Erosion Stability of Wide-Graded Quarry-Stone Material under Unidirectional Current

Abstract

Scour protection around hydraulic structures in fluvial, estuarine, and coastal waters is an essential component of a meaningful and durable design. The continuous optimization of scour protection systems and design approaches leads to faster and more cost-effective construction processes. Although scour protection now often consists of a two-layer design, approaches that incorporate only one layer depict a major step forward. Therefore, this research focuses on the stability of a wide-graded quarry-stone mixture consisting of crushed granodiorite (Jelsa quarry, Norway) with fractions ranging from 0.063 to 200 mm. The material was exposed to an incrementally increased unidirectional current in a closed-circuit flume. The induced flow field and leading parameters were measured at various positions horizontally and vertically, whereas the erosion rates were determined behind the test bed specimen. With increasing flow velocity the development of a static armor layer was observed at the bed surface. Bed-shear stresses were determined to be strongly variable across the rough test bed. Fractional critical shear stresses indicate highly selective mobility of individual fractions. Least-square fitting of the determined critical shear stresses based on the dimensionless reference grain size d i =d s (with d s as the product of the geometric mean size d g and the geometric standard deviation s g) is suitable for describing the stability behavior of the investigated material.

Role and Impact of Hydrograph Shape on Tidal Current-Induced Scour in Physical-Modelling Environments

“…As large parts of the experimental setup are identical, this chapter describes only the essential parts of the experimental setup ( Figure 1 shows a schematic view of the experimental setup) and focuses on differences in test procedure and modelling of tidal currents by means of different velocity time series. More detailed information about the facility can also be found in Schendel et al [16] and comprehensive descriptions of the experimental setup and procedure are given in Schendel et al [14,15]. As material for the sediment bed, crystal quartz sand with a median diameter 50 = 0.19 mm and a density of = 2.65 g/cm³ was used in all tests.…”

“…In addition, the findings of this study can be of great importance for the physical modelling of tidal currents in facilities which are not able to change flow direction or continuously adapt the flow velocity. Notation c 1 , c 2 , c 3 = fitting coefficients; D = pile diameter; d 16 = grain size for which 16% of the material by weight is finer; d 50 = grain size for which 50% of the material by weight is finer;…”

Probabilistic Comparison of Static and Dynamic Failure Criteria of Scour Protections

“…Reference [3] states that in wide graded scour protections the smaller stones are better sheltered thanks to the larger stones, thus it recommends that the critical bed shear-stress is obtained with D 67.5 . Recently, References [25,26] conducted a physical model study, concluding that wide graded scour protections provide high stability against wave loading, thus being suitable for a dynamically stable design. Although using D 67.5 increases the resistance parcel (τ cr ), the approach proposed in Reference [3] considers θ cr = 0.035 instead of 0.056, which contributes to a decrease in the critical shear-stress.…”

“…However, it was not possible to prove beyond doubt that damage stabilization was indeed occurring. In References [25,26] tests are performed until 9000 waves, still it was not possible to prove that stabilization occurred. The present study concerns to N = 3000 waves as applied in Reference [4].…”

Large-Scale Experiments to Improve Monopile Scour Protection Design Adapted to Climate Change—The PROTEUS Project

“…Schendel et al [13,14] presented large scale experiments of scour protection design under waves and currents. The scale used for wave tests which included a monopile was 1:5, whereas the scale for current tests without a monopile was 1:1.…”