Engineer Mechanical Properties And Application Of Lignin-improved Loess

In the construction of loess areas,the first problem is to solve the problem of poor engineering performance of loess,reduce or eliminate the collapsibility of loess,improve the strength of loess,and reduce the high compressibility of loess.The engineering construction can be carried out only after the engineering performance index is improved.There are many methods of loess improvement,including physical improvement,chemical improvement and biological improvement.Facing the increasingly sharp problem of ring mirror change,lignin with less impact on the environment and better environmental protection performance is selected as the soil strength reinforcement material in this paper.The goal is to improve the mechanical properties of loess soil.Based on the triaxial test,the mechanical properties of loess reinforced with lignin are analyzed.Combined with the finite element analysis software,the Improved Loess body is used to strengthen the slope body,improve the slope stability and reduce the occurrence of slope slip,so as to provide a certain theoretical basis for the prevention and control of slope disasters.The main results of this paper are as follows:（1）The plastic limit index of soil was increased by adding only lignin.The optimal dry density of lignin-modified loess was higher than that of plain loess under compaction test.Lignin can strengthen the soil skeleton and fill the soil skeleton,so that the modified soil can obtain higher density.A small amount of lime coupled lignin can reduce the maximum dry density of soil and improve the optimal water content of soil.（2）Combined with conventional triaxial test,the stress-strain curves of lignin modified loess are weak hardening.When the lignin content was 1%-5%,the loess strength was significantly improved.When lignin content continued to increase,the strength of modified soil increased little.When lignin content is too high,the soil strength decreases,and when lignin content continues to increase,the strength of modified soil is lower than that of plain soil.Lignin significantly enhanced the cohesion of modified soil.According to the results of this test,when the optimal single lignin content is 3%,the improved loess body can obtain better mechanical indexes.（3）Triaxial tests show that most of the stress-strain curves of lignin-lime modified loess show softening type under low confining pressure,while the curves show strong hardening type under high confining pressure.A small amount of lime helped to improve the level of lignin-modified loess,and the improvement strength increased significantly,which was better than that of ligninmodified loess.The improvement of internal friction Angle was not obvious,and the improvement change was less than 8°.The maximum increase of cohesion is twice of the initial cohesion.（4）Abaqus was used to analyze the slope reinforced by modified loess soil.The results showed that 3% lignin could improve the slope safety.Slope stability is improved.Lignin-lime ratio of 5:6 is better than that of lignin alone,and the displacement of monitoring point is obviously smaller than that of other additives when the through-plane is formed.The reinforcement effect can be increased with the increase of layer thickness,and the improvement of safety factor is positively related to the increase of improved thickness.Considering economic factors,it is recommended to use 3m as the reinforcement thickness for slope reinforcement.