Evaluation and Analysis of the Effect of Lignin Amelioration on Loess Collapsibility

The road subgrade and road surface in collapsible loess area are prone to many engineering diseases such as uneven subgrade settlement, insufficient bearing capacity of soaked foundation, collapse and instability of subgrade side slope due to the special properties of loess. As an environment-friendly, low-cost soil modifier with good adhesion and chelation properties, lignin has been considered to be used in highway subgrade construction. In order to explore the effect of lignin on loess, the compressive and collapsible properties of modified loess with different lignin contents were analyzed based on consolidation compression test. The improvement mechanism of lignin on loess collapsibility was studied by means of infiltration test and SEM test. The results show that lignin fibers can promote the agglomeration of loose particles and form a network structure in the soil particle pores, enhance the cementation strength between particles and soil skeleton, and reduce the permeability of loess. With the increase of lignin fiber content, the improvement degree of loess collapsibility shows a trend of first increasing and then decreasing. When the lignin fiber content is 2%, the effect is the best, and the improved loess collapsibility is eliminated.