(1. Engineering Faculty,China University of Geosciences,Wuhan,Hubei 430074,China; 2. Institute of Rock and Soil Mechanics,Chinese Academy of Sciences,Wuhan,Hubei 430071,China)
The mixed soil of precast pile with extrusion method is a new technique for soft foundation treatment. A single pile is pressed with the mixed soil in a soil extruding pile machine and then maintained. A total of 17 single piles of different recipes were designed and extruded under the optimal water content of soil. These piles were measured for unconfined compressive strength and water stability after 28 days. According to the test results,we found laws including:(1) The strength of the sample increased with the cement incorporation ratio when no or little lime was mixed,but decreased after an increase when adopting a relatively high lime incorporation ratio. (2) The strength of the sample increased with the lime incorporation ratio when no or little cement was mixed,but increased at 3% point after a decrease under a condition of comparable high cement incorporation ratio(4%,6%). (3) The water stability test showed that the water stability of the sample reached a good state with a 2% or 4% cement incorporation ratio. The strength maintenance coefficient increased with the increasing lime mixing ratio. The strength of different samples decreased fast in a 10-day or 20-day immersion but then tended to be stable after that. Based on the results mentioned above,the best formula for the pile of mixed soil was selected as cement 2% + lime 7%. This formula can provide support for the popularization and application of mixed soil of precast pile with extrusion method.
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