A Lab Study on the Factors Effecting Settlement and Electrical Resistivity of Gypsum Sands

A large number of engineering hazards on constructions based on gypsum soils have been documented all over the world. Gypsum sands are especially found in the dry parts of the world. The problem of dissolution and settlement is one of the most widespread among gypsum soils. Gypsum sands are complex materials and the effect of the geotechnical parameters on settlement behavior of gypsum soils has been studied by several researchers over the years, but the results were found to be varying. Also, there have not been many geophysical investigation techniques that were used to study gypsum soils. In this study, the effect of several factors like gypsum content, water content, leaching and dissolution of gypsum and time on the settlement of reconstituted gypsum sands were investigated. Settlement due to initial moisture and leaching was studied by subjecting the soil specimens to a rapid drained loading of 200 kPa. The long-term settlement of the soil samples was studied using the consolidation test setup. Further, electrical resistivity tests were conducted on the soil samples using a four-electrode soil resistivity box. The effect of moisture content, gypsum content and density on electrical resistivity was investigated. The studies showed that settlement of the gypsum sands increased with gypsum content, initial moisture, leaching and time. The soil box resistivity tests showed that, moisture content had a major influence on resistivity, while gypsum content and density had less influence on the resistivity. Based on the results, it was concluded that electrical resistivity testing could be a moderately successful method for estimating the settlement of gypsum sands.