Experimental study on the dynamic response of lignin-modified loess under traffic vibration and seepage wetting

Lignin can significantly enhance the mechanical properties of loess, showing promising application prospects. For many geotechnical conditions, such as subgrade, fatigue caused by traffic vibration and softening due to rain infiltration are the main damage factors. However, the dynamic response of lignin-modified loess under combined water-load action remains unclear. To address this, studies on the dynamic characteristics and microscopic enhanced mechanisms of lignin-modified loess under combined water-load action were conducted by considering the effects of traffic vibration, water content, confining pressure, and compactness. The dynamic triaxial test results showed that the optimal lignin content is 1.5 %, consistent with the results based on the static test. The dynamic strength and maximum dynamic shear modulus increased by 60.05 %, and 12.39 %, respectively. The results indicate that lignin can effectively enhance the loess’s resistance to combined water-load erosion. Additionally, as the amplitude increases, the deterioration rate of dynamic properties of the modified loess under combined water-load action significantly slows down. Furthermore, sensitivity analysis based on variance indicates that water and lignin content have the most significant effect on dynamic properties, followed by compactness and confining pressure. An empirical mechanical model for dynamic shear modulus and damping ratio under multi-factor influence was also established. Finally, combined with microscopic test analysis, the filling and bridging of lignin can effectively reduce the “promoting infiltration” and “promoting cracking” effects caused by water-load combined action, thereby enhancing its dynamic characteristics. The research results can provide a theoretical basis for road design and maintenance in loess regions. • Using a new eco-friendly material, lignin, for dynamic reinforcement of loess subgrade. • Study the dynamic response of lignin-modified loess under the influence of multiple environmental factors. • Combining with variance analysis, an empirical model was proposed to predict the dynamic parameters of the modified soil. • Through SEM, analyze the three-phase changes of soil and elucidate the microscopic mechanism of lignin-modified soil.