Influence of Excavation Pits on the Wave Hydrodynamics of Fringing Reefs under Regular Waves

Abstract

Dredging materials from reef flats have become an important source of sand and aggregates for meeting the infrastructure needs of coral-lined shores in subtropical and tropical regions, especially for low-lying atoll islands. Dredging at the reef flats can generate artificial excavation pits, which not only have profound influences on coral ecological stability but also deeply affect the hydrodynamic characteristics of coral reefs. To deepen the understanding of the influence of excavation on the wave hydrodynamics of fringing reefs, the wave propagation, wave transformation, wave setup, and wave runup processes of regular waves on fringing reefs with artificial pits have been systematically analyzed using a non-hydrostatic numerical wave solver (NHWAVE). The effects of some significant factors have been carefully investigated. According to the study findings, the existence of artificial pits can result in a slight decrease in the wave height around the artificial pit. The time-mean maximum of wave runup height at the backreef slope can be reduced to some extent when the artificial pit is present. When placed close to the reef edge, the artificial pit can have noticeable effects on the hydrodynamic characteristics of fringing reefs, particularly the wave setup along the reef flat. It is hoped that the study findings can provide further reference for evaluation of the influences of artificial pits on the wave hydrodynamics of fringing reefs.

Deformation Characteristics of Pipelines Due to Adjacent Excavation in Riprap Reclamation Strata

“…The maximum internal force and strain occurred at an inclined angle of 45° in the pipeline section, and the overall distribution was symmetric around the pipeline section. (3) The first layer of lateral support of the excavation plays a crucial role in controlling the deformation of the foundation pit, and increasing the stiffness of the lateral support of the excavation can be appropriated. For the lateral support with small axis force, the stiffness of excavation support can be relatively reduced.…”

“…Especially in coastal cities, some land is formed via reclamation from the sea, which poses significant risks to engineering construction. This surge in activity is marked by a trend towards deeper and more extensive diggings [1][2][3]. Consequently, the excavation of foundation pits unavoidably brings safety risks to neighboring pipelines.…”