Whereas rock and sand structures are flexible to some extent, monolithic structures are often rigid. in the articles Seawalls and revetments, Human causes of coastal erosion and Detached breakwaters. Coastal structures can influence the shoreline morphology in several ways this influence is described e.g.
sand-filled geocontainers and geotubes these structures are dealt with in the articles Artificial reefs and Sand-filled geosystems in coastal engineering). A special category of coastal structures are gabions and geosystems (e.g. armor layers of rock and/or artificial armor units, block revetments underlayers made of rock, clay or sand and a structure core made of sand or rubble). They can either be monolithic (such as seawalls, caisson breakwaters or crest elements directly cast from concrete) or made of individual layers which interact with each other (e.g. breakwaters, dikes, revetments, groynes, seawalls/quay walls. Here, the focus is on coastal structures. Shore protection structures can be divided into coastal (protection) structures and river (protection) structures. Shore protection structures are generally built to protect shorelines from ongoing erosion or to shelter areas from strong wave and current action.
3.5 Washout of fine sediments from the core of the structure.3.4 Erosion at the top of a berm protection revetment.3.3 Erosion of the rear side (lee side) of a rubble mound breakwater.3.2 Scour (erosion) at the toe of the construction.3.1 Hydraulic instability of the armor layer.2 Design of shore protection structures.trapezoidal caissons and dual cylinder caissons are introduced with the present states of their developments. In the paper, several new breakwater structures such as sloping top caissons, multi-scelluar, caissons, curved slit caissons, wave power extracting caissons. In particular, necessity of constructing breakwaters in deep and rough seas results in the marked increase of the cost, and demands the development of new economical breakwater structures. On the other hand, changes of surrounding conditions related to breakwater constructions are recently emerging. In particular, experimental data on the transformation of irregular waves transmitted behind a breakwater during the propagation are newly presented. In the paper, the hydraulic characteristics of those conventional breakwaters are first described including already established formulae. Mixed type breakwaters of which the upright sections are covered with wave dissipating concrete blocks are also popular in Japan. The major structure type of breakwaters in Japan is a mixed type which consists of a rubble mound foundation and an upright section. Hydraulic Engineering Division Breakwaters Laboratory Katsutoshi TANIMOTO,Shigeo TAKAHASHI,Katsutoshi KIMURA
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