循环加卸载下纤维增强泡沫轻质土变形特性

Deformation characteristics of fiber-reinforced foam lightweight soil under cyclic loading and unloading

为了研究聚丙烯纤维增强泡沫轻质土的损伤变形特性,选用UNSAT非饱和土三轴仪开展50 kPa围压作用下的循环加卸载试验.以泊松比、弹性模量提高率及弹塑性变形趋势为参数,分析不同纤维质量分数条件下聚丙烯纤维增强泡沫轻质土的力学特性和变形规律.研究结果表明:当纤维质量分数达到0.50%~1.00%时,初次弹性模量提高率为56.88%~69.43%,纤维对泡沫轻质土内部初始缺陷的改善作用最佳;纤维增强泡沫轻质土试样的弹性模量提高率随着循环次数的增加呈先增大后减小的趋势,泊松比随着循环次数的增加而增大,在经历最初的2、3次循环荷载作用后趋于稳定直至试样破坏;随着循环次数的增加,纤维增强泡沫轻质土的轴向弹性应变与总应变之比逐渐降低,试样内部损伤变形逐渐累积.

The UNSAT unsaturated soil triaxial instrument was used to conduct cyclic loading and unloading tests under 50 kPa confining pressure in order to analyze the damage and deformation characteristics of polypropylene fiber-reinforced foamed lightweight soil. The mechanical properties and deformation laws of polypropylene fiber reinforced foam lightweight soil under different fiber mass fraction conditions were analyzed by using Poisson’s ratio, elastic modulus increase rate and elastic-plastic deformation trend as parameters. The research results showed that the initial elastic modulus increase rate was 56.88%-69.43% when the fiber mass fraction reached 0.50% to1.00%. The fiber has the best effect on improving the initial defects of the foamed lightweight soil. The elastic modulus increase rate of the fiber-reinforced foamed lightweight soil sample firstly increases and then decreases with the increase of the number of cycles. The Poisson’s ratio increases with the increase of the number of cycles, and tends stable after the first 2 and 3 cycles of loading until the sample is broken. The ratio of the axial elastic strain to the total strain of the fiber-reinforced foam lightweight soil gradually decreases as the number of cycles increases,and the internal damage and deformation of the sample gradually accumulate.