Instability evaluation of rubble mound for breakwaters subjected to tsunami-induced overflow and seepage flow

Kasama, Kiyonobu; Zen, Kouki; Nakagawa, Yasuyuki; Furukawa, Zentaro

doi:10.1016/j.sandf.2020.10.006

Cited by 5 publications

(12 citation statements)

References 4 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…On the other hand, for caisson blocks that do not allow water to pass through to the inside, a resolved coupling is implemented in which ISPH wall particles are placed on the surface and treated as a moving wall boundary. We performed a numerical analysis corresponding to the seepage collapse experiment by Kasama et al [21]. The simulation qualitatively reproduced the overall failure morphology of the breakwater, including deformation of the rubble mound due to seepage flow and sliding and rotating of the caisson block due to horizontal forces.…”

Section: Discussionmentioning

confidence: 89%

“…The comparison of piezo head distribution between proposed simulation and the experimental data of Kasama et al [21] Figure 11 Distribution of the porosity on DEM particles Figure 12 ISPH-DEM coupling simulation result…”

Section: Discussionmentioning

confidence: 98%

“…The main validation for the seepage failure prediction is given here. Kasama et al [21] conducted a series of hydraulic model tests on a scale of 1/100 for the Kamaishi Harbor Mouth Breakwater. In this experiment, seepage flow is generated in the rubble mound due to the water head difference in water level between the seaside and inner harbor side.…”

Section: Isph-dem Coupled Simulation For Estimating the Seepage Failu...mentioning

confidence: 99%

“…In this study, the ISPH-DEM coupling method, which is given in the previous section, is firstly applied to represent this experimental test [21]. Then, the additional failure criteria based on Terzaghi's critical hydraulic gradient will be introduced to improve the accuracy of the seepage failure prediction.…”

Section: Isph-dem Coupled Simulation For Estimating the Seepage Failu...mentioning

confidence: 99%

“…Our new contribution in this paper is how to model the interaction forces as an unresolved coupling between seepage flow simulated by ISPH and rubble mound particle modeled with DEM. A seepage collapse experiment conducted by one of the authors [21] on the Kamaishi breakwater is selected as the validation test.…”

Section: Introductionmentioning

confidence: 99%

See 4 more Smart Citations

Seepage failure prediction of breakwater using an unresolved ISPH-DEM coupling method incoprporated with Terzaghi's critical hydraulic gradient

Tsuji

Asai²,

Kasama

2022

Preprint

Self Cite

View full text Add to dashboard Cite

This study develops a new numerical simulation model for rubble mound failure prediction caused by piping destruction under seepage flows. The piping has been pointed out as a significant cause of breakwater failure during tsunamis. Once boiling and heaving occur on the mound surface, the piping suddenly propagates in the opposite direction of seepage flow. For the seepage failure prediction, a coupled fluid-soil-structure simulator is developed by combining the ISPH for fluid and the DEM for rubble mounds and caisson blocks. The ISPH, a Lagrangian particle method for incompressible fluids, can simulate seepage and violent flows such as tsunamis. The DEM has been applied for discrete particle and rigid body simulations that include discontinuous deformation as in the rubble mounds failure and large displacement of the caisson block. ISPH-DEM coupling simulations have already been proposed as a technique for multi-phase flows. Still, the technique cannot reproduce the sudden onset of piping from a stable mound. Two simple assumptions are applied to reduce the numerical cost for the fluid-soil-structure simulators of a breakwater structure composed of rubble mound and the caisson block. Firstly, each rubble is modeled as an idealized spherical DEM particle with the mean diameter of rubble. The ISPH particle size is assumed to be the same size as the DEM particle. Under these assumptions, the unresolved coupling model between rubble mound particle and fluid, which obtains the interaction through empirical drag force, should be applied. Whereas the interaction between the fluid and the caisson block is fully resolved with the spatial resolution with the ISPH and DEM particle size. Our new contribution in this paper is how to model the interaction as an unresolved coupling between seepage flow simulated by ISPH and rubble mound particle modeled with DEM. Our original seepage failure experiment is simulated using the proposed ISPH-DEM coupling simulator. We recognized the conventional drag force models as the unresolved coupling model are insufficient to initiate the boiling and piping observed in the experiment. It may be due in one part to excessive averaging of flow velocities caused under unresolved coupling. Therefore, Terzaghi's critical hydraulic gradient is introduced to initiate the boiling and heaving. Unstable DEM particles, judged by Terzaghi's critical hydraulic gradient, gradually lose their mass to represent unresolved suspended fine rubble mound particles. Our models qualitatively reproduce the sand boiling and backward erosion in the opposite direction of the seepage flow, as shown in the experiment.

show abstract

Section: Discussionmentioning

confidence: 89%

Section: Discussionmentioning

confidence: 98%

Section: Isph-dem Coupled Simulation For Estimating the Seepage Failu...mentioning

confidence: 99%

Section: Isph-dem Coupled Simulation For Estimating the Seepage Failu...mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations