玄武岩和聚丙烯混合纤维改良西宁黄土力学和热学特性分析

Analysis of mechanical and thermal properties of Xining loess improved by basalt and polypropylene mixed fiber

摘要:

在工程建设中，地基强度至关重要。因此，针对土体强度的改良研究始终处于学界的前沿地位。为了探究混合纤维对黄土加筋效果、作用机理及其影响因素，对青海东部的黄土进行改良研究。以取自西宁市的黄土为研究对象，通过常规三轴试验、冻融循环试验和热常数分析试验，确定出适合西宁地区单体纤维的最佳掺量和混合纤维的最佳掺量比；探讨在不同含水率和不同冻融循环次数影响下素黄土和混合纤维加筋黄土的力学和热学特性，并通过SEM从微观结构的角度评价加筋黄土的加固机理。研究结果表明：(1)在B:P=3:2时，混合纤维加筋相较于玄武岩和聚丙烯单体纤维加筋，土体强度分别提升了23.2%和13.2%；(2)当含水率分别为10%、12%、14%、16%和18%时，混合纤维加筋黄土的粘聚力和弹性模量表现出随含水率增加先升高后降低的变化趋势，当含水率为14%时，对土体强度提升最大，加筋效果最好；而内摩擦角和导热系数随含水率增加而呈现下降趋势，相较于素黄土，变幅较小。(3)在冻融循环影响下，试样的粘聚力、内摩擦角、弹性模量及导热系数均随冻融循环次数的增加呈现出下降趋势。当冻融循环次数达到20时，混合纤维加筋黄土与素黄土的强度损失率差值达到最大值9.8%。研究成果可为混合纤维加筋土的工程设计提供一定的理论依据和科学参考。

Abstract:

In the field of civil engineering, the strength of foundations is of paramount importance. Therefore, research on the improvement of soil strength remains at the forefront of academic interest. A study on the reinforcement effects, mechanisms, and influencing factors of mixed fibers on loess was conducted in eastern Qinghai. The loess from Xining City was chosen as the subject of this research. Through conventional triaxial tests, freeze-thaw cycle tests, and thermal constant analysis tests, the optimal dosage of individual fibers and the optimal mixing ratio of mixed fibers suitable for the Xining area were determined. The mechanical and thermal characteristics of the reinforced loess with mixed fibers under different moisture contents and freeze-thaw cycle counts were explored, and the reinforcement mechanism of the reinforced loess with was evaluated from a microstructural perspective using SEM. The results show that: (1) when B:P=3:2, the soil strength of mixed fiber reinforcement increases by 23.2% and 13.2%, respectively, compared with basalt and polypropylene monomer fiber reinforcement. (2)The cohesion and elastic modulus of the reinforced loess with mixed fibers exhibited an initial increase followed by a decrease as the moisture content rose from 10% to 18%. The maximum improvement in soil strength occurred at 14% moisture content, where the reinforcing effect was most effective. However, the angle of internal friction and thermal conductivity showed a declining trend with increasing moisture content, with smaller variations compared to plain loess. (3)Under the influence of freeze-thaw cycles, the cohesion, angle of internal friction, elastic modulus, and thermal conductivity of the samples all demonstrated a downward trend as the number of freeze-thaw cycles increased. When the number of freeze-thaw cycles reached 20, the difference in strength loss between the reinforced loess with mixed fibers and plain loess reached a maximum of 9.8%. These results provide theoretical support and scientific reference for the engineering design of soil reinforcement with mixed fibers.