棉纤维加筋土无侧限抗压强度试验研究

Unconfined compressive strength of synthetic cotton fibers reinforced soil

为研究棉纤维加筋土的强度和变形特性,对加筋量为0.5%,1.0%,1.5%,2.0%,2.5%和3.0%,加筋长度为1.25 cm,2.50 cm,3.75 cm和5.00 cm,加筋方式为纤维随机分布、成层十字交叉分布和成层单向分布的加筋土开展无侧限抗压强度试验。试验结果表明:纤维加筋土的无侧限抗压强度随加筋量的增加和加筋长度的增加呈先增大后减小的趋势,并由此确定最优加筋量和最优加筋长度为1.0%和2.50 cm;在最优加筋条件下,纤维随机分布加筋土的平均强度较素土增加了24.8%,成层十字交叉分布加筋土的平均强度与素土基本相同,成层单向分布加筋土的平均强度较素土降低了15.1%;加筋土的应力应变特性表现为应变硬化型;加筋土的平均变形模量随加筋量的增加和加筋长度的增加先增大后减小,变化范围是0.56~1.26 MPa。通过合理方式控制纤维在土体中的分布,使其和土中拉应力方向一致时可以更加有效地控制土体的径向变形,提高土体的无侧限抗压强度。

To examine the strength and deformation properties of synthetic cotton fibers reinforced soil, an experiment is conducted to measure its unconfined compressive strength with six different fiber contents （0.5%, 1.0%, 1.5%, 2.0%, 2.5% and 3.0% by weight）, four different fiber lengths （1.25, 2.50, 3.75 and 5.00 cm）, and three different patterns of fiber distribution （random distribution, layered cross distribution and layered one-way distribution）. Results show that as both fiber content and fiber length increases, the compressive strength is increased first and then decreased, with a peak strength in the condition of fiber content of 1.0% and fiber length of 2.50 cm. Under this optimum condition, the strength is increased by 24.8% when the reinforcing fibers are added in the pattern of random distribution and decreased by 15.1% when added in layered one-way distribution, while it remains nearly the same if the fibers in layered cross distribution. The stress strain characteristics of the reinforced soil are strain hardening. With both fiber content and fiber length increasing, its average deformation modulus is increased first and then decreased, varying in the range of 0.56 - 1.26 MPa. This experiment demonstrates that the reinforcing fibers will help restraining soil radial displacement and increasing soil strength if certain reasonable and practical means can be used to control their distribution patterns so as to keep them oriented along the local tensile stress.