Hoek Brown Elastoplastic Damage Model Considering Pore Water Pressure and Its Application to Subsea Tunnel Engineering

Compared with land tunnels, subsea tunnels are more prone to disasters such as water inrush. In order to calculate the deformation and the excavation damage zone (EDZ) of subsea tunnel, an elastoplastic damage constitutive model based on Hoek Brown (HB) criterion is proposed. Moreover, the modified effective stress principle considering pore water pressure is introduced and a finite element constitutive integral algorithm is established. To overcome the "singularity" problem in the numerical implementation, a complete implicit return mapping algorithm is deduced for solving the elastic-plastic HB damage (HBD) model, the plasticity correction process for three cases in which the flow vector returns to the main plane, the left and right prisms, and the tip, respectively. Furthermore, the 3D numerical program is then developed based on Abaqus' user subroutine interface. And the stability and accuracy of the algorithm is verified by uniaxial and triaxial laboratory compression tests. Finally, based on the proposed HBD model and program, the three-dimensional numerical calculations were carried out for the shield tunnel of the Dalian subsea project of China, which can reasonably reflect the displacement and damage evolution of the surrounding rock with different shield construction sequence, different pore water pressure and different support pressure. The model and program provided an effective means to analyze the EDZ of the surrounding rock for subsea tunnel engineering.