Velocity and water-layer thickness of overtopping flows on sea dikes: Report of measurements and formulas development
The study aims to establish a set of formulas estimating velocity and depth of overtopping flows at sea dikes including seaward-side slope, crest and landward-side slope. These formulas are applicable to flows which are generated by natural waves and the simulator giving associated characteristics of any arbitrary value of exceedance probability. Note that the probability is based on the total number of incident waves and not to be confused with the total number of overtopping events. The difference between the fictitious wave run-up level and the crest level (Ru2% - Rc) is widely considered as a measure of the (potential) energy of wave overtopping. This term is therefore used to estimate values of the mean overtopping discharges, ow velocities, water-layer thickness and overtopping volumes. In line with many existing research works and guidelines, the potential term is crucial to derive other parameters. Experimental data of Van Gent [2002] is reanalyzed with a slightly different perspective to achieve the study objective. The analysis procedure basically consists of three main steps:  from wave conditions and dike cross-section to calculate wave run-up levels;  from wave run-up levels to estimate flow parameters on the dike crest;  from flow parameters on the dike crest to further compute the corresponding parameters on the landward slope. The obtained equations are verified with flow measurements of the simulator on real dike slopes. Consequently, feasible values representing the roughness of different grass coverings are determined.
Stability of Single-Layer Cubes on Lee-Side of Breakwaters: Quantative Research on the Stability of a Single Cubic Armour Layer on the Lee-Side of Breakwaters using a Wave Overtopping Simulator
Breakwaters are hydraulic structures used to create calm and steady environments for moored ships in harbors. They dampen the wave by dissipating the energy through wave breaking. Most studies of breakwaters have only been carried out on the seaward slope of the structure. However, few have conducted research on the landward-, inner-, slope of breakwaters. The existing accounts re all empirical design formulae, commonly denoted as applicable for conceptual design. Improvement of the design of the armour layer of the inner slope leads to economical advantages.This research focused on three main goals: (1) Presenting a theoretical methodology for the waves tested, (2) It veried the Wave Overtopping Simulator as built by Rietmeijer (2017) and (3) Performed stability tests for the inner slope by conducting physical model tests in the Fluid Mechanics Laboratory of Delft University of Technology. The first goal of this research has been to develop a theoretical approach to overtopping waves in combination with a simulator. This has been done by linking certain storm characteristics, being the significant wave height Hs and peak period Tp to wave characteristics; water volume, water layer thickness and the front velocity of the water body. These three combined lead to an impinging wave on the rear slope causing damage. Subsequently the storms have been altered to only select the highest percentage of waves, since these were marked as extreme storm conditions. This resulted in dierent signicant wave heights which were tested. To verify the Wave Overtopping Simulator tests have been performed and specic elements have been measured and analyzed. This has resulted in relationships between theoretical wave characteristics and simulator settings. The relationships are the required water level in the reservoir to obtain a certain front velocity of the water body. To adjust the water layer thickness the valve settings have been changed. For a specic volume the overtopping period has been altered. These three elements have been measured using wave gauges and a high speed camera after which the data was carefully analyzed. The stability tests have been executed using a model of a breakwater in the Fluid Mechanics Laboratory of Delft University of Technology. Results of the preparatory calculations together with results obtained from former research have led to the design of the test set-up. A single armour layer of 20 mm cubes with an porosity of nearly 40% was built with an fixed toe. This configuration was tested with increasing storm intensities until failure. Subsequently the damage has been measured using photo camera's and laser technique. This research has successfully verified the wave overtopping simulator by measuring individual waves and their specific discharge, water layer thickness and velocity. These measurements have been compared to an other method, using a high speed camera. The found values have been checked with found literature and it has been concluded that the Wave Overtopping Simulator together with the test set-up as built in the Fluid Mechanics Laboratory is useful for this research. By measuring the displacement of cubes by means of video camera and laser technique, the research has been able to identify damage and failure cases. The horizontal displacement has been divided into several classes ranging from settlement of the armour layer, to instant failure. In addition, this research has presented a possible link between the stability of a single cubic armour layer and the number of rows beneath the waterline.
Archaeological Survey of Dangoyama Kofun by 3DGPR
We presented a three-dimensional ground penetrating radar (3DGPR) system for the archeological investigation in a harsh site, where we have to deal with many trees and/or great topographic variations. This system consists of a commercial GPR system with a laser positioning system. With this system, we can move the GPR antenna freely, on which a positioning detector can record accurate position for each GPR data trace. We applied our 3DGPR system at Dangoyama Kofun, a burial mound, in Fukushima prefecture, Japan. A lot of trees and bushes covered the survey area and cannot be cut. We acquired six datasets in two days in this area. We successfully imaged the boundary between the original surface of the burial mound and the covering soil clearly at about 0.3 m depth around the mound. Furthermore, we found some strong reflections appeared at 0.8 m depth in the top area of the mound, which can be from the artificial parts of the burial mound. The results would greatly aid the following archaeological excavation. In addition, we compared the non-interpolated depth slice with interpolated depth slice at same position and demonstrated that the interpolation process on threedimensional GPR data may introduce some artifacts which might mislead our interpretation.