生物胶-纤维固化黄土的三轴剪切特性研究

Triaxial Shear Characteristics of Biological Gum-fiber-reinforced Loess

为了研究生物胶-纤维固化土护坡材料在三维受力下的剪切强度特性,以瓜尔豆胶为胶凝材料,以聚丙烯纤维为增韧筋材,在控制胶-筋配比条件下对黄土开展了一系列三轴压缩试验,分析了应力-应变曲线特征,抗剪强度参数变化规律以及主要破坏形式,并讨论了瓜尔豆胶、聚丙烯纤维对黄土的协同固化机理。试验结果表明:瓜尔豆胶能有效提升小应变时的偏应力值,聚丙烯纤维能有效改变应力-应变曲线形状,当两者同时加入黄土时,不同围压下的应力-应变曲线均表现为持续硬化型,具有良好的破坏韧性及较高的偏应力值,且不受应变大小的影响;瓜尔豆胶和聚丙烯纤维混合有利于提高土体的抗剪强度,随着生物胶含量或纤维含量增加,抗剪强度先增大后减小或逐渐增大,当瓜尔豆胶含量为1.0%,聚丙烯纤维含量为0.5%时,固化黄土的抗剪强度达到最优,相较于素黄土,黏聚力提升了230.6%,内摩擦角提升了24.8%;瓜尔豆胶-聚丙烯纤维搭配可有效抑制土体的侧向变形,最优胶-筋配比下的土样破坏形态为轻微的鼓胀破坏。在瓜尔豆胶的凝胶作用、聚丙烯纤维的拉筋作用及其互促作用的协同下,土体的三轴剪切特性得到全面提升,可为路基边坡防护工程设计参数的选取提供重要的理论依据。

This study aims to investigate the shear strength characteristics of biological gum-fiber-reinforced soil slope protection material under three-dimensional stress.Guar gum(GG)is used as the binding reinforcement material,and polypropylene fiber(PF)is used as the toughening reinforcement material.A series of triaxial compression tests were performed on loess under controlled biological gum-fiber ratio conditions.The characteristics of the stress-strain curves,variations in shear strength parameters,and main failure modes were analyzed.Additionally,the cooperative reinforcement mechanism for GG and PF in loess was discussed.The results show that GG can effectively increase the deviatoric stress value under a small strain and that PF can significantly change the shape of the stress-strain curve.When both are added to the loess,the stress-strain curves under different confining pressures exhibit persistent hardening behavior,good failure toughness,and high deviating stress values,and are not affected by strain.A mixture of GG and PF is beneficial for improving the shear strength of soil.With an increase in the GG or PF content,the shear strength initially increases and then decreases or increases gradually.When the GG and PF contents are 1.0%and 0.5%,respectively,the shear strength of the reinforced loess is optimized.Compared with plain loess,the cohesion increases by 230.6%and the internal friction angle increases by 24.8%.The combination of GG-PF effectively inhibit the lateral deformation of the soil,and the damage pattern of samples with an optimum biological gum-fiber ratio show slight swelling damage.The triaxial shear strength characteristics of the soil are comprehensively improved by the hydrogel action of GG,reinforcing effect of PF,and their mutual promotion effect.These results provide an important theoretical basis for the selection of design parameters in subgrade slope protection engineering.