Abstract: In an attempt to accelerate the drainage consolidation of soft soil of high water content, calcium hydroxide and anionic polyacrylamide (APAM) were mixed into the slurry of high water content in the borehole at a construction site in Shanghai. The optimum dosages of calcium hydroxide and APAM were determined according to the laws of slurry porosity, consolidation coefficient, and permeability coefficient varying with load obtained by one-dimensional oedometer test. Furthermore, vacuum preloading model test was conducted on the slurry modified with calcium hydroxide and APAM of optimum dosages. Results show that: (1) In one-dimensional oedometer test, the consolidation coefficient and permeability coefficient of modified waste slurry both increased, which accelerated the drainage consolidation. (2) In the meantime, the optimal dosage of calcium hydroxide and APAM solution with 0.2% mass fraction is about 0.8% and 11.2% mass fraction of the waste slurry, respectively. Beyond that optimum dosage, the consolidation coefficient and permeability coefficient both declined. (3) During vacuum preloading, the consolidation coefficient of waste slurry modified by calcium hydroxide increased evidently, with its average radial coefficient of consolidation 5.1 and 7.2 times of that modified by APAM and original slurry, respectively; the average radial coefficient of consolidation of the waste slurry conditioned with APAM is 1.4 times of that of the original waste slurry. In conclusion, the drainage consolidation of slurry can be effectively accelerated by adding calcium hydroxide combined with vacuum preloading.

Key words: slurry with high water content, calcium hydroxide, APAM, consolidation property, microstructure