Impact of environmental acidity on the geomechanical and mineralogical behavior of marine clay

The geotechnical behavior of clay is known to be influenced by its external environment chemistry. In this study, a series of experiments were conducted to investigate the geomechanical behavior, mineralogical behavior, and microscopic characteristics of Tianjin marine clay when subjected to an acidic environment. The micro-mechanisms of these phenomena were thus revealed. It is interesting to note that the increasing environmental acidity would promote the illitization in illite-smectite and conversion in part of the smectite component in illite-smectite to chlorite. In addition, our results indicate that a critical pH developed with the increasing environmental acidity, leading to phased variations in strength and compressibility. When the environment pH was greater than its critical value, the increasing environmental acidity led to an increase in strength together with a decrease in compressibility, which was mainly related to the reduced thickness of the diffuse double layer and improved intermolecular force between soil particles. However, with an environment pH lower than its critical value, the geotechnical behavior of Tianjin marine clay was deteriorated as a result of more open, flocculated microscopic structures and low intergranular cementation strength in the marine clay, such that the strength decreased while compressibility increased as the environment became more acidic.