Effects of Acidic/Alkaline Contamination on the Physical and Mechanical Properties of Silty Clay

Contaminated soil management and renovation is one of the major environmental geotechnical issues in China. Due to their special strength and stiffness properties, contaminated soil has attracted extensive attention in foundation and slope stability design. For the differentiated influence of acidic/alkaline contamination on the geotechnical physical and mechanical characteristics of soil, this study mainly introduced a remodeled silty clay sample contaminated by acidic and alkaline solutions in the laboratory and conducted research into its basic physical properties, compressive properties, shear strength, and microstructure. It was shown that when the hydrochloric acid concentration increased from 1% to 7%, the density and specific gravity decreased by 7.07% and 3.11%, respectively. The void ratio showed a descending trend with increasing concentration of acid. The acidic solution concentration was negatively correlated with the cohesion of the soil, but the internal friction angle remained constant with a concentration of 1-5%. Alternatively, when the sodium hydroxide concentration increased from 1% to 7%, the density and specific gravity increased by 1.88% and 2.67%, respectively. The void ratio decreased linearly with the increase in consolidation pressure. Alkaline concentration could affect the internal friction angle and cohesion in a positive correlation. Through the observation of microstructure, the surface of acidified soil particles was smooth and flat, while the surface of alkalized soil particles was rough and uneven. The results can provide reference for the evaluation of the mechanical properties of soil contaminated by acid and alkali.