Hanoi Cohesive Soil in Salt-Affected Conditions: Soil Properties and 2D Consolidation Analysis

The paper focuses on the geotechnical experiments and numerical simulation of 2D consolidation analysis for the cohesive soils fully saturated by solutions of four salt concentrations, i.e. 0.0, 9.9, 19.8, and 33.0 g/L. The experiments were carried out on undisturbed soil samples taken from the boreholes in Hanoi area where the subsoil has not been affected by saline intrusion yet. The composition and properties of the cohesive soil in salt-affected conditions were investigated with transmission electron microscopic method and other geotechnical experiments. Consolidation analysis with finite element method was applied to an assumed embankment on saline subsoil. The analytical results showed that swelling mineral of montlorillonite is present in the Hanoi cohesive soils. The water content of the studied soils decreases as the salt concentration increases. Meanwhile, the bulk density unclearly changes in the same testing conditions. The coefficient of consolidation reduces, respectively, with the salinities, from 22 to 50% as salinities rise up to 33.0 g/L. Compressibility index increases linearly and proportionally with the salinities. In 2D analytical model, the settlement or vertical displacement of the subsoil in HD1 site reaches 14.8% and that of GL2 site is 18.7% at saline solution of 33.0 g/L. The horizontal displacement of the subsoil reaches 13.90% in HD1 site and 17.55% in GL2 site from the baseline. The time at primary consolidation completion is longer as saturated solution is saltier. The prolongation of primary consolidation time gets over 30% if the subsoil is at the most salty. These changes illustrate the degradation of soils in the saline media.