A coupled mathematical model of microbial grouting reinforced seabed considering the response of wave-induced pore pressure and its application

Wave-induced instability of the sandy seabed has become an issue that cannot be ignored in the design of offshore foundations. Microbially induced calcium carbonate precipitation (MICP) is believed as a potential method to reinforce seabed against liquefaction. A bio-chemo-hydro-wave (B-C-H-W) coupled theoretical model of microbial grouting reinforced seabed considering the response of wave-induced pore pressure was developed in this study. The stability of MICP-reinforced seabed under wave actions with flower grouting and spot grouting conditions was also analyzed in detail. Results show that MICP reaction generates local calcium carbonate, which reduces the porosity and permeability coefficient, and enhances the stiffness of seabed, thereby reducing the amplitude of oscillating pore pressure. The mechanism of MICP reaction to resist seabed liquefaction include: increases the weight of seabed, provides a degree of cohesion, and reduces the amplitude of oscillating pore pressure. Different grouting methods determine the distribution pattern of calcium carbonate. Flower grouting has a larger effective protection length than spot grouting at the same conditions. There is a critical distance during double-tube grouting, it is recommended to arrange grouting tubes according to the critical distance and consider a certain safety factor in actual operation.