Effects of Salinity on Geochemical and Geotechnical Properties of High Plastic Clayey Soils

Abstract

Soil salinization is a growing concern in arid and semi-arid regions, where the accumulation of salts in surface soils compromises agricultural productivity and civil infrastructure stability. In areas like Belle Fourche, South Dakota, this challenge is particularly acute for impoundment dams constructed on high plastic soils derived from the Cretaceous Pierre Shale Formation. These dams are increasingly vulnerable to salinity-induced deterioration, which threatens water storage reliability and ecosystem sustainability. This study investigates the impact of pore fluid salinity on the geochemical and geotechnical properties of high plastic soils, focusing on their implications for dam stability and rehabilitation. This study investigates the effects of pore fluid salinity on the geotechnical and geochemical properties of high plastic soils, specifically focusing on soils derived from the Cretaceous Pierre Shale Formation in Belle Fourche, South Dakota. The primary aim is to understand the impact of increasing salinity on critical soil properties, including compaction, Atterberg limits, shear strength, and ion exchange characteristics. A series of geochemical tests, including electrical conductivity (EC), cation exchange capacity (CEC), sodium adsorption ratio (SAR), and exchangeable sodium percentage (ESP), were performed to assess the salinity levels and their influence on the soil's behavior. Geotechnical tests, including mineralogy, sieve analysis, Atterberg limits, compaction, and vane shear tests, were conducted to examine soil structure and strength changes under varying salinity conditions. The study identified the correlations between key geochemical and geotechnical parameters, allowing for predicting soil behavior based on readily measurable field indicators. The results highlight that increasing salinity decreases undrained shear strength (Su) at a given moisture content, emphasizing the need for an intervention framework to manage saline-affected soils. To support rehabilitation planning, Multiple Account Analysis (MAA) framework was developed to evaluate intervention strategies. This decision making tool integrated technical, social, economic, and environmental indicators, enabling transparent comparison and ranking of alternatives. The MAA framework’s adaptability allows stakeholder-specific adjustments, making it a robust tool for sustainable dam management in rangeland management for sustainable water management practices.