Following the failure of, or damage to, a number of large breakwaters, PIANC”s Permanent Technical Committee II (PTC II) produced a report in 1985 on the stability of rubble mound breakwaters in deeper water. This identified areas of uncertainty in the analysis, design and construction of such structures. In 1986 a further working group of PIANC (WG 12) was set up for the Analysis of Rubble Mound Breakwaters.
This report summarises the work of Sub-group A of WG 12 of PTC II. The objective of this sub-group was to identify functional relationships between the main environmental/structural parameters, and the structure responses for as many types of rubble mound breakwater as possible. Data were sought from fundamental analysis; empirical formulae; hydraulic model studies; and from field measurements. Estimates of the degree of uncertainty in the result have been made where possible. Five main types of breakwater were considered.
Many important response functions are described in this report. Some estimates have been made of the uncertainties inherent in the fitting of relatively simple formulae to complex and stochastic processes. The data described here are however limited to relatively few of the possible failure modes of these structures.
Data were hoever provided to the other Sub-groups, particularly to enable subgroup F to ana lyse the performance of Type 2 breakwaters with respect to :
- Hydraulic stability of the main armour using Hudson and van der Meer formulae;
- Hydraulic stability of low-crest rock breakwaters;
- Hydraulic stability of rock toe berm armour;
- Wave run-up on rock armoured slopes.
For many other structure types, information is limited to a few wave conditions, or to restricted and simplified structural configurations. No significant data are available to identify the uncertainties that will arise when a formula derived for an idealised configuration in the laboratory is then used in the design of typically more complex structures. The methods identified are also limited to single response functions. Failures often however involve interacting failure modes. It is therefore recommended that future efforts should be directed to identifying prediction formulae or other techniques that allow interacting failure modes to be studied.
