Study on Dewatering Effect and Heavy Metal Removal Mechanism of Riverbed Mud Treated by Vacuum Preloading - Radial Electroosmosis Technology

The disposal and resource utilization of riverbed mud are crucial for ensuring the safety of engineering projects and the quality of the environment. When traditional vacuum preloading is employed to treat riverbed mud, issues such as poor dewatering effect and failure to meet the standards for heavy metal removal become prominent. In this paper, a vacuum preloading - radial electroosmosis technology, which is capable of both dewatering and heavy metal removal, is proposed in accordance with the concept of "reducing and harmlessly treating" mud. To systematically illustrate the dewatering effect and heavy metal removal mechanism of the vacuum preloading - radial electroosmosis technology in treating riverbed mud, a model device of vacuum preloading - radial electroosmosis technology and a radial electrode have been independently developed. Model tests of vacuum preloading - electroosmosis, vacuum preloading - cathode radial electroosmosis, vacuum preloading - anode radial electroosmosis, and vacuum preloading - anode and cathode radial electroosmosis have been conducted. The variation laws of indicators such as drainage volume, settlement volume, degree of consolidation, undrained shear strength after dewatering, water content, and heavy metal Cu²⁺content have been analyzed. Based on Coulomb's Law, a heavy metal ion migration model has been established to reveal the heavy metal ion removal mechanism of the radial electroosmosis technology. It has been demonstrated by the research that compared with the traditional vertical electrode, the radial electrode has a significant advantage in dewatering and heavy metal removal of riverbed mud. In terms of dewatering, within 48 hours of electroosmosis, the drainage volume is increased by 3.09% - 6.93% and the final settlement volume is increased by 3.26% - 7.07% by vacuum preloading - cathode radial electroosmosis, vacuum preloading - anode radial electroosmosis, and vacuum preloading - anode and cathode radial electroosmosis compared with vacuum preloading - electroosmosis. Meanwhile, the difference in water content on the surface of the soil is significantly reduced, and the undrained shear strength is significantly increased, with the highest increase of 21.38%. In terms of heavy metal ion removal, the removal effect of Cu²⁺is increased by 8.15% - 21.66%. By comparing the mechanisms of heavy metal ion migration between radiation electrode electroosmosis and traditional vertical electrode electroosmosis, it was found that the migration time of heavy metal ions in traditional vertical electrode electroosmosis was shorter than that in radiation electrode electroosmosis (proportional to . This proves that heavy metal ions at the same position are subjected to stronger electric field strength and faster ion migration speed in radiation electrode electroosmosis. The research results can broaden the application scope of traditional vacuum preloading technology and provide scientific references for green and safe design and construction of foundations.