Effect of confining pressures on the shear modulus of sand treated with enzymatically induced calcite precipitation

Abstract

Enzymatically induced calcite precipitation (EICP) is a new breakthrough for liquefaction prevention. This approach uses urease enzyme directly instead of bacteria to hydrolyze urea that precipitated as calcite crystal by the availability of calcium ion. Cyclic triaxial shear test under undrained condition incorporated with bender element test were conducted conscientiously on the EICP-treated sands. The parameters study reviewed includes: size of the sand particle, confining pressure, calcite contents, and saturation degrees along curing. The effects of those factors on the shear modulus are systematically investigated and compared. It was revealed that the precipitated calcite wraps the sand particles, which supports simultaneously to the mechanical properties’ improvement. The sum of materials needed of urea and CaCl2 to reach a target of maximum shear modulus can be diminished prominently by reducing the saturation degree along curing. It is also revealed that the formation of the precipitated calcite is more significant than its amount on the strength improvement. The maximum shear modulus (Gmax) of the sands treated with EICP increases with increasing in the calcite content, confining pressure, and decreasing in the saturation degrees during curing but the influence of the sands grain size is insignificant.