Effect of lead (II) on the mechanical behavior and microstructure development of a Chinese clay

• The soil became aggregate with lead added.
• Expansion rate decreased first then increased with increasing lead concentration.
• Increase of silt content and decrease of clay content was founded.
• Increased lead concentration led to an increase in C value and an unchanged φ value.
• Changes occur in mineral transformations and diffuse double layer.

BackgroundThe heavy metal contaminated soils (HMCS) are not only a challenge for the environmentalists but also for the geotechnical engineers.MethodsTypical clay in China was chosen as the medium, and the significance of the change in physical and engineering properties including particle size distribution, compaction, Atterberg limits, permeability, shear strength, compression and swelling of soil due to the pollution of lead (II) with different concentrations was investigated. Changes in the soil structure were interpreted by detailed mineralogical, scanning electron microscope (SEM) observations and mercury intrusion porosimetry (MIP) tests, which were coupled with index, swelling, consolidation, and strength properties.ResultsResults indicated that lead (II) could have a considerable effect on the geotechnical properties of the clay.ConclusionThe main reason of such effects is the changes which occur in mineral disintegrations and transformations and diffuse double layer of clay particles.