Sinkage control of North-West corner of Kolkata high court by consolidation grouting and stabilization using Drucstone chemical grout: A case study

Abstract

The North-West corner of the Kolkata high court started developing cracks and showing signs of differential subsidence due to unstable soil conditions below its foundation. Investigations indicated that the brick foundation of the high court rested on backfilled material and low strength soil, which had now developed greater instability due to possible soil liquefaction as a result of the proximity of Hooghly River. Based on the damage monitoring of the structure, a two-phase grouting operation was executed at the N-W corner of the building which involved consolidation grouting below and surrounding the brick foundation, and curtain grouting around the corner periphery. The grouting operation was performed using Drucstone chemical grout, which is a two-component low-foaming polyurethane-based chemical, capable of substantially improving the properties of the deteriorated soil mass. This stopped the sinkage of the building completely, which was confirmed by deformation monitors installed throughout the N-W corner of the building. The settlement of the N-W corner was arrested at 19.48 mm depth, while the rate of settlement, which was initially 0.25 mm/day, was finally reduced to 0.015 mm/day and gradually arrested. This project also proved the effectiveness of Drucstone in such scenarios by showcasing its efficient soil improvement and consolidation properties indicated by an increase in soil cohesion by 90% and its shear modulus by 300%.