Evaluation of Biogrouting Method in Sandy Soil improvement in Column Injection Experiments

Improvement of soils is among the major concerns in civil engineering. For this, a variety of approaches have been employed for different soil types. The annual budget of implementing the projects of this kind in countries clearly implies the importance of the subject. The loose granular soils and sediments have always imposed challenges due to their low strength and bearing capacity as well as difficulties in drilling and excavation. Biogrouting has recently been introduced as a novel link of biotechnology and civil engineering for improving the problematic soils, i.e. utilizing some bacteria to precipitate calcite on the soil particles. In the present study, the Sporosarcina pasteurii PTCC 1642 (DSM 33) was used as the bacterial agent to improve soil strength parameters in a two-phase injection approach. Bacterial injection to a sandy soil column was followed by nutrients injection containing CaCl2 and urea and the soil columns were settled in the ambient temperature. Experiments were performed in triplicates and conducted for two types of sandy soils. The unconfined compressive strength of soil specimens was evaluated after 15 days of the last injection. The results show significant increase in the soil strength with values of 1.78 and 2.83 Kg/cm2 for the two investigated soil types according to t test.

Keywords:

Biogrouting , Soil improvement , Bacteria , Column injection , Sandy soil