Keywords: residual pore pressure, consolidation, marine sediment, wave nonlinearity.

The evaluation of the wave-induced soil response in marine sediments is particularly important for coastal engineers involved in the design of the foundations of many marine installations, e.g., offshore mono-piles, breakwaters, pipelines and platforms etc. Predictions of the wave-induced excess pore pressure is a key procedure in the analysis of seabed instability such as liquefaction and scour. Therefore, it is necessary to have a better understanding of the mechanism of the wave-induced pore pressure in marine sediments.

In general, two mechanisms for wave-induced pore pressure have been observed in field measurements and laboratory experiments [1]. The first mechanism results from the transient or oscillatory excess pore pressure and is accompanied by attenuation of the amplitude and phase lag in the pore pressure changes [2]. The second mechanism is termed the residual pore pressure, which is the build-up of excess pore pressure caused by contraction of the soil under the action of cyclic loading [3]. Recently, a series of analytical approximations for the wave-induced accumulated pore pressure in marine sediments have been proposed by the author [5]. Both cases of infinite and finite soil layers were considered in the models. A simplified universal formula was proposed for the case of an infinite seabed [4]. However, all these approximations were limited to linear regular wave loadings, although they should be non-linear waves in natural environments.

In this paper, the models developed by the author [4,5] are further extended to non-linear wave loadings. The new model is verified with experimental data [6], and provide a better prediction of pore pressure accumulation than the previous solution with linear wave theory. The parametric study concludes that the influence of wave non-linearity increases as wave steepness (H/L) and the residual parameter (alpha) increases. However, an opposite trend is found for another residual parameter (beta).

1

H. Nago, S. Maeno, T. Matsumoto and Y. Hacgiman, "Liquefaction and densification of loosely deposited sand bed under water pressure variation", Proceedings of the 3rd International Offshore and Polar Engineering Conference, Singapore, 578-584, 1993.

2

T. Yamamoto, H. Koning, H. Sellmejjer, E. van Hijum, "On the response of a poroelastic bed to water waves", Journal of Fluid Mechanics, 87, 193-206, 1978. doi:10.1017/S0022112078003006

3

H.B. Seed and M.S. Rahman, "Wave-induced pore pressure in relation to ocean floor stability of cohesionless soil", Marine Geotechnology, 3(2), 123-150, 1978. doi:10.1080/10641197809379798

4

D.-S. Jeng and B.R. Seymour, "A simplified analytical approximation for pore-water pressure build-up in a porous seabed", Journal of the Waterway, Port, Coastal and Ocean Engineering, ASCE, 133(4), 309-331, 2007. doi:10.1061/(ASCE)0733-950X(2007)133:4(309)

5

D.-S. Jeng, B.R. Seymour and J. Li, "A new approximation for pore pressure accumulation in marine sediment due to water waves", International Journal for Numerical and Analytical Methods in Geomechanics, 31(1), 53-69, 2007. doi:10.1002/nag.547

6

E.C. Clukey, F.H. Kulhawy, P.L.-F. Liu, "Laboratory and field investigation of wave-sediment interaction", Joseph H.Defrees Hydraulics Laboratory, School of Civil and Environmental Engineering, Cornell University, Ithaca, NY, 1983.

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