Effect of pore water chemistry on the hydro-mechanical behaviour of Lianyungang soft marine clay

• Field investigation suggests a significant effect of pore water chemistry.
• Clays rich in bentonite move toward “A” line when increasing salinity.
• A clay with a higher salinity behaves more as a silt.
• Clays with higher salinity show less compression and swelling.
• Clays with higher salinity show higher permeability.

The effect of pore water chemistry on the hydro-mechanical behaviour of soft marine clay of Lianyungang was investigated. Field investigation and piezo-cone penetration tests at two sites with 0.56% and 4.91% salinity respectively were first performed, and a significant difference was observed in terms of Atterberg's limits (LL and PL), density, net tip resistance, sleeve friction and pore water pressure parameter, suggesting a significant effect of pore water chemistry. To confirm this observation, identification tests were extended to an artificial soil corresponding to a mixture of kaolinite/bentonite with different salinities. The results obtained confirm the significant effect of pore water chemistry. To further clarify this effect, oedometer tests were performed with both site water and deionised water. The results indicated that the compression index, swelling index, and secondary consolidation coefficient are higher in the case of deionised water, whereas the oedometer modulus, consolidation coefficient and hydraulic conductivity are larger in the case of site water. However, the ratio between secondary consolidation coefficient and compression (or swelling) index indicates no significant effect of pore water salinity. After completion of the oedometer tests, the microstructure features were studied by the mercury intrusion porosimetry. The results showed that deionised water led to an increase of porosity, whereas the site water led to a decrease of porosity.