Effects of Freeze-thaw Cycles on the Strength of Straw Fiber-reinforced Soil
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摘要: 秸秆纤维加筋是一种优良的土质改良技术，但季节性的温度变化会导致纤维土的强度劣化，影响工程的安全稳定。为了探究冻融作用对秸秆纤维土力学特性的影响，对经历不同冻融次数的纤维土进行无侧限抗压与直剪试验。结果表明素土和纤维土的抗压强度和黏聚力随着冻融次数的增加呈指数下降的趋势，且纤维土的抗压强度和黏聚力下降幅度均明显小于素土；纤维土和素土的内摩擦角随着冻融次数的增加呈指数上升的趋势。通过SEM发现冻融后素土出现孔隙和微裂隙，造成土体强度衰减。冻融后的纤维土中包裹纤维的土体出现松动，导致筋土界面强度下降，但纤维与纤维之间的三维受力网仍发挥加筋作用，提高冻土的稳定性。Abstract: Straw fiber-reinforcement is a newly developed soil improvement technology. The variation in soil strength caused by seasonal temperature changes damages the safety and stability of geotechnical engineering projects. To investigate the effects of freeze-thaw cycles on the strength of fiber-reinforced soil, the unconfined compressive tests and the direct shear tests of reinforced samples are carried out after different freeze-thaw cycles. The test results indicates that unconfined compressive strength and the cohesion of the soil samples decreases exponentially with the increasing number of freeze-thaw cycles. However, the decrease ratio of the reinforced soil is smaller than that of the unreinforced soil. The internal friction angle of the soil samples increases exponentially with the increasing number of freeze-thaw cycles. Moreover, SEM indicates that a very distinct increase in the amount of pores and microfissures is found in the unreinforced soil after the cycles. This leads to the decrease of soil strength. The soil surrounding the fiber becomes less dense after freeze-thaw cycles, which indicates the decrease in the interfacial strength of the fiber/soil. However, the complex spatial stress network established by fibers still plays an role in the reinforcement of the fibers, which can improve the stability of frozen soil.
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Key words:
- straw fiber-reinforcement /
- freeze-thaw action /
- spatial stress network
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表 1 土的物理力学性质
天然含水率
w /%液限
wL /%塑限
wp /%塑性指数
Ip比重
eo最优含水率
wd /%最大干密度ρd /(g·cm−3) 34.3 41.09 21.71 19.38 2.65 18.36 1.87 
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