季冻区粉煤灰加固路基土力学性能试验研究

为探究冻融循环作用对粉煤灰加固路基土力学性能影响,对冻融循环次数、含水率、粉煤灰掺量不同的盐渍土开展无侧限抗压试验和三轴剪切试验,研究冻融循环后土体的应力-应变曲线、无侧限抗压强度、黏聚力和内摩擦角的变化情况。使用Design-Expert 8.0软件,研究冻融循环次数、粉煤灰掺量、含水率及各因素交互作用对盐渍土力学性质影响的显著性程度。结果表明:多次冻融循环后,盐渍土无侧限抗压强度、黏聚力和内摩擦角均有下降,经历1~7次冻融循环时,土体各力学参数下降速率较快;随着粉煤灰掺量的增加,盐渍土的内摩擦角、黏聚力、无侧限抗压强度和抗剪强度呈现出先升高后下降的变化趋势。基于显著性分析理论,冻融循环次数与含水率的交互作用对盐渍土无侧限抗压强度和黏聚力的影响较为显著,粉煤灰掺量与冻融循环次数的交互作用仅对无侧限抗压强度影响较为显著。为提高路基土强度及抗冻融的能力,加快粉煤灰综合利用进度,根据软件和公式模拟结果,推荐在路基土中依据质量比掺加15%粉煤灰,并将经历7次冻融循环后压实盐渍土的力学指标作为工程设计参考值。

Mechanical Properties of Fly Ash Reinforced Subgrade Soil in Seasonally Frozen Area

In order to investigate the influence of freeze-thaw cycle on the mechanical properties of subgrade soil reinforced with fly ash, unconfined compression test and triaxial shear test were carried out on saline soil with different freeze-thaw cycle times, moisture content and fly ash content. What's more, the changes of stress-strain curve, unconfined compressive strength, cohesion and internal friction angle of soil after freeze-thaw cycle were studied. Based on Design-Expert 8.0 software, the influence of freeze-thaw cycle times, fly ash content, moisture content and the interaction of various factors on the mechanical properties of saline soil was explored. The results show that the unconfined compressive strength, cohesion and internal friction angle of saline soil decrease after several freeze-thaw cycles, and the mechanical parameters of soil decrease rapidly after 1 to 7 freeze-thaw cycles. With the increase of fly ash content, the internal friction angle, cohesion, unconfined compressive strength and shear strength of saline soil increase at first and then decrease. Based on the theory of significance analysis, the interaction between freeze-thaw cycles and moisture content has a significant effect on the unconfined compressive strength and cohesion of saline soil. The interaction between fly ash content and freeze-thaw cycles only has obvious significance on unconfined compressive strength. In order to improve the strength and frost-thaw resistance of subgrade soil and speed up the comprehensive utilization of fly ash, it is recommended to add 15% fly ash to subgrade soil according to the mass ratio. The mechanical index of compacted saline soil after seven freeze-thaw cycles is taken as the reference value of engineering design.