Journal of Waterway, Port, Coastal, and Ocean Engineering

When dredging in sensitive environments, efforts have to be made to limit the free dispersal of suspended fine sediment from the dredging spill. The use of hanging silt curtains as an environmental mitigation measure is especially widespread. Despite frequent application, their ability to reduce turbidity levels through vertical diversion of sediment-laden currents remains the subject of debate. This paper addresses a series of laboratory measurements and numerical model simulations to determine the efficiency of hanging silt curtains, defining a new efficiency parameter. The model was validated against the laboratory experiments. Model simulations focusing on vertical diversion of the sediment-laden current suggest that hanging silt curtains do not have a favorable influence on the settling of suspended sediment when applied in crossflow. The diversion of currents underneath the curtain causes flow separation and intense turbulent mixing, which counteracts settling of suspended sediment particles. The results imply that the widespread application of hanging silt curtains should be reconsidered from a physical point of view.

Available 17-day field data in Korea are analyzed to investigate the cross-shore wave transformation, currents and sand suspension in the intertidal zone, and beach profile changes of a macrotidal pocket beach with a gentle slope of 0.02 and tidal ranges of 4–7 m. The measured beach profile changes were less than 0.5 m despite the occurrence of two consecutive storms with significant wave heights exceeding 2 m. A cross-shore numerical model is shown to reproduce the gradual wave height decay in the migratory surf zone, the cross-shore current of the order of 0.1 m/s affected by flood and ebb tides, the suspended sand volume varying with the tidal cycle, and the small beach-profile changes. The computed cross-shore and longshore sand-transport volumes per unit width for the 17-day interval are relatively small, but extend the 400-m-wide cross-shore zone. The small volume and wide zone reduces the local erosion or accretion.

Most offshore wind-turbine foundations are monopile foundations. Monopile foundations have the advantages of simple structures and are convenient to construct. In recent years, large-diameter monopile foundations, with diameters larger than 4 m, have been used in engineering applications to increase the bearing capacity of wind turbines. Increasing the foundation pile diameter changes the bearing characteristics from those of traditional small-diameter steel-pipe piles. However, research on the bearing characteristics of large-diameter steel-pipe piles is lacking; no mature method exists to estimate the bearing capacity. On the basis of numerical simulations, the differences between the stress and deformation characteristics of the pile body and the soil around it between large-diameter and small-diameter steel-pipe piles subjected to vertical loads and horizontal loads in sand are investigated in this study. A method to calculate the vertical bearing capacity, considering the soil-arching effect, is proposed. In addition, a method to calculate the lateral displacement, based on the shell theory, is proposed. The applicability of the proposed method is verified using laboratory experiments. The result shows that the vertical ultimate bearing capacity calculated by the method considering the soil-arching effect is significantly higher than that predicted by the American Petroleum Institute (API) code method, and the lateral displacement at the pile top using the method based on the shell theory is 5–45% greater than that predicted by the $p–y$ curve method in the API code.

Three enhanced versions of two existing nonlinear Boussinesq-type models are herein derived. These models, along with two other similar solvers, were investigated with respect to their nonlinear and dispersive characteristics. In particular, this study comprises Fourier analysis at first-order, second-order, and third-order harmonics; an investigation of linear and nonlinear dispersion; linear shoaling analysis; and an estimation of transfer functions for subharmonics and superharmonics. The models are also validated against demanding experimental tests of wave propagation over a submerged bar. Conclusions of both a special and a general nature are drawn and discussed concerning the scope of nonlinear upgrade of Boussinesq-type equations, their numerical implementation, and the limitations of such models.

A mechanism for the growth of waves by wind is included in a time-domain Boussinesq-type model. To facilitate direct analysis of the effect of wind on nonlinear wave–wave interactions over a flat bottom, a set of three harmonic evolution equations is derived from the time-domain model. These equations simulate the evolution of the principal components of three-wave (triad) nonlinear interactions, now including the effect of wind. A case of wave recurrence, in which energy is cycled between three harmonics, shows that a following wind can increase energy exchange to higher harmonics owing to nonlinearity, whereas an opposing wind suppresses this interaction. The time-domain model is then used to simulate wave propagation over a planar slope in the presence of wind. It is shown that wave growth is assisted by onshore winds and hindered by offshore winds. In addition, wave skewness and asymmetry, which quantify wave shape, are also similarly affected by wind direction. The results also show that the skewness and asymmetry undergo cyclic oscillation during the shoaling process; the degree to which these statistics exhibit the effect of wind is thus spatially dependent and can likely explain earlier laboratory studies regarding the increased dependence of wave-shape statistics on wind speed in shallow water relative to that seen in deeper water.

The assessment of the productivity growth of ports is essential to improve their performance and competitiveness. Although there are several nonparametric methodologies to compute the productivity change, the Hicks–Moorsteen productivity index is the only multiplicatively completed index that can be computed without price data. For the first time, the total factor productivity (TFP) change of a sample of ports is evaluated. The analysis covers the 28 ports comprising the Spanish port system, using data over the period 2005–2012. The drivers of TFP—technical change, technical efficiency, mix efficiency, and residual scale efficiency—are also investigated. The results indicate that from 2005 to 2009, the TFP declined significantly owing to the technical change, whereas from 2009 to 2012, the TFP improved significantly. The TFP decomposition illustrates that 10 out of the 28 ports improved their technical change, and 9 out of the 28 ports increased their efficiency change. From a policy and managerial perspective, this study illustrates the importance of separating TFP change into the technical-change and efficiency-change components.