Coupling of electrochemical–temperature–mechanical processes in marine clay during electro-osmotic consolidation

Abstract

electro-osmotic consolidation has been applied in several geotechnical engineering applications that contain a series of complex processes, including electrochemical processes, temperature changes, and mechanical evolution. to explore the combination of electrochemical-temperature-mechanical processes in marine clay, electro-osmotic consolidation experiments were conducted using a selfmade electro-osmotic consolidation system under various durations and voltages. The following findings was obtained: (1) the change in the pH value increased during electro-osmotic consolidation and as the voltage rise; (2) the temperature increased with a rise in voltage in the initial stage of the experiments, which was induced by Joule heating; (3) the temperature rise promoted the electroosmotic consolidation process, which included a rise in the coefficient of consolidation and a reduction in water content; (4) horizontal shrinkage occurred when the horizontal stress increment was greater than the critical stress condition. In addition, the volume difference reached a constant value, and was proportional to the voltage rise. After the discussion, a coupling analysis was conducted, which can help to better understand the mechanism of electro-osmotic consolidation and can provide reference for engineering applications. Civil engineers attempt to use the offshore reclamation method to satisfy the development requirements of coastal cities. For example, Australia (Brisbane, Queensland) 1 , China (Dalian, Jinzhou Bay) 2 , and Singapore 3 carried out coastal reclamation engineering for city planning purposes. Surcharge preloading and vacuum preloading can both be applied successfully in the area of reclamation. However, these two methods face a long construction period in the development of soft clay because the permeability coefficient of clay is low, which is in the range of 10-8 m/s 4. In comparison, electro-osmotic consolidation is independent of the size of soil particles 5. Direct current causes pore water to move from the anode to the cathode 6. Therefore, electro-osmotic consolidation is an effective method to improve the foundation, slope, and subgrade of soft clay. Electro-osmotic consolidation is a complex process, involving electrochemical processes, temperature changes, and mechanical evolution 5. An electrochemical process is a particularly important process during electro-osmotic consolidation. It is responsible for the electrolysis reaction and the transport of ions. Liaki et al. 8 measured the pH value of clay after different electro-osmotic consolidation treatment durations using a stainless steel anode. They found that the pH value steadily decreased near the anode and increased near the cathode. Xue et al. 9 observed that the pH value of clay near a copper anode was higher than that of a stainless steel anode, which was mainly because the product of chlorine consumed the electric charge and there was not much electric charge on the product of H + in copper anode condition. Wu et al. 10 measured the pH value after ...

Consolidation Assessment of Marine Clay Using Electrokinetic Coupled with Constant Load

“…In addition, with an increase in voltage, the movement of H+ and OH-ions will increase which results in a higher variation of pH value. Similar observations were also reported by other researchers [9,29,44,45]…”

“…This voltage loss results from the precipitation of metal hydroxides near the cathode and the desorption of metal ions at the anode. The efficiency factor was increased with an increase in applied voltage; the same was observed by other researchers also [29,30]. The results indicate that an increase in voltage gradient improves the effective voltage with reference to the output voltage during the early stage of the electro-osmotic process.…”

“…This additional settlement is due to the electro-osmotic flow process, which includes the transport of ions under an electric gradient. The ion transport in the phenomenon includes diffusion, electromigration and electro-osmotic flux advection [30]. Thus it results in faster dissipation of excess pore water that alters the soil fabric due to pore fluid flow, ion migration, and charged particle flow [31,32]The electro-osmotic flow was directly proportional to the applied electric potential.…”

“…Many other researchers also contributed to the advancement of EK technology in geotechnical and geoenvironmental applications. The problems associated are excessive deformation in foundations, decrease of swelling and shrinkage in capacity, increase in friction pile capacity, stabilization and strengthening of soft clays, consolidation of marine and dredged sediments for land reclamations and dewatering of slurries, sludges and mine tailings [4][5][6][7][8][9][10][11]. In the current era of technology, Electro-osmotic (EO) consolidation is a potential technique for accelerated pore pressure dissipation and resulting in the early consolidation of soft soils and dredged sediments with high moisture content, low compressibility, low permeability and low bearing capacity.…”

Experimental study on soil improvement by electrochemical injection of calcium chloride solutions with time interval

“…However, this clogging effect would also hinder the ow of water and reduce the overall permeability of the soil, resulting in a progressive decrease in drainage e ciency 26,28 . In addition to the clogging effect mentioned above, the electric resistance of the entire sample of S3 and S4 should be further discussed, as the e ciency of electroosmotic treatment is substantially controlled by the electric resistance of system 1,29 .…”