Laboratory investigation, including a series of consolidation tests, was conducted on three marine deposits in order to study the effects of acidic contamination on the geotechnical properties of soils from coastal areas in Japan. Solutions of sulfuric acid were used to leach the clays for defined time periods ranging from 3 to 6 months, thus simulating the process of long-term soil-acid interaction that occurs during municipal and industrial waste storage. The obtained results showed that acidic contamination could affect the compressibility of the clays, and the factors determining the degree of such changes were clay mineralogy, soil structure, and the duration of clay-acid interaction.
In mountainous countries like Japan, municipal development has generally concentrated along the coastal line. As the land available for construction in such countries is limited, new development projects often face the problem of soil contamination caused by mismanagement of the land in previous years. At the present time, little is known regarding the effects of contamination on the physicochemical properties of marine deposits. Sridharan et al. (2002) and Imai et al. (2006) studied the influence of ions on the mechanical properties of clays from Osaka Bay and Ariake Bay and reported that changes in soil's plasticity, compressibility, and strength occurred during soilwater- contaminants interaction. It has been already recognized that such changes strongly depend on the mineral composition of clay. For example, the compressibility of kaolinitic soils typically increases due to soil-acid interaction (Sridharan et al. 1981; Gratchev and Towhata, 2008), while for bentonite the opposite effect may occur (Gajo and Maines 2007). Yet the majority of natural clays contain a variety of clay minerals, and thus the effect of contamination on the properties of such clays still remains unclear. Also, due to the low permeability of natural clays, it has become common practice to use remolded soils for testing, as it provides satisfactory results within a reasonable period of time.