Compaction grouting is a ground improvement method which involves the injection of very stiff and high viscosity grout material under relatively high pressure. It has been successfully used to prevent earthquake induced soil liquefaction by means of displacing and compacting the soil in-place. This study proposes a numerical model that describes the mechanism of compaction grouting in terms of radial displacement and densification of surrounding soil. The numerical model was developed using Discrete Element Method (DEM) EDEM Simulation, which is a commercial DEM software, was used to carry out the computation work. The model was calibrated with slump test and vane shear test to determine the parameters of grout mortar and soil needed to generate a compaction grout bulb in the grouting process. After the grout bulb (40 mm in diameter) was generated, the radial displacement of particles and the void ratio changes were calculated and studied. Approximately, an amount of 7.5% void ratio decrease at the distance of 50 mm (1.75r/D) from the injection point was observed. The densification effect decreases with radial distance from nozzle and has no effect on the soil density beyond 150 mm (5.5r/D) in radial distance. The radial displacement at the depth of the bulb was found having the similar trend as the void ratio change, from 4.0 mm and 7.5% at distance of 50 mm reducing to 0.1 mm and 0.5% at distance of 200 mm for displacement and void ratio changes respectively in radial distance. The spacing of injection two grout bulbs affected the densification which resulted the increasing of void ratio change 5% for 100 mm spacing and only 1.3% for 200 mm spacing. This result can be used for optimizing the layout of compaction grout bulbs to densify the in-situ soft soil.

Compaction grouting is a ground improvement method which involves the injection of very stiff and high viscosity grout material under relatively high pressure. It has been successfully used to prevent earthquake induced soil liquefaction by means of displacing and compacting the soil in-place. This study proposes a numerical model that describes the mechanism of compaction grouting in terms of radial displacement and densification of surrounding soil. The numerical model was developed using Discrete Element Method (DEM) EDEM Simulation, which is a commercial DEM software, was used to carry out the computation work. The model was calibrated with slump test and vane shear test to determine the parameters of grout mortar and soil needed to generate a compaction grout bulb in the grouting process. After the grout bulb (40 mm in diameter) was generated, the radial displacement of particles and the void ratio changes were calculated and studied. Approximately, an amount of 7.5% void ratio decrease at the distance of 50 mm (1.75r/D) from the injection point was observed. The densification effect decreases with radial distance from nozzle and has no effect on the soil density beyond 150 mm (5.5r/D) in radial distance. The radial displacement at the depth of the bulb was found having the similar trend as the void ratio change, from 4.0 mm and 7.5% at distance of 50 mm reducing to 0.1 mm and 0.5% at distance of 200 mm for displacement and void ratio changes respectively in radial distance. The spacing of injection two grout bulbs affected the densification which resulted the increasing of void ratio change 5% for 100 mm spacing and only 1.3% for 200 mm spacing. This result can be used for optimizing the layout of compaction grout bulbs to densify the in-situ soft soil.

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