Induced water pressure profiles due to seismic motions

Wang

Computers and Geotechnics

et al. 2018

The evaluation of seismic-induced response in the porous seabed is a fundamental problem in geotechnical and coastal engineering. Although the ground motions generally include both horizontal and vertical components, most previous theoretical investigations assumed vertically propagating shear waves in a horizontally layered soil-rock system and simply ignored the effect of site response to vertical earthquake motion. In this paper, the dynamic response and instantaneous liquefaction of porous seabed, induced by vertical earthquake loading, is studied using an analytical method. The seabed is treated as a two-layer poro-elastic medium and characterized by the fully dynamic formulation of Biot theory. The analytical solutions for the response variables, such as induced displacement, pore pressure and vertical effective stress, are respectively derived and the mechanism of instantaneous liquefaction in the liquefiable sediment is investigated based on the excess pore pressure criterion. A set of parametric analysis is carried out to discuss the effects of seawater, seabed and earthquake parameters on the seismic response and maximum liquefaction depth. It is worth noting that the properties of surface seabed layer have significant influence on the seismic response and consequently the potential stability of the seabed, which is important in the analysis of foundations for offshore structures.

Section: Analytical Solutions For the Seismic Response Variablesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Effect of vertical seismic motion on the dynamic response and instantaneous liquefaction in a two-layer porous seabed

Wang

Computers and Geotechnics

et al. 2018

“…On the other hand, apart from the ocean-waves, catastrophic damage to offshore structures has also been recorded in the past earthquakes [11,12]. However, the analytical and numerical investigations on seismic dynamics of porous seabed are still limited to date [13][14][15][16]. The behaviors of the loads from ocean-waves and earthquake are both periodic but have notably different characteristics (see Table 1).…”

Section: Introductionmentioning

confidence: 99%

Momentary liquefaction of porous seabed under vertical seismic action

Jeng

et al. 2018

Applied Ocean Research

The evaluation of potential liquefaction is an important part in the design of marine structures and offshore installations. However, the liquefaction phenomenon of porous seabed under the action of strong earthquake is traditionally been ignored. This paper aims to explore the momentary liquefaction mechanism of porous seabed through the newly analytical solutions of seabed response induced by vertical seismic excitation. Based on the boundary conditions at the surface and bottom of the seabed, the induced displacements and pore pressure in the sediment are rigorously derived as a function of seawater depth, seabed parameters and seismic characteristics of bedrock. A criterion of earthquake liquefaction in the seabed is developed, employing the concept of induced excess pore pressure. The representative cohesionless marine soils with different properties are selected in the parametric analysis. The results show that the liquefaction of seabed could be influenced by seawater parameters, seabed parameters and earthquake ground motion parameters. The significant finding is that current understanding that the vertical motion effect on soil liquefaction is negligible may not always hold true.

“…Boundary integral equations have been also used to calculate the hydrodynamic pressure caused by seaquake in layered media (Higo, 1997), and for three dimensional cases in Jang and Higo (2004). Recently, the boundary element method and the discrete wave number method have been used to determine pressures near the interface of fluid-solid models (Flores-Mendez et al, 2012, Rodríguez-Castellanos et al, 2011, 2014.…”

Section: Introductionmentioning

confidence: 99%

Effects of the soil properties on the sea pressure profile due to seismic motions

Rodríguez-Castellanos

Ávila-Carrera

Pineda-León

et al. 2017

GeofInt

Self Cite

Large number of earthquakes have epicenters in offshore areas and their effects are a matter of great concern. This paper applies, for two dimensional problems, the Indirect Boundary Element Method to calculate the seismic pressure profile with the water depth due to the incidence of P- and SV-waves on the seabed, which can be characterized using the soil properties. Moreover, seismic amplifications of the seabed are highlighted. Our formulation can be considered as a numerical implementation of the Huygens’ Principle in which the diffracted waves are constructed at the boundary from which they are radiated. Thus mathematically, it is fully equivalent to the classical Somigliana’s representation theorem. Numerical results show the importance of knowing the properties of the marine soil because the pressure profile has an enormous dependence with respect to them. In some cases, pressure amplifications of six times between extreme values of soil materials can be expected. In addition, results from a layered numerical model evince that large seismic amplifications may be found, they can reach values up to 15.57 and 18.36 times the incident P- and SV-waves, respectively.