· · · Repository Hydraulic Engineering Reports

Overview of application of the Van der Meer formula in a probabilistic environment.

Investigations on reshaping of berm breakwaters. Based on test at Delft Hydraulics. Focus on incipient motion (threshold of movement).

Bij WL is onderzoek uitgevoerd naar stabiliteit van breukstenen taluds bij (zeer) ondiepe voorlanden. De paper voor Coastal Structures 2003 "Stability of rock slopes with shallow foreshores" door van Gent, Smale en Kuiper is een samenvatting van het werk. Hierin wordt voorgesteld een andere periodemaat te nemen dan in de van der Meer formule en daarbij de coëfficiënten opnieuw te kalibreren. Uiteindelijk wordt een nieuwe formule voorgesteld waarin de periode invloed volledig is verdwenen.

The coastal team of Delta Marine Consultants [DMC] have taken the initiative to develop a new concrete armour unit for application on breakwaters and shore protections. Following the preliminary model tests conducted at DMC, 2-D hydraulic model tests have been carried out at Delft Hydraulics in October 2002. The experimental set-up and test procedure as well as the main results are briefly reported by Delft Hydraulics [report H4185, Jan 2003]. A comprehensive description of the 2-D hydraulic model tests, test results and further analysis on wave overtopping and hydraulic stability is presented in this report.

This is the second of two reports relating to a collaborative prograrmne of random wave flume tests to quantify the effect of rock shape on stability. The first report, SR 150, by Hydraulics Research, Wallingford, gives a summary of recent advances in design methods for rock armoured coastal structures and presents a detailed description of the test programme with an early interpretation of the results. This second report is a collation of the recent results from several parallel research studies carried out at Queen Mary College, the principal subject being armour stone shape and rounding .. Practical and theoretical developments in image analysis techniques are given for gross shape and surface texture measurement of prototype and model armour blocks. The five shape classes of armour used in the flume tests, namely tabular (including elongate), equant (cubic), fresh (angular), semi-round and very round were described using the new techniques. Samples of test material used in the development of Van deT MeeT's design equations were also subjected to the shape analysis techniques. A detailed discussion of Van der Meer's formulae is given in relation to the new flume test results and an indication of the relationships between rounding and instability is deduced, using a new shape parameter For the impermeable core conditions tested, stability is more sensitive to shape under surging wave than under plunging wave conditions Long-term degradation resulting in rounding of prototype armour stone is considered within a quantitative framework for different environmental conditions, initial block sizes, rock types and with reference to limited field data.

Forces by uprush and downrush, the imporatnace of permeability, the resonance phenomenon, friction between armor blocks and between armor and sublayer, slope geotmetry and practical design principles

The development of interest in the hydraulic forces acting on a body in a moving fluid from the seventeenth century to the present time is traced. Various formulas pertaining to bed-load movement, rock-filled dams, breakwaters, and drag coefficients are studied. The formulas are transposed to show their interrelationship. Available data pertinent to the design of riprap and river closures are discussed and summarized. Suggested design curves are given. The effect of bed slope on rock stability is considered.

Paper describing the development of the "Hudson formula" for the stability of armor on a breakwater.

This memorandum provides design guidance for sizing toe berm armor on breakwater and jetty trunks exposed to depth limited breaking waves whose crests approach at or near parallel to the structure

Overview of computational rules for Accropede and Xbloc in Cress

The Core-Loc, invented and developed at the Waterways Experiment Station (WES), is a new-generation, optimized breakwater concrete armor unit for protecting shoreline and navigation structures.Because of the very difficult construction, in-service, and repair conditions associated with high-energy wave environments, a need was identified to characterize the dynamic impact structural response of the Core-Loc. The most common method of accomplishing this goal is the drop test. Drop tests are used to evaluate the structural performance of a given armor unit when it is exposed to impact loads. During the test, the armor unit is dropped from incrementally increasing heights onto a rigid concrete base until the unit breaks apart. In this case, the drop heights were increased in 25-mm increments until the units totally failed.

Onderzoek naar begin van beweging en de stabiliteit van zeegrind onder invloed van stroom. In dit onderzoek is het effect van de taludhelling onderzocht. De helling van het grindbed is gevarieerd, helling van 1:3 en 1:6 zijn onderzocht. Er is grind gebruikt met een d50 van 1.65 cm.

This report is a compilation of facts and information that summarizes the present state of knowledge related to wave attack on the flood side of earthen levees. Particular emphasis was placed on the need for providing flood-side armoring (beyond the protection afforded by grass) for the New Orleans Hurricane & Storm Damage Risk Reduction System (HSDRRS). The report includes: (1) a summary of observations from Hurricane Katrina; (2) an extensive overview of large-scale experiments conducted in Europe, (3) a critical examination of proposed methodologies for predicting wave-induced damage on flood-side grass and bare-clay slopes, (4) an analysis of wave-induced erosion expected to occur on the flood side during hypothetical storms approximating the 100-yr and the 500-year events, (5) and a comprehensive list of conclusions and associated caveats. The erosion estimation methodologies for wave-induced erosion discussed in this report were applied to three sets of hypothetical extreme storm parameters to assess the need for providing wave erosion protection (i.e., armoring) on grass-covered and bare-clay flood-side slopes.

Local scour can occur at a breakwater constructed on a sandy seabed and may endanger the overall stability due to sliding of the main armour layer if the toe and scour protection is failing. The scouring pattern is a function of the water depth, wave conditions, sediment characteristics, and breakwater configuration and reflection characteristics as described by Arneborg et al (1996). A simultaneous current at the breakwater will significantly influence the scouring. Scouring in front of a berm breakwater constructed without a sufficient scour protection layer may result in berm stones to be moved into the scour hole, which will lead to further reshaping of the protecting berm. Physical two-dimensional (2D) model tests were made for qualitatively studying the scour development in front of a berm breakwater. Four test series were carried out in order to study the influence on the scouring and breakwater performance of varying the steepness of the incoming waves and of two types of scour protections.