Performance of microbially induced calcite precipitation (MICP) as a local scour countermeasure for offshore wind turbine monopile foundation

Abstract

Microbially induced calcite precipitation (MICP) is an emerging method for mitigating scour and erosion. The present study experimentally investigates the efficacy of MICP as a local scour countermeasure for offshore wind turbine monopile foundations under both clear water and live-bed conditions. Bacteria were enriched using activated sludge. Analyses conducted included urease activity monitoring, unconfined compression testing, and examination using scanning electron microscopy. Various depths for the MICP protection elevation were tested in clear water conditions, and the resulting scour topography was mapped using photogrammetry techniques. Investigations were conducted on bedform migration and leading-edge scour upstream of the MICP protection, considering various protection elevations. The results indicated that MICP protection can provide effective scour protection under both clear water and live-bed conditions. Discussions in this study also extend to the erosion and potential collapse of the MICP protection structure. Flow undercut rate were also examined for evaluating potential failure of MICP protection structures, and the elevation of MICP protection has a significant influence on mitigating flow undercutting. Full protection efficiency was observed under clear water conditions when the MICP protection elevation was at the bed level and the flow intensity was relatively low (V/V_c = 0.65), while the highest average protection efficiency (47.73%) among all flow intensities was recorded when the MICP protection elevation was at 0.6D below the bed.