Experimental Investigation of Automatic Drainage Reinforcement for Overwet Subgrades in Yellow River Alluvial Plain of China

During the operation period of the subgrade in the Yellow River Alluvial Plain of China, the moisture content significantly increased due to high groundwater levels and freeze–thaw cycles, which resulted in the modulus decline, deformation increase, and severe pavement diseases. Electro-osmosis is a promising technology to control the moisture content of subgrades. However, the practical application is limited by the insufficient understanding of electro-osmosis treatment on unsaturated subgrade soils. Therefore, combined with the practical subgrade structure, a special apparatus was constructed to conduct three-dimensional electro-osmosis drainage physical model tests. The drainage volume, moisture distribution, settlement deformation, voltage loss, and energy consumption based on three electrification methods, four voltage gradients levels, and three initial moisture content types were analyzed. And the effectiveness and feasibility of electro-osmosis control of subgrade moisture content were investigated. The test results show that the intermittent polarity reversal electrification method is suitable for the electroosmotic in-filed treatment of unsaturated subgrade and the reduction in moisture reached 12.5–19.9%, while the traditional continuous electrification method was 5.4–13.9%. The critical voltage gradient of electroosmotic treatment of unsaturated subgrade soil was about 1.8 V/cm. The subgrade volumetric moisture content of less than 30.9% was not suitable for directly dewatering reinforcement by electro-osmosis. Additionally, the electroosmotic method with bilayer iron electrodes can ensure the saturation of overwet subgrade soil close to the optimal moisture content and increase the subgrade treatment thickness. It can provide reliable references for the design of treatment overwet subgrade soils in the Yellow River Alluvial Plain.