Behaviour of loose sand treated using bio-gelation method

Bio-gelation is a new method for improving the hydraulic and mechanical properties of sandy soil through the production of polymeric gel to fill in the pores of the soil. In this paper, a study on the engineering behaviour of loose sand treated using this method is presented. A series of permeability and undrained monotonic and cyclic triaxial tests was carried out on both clean sand and bio-gelled sand. The test results showed that the coefficient of permeability was reduced by three to four orders of magnitude in the bio-gelled sand samples, and the higher the alginate concentration, the lower the permeability. In the monotonic triaxial tests, sand samples that would have liquefied under static conditions manifested strain-hardening behaviour after treatment. The shear strength of the bio-gelled sand also increased, as was indicated by an increase in the slope of the failure line from 1 center dot 08 to 1 center dot 27. In the cyclic triaxial tests, the number of cycles at failure increased from 183 for clean sand to 485 for bio-gelled sand, and the excess pore water pressure response was also much reduced. The hydrogel produced by the bio-gelation process was stable under both hydrostatic and seepage conditions. The other advantages of the bio-gelation method include: (a) the massive formation of hydrogel can be controlled to be 28 h later after injection; (b) the pH value of the soil fluid can be maintained at neutral; and (c) it is cost-effective for liquefaction or seepage control for sand compared with other conventional methods.