安全与环境学报

为了使湿陷性黄土满足工程填料的要求，利用黄原胶和聚丙烯腈纤维对黄土进行改良，开展改良土的无侧限抗压强度试验、湿陷性试验和微观试验研究，并综合分析各项试验结果以探究改良机理。结果表明：随着黄原胶和聚丙烯腈纤维质量分数的增加，试样强度呈现先上升后下降的趋势，当黄原胶掺量为1.5%且聚丙烯腈纤维掺量为0.6%时，改良土抗压强度达到峰值。同时该掺量下改良土的抗湿陷能力最强，养护28 d后的湿陷系数降至0.012,属于非湿陷性黄土，说明混掺材料改良黄土能够有效消除土体的湿陷性；黄原胶可以与土颗粒之间产生胶结作用、分子键作用，聚丙烯腈纤维能够有效地包裹和缠绕土颗粒，两种材料联合时能够形成固化剂-纤维-土颗粒的耦合模式，进一步提高对黄土的改良作用。

This study examines how collapsible loess can satisfy engineering fill requirements. Initially, the optimal dosage of xanthan gum was determined through Unconfined Compressive Strength(UCS) testing. Subsequently, a composite modification was performed by incorporating varying amounts of Polyacrylonitrile(PAN) fibers. The modified soils were subjected to UCS testing, collapsibility assessments, and microscopic structural analyses. A thorough evaluation of all test results was conducted to identify the optimal composite dosage. Additionally, pore characteristic investigations were conducted to clarify the underlying reinforcement mechanisms. The results indicated that in the single-additive tests, xanthan gum significantly enhanced the compressive strength of the specimens, peaking at a dosage of 1.5%. Strength improved with increased curing time; however, the specimens typically exhibited brittle failure. In the composite modification tests, the strength of the specimens initially increased before declining as the dosages of xanthan gum and PAN fibers were raised. This trend indicates that excessive amounts of gel and fiber can clump together within soil pores, thereby diminishing cohesion between soil particles. At the optimal dosage of 1.5% xanthan gum and 0.6% PAN fiber, the modified soil achieved its peak compressive strength. Notably, at this optimal dosage, the stress-strain curve did not exhibit a clear peak, and the residual strength was significantly improved. Furthermore, at this dosage, the anti-collapsibility performance was maximized, with the collapsibility coefficient decreasing to 0.012 after 28 days of curing, classifying the soil as non-collapsible loess. As the curing time increased, the resistance to collapsibility of specimens at all dosage levels gradually improved, indicating that the combined additives effectively mitigate the collapsibility of loess. Microscopic tests revealed that xanthan gum primarily enhances soil properties through cementation and molecular bonding with soil particles. In contrast, PAN fibers provide physical reinforcement by effectively wrapping around and interweaving with the soil particles. When used together, xanthan gum and PAN fibers create a binder-fiber-soil particle coupling system that further amplifies the modification effects on loess.