Study On Influence Factors And Mechanism Of Reinforced Soil With Bio-based Soil Stabilizer

Loess is widely distributed in the loess plateau of Shanxi, Shaanxi, and Gansu in China. Loess has large pore structure and contain relatively large amounts of calcium carbonate. The disintegration will occur when loess encountered in water. So loess is particularly sensitive to water. Therefore, the foundations, channels and other projects in loess areas usually require reinforcement.One or more of lignin polymer compounds, cement and snail organisms are used as reinforcement material to stabilize loess. The experiment studies on the effect of content and curing period on compressive strength and water stability of Yangling and Yan’an loess. The engineering properties such as compressive strength, shear strength, penetration resistance and water stability of loess solidification in different curing period and content of lignosulfonate have been carried out. Through analyzing the changes of physical and chemical properties, microstructure characteristics, material composition before and after reinforcement, the stabilization mechanism of calcium lignosulfonate is discussed. The results of the experiment show that:(1) Low content of calcium lignosulfonate can improve the early strength of soil cement, but its long-term strength gradually reduces. Calcium lignosulfonate has inhibitory effect on soil reinforced by high content of cement. Therefore, calcium lignosulfonate is not suitable for use to stabilize loess with high content of cement.(2) Strength loss rate of soil reinforced by calcium lignosulfonate and snail organisms reduce greatly before and after immersion. As the curing time increasing, compressive strength loss rate of stabilized soil is lower and lower. By this token, calcium lignosulfonate and snail organisms could reduce sensitivity of soil to the moisture. It shows that water resistance of stabilized soil has improved, but further research on its long-term strength is still needed.(3) Calcium lignosulfonate can improve mechanical properties of loess such as compressive strength and impermeability. With the content of calcium lignosulfonate increasing, the tensile strength and shear strength indices increase at first and then decrease; the permeability decreases. The paper suggested that the suitable mixing amount of calcium lignosulfonate is about 1.0%; the curing age is at least 7 days; moisture content is slightly lower than the optimum moisture content and the compactness should be increased as far as possible. For different types of soil, the optimum content of calcium lignosulfonate may be different.(4) Through analyzing the changes of physical and chemical properties of soil before and after reinforcement, it shows that calcium lignosulfonate can increase alkalinity of soil. Liquid limit of stabilized soil decreases significantly and plastic limit basically remain the same or has small variations in relative to liquid limit, so the plastic index decreases. The clay content of soil mixed with calcium lignosulfonate increases.(5) It showed that strength of loess increased, water stability improved and permeability decreased when loess mixed with calcium lignosulfonate. The stabilization mechanism of soil stabilized by calcium lignosulfonate was discussed. On one hand, calcium lignosulfonate made rearrangement of soil particles by dispersion and cementation. On the other hand, calcium lignosulfonate could fill pores between particles. In addition, the hydrophilie-group of calcium lignosulfonate could combine with clay particle. In this way, the adsorbed water of clay surface could be forced out by hydrophobic-group. Because the comprehensive function of these aspects made the bonding force and molecular force between soil particles to increase and porosity to decrease, the integrity of soil improved.