Study On The Characteristics Of Ground Motion Of Lignin-improved Loess Subgrade

Loess is a Quaternary sediment with special properties such as seismic vulnerability and water sensitivity.It is prone to landslides,seismic subsidence and liquefaction under the action of earthquakes.As a new foundation treatment material with environment friendly and cost-effectively,lignin can effectively improve the seismic performance of loess subgrade under appropriate dosage.However,the application of lignin in the seismic treatment of subgrade is still insufficient at this stage.Moreover,it is necessary to study the dynamic response characteristics of ligninimproved loess subgrade under earthquake.In this paper,by consulting relevant research materials,based on laboratory test results of the lignin-improved loess,a variety of methods of on-site wave velocity test,finite element numerical simulation and regression analysis are used in the study process.The wave velocity characteristics of lignin-improved loess sites are analyzed.The self-vibration characteristics,stress characteristics and vertical displacement characteristics of lignin-improved loess subgrade are obtained.The influence laws of the thickness of lignin-improved loess and lignin content on the seismic performance of lignin-improved loess subgrade are proposed.The main research work and conclusions are summarized as follows:（1）The variation law of the wave velocity of lignin-improved loess with the thickness of the improved loess conforms to the power function model.The variation law of wave velocity of lignin-modified loess with the thickness of modified loess and lignin content conforms to the relationship of Poly surface.The wave velocity of ligninimproved loess first increases and then decreases significantly with the increase of lignin content.When the content of lignin is 1 %,the wave velocity value of ligninimproved unsaturated loess is the largest.When the content of lignin is 3 %,the wave velocity value of lignin-improved saturated loess is the largest.（2）The self-vibration frequency of lignin-improved loess subgrade ranges from1.58 Hz to 1.68 Hz,and increases gradually with the thickness of the improved loess and the content of lignin.The law of self-vibration frequency of lignin-improved loess subgrade model with the thickness of the improved loess and lignin content conforms to the relationship of Poly surface,and the vertical relative displacement coefficient also conforms to this law.The variation law of amplification factor of peak ground acceleration of lignin-improved loess subgrade model with the thickness of the improved loess and lignin content conforms to the relationship of Parabola surface.（3）When the subgrade soil is all lignin-improved loess,the inhibition effect on earthquake amplification effect and vertical displacement reaches the maximum.When the content of lignin is 1 %,the seismic performance of lignin-improved unsaturated loess subgrade is the best.When the content of lignin is 3 %,the seismic performance of lignin-improved saturated loess subgrade is the best.（4）The anti-seismic reinforcement mechanism of lignin-improved loess subgrade is mainly that lignin fiber increases the compactness of soil by filling pores,increases the bonding degree of soil by binding soil particles,improves the bonding strength of soil by exchanging ions with fine soil particles and free water to form aggregates,and reduces the thickness of double electric layer of soil by hydration and protonation.