Moisture intrusion into the subgrade can significantly increase its moisture content, leading to a decrease in stiffness and strength, thereby compromising the serviceability performance of the pavement. Electro-osmosis has been used as an effective method for reducing moisture content and improving subgrade mechanical properties. However, its impact on mechanical properties has not been well understood. This study evaluated the mechanical behavior of electro-osmosis-treated subgrade soil through laboratory experiments that included bender element and cyclic triaxial tests. The study analyzed the effects of supply voltage and soil compaction degree on electro-osmosis treatment. The results showed that after treatment, the shear wave velocity increased by 26.0 to 59.2%, and the dynamic resilient modulus improved by a factor of three. Increasing the supply voltage and degree of compaction was found to lead to more significant improvements. Further analysis revealed that the reduction in moisture content alone was insufficient to contribute to the improvement. Cementation of colloids generated by the electrochemical reaction between soil particles also contributed to the improvement. It is worth noting that the nonuniform distribution of moisture and colloid in electro-osmosis-treated soils resulted in heterogeneity, with soil close to the anode being the weakest in terms of mechanical strength. Chemical injection or polarity reversal was suggested to enhance the uniformity of distribution and improve the overall treatment effectiveness. Overall, the study highlights the potential of electro-osmosis as a viable method for improving the mechanical properties of subgrade soil, but further research is required to investigate the heterogeneity of the distribution of moisture and colloid.

The combination of vacuum electro-osmosis treatment and electrokinetic remediation allows for the simultaneous consolidation and remediation of contaminated sediments, involving multiple coupled fields such as electrical field, hydraulic field, mechanical field, and chemical field. This study couples the charge conservation, vacuum electro-osmosis consolidation, and contaminant transport equations under vacuum electro-osmosis conditions to establish a numerical model for the consolidation and remediation process. Laboratory experiments were conducted for comparative analyses. The numerical results show that the electric field intensity decays from both sides towards the center. However, the other positions align well with the experimental results, indicating the ability of the numerical model to reflect the non-uniform distribution of soil potential. The anode and cathode regions become negative pressure centers, resulting in an increasing seepage velocity towards the negative pressure centers. The numerical results accurately capture the trend of pore water pressure development before 40 h, although the absolute value obtained after 40 his slightly overestimated. Additionally, the numerical results demonstrate a 47% removal efficiency of copper at the anode after 48 h, which is consistent with the experimental results. The distribution of electric field and contaminants are affected by the shape of the electrode board.

This case study proposed a novel electro-osmosis PRD vacuum preloading method to solve dredging sludge treatment issues: difficulty in draining from soil showing large volume, non-uniform settlement, and low strength. To verify the effectiveness of the new method, four kinds of physical model tests integrating particle image velocimetry (PIV) technique of traditional vacuum preloading (VP), prefabricated radiant drain vacuum preloading (PRD-VP), electro-osmotic vacuum preloading (EO-VP), and EO-PRD-VP methods are conducted. The water discharge, average surface settlement, pore water pressure, water content, and undrained shear strength after treatment, clogging range, relationship between clogging range and water discharge rate, and relationship between clogging range and average surface settlement are investigated. For those model tests, it is demonstrated that EO-PRD-VP method has the best advantage in volume reduction, uniform settlement, and strength improvement. Water discharge is enlarged by 13-33%. The differential settlement can reach 2.3 cm, decreased by 28-56%. The undrained shear strength can reach 12 kPa, increased by 1-2 times. In addition, the clogging range development is described, for the given water discharge rate and average surface settlement, clogging range of EO-PRD-VP method is the minimum. The empirical equations between clogging range and water discharge rate, clogging range, and average surface settlement are established to predict the clogging range, which can lay the foundation for developing the consolidation theory of EO-PRD-VP method.

Mining and using underground resources demand high water usage, producing significant waste with environmental risks. Methods like electrokinetics prove effective in accelerating dewatering and stabilizing structures. This research provides the results of experimental investigation on dewatering silty tailings obtained from Sungun Tailings Dam (East Azerbaijan, Iran) using the electrokinetic water recovery method. Previous studies primarily examined the electrokinetic process in steady-state flow and saturated soil, with limited exploration of unsaturated soil parameters. In this research, the electrokinetic process in steady-state flow was initially investigated, and the saturated electro-osmotic permeability was determined. Subsequently, experiments were conducted in non-steady-state flow and unsaturated conditions, measuring the influential parameters with soil moisture sensors and tensiometers. Results show that decreasing sample moisture through electro-osmotic flow increases negative pore water pressure. Tailings' electrical conductivity is more influenced by moisture content, with a steeper reduction slope concerning volumetric moisture reduction over time. pH assessments show soil acidity on the anode side and alkalinity on the cathode side. Higher applied voltage gradients result in increased maximum power consumption. Importantly, the results caution against assuming that higher applied voltage improves the electro-osmotic process, as it may lead to issues such as deep sample cracking, void space creation, interrupted electrical flow, and energy loss.

Existing solutions for electro-osmotic consolidation assume a linear voltage distribution, which is inconsistent with the experimental findings. The present study introduces a novel two-dimensional electro-osmotic consolidation model for unsaturated soils, which considers the influence of non-linear voltage distribution. The closed-form solution is derived by employing the eigenfunction expansion method and the Laplace transform technique. The accuracy of the analytical solutions is validated through the implementation of finite element simulations. The findings from the parametric studies indicate that the excess pore water pressure (EPWP) observed in electro-osmotic consolidation is influenced by the distribution of voltage. The dissipation rate of EPWP is observed to be higher when subjected to non-linear voltage conditions compared to linear voltage conditions. Moreover, the impact of non-linear voltage distribution becomes more pronounced in unsaturated soil characterised by higher electro-osmosis conductivity and a lower ratio of kx/ky. In contrast, the excess pore air pressure (EPAP) remains unaffected by the voltage distribution.