The overall testing program included wave calibration

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Unformatted text preview: eakwater stability tests were undertaken at a scale of 1:50 in a 24 x 30 m wave basin at HR Wallingford. The overall testing program included wave calibration tests, two tests of the interim cross-section and three tests of the full cross-section. Most of the tests were undertaken with the critical wave direction (East), but the final test was repeated with SE waves. Test conditions ranged from typical swell conditions (Hs = 2 m) up to extreme cyclone waves (Hs = 10.5 m), with depth-limited breaking waves at the breakwater. Figure 8 presents an overview of the model at HR Wallingford. Figure 8 – Overview of 1:50 Scale Model of Breakwater and Port The first test of the interim cross-section (crest at working level of +4 m MSL, with outer slope protected by two layers of 2-6 t armour stone) showed no damage at Hs = 2 m (average wave condition), with “tolerable damage” in most areas at Hs = 4 to 6 m. Severe damage to the interim armour layer, and overwash of the working platform, was noted along the outer 200 m of the breakwater due to wave focusing effects caused by a shoal. A second test with a more robust cross-section (6-12 t armour stone and working level of +6 m MSL) showed “tolerable damage” in this critical area. The first test of the full cross-section was successful, with the model breakwater surviving exposure to extreme breaking wave conditions without significant profile development. However, initial stone motion was observed under moderate wave conditions (Hs = 4 m, an annual event), with continued exposure to waves resulting in down slope displacement of the 12-18 tonne 10 armour stone from the primary berm (i.e. the initial stage of development of an S-shaped profile). This is illustrated in Figure 9 (the templates show the as-built profile). Figure 9 – Profile Development Following First Test of Full Cross-Section Although the overall performance of the breakwater in this first test of the full cross-section was deemed acceptable, the stone motion was considered to be undesirable for two reasons: • Stone moti...
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