The effects of cracks (soil disengagement) and grouting time at the interface between slab and soil on the osmotic consolidation process of soft soil were studied through one-dimensional electroosmosis consolidation test. The "grouting time" control test was performed by injecting CaCl₂ solution and Na₂SiO₃ solution in a tight sequence. Based on the combined effects of "precipitation or colloid" and "ion" on electroosmosis consolidation, the variation of current, drainage, soil moisture content and shear strength, cracks and body shrinkage and energy consumption of electroosmosis with grouting time were studied. The test results show that cracks at the interface between slab and soil (slab detachment) always occur before other parts, and the sharp decrease of current value caused by slab detachment is the main reason of the reduction of electroosmotic effect; During the consolidation process, there is a time t_cr for the fast development stage of crack at the slab-soil interface. Using t_cr as the indicator to determine the optimal grouting time can achievethe best electroosmosis effect. In order to prevent the obvious abrupt change of water content in the soil, it should be noted that the grouting time should be not earlier then 1/3 t_cr, and grouting at 2/3 t_cr can achieve the best electroosmotic consolidation effect.