Geotextiles revetments

Lawson, C.R., 1992. Geotextile revetment filters. Geotextiles and Geomembranes 11,431—448. 

EN 13253, Geotextiles and geotextile-related products. Characteristics required for use in erosion control works (coastal protection, bank revetments), 2001. 

There has been an increasing need in recent years for reliable information on design methodology and stability criteria of revetments exposed to wave and current action. The use of revetments, such as riprap, blocks and block mats, various mattresses, and asphalt in civil engineering practice is very common. The granular filters, and more recently the geotextiles, are more or less standard components of the revetment structure. T4,20,22,23,26,28-30 jjowever, the proper design rules are not always available. 

A system without a filter layer is (directly on sand or clay and geotextile) not the permeability of the filter layer, but the permeability of the subsoil (eventually with gullies/surface channels) is filled in. For the thickness of the filter layer, it is examined to which depth changes at the surface affect the subsoil. One can fill in 0.5 m for sand and 0.05 m for clay. The values for D and A depend on the type of revetment. 

Granular and/or geotextile filters can protect structures subjected to soil erosion when used in conjunction with revetment armor such as riprap, blocks and block mats, gabions and mattresses, asphalt or concrete slabs, or any other conventional armor material used for erosion control. 

According to some researchers the forming of a natural filter is only possible for stationary flow. However, for small values of the hydraulic gradients, this is also possible for nonstationary flow. For heavy wave attack (i.e., exposed breakwaters, coastal revetments), this is usually not the case. In extreme situations, soil liquefaction is even possible. In such situations the soil particles can still reach the surface of a geotextile and be washed out. 

A (concrete) block mat is a slope revetment made of (concrete) blocks that are joined together to form a mat see Fig. 19.8. The interconnection may consist of cables from block to block, of hooks connecting the blocks, or of a geotextile on which the blocks are attached with pins, glue, or other means. The spaces between the blocks are usually filled with rubble, gravel, or slag. 

In the case of loose blocks, an individual block can be lifted out of the revetment with a force exceeding its own weight and friction. It is not possible with the cover layers with linked or interlocking blocks. Examples of the second type are block mattresses, ship-lap blocks, and cable mats. However, in this case, high forces will be exerted on the connections between the blocks and/or geotextile. In the case of blocks connected to geotextUes (i.e., by pins), the stability should be treated as... 

Table 19.4. Recommended values for the revetment parameter F for blockmats (the lower values refer to blocks connected to geotextile while the higher ones refer to cabled blocks).

PIANC, Guidelines for the design and construction of flexible revetments incorporating geotextiles for inland waterways. Report WG 4, PTC I, Supplement to Bulletin No. 57, Bmssels, Belgium (1987). 

Fig. 21.9. Beach and dune reinforcement with geotextile sand containers, (a) Beach reinforcement in Australia, (b) Stockton Beach Revetment, and (c) Dune Reinforcement in Wangerooge, North Sea/Germany. ...

J. Recio and H. Oumeraci, Effect of the deformation on the hydraulic stability of revetments made of geotextile sand containers, Proc. Int. Symp. Tsunami Reconstruction with Geosynthetics , Bangkok, Thailand (2005), pp. 53-68. 

Typical applications of geotextiles using the filter function are drainage trenches, earth dams, bank revetments, coastal structures, retaining walls, landfill cover system, etc. 

Geotextile bags are used for a range of marine engineering applications. These include revetments (Fig. 20.3(a)), groins (Fig. 20.3(b)), artificial reefs (Fig. 20.3(c)), slope buttressing (Fig. 20.3(d)), scour prevention (Fig. 20.3(e)) and temporary protection dykes (Fig. 20.3(f)). Some of these applications are discussed in further detail later in this chapter. 

Geotextile tubes are used for a range of marine engineering applications including revetments (Fig. 20.8(a)), offshore breakwaters (Fig. 20.8(b)), protection dykes... 

Figure 20.8 Marine engineering applications of geotextile tubes, (a) Revetments — exposed and submerged, (b) offshore breakwaters, (c) protection dykes, (d) containment dykes, (e) training walls and (f) groins.

Figure 20.11 Three different revetment structures using geotextiles. (a) Rock revetment utilising geotextile filter, (b) revetment utiUsing geotextile bags and (c) revetment utilising geotextile tubes.

Figure 20.12 Concrete and rock seawall revetment using a geotextile filter. Courtesy C. Lawson.

---