Laboratory Tests and Numerical Simulation on the Loess Subgrade Improved by Lime-Lignin

Abstract

Conventional techniques individually incorporating the inorganic or organic modifiers are insufficient to achieve the amelioration of loess roadbed in practices, which has restricted the development of infrastructures. This paper utilizes the lime-lignin to modify the loess, for which a series of mixing samples with various additives dosages (i.e. 0,2%:1%,4%:2%,6%:3% and 8%:4%) was adopted. Laboratory experiments and numerical simulation were carried out to investigate the mechanical properties of amended loess. Test results showed that both the compressive and shear strengths of the improved loess exhibit an initial rise followed by a decline as the contents of lime and lignin increase, with the optimal improvement effect achieved at a lime-to-lignin mixing content of 2%:1%. The results also indicated that numerical simulation can well corroborate the laboratory results, which are manifested in reduced roadbed settlements and favourable stress transfer mechanisms. An intricate three-dimensional network structure established by lignin fibers and a cement-soil skeleton formed between lime hydrate and soil particles jointly improve the strength of the soil matrix. The main research findings can offer valuable theoretical references for the enhancement of the loess subgrade.