Abstract: Soybean Urease Induced Calcium Carbonate Precipitation（SUICP） is a newly improveed technology of soil. The bearing capacity of ground is likely to be improved by filling effects and cementing function of precipitated calcium carbonate. In order to quantitatively investigate the improving effects of the SUICP on the bearing capacity of sand ground, we conducted a sand
column model test, which was 38.5 cm in diameter and 100 cm in height. The calcium carbonate deposition was 3% of the mass of sand. The improving effects on the bearing capacity of sand ground was studied by static cone penetration tests. The results show that the average value of cone tip resistance of the sand ground increased by 38.9%, from 0.564 MPa to 0.783 MPa. The average shaft friction increased by 49.83%, from 19.08 kPa to 26.92 kPa. The average bearing capacity of sand ground increased by 45.09%, from 79.02 kPa to 108.64 kPa. There are two mechanisms for the improvement of bearing characteristics of sand ground. On one hand, sands of coarser particles were connected to each other by calcium carbonate. On the other hand, sands with denser pores were filled by precipitated calcium carbonate. The results confirm the SUICP grouting effects on the bearing capacity of sand ground and the mechanisms were analyzed. It is found that the uniformity of improvement in the sand column was not ideal, suggesting the need to explore the mechanism and to develop better technology in the future.

Key words: soybean urease induced calcium carbonate precipitation, sand, ground improvement, model test, static cone penetration test