二次纤维水泥土力学特性研究

为弥补水泥土材料受压破坏后承载能力迅速衰减的缺陷,借鉴纤维改善水泥基材料性能的方法,以废纸降解获得二次纤维制成的二次纤维水泥土为研究对象,通过无侧限抗压试验分析其抗压强度、变形特征和破坏形态,提出考虑纤维掺量的应力-应变关系,探索水泥土改良新措施及废纸资源利用新途径。结果表明,1)养护28 d时,同样产生1.42%应变时,水泥土强度下降39%,而掺量为2%的二次纤维水泥土强度下降仅为27%,掺入2%二次纤维不仅可以提高水泥土强度0.42%,也可使水泥土达到峰值应力时产生的应变延后1.82%;2)纤维掺量存在一个阈值,当掺量高于阈值时纤维水泥土强度随养护时间的增加而降低,当掺量低于阈值时变化规律则相反;3)掺入2%和4%的二次纤维使水泥土由中部劈裂破坏转变为土体典型的剪切破坏,破坏时保留了水泥土产生裂纹较少,无明显挤压变形等优点。添加二次纤维可以在保持强度的同时减少水泥土工程缺陷,研究结果丰富了纤维水泥土理论,可为水泥土工程应用及基础研究提供参考。

Study on mechanical properties of secondary fiber cement-soil

In order to remedy the rapid decline of bearing capacity of cement-soil materials after compression failure, learning from the method for improving the properties of cement-based materials by fiber, the secondary fiber cement soil made from waste paper degradation was taken as the research object. Through unconfined compression test, the compressive strength, deformation characteristic and failure mode were analyzed, and the stress-strain relationship considering fiber content was proposed to explore new measures for improvement of cement-soil and new ways for utilization of waste paper resources. The results show that: 1) After 28 days of curing, both two kinds of cement-soil produce the strain of 1.42%, the strength of cement-soil decreases 39%, while the strength of cement-soil with 2% fiber decreases 27%, and the strength of cement-soil with 2% secondary fiber can be increased by 0.42% and the strain, produced when the peak stress is reached, can be delayed by 1.82%. 2) There is a threshold value for fiber content. When the content is higher than the threshold value, the strength of fiber cement-soil decreases with the increase of curing time, while when the content is lower than the threshold value, the change rule is opposite. 3) Adding 2% and 4% of secondary fiber makes the cement-soil change from the middle split failure to the typical shear failure of the soil, which retains the advantages of less cracks and no obvious extrusion deformation. Adding secondary fiber can not only maintain the strength but also improve the defects of cement-soil engineering. The research content enriches the theory of fiber cement-soil and provides reference for the application and basic research of cement-soil engineering.