为了对比分析不同类型纤维的加筋效果及其作用机制,选取玄武岩纤维、聚丙烯纤维、聚酯纤维和玻璃纤维4种常用的人工合成纤维,以黄土为研究对象,在控制试样含水率、干密度、纤维长度和掺量等参数一定的条件下,制备5组试样进行直剪试验。试验结果表明:①纤维加筋前,土体的剪应力-剪切位移曲线存在比较明显的应变软化特征,纤维加筋后的曲线逐渐由应变软化转化为应变硬化。②纤维的掺入能够有效提高土体的抗剪强度。比较而言,玄武岩纤维的增强效果较其他纤维更好,玄武岩纤维加筋土的黏聚力和内摩擦角增幅分别为52.03%和24.30%;聚丙烯纤维次之,增幅分别为45.94%和16.01%;聚酯纤维和玻璃纤维增强效果相对较差。③加筋土黏聚力的提升与纤维-土界面的黏结力、纤维自身的抗拉强度有关,内摩擦角的提升主要与纤维-土之间的界面摩擦力有关。比较而言,玄武岩纤维的表面粗糙,抗拉强度大,使得加筋土的抗剪性能提升明显。相关分析结果可为比选纤维加筋土类型提供较好的参考。

The aim of this research is to compare and analyze the reinforcement effect and mechanism of different types of fibers. Four commonly used synthetic fibers, namely, basalt fiber, polypropylene fiber, polyester fiber, and glass fiber, were selected to prepare five groups of reinforced loess specimens for direct shear test by controlling water content, dry density, fiber length, and fiber content. Results demonstrated that: 1) before fiber reinforcement, the curves of shear stress versus shear displacement of loess displayed evident strain softening features; after fiber reinforcement, the strain softening turned into strain hardening. 2) Fibers escalated the shear strength of soil. Among the tested four fibers, basalt fiber has the best reinforcement effect by enhancing the cohesion and internal friction angle of soil by 52.03% and 24.30%, respectively, followed by polypropylene fiber with an increment by 45.94% and 16.01%, respectively. 3)The improvement of the cohesion of reinforced soil is related to the cohesive force of fiber-soil interface and the tensile strength of fiber itself; the increase of internal friction angle is mainly related to the interface friction between fiber and soil. Basalt fiber is of rough surface and large tensile strength, which significantly improves the shear properties of reinforced soil.

冻融循环作用与外界环境的侵蚀是影响水泥土强度的主要因素,探索如何提高水泥土在寒冷地区盐水侵蚀环境下的强度及其发展规律是一个重要的课题。通过盐冻试验和无侧限抗压强度试验,研究了玄武岩纤维水泥土在不同溶液(3.5%(质量分数,下同)NaCl溶液、3.5%Na₂SO₄溶液、3.5%(NaCl+Na₂SO₄)混合溶液、清水)与冻融循环作用耦合下的力学性质与表观特征,探讨了养护温度、侵蚀溶液类型、冻融循环次数等变量对水泥土性能的影响。在此基础上,采用Logistic生长模型,对不同环境下水泥土试块的强度进行回归分析。研究结果表明:低温养护环境会抑制水泥土强度的发展;随着冻融次数的增加,试块出现了不同程度的质量损失、表面破坏,以及无侧限抗压强度降低的现象;在相同冻融次数下,玄武岩纤维水泥土的破坏程度由强到弱依次为硫酸盐冻＞混合盐冻＞氯盐冻＞水冻;而掺入玄武岩纤维可使水泥土经历更多次的冻融循环,有效降低强度损失率,提高水泥土的抗冻性;通过回归分析,得到不同试验组的强度衰减模型和预期强度。

The effects of freezing-thawing cycles and erosion of external environment are the main factors affecting the strength of cemented soil. It is an important subject to explore how to improve the strength characteristics and development law of cemented soil under saline erosion environment in cold areas. Based on salt frozen and unconfined compressive strength test, the mechanical properties and apparent characteristics of basalt fiber reinforced cemented soil under the coupling of different solutions (3.5% (mass fraction, the same below) NaCl solution, 3.5%Na₂SO₄ solution, and mixed solution of 3.5% (NaCl+Na₂SO₄), freshwater solution) and freezing-thawing cycles were studied. The effects of the curing temperature, erosion solution type, and freezing-thawing cycle on the mechanical properties of the cemented soil were discussed. On this basis, the Logistic growth model was used to carry out a regression analysis on the strength of the cemented soil samples in different environments. The results show that the low-temperature curing environment inhibits the strength development of the cemented soil. As the number of freezing-thawing cycles increasing, the samples have different degrees of quality loss, surface damage and unconfined compressive strength decreases. With the same freezing-thawing cycles, the damage degree of basalt fiber reinforced cemented soil from strong to weak is sulfate frozen > mixed salt frozen > chloride salt frozen > water frozen. The addition of basalt fiber makes the cemented soil undergo more freezing-thawing cycles, effectively reduces the strength loss rate, and improves the frost resistance of the cemented soil. The regression analysis is used to obtain the intensity attenuation models and the expected strength of different test groups.