Chapter 9 - Materials for LCSs

Abstract

Materials used to construct coastal engineering projects are critically important for the success and longevity of a project. Material selection is mainly dictated by availability and cost, and execution methods. The vast majority of LCSs is built as rubble mounds armored with quarried natural rock because this material is generally available from nearby quarries, and it is suitable for the structures subjected to waves. Economical considerations have recently promoted the application of bags or tubes made of geotextiles filled with sand or gravel. The so-called Longard tubes are used along northern Adriatic beaches because of the lack of local rock quarries. This type of structure is relatively cheap, easy to place, flexible to allow for settlements, and with little harm to swimmers. However, it is relatively impermeable, reflective (inducing toe scour), and easily vulnerable to vandalism and cutting for mussel collection with knives. Experience shows that their service life is rather limited. However, they might be used as core material for rubble mounds. Strength, elasticity, strain, creep, durability, mass density, and cost are the important parameters for the selection of type and material of a geotextile. Basic materials are polyester, polyamide, polypropylene, and polyethylene. A textile can be of woven, non woven, and knitted types. The different types of basic material and textiles provide different performances.