Journal of Waterway, Port, Coastal, and Ocean Engineering

A series of laboratory tests was performed to evaluate the effect of clay fabric, altered due to the addition of hydrated lime into slurry, on the primary and secondary consolidation behavior of dredged mud samples. In this research, the seepage-induced consolidation test is proposed as a technique to determine the threshold value of lime, below which maximum flocculation of the clay particles takes place. A series of oedometer tests was conducted on lime treated samples in both normally consolidated (NC) and artificially over- consolidated (OC) states. The results obtained in NC range showed that both the coefficient of consolidation and compression index increased as the lime content increased. Under the same value of effective stress, with varying the amount of lime, the compression index increased and secondary compression index reduced, resulting in a gradual reduction of $C_{\alpha }/C_c$ value. The laboratory results show that in the OC state and with surcharging, both the secondary compression index and recompression index reduced when the percentage of lime increased. However, it was observed that the surcharging effort has less impact on secondary compression as the percentage of lime increased. This study may encourage an innovative ground improvement technique, in which dredged mud slurry can be mixed with lime prior to discharging into a containment pond in order to optimize the effectiveness of preloading on the dredged mud layer.

Two-dimensional tidal flows within the Loxahatchee River estuary (Southeastern Florida) are simulated in order to assess the effects of incorporating the Atlantic Intracoastal Waterway (AICWW) versus including the surrounding tidal flats in the computational domain. The region of interest is modeled with three variations of an unstructured, finite-element mesh, including a localized mesh with and without tidal flats, and an extended mesh that describes the AICWW. Phase and amplitude errors between model output and historical data are quantified in terms of water surface elevations at five locations within the Loxahatchee River estuary to assess the relative performance of the various computational meshes. While it is shown that the surrounding tidal flats provide some benefit to the numerical model, the hydrodynamics resulting from the inclusion of the AICWW results in a more significant improvement in the simulated water levels—an important modeling consideration that is commonly disregarded in practice. The application of additional boundary conditions enables for both hydrodynamic factors (AICWW; surrounding tidal flats) to be included in the numerical simulation. As a corollary, velocity residuals are computed on a domain-wide basis to reveal significantly different net circulation patterns within the Loxahatchee River estuary, depending on the level of description of the AICWW, and further demonstrate the importance of including the AICWW in the numerical model.

The hydrodynamic interaction of regular and random waves with a model offshore deck has been investigated in a wave flume. The hydrodynamic pressures and forces on the model as well as its reflection and transmission characteristics are investigated in a dimensionless form. The experiments were carried out for three different clearances $\left(e\right)$ between the still water level and the subface of the model. In order to investigate the effects of relative clearance of the deck ( $e/H$ in case of regular waves and $e/H_s$ in case of random waves), different wave steepnesses ( $H/L$ in case of regular waves and $H_s/L_p$ in case of random waves) were employed by varying wave height $\left(H\right)$ and wavelength $\left(L\right)$ . The effects of the wave steepness, relative clearance of the deck, relative length of the model ( $B/L$ in case of regular waves and $B/L_p$ in case of random waves) on the pressures and forces on the deck slab are investigated with a well controlled experimental program. The variation of the pressures along the length of the model was also investigated in terms of the relative position, $b/B$ . The experimental data was used to derive multivariate predictive equations for uplift (pull-out) forces that could act on actual deck slabs due to waves of various characteristics. It is observed that the maximum nondimensional crest and trough pressures due to random waves occur for a relative clearance of $e/H_s=0.3$ .

The Mandovi and Zuari are two tropical estuaries along the west coast of India, characterized by mixed tides with semidiurnal dominance and heavy fresh water influx during the southwest monsoon (June to September). Previous observations of tides in these estuaries show that the tidal effects in the upstream regions are subject to decay due to freshwater influx during the southwest monsoon. The longitudinal distribution of salinity in these estuaries undergoes large variations between the southwest monsoon and the dry season (February to May). The main objectives of the present study were to simulate the tidal circulation, the longitudinal distribution of salinity, and the freshwater influence on tides and the salinity distribution. Another objective was to study the intraseasonal variations of salinity during the breaks in the southwest monsoon. A hybrid network numerical model was used for the present study to simulate the tidal circulation and the salinity distribution in these estuaries. The model reproduced observed tides accurately during the dry and wet seasons. The model could reproduce the longitudinal distribution of salinity well during the dry season and the simulation of salinity distribution was reasonably well during the wet season. The simulated tidally averaged salinities over the $M_2$ tidal period for varying river discharges show that even a small freshwater influx can affect the longitudinal distribution of salinity to a great extent in this type of estuaries.

Leixões Harbor, near Porto, Portugal, has undergone various improvements over recent decades, especially an expansion inland with excavation for new docks, the raising, and seaward extension of the original breakwater, and the construction of a new submerged breakwater to protect the head of the breakwater extension. Faced with demanding goals and the need for new strategies, the Leixões Harbor authority decided that the operational conditions of oil terminal “A” needed to be improved. In order to meet those requirements eleven alternative configurations were built and tested in a two-dimensional physical model to compare performance for the same regular wave conditions in regard to stability and the overtopping phenomena. Each configuration was also tested for different tide levels. This paper presents the characteristics and results of those tests.

Wave overtopping and subsequent flooding during coastal storms result in significant damages in many areas. However, balancing engineering design functionality with public and community desire to maintain beach and waterfront views are often a challenge. Here, a variable-height bulkhead design concept is introduced. This bulkhead is designed to rise and fall with floodwaters to achieve design overtopping protection while maintaining views during nonstorm conditions. In this technical note, the functional variable-height bulkhead design is presented and laboratory tested. The design requirement that the bulkhead rise and fall with water levels was validated through this testing. Experimental results indicate that the variable-height bulkhead provides overtopping protection comparable to that of a static vertical wall with the same freeboard, showing that the variable-height bulkhead concept is, in terms of overtopping, a viable alternative for coastal storm protection. Testing has been carried out mainly for low energy conditions occurring, for example, in coastal bays and harbors. Further testing is required to include higher-energy environments such as the open coast. Finally, testing the structural design of the system is of primary importance.