Electrokinetic treatment of soft soils: experimental study and numerical models

Abstract

Soft soils have a high compressibility, and low shear strength, and constructions on such soils often require the use of ground-improvement techniques. This paper compares the use of an electrokinetic (EK) treatment of soft soils using the ionic solutions calcium chloride and sodium carbonate. The effects of the ionic-solution type, the EK-treatment duration, the cation exchange capacity (CEC), the specific surface area (Sa), the pH, the electrical conductivity (σ), and the ionic strength (Is) were considered in this study. Examining the parameters and evaluating their effects on soil behavior are difficult and complex. The design of experiments (DOE) software program was used to evaluate the effects of the parameters and determine the significant input factors for the EK treatment on soft soils. The analysis and optimization of the data produced the threshold values using the design-expert® software. In this study, the EK-treated soil with CEC = 4.9 meq 100/g, Sa = 4.5 m2/g , pH = 9.5, σ = 6.0 S/m, Is = 1.55·10-4 mol/L, and electrolyte-type setup of CaCl2-Na2CO3 gave better soil strengthening. The gain in strength is attributed to the flocculation and aggregation of the EK-treated soil particles. The analysis of the data by DOE indicated that it could be used to assess the significant effects of the input factors on the unconfined compressive strength, qu of the EK-treated soft soils.