Uplift soil resistance to a shallowly-buried pipeline in the sandy seabed under waves: Poro-elastoplastic modeling. (February 2020)

• Record Type: Journal Article
• Authors: Qi, Wen-Gang; Shi, Yu-Min; Gao, Fu-Ping
• Is Part Of: Applied ocean research. Volume 95(2020)
• Publication Date: 2020-02
• Subjects: Wave-seabed-pipeline interaction -- Poro-elastoplastic model -- Buried pipe -- Transient pore-pressure response -- Vertical soil resistance; Ocean engineering -- Periodicals; 620.416205
• DOI: 10.1016/j.apor.2019.102024
• Languages: English
• ISSNs: 0141-1187

Abstract

Highlights: A poro-elastoplastic model for concurrently simulating pore-pressure and elastoplastic responses while uplifting a buried pipeline. Influence of wave-induced pore-pressure on the uplift resistance to a buried pipe is intensively examined. Parametric study is made on the effect of wave period, water depth, the internal friction angle and the elastic modulus of the soil. Variation of the ratio of peak soil resistance under waves to that without waves with the normalized amplitude of pore-pressure is obtained. Abstract: A reasonable evaluation of the vertical soil resistance to a buried pipeline is crucial for upheaval buckling analyses. Under wave troughs, the effective stress in the seabed could be reduced significantly due to the upward seepage caused by vertical pore-pressure gradients. To investigate the influence of wave loading on the vertical soil resistance to a buried pipe, a plane-strain poro-elastoplastic model is proposed and verified with the existing pipe-soil interaction test results and DNV GL predictions. The model is capable of sequentially simulating the pore-pressure generation in a sandy seabed under waves and the plastic-zone development while uplifting the pipe. Numerical results show that the presence of wave troughs could not only reduce the soil effective stress, but also generate an additional uplift force on the buried pipe due to non-uniform distribution of pore-pressures along the pipe periphery. The normalized additional uplift force generally increases linearly with normalized amplitude of wave pressures at seabed mudline. Parametric study is then performed to examine the influence of wave parameters and soil properties. Moreover, to qualitatively characterize the effect of wave loading, a resistance-reduction coefficient is introduced and found to decrease linearly with the increase of normalized amplitude of wave pressure at seabed mudline.