抗拉强度和极限拉应变明显增大;纤维加筋砾质黏土的抗拉强度和极限拉应变与其中的纤维含量呈正相关关系,但随着砾质黏土中砾石含量的增大,纤维的掺入对其抗拉强度的提升作用明显降低。电镜扫描分析表明,纤维与土颗粒界面产生的摩擦作用是导致加筋砾质黏土抗拉强度提高的主要原因,砾石含量为0%的纯黏土试样,因仅存在纤维/土颗粒界面的I类纤维,土体的抗拉强度提高非常明显;随着砾石含量增大,纤维/土颗粒/砾石界面II类纤维的占比增加,纤维的掺入对其抗拉强度的提升作用明显降低。最后,基于60个试样的试验结果,提出了一个纤维加筋砾质黏土的抗拉强度的多元回归模型,可快速预测不同砾石含量和纤维含量下砾质黏土的抗拉强度。相关试验结果可为高土质心墙坝防渗心墙的抗裂设计提供参考。

A series of tensile tests was conducted on gravelly soil based on a new self-developed soil tensile device.The different gravel contents and fiber contents were considered in the test.It is found that the tensile strength of gravelly soil decreases with the increase of gravel content,and the tensile strength and ultimate tensile strain of gravelly soil increases significantly after polypropylene fiber is added.The tensile strength and ultimate tensile strain of fiber-reinforced gravelly soil are positively correlated with the fiber content.However,as the gravel content in the gravelly soil increases,the effect of fiber incorporation on its tensile strength is significantly reduced.Scanning electron microscope analysis shows that the friction of interface between the fiber and the soil particle is the main reason for the increase of the tensile strength of the fiber-reinforced gravelly soil.For the pure clay specimen with a gravel content of 0%,the tensile strength of the soil is dramatically improved because there are only type-I fibers at the fiber/soil particle interface.As the gravel content increases,the proportion of type-II fibers at the fiber/soil particle/gravel interface increases,and the effect of fiber incorporation on the improvement of its tensile strength is markedly reduced.Finally,based on the test results of 60 specimens,a multivariate regression model for the tensile strength of fiber-reinforced gravelly soil is proposed,which can quickly predict the tensile strength of gravelly soil with different gravel contents and fiber contents.The test results can provide references for the anti-cracking design of core wall of high earth core wall dams.