scholarly journals Physical model tests and numerical simulation for assessing the stability of brick-lined tunnels

2016 ◽  
Vol 53 ◽  
pp. 109-119 ◽  
Author(s):  
Han-Mei Chen ◽  
Hai-Sui Yu ◽  
Martin J. Smith
Keyword(s):  
Numerical Simulation ◽  
Physical Model ◽  
Model Tests ◽  
Physical Model Tests ◽  
The Stability

scholarly journals Stability of Rubble Mound Breakwaters—A Study of the Notional Permeability Factor, Based on Physical Model Tests

Water ◽  
2019 ◽  
Vol 11 (5) ◽  
pp. 934 ◽  
Author(s):  
Mads Røge Eldrup ◽  
Thomas Lykke Andersen ◽  
Hans Falk Burcharth
Keyword(s):  
Physical Model ◽  
Slope Angle ◽  
Model Tests ◽  
Permeability Factor ◽  
Physical Model Tests ◽  
Stability Model ◽  
The Stability ◽  
Rubble Mound Breakwaters ◽  
Layer Composition

The Van der Meer formulae for quarry rock armor stability are commonly used in breakwater design. The formulae describe the stability as a function of the wave characteristics, number of waves, front slope angle and rock material properties. The latter includes a so-called notional permeability factor characterizing the permeability of the structure. Based on armor stability model tests with three armor layer compositions, Van der Meer determined three values of the notional permeability. Based on numerical model results he added for a typical layer composition one more value. Based on physical model tests, the present paper provides notional permeability factors for seven layer compositions of which two correspond to the compositions tested by Van der Meer. The results of these two layer compositions are within the scatter of the results by Van der Meer. To help determination of the notional permeability for non-tested layer compositions, a simple empirical formula is presented.

scholarly journals Statistical Analysis of the Stability of Rock Slopes

2019 ◽  
Vol 7 (3) ◽  
pp. 60 ◽  
Author(s):  
Marcel van Gent ◽  
Ermano de Almeida ◽  
Bas Hofland
Keyword(s):  
Statistical Analysis ◽  
Physical Model ◽  
Model Tests ◽  
Water Levels ◽  
Test Series ◽  
Length Effect ◽  
Wave Flume ◽  
Physical Model Tests ◽  
Erosion Area ◽  
The Stability

Physical model tests were performed in a wave flume at Deltares with rock armoured slopes. A shallow foreshore was present. At deep water, the same wave conditions were used, but by applying different water levels, the wave loading on the rock armoured slopes increased considerably with increasing water levels. This allowed an assessment of the effects of sea level rise. Damage was measured by using digital stereo photography (DSP), which provides information on each individual stone that is displaced. Two test series were performed five times. This allowed for a statistical analysis of the damage to rock armoured slopes, which is uncommon due to the absence of statistical information based on a systematic repetition of test series. The statistical analysis demonstrates the need for taking the mean damage into account in the design of rock armoured slopes. This is important in addition to characterising the damage itself by erosion areas and erosion depths. The relation between damage parameters, such as the erosion area and erosion depth, was obtained from the tests. Besides tests with a straight slope, tests with a berm in the seaward slopes were also performed. A new method to take the so-called length effect into account is proposed to extrapolate results from physical model tests to real structures. This length effect is important, but is normally overlooked in the design of rubble mound structures. Standard deviations based on the presented model tests were used.

Artificial Intelligence and Rubble-Mound Breakwater Stability

2012 ◽  
pp. 1499-1506
Author(s):  
Gregorio Iglesias Rodriguez ◽  
Alberte Castro Ponte ◽  
Rodrigo Carballo Sanchez ◽  
Miguel Ángel Losada Rodriguez
Keyword(s):  
Physical Model ◽  
Model Tests ◽  
Wave Action ◽  
Ann Model ◽  
Climate Conditions ◽  
Wave Flume ◽  
Physical Model Tests ◽  
Rubble Mound ◽  
The Stability ◽  
Rubble Mound Breakwaters

Breakwaters are coastal structures constructed to shelter a harbour basin from waves. There are two main types: rubble-mound breakwaters, consisting of various layers of stones or concrete pieces of different sizes (weights), making up a porous mound; and vertical breakwaters, impermeable and monolythic, habitually composed of concrete caissons. This article deals with rubble-mound breakwaters. A typical rubble-mound breakwater consists of an armour layer, a filter layer and a core. For the breakwater to be stable, the armour layer units (stones or concrete pieces) must not be removed by wave action. Stability is basically achieved by weight. Certain types of concrete pieces are capable of achieving a high degree of interlocking, which contributes to stability by impeding the removal of a single unit. The forces that an armour unit must withstand under wave action depend on the hydrodynamics on the breakwater slope, which are extremely complex due to wave breaking and the porous nature of the structure. A detailed description of the flow has not been achieved until now, and it is unclear whether it will be in the future in view of the turbulent phenomena involved. Therefore the instantaneous force exerted on an armour unit is not, at least for the time being, amenable to determination by means of a numerical model of the flow. For this reason, empirical formulations are used in rubble-mound design, calibrated on the basis of laboratory tests of model structures. However, these formulations cannot take into account all the aspects affecting the stability, mainly because the inherent complexity of the problem does not lend itself to a simple treatment. Consequently the empirical formulations are used as a predesign tool, and physical model tests in a wave flume of the particular design in question under the pertinent sea climate conditions are de rigueur, except for minor structures. The physical model tests naturally integrate all the complexity of the problem. Their drawback lies in that they are expensive and time consuming. In this article, Artificial Neural Networks are trained and tested with the results of stability tests carried out on a model breakwater. They are shown to reproduce very closely the behaviour of the physical model in the wave flume. Thus an ANN model, if trained and tested with sufficient data, may be used in lieu of the physical model tests. A virtual laboratory of this kind will save time and money with respect to the conventional procedure.

scholarly journals EFFECTS OF WATER LEVEL VARIATIONS ON THE STABILITY OF ROCK ARMOURED SLOPES

2018 ◽  
pp. 44 ◽  
Author(s):  
Marcel R.A. Van Gent ◽  
Suzanna A.A. Zwanenburg ◽  
Jan Kramer
Keyword(s):  
Water Level ◽  
Physical Model ◽  
Model Tests ◽  
Water Levels ◽  
Level Variation ◽  
Water Level Variation ◽  
Stepwise Approach ◽  
Physical Model Tests ◽  
Water Level Variations ◽  
The Stability

Physical model tests on the stability of rock armoured slopes have been performed to demonstrate the importance of water level variations during a storm, due to a tide or a storm surge. For the stability of rock armoured slopes also the importance of the sequence of storms at various water levels has been studied. The test results indicate that a smooth sinusoidal water level variation leads to an increase in damage compared to the same wave conditions at a constant water level. Furthermore, a stepwise approach of the sinusoidal water level elevation leads to other results than the approach with a continuous water level variation, whereas the continuous water level variation resembles the peak of a storm or the tidal water level variation better than a stepwise approach. If storms with different water levels attack the armour layer, the damage is generally smaller than if all storms attack the armour layer at the same water level. Furthermore, the results have been discussed based on earlier analyses where the statistics of rock armoured slopes have been addressed and the importance of the length effect has been illustrated using a method to apply results from physical model tests to real structures.

scholarly journals WAVE REFLECTION FROM BERM BREAKWATERS

2020 ◽  
pp. 7
Author(s):  
Karthika Krishna Pillai ◽  
Amir Etemad-Shahidi ◽  
Charles Lemckert
Keyword(s):  
Physical Model ◽  
Wave Reflection ◽  
Model Tests ◽  
Reflection Coefficients ◽  
Data Sets ◽  
Empirical Formulas ◽  
Reflected Waves ◽  
Physical Model Tests ◽  
The Stability

Wave reflection from berm breakwaters is an area less focused as these structures are generally considered to have relatively low reflection levels. However, the reflected waves may compromise the stability of the structure by inducing scour at the toe and may enhance harbour access risk (Zanuttigh et al., 2013). Hence, it is necessary that the reflection coefficients are predicted accurately. Several empirical formulas such as Postma (1989), Alikhani (2000), Zanuttigh and Van der Meer (2008) and Van der Meer and Sigurdarson (2016) have been suggested for the prediction of wave reflection, Kr. In this study, physical model tests were conducted to supplement the existing berm breakwater data sets in the CLASH database (Zanuttigh et al., 2016). The measured reflection coefficients were then compared with those of the existing formulas to evaluate their performance.Recorded Presentation from the vICCE (YouTube Link): https://youtu.be/WXIoa_ae-1Y

Testing the Effectiveness of Scour Countermeasures by Physical Modeling

2000 ◽  
Vol 1696 (1) ◽  
pp. 251-257
Author(s):  
Norbert O. Eisenhauer ◽  
Bernd Rossbach
Keyword(s):  
Physical Model ◽  
Physical Modeling ◽  
Ad Hoc ◽  
Model Tests ◽  
Rhine River ◽  
Flood Events ◽  
Mean Flow ◽  
Negative Effects ◽  
Physical Model Tests ◽  
The Stability

The physical modeling of the scouring process at bridge piers is a proven method to obtain information about the size of the scour and the flow velocities that generate the scour. On the basis of this information, appropriate countermeasures can be designed. The advantage of the physical model is its application to all, even the most complex, pier geometries. Because approach flow is uniform in most cases, physical model tests can be carried out in a hydraulic flume, a method that gives fast and reliable results. The Federal Waterways and Engineering Institute (Bundesanstalt für Wasserbau) in Karlsruhe, Germany, conducted such model tests using piers of a new bridge over the Rhine River between the cities of Mannheim and Ludwigshafen. Shortly after sheet piles were driven into the riverbed as a formwork for the lower part of the pier, severe scouring of the riverbed occurred. Consequently, the stability of the sheet pile formwork was endangered. The ad hoc countermeasure of placing riprap into the scour did not stop local scouring. An additional cover layer of coarser stones was placed on top of the previous layer, stopping the erosion process at mean flow. Model tests were conducted to estimate the durability and stability of the ad hoc countermeasure for flood events. The tests proved that the riprap was stable, even at flood events, and that the scour had shifted away from the pier to the joint between the riprap and the original riverbed. A flood event with a peak of 3 days above the tested flood water level occurred in March 1999. No negative effects on the riprap have been observed until now.

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