The rock type used in coastal engineering structures impacts biodiversity, but its effect has been understudied to date. We report here on whether different combinations of rock material and rock ...mass properties can improve habitat suitability and early phase ecological outcomes on coastal engineering structures. We examine two coastal engineering schemes that used different granites during construction. At site one, Shap granite boulders with a high number of cm-dm2 surface features (e.g. ledges) were deliberately positioned during construction (called passive enhancement), to a) maximise the provision of cm-dm scale intertidal habitat and b) determine which scale of habitat is best for ecological enhancement. At site two, Norwegian granite boulders were installed without passive enhancement, allowing for a direct comparison. Passive positioning of Shap granite boulders led to an increase in limpet (Patella vulgata, Linnaeus, 1758) abundance within two years but few limpets were recorded on the non-enhanced Norwegian granite. Positioning of boulder thus exerts a strong control on the mm and mm-dm scale geomorphic features present, with clear ecological benefits when suitable features are selected for and optimally positioned (i.e. passive enhancement) to maximise habitat features. An EcoRock scoring matrix was developed to aid in the selection of the most ecologically suitable rock materials for coastal engineering worldwide; this can help improve habitat provision on engineered structures in a rapidly warming world.
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•Rock properties can improve habitat suitability and heterogeneity for gastropods.•Novel ecological sampling measured richness and abundance on geomorphic features.•Passive positioning of ledges significantly increased limpet abundance in two years.•Rock type exerts a strong control on geomorphic and habitat features present.•Selecting suitable features in passive positioning rock armour has clear ecological benefits.
The present paper presents new formulae for hydraulic stability of the main armour layer on rock armoured conventional rubble mound structures. In the present study, new stability tests were ...performed covering both mild (1:100) and steep (1:30) foreshores. The tests covered nonbreaking and breaking waves on the foreshore and also waves of very low steepness. The tests with the 1:30 foreshore showed the armour layer to be significantly more stable in the surging domain than predicted with the Van Gent et al. (2004) formulae. This was attributed to nonlinear waves with significantly larger H1/3 than Hm0. New stability formulae are presented and fitted to existing and present stability data. The new formulae provide a significant increase in the reliability for nonlinear waves compared to the Van Gent et al. (2004) formulae.
•New model tests with rubble mound rock armour stability are performed with 1:100 and 1:30 foreshores.•The tests include linear and highly nonlinear wave conditions with shallow foreshore.•The highly nonlinear waves show that Hm0 is better to describe the stability compared to H1/3 and H2%.•New stability formulae are given valid for shallow water foreshores with mildly nonlinear and highly nonlinear waves.
This work deals with the problem of assessing armourstone structures focusing on strengthening the combination of geo-marine techniques and geotechnical properties. The research has two main ...purposes: (i) to establish an integrative coastal geo-engineering approach for better assessment of the hydraulic structures; and (ii) to draw attention to the importance of quarry evaluation in order to improve armourstone quality and durability. Several studies have demonstrated the relevance of a holistic approach to coastal design issues. The suggested approach couples GIS-based mapping with geo-engineering techniques assessment along five pilot sectors of the Espinho coastal system in Northwestern Portugal. This investigation allowed us to propose zoning a coastal structure according to its degree of deterioration, geomechanical properties and geomaterial status. Replacement of the primary armour layer in only selected sections or components of the structure will reduce the cost of maintenance, repair and reinforcement work. All the gathered data about the preservation status of the armour layer and the quarry inventory have been compiled in a powerful GIS geo-database. The paper argues for the wider use of combination of coastal geo-engineering and GIS analysis in planning the monitoring and/or maintenance of marine works using armourstone.
The aim of the paper is to describe hydraulic stability of rock-armoured low-crested structures on the basis of new experimental tests and prototype observations.
Rock armour stability results from ...earlier model tests under non-depth-limited long-crested head-on waves are reviewed.
Results from new 2-D and 3-D model tests, carried out at Aalborg University, are presented. The tests were performed on detached low-crested breakwaters exposed to short-crested head-on and oblique waves, including depth-limited conditions. A formula that corresponds to initiation of hydraulic damage and allows determining armour stone size in shallow water conditions is given together with a rule of thumb for the required stone size in depth-limited design waves.
Rock toe stability is discussed on the basis of prototype experience, hard bottom 2-D tests in depth-limited waves and an existing hydraulic stability formula. Toe damage predicted by the formula is in agreement with experimental results. In field sites, damage at the toe induced by scour or by sinking is observed and the volume of the berm is often insufficient to avoid regressive erosion of the armour layer.
Stone sinking and settlement in selected sites, for which detailed information is available, are presented and discussed.
Armor layers of mound breakwaters are usually designed with empirical formulas based on small-scale tests in non-breaking wave conditions. However, most rubble mound breakwaters are constructed in ...the depth-induced breaking zone, where they must withstand design storms having some percentage of large waves breaking before reaching the structure; in these cases, the design formulas for non-breaking wave conditions are not fully valid. To characterize double-layer rock armor damage in breaking wave conditions, 2D physical model tests were carried out with a bottom slope m = 1/50. In order to develop a simple method to determine the wave parameters in the depth-induced breaking zone, experimental wave measurements were compared to the numerical estimations given by the SwanOne model. An analysis was conducted to select the best characteristic wave height to estimate rock armor damage when dealing with depth-induced breaking waves; the spectral significant wave height, Hm0, estimated at a distance of 3hs seaward from the structure toe, was found to be the most adequate. A new hydraulic stability formula is proposed for double-layer rock armors in breaking wave conditions, considering the observed potential 6-power relationship between the equivalent dimensionless armor damage and the Hm0 at 3hs seaward distance from the structure toe.
•Design formulas for rock armors are based mostly on physical tests in non-breaking wave conditions.•In breaking wave conditions, most armor hydraulic stability formulas are not fully valid.•In breaking wave conditions, armor damage shows a 6-power relationship with Hm0 at 3hs seaward distance from the structure.•The SwanOne numerical model is a suitable tool to estimate wave characteristics in breaking wave conditions.
Riprap, consisting of large boulders or concrete blocks, is extensively used to stabilize streambanks and to inhibit lateral erosion of rivers, yet its effect on river morphology and its ecological ...consequences have been relatively little studied. In this paper, we review the available information, most of it culled from the “grey” literature. We use a simple one‐dimensional morphodynamic model as a conceptual tool to illustrate potential morphological effects of riprap placement in a gravel‐bed river, which include inhibition of local sediment supply to the channel and consequent channel bed scour and substrate coarsening, and downstream erosion. Riprap placement also tends to sever organic material input from the riparian zone, with loss of shade, wood input, and input of finer organic material. Available information on the consequences for the aquatic ecosystem mainly concerns effects on commercially and recreationally important fishes. The preponderance of studies report unfavorable effects on local numbers, but habitat niches created by openings in riprap can favorably affect invertebrates and some small fishes. There is a need for much more research on both morphological and ecosystem effects of riprap placement.
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.
This book is the result of a stimulating Special Issue of Water, focusing on the “Interaction between waves and Maritime Structures”. This broadly inclusive title allowed the gathering of articles on ...different topics of engineering concern, making the book appeal to both scientists and practical engineers. Original contributions on evergreen problems, such as wave overtopping at conventional and unconventional coastal structures, wave-induced pressures at vertical walls, hydraulic stability of rubble mound breakwaters and dynamics of crown-walls indeed represent the main core of the book; however, other intriguing research topics are also tackled, including the solution of the Navier–Stokes equations for biphase flows, the downscaling of large maritime structures in a physical lab, floating bodies mechanics and the numerical modeling of coastline evolution.
Adding a surface rock layer (also called rock armor or rock mulch) to constructed slopes improves erosion resistance but has had mixed effects on revegetation. This study investigated the effects of ...rock layer depth (no rocks, 10-, 15-, and 20-cm rock layers) and rock size (5-20 cm diameter rocks) on vegetation cover. Seeding was applied four times in the first 2 years. After 3 years, plots with a rock layer averaged 7% vegetative cover compared to 85% on plots without a rock layer. There was a nonsignificant trend toward less vegetation with a deeper rock layer.
Yan, S.; Guo, B.; Sun, L., and Lei, Z., 2015. Theoretical analysis and model test of rock berm protection. Submarine pipelines are exposed to the risk of damage from dragged anchors of ships that ...lose control during severe storms. Rock armor berms are commonly employed to protect the pipelines by deflecting the dragged anchors. Theoretical work and model tests are implemented in this study to understand the protection mechanism provided by rock berms. A limit equilibrium method is proposed to address the interaction between the dragged Hall anchor and the developed soil wedges. The total drag force on the anchor is obtained as the sum of the drag force on the anchor crown and that on the anchor fluke. Model tests are performed with three model anchors with different linear scales. The drag forces measured in the model tests agree well with those calculated by the theoretical approach. Results show that when the anchor is dragged into the rock armor berm from the soil foundation, an unbalanced moment is induced on the anchor; this moment causes the dragged anchor to rotate and the fluke tip to rise up. Such prediction may be helpful to berm designers.
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