Indoor simulation test of step vacuum preloading for high-clay content dredger fill

Abstract

ABSTRACTVacuum preloading is a soft ground improvement method that has been successfully used by geotechnical engineers and specialists to accelerate the rate of consolidation. However, consolidation efficiency is low when dealing with newly reclaimed high-clay content dredger fills because of sludge plugging of the prefabricated vertical drains. In this study, step vacuum preloading was proposed to reinforce a high-clay content dredger fill by applying the vacuum load gradually to consolidate the dredger fill fully and to reduce the migration of fine particles. An indoor simulation test was conducted, and monitoring data were obtained. Results showed that the settlements increased gradually, the pore water pressures and flow velocities decreased over time, and all the changes tended to be stable by the end of the test. The settlements at each stage were more than that at the previous stage, illustrating that changing the method of drainage consolidation in a timely manner, or increasing the vacuum pressure, can more fully consolidate the dredger fill at each stage, thus improving the consolidation efficiency of the dredger fill. The reinforcement effect of the high-clay content dredger fill was also analyzed. The results show that the moisture contents and porosities decreased gradually, the bearing capacity increased gradually in the consolidation process, and each property index of the dredger fill changed with the increase in degree of consolidation, and the regularity of the distribution of the indices showed that obvious siltation did not occur in the consolidation process. Overall, the consolidation efficiency was effectively improved. Thus, the step vacuum preloading method is suitable for high-clay content dredger fills. This method can improve the consolidation efficiency and the uniform reinforcement effect.