SOIL IMPROVEMENT METHOD CARRYING OUT LAP WORK BY USING EFFICIENCY RETARDANT STABILIZER

PROBLEM TO BE SOLVED: To provide a soil improvement method capable of using an slow-acting stabilizer as a soil improvement material, easily carrying out work after approximately three days age of the existing improved pile, at the same time, revealing specific strength after the solidification in lap work of the soil improvement method such as powder injection stirring method or the like. SOLUTION: The grained soil improvement material is discharged into the ground together with air in a rotational area of one or more stirring wings radially provided to the lower part of a rotary shaft, in-site soil and the soil improvement material are stirred and mixed to form the improved pile, and in the soil improvement method carrying out the lap work combined with part of the existing improved pile to the existing improved pile, the soil improvement method is executed by means of the efficiency retardant stabilizer as the soil improvement material containing calcium oxide 30 to 70%, silcon dioxide 10 to 40%, aluminium oxide 5 to 20% and sulfur trioxide 1 to 10%.