Marine engineering geotextiles

Geotextiles are commonly used to prevent erosion and improve stability in marine engineering structures. Their relevant hydraulic, mechanical and durability properties are crucial to the performance of the resulting marine engineering structure. Selection of the appropriate geotextile solution is based on its ability to meet specific performance requirements. 

Geotextiles and geotextile containment units used in marine engineering... 

Figure 20.1 Types of geotextiles used in marine engineering, (a) Woven geotextiles, (b) nonwoven geotextiles and (c) composite geotextiles.

Sand fill is normally used for geotextile containment units in marine engineering applications because it is permeable, it is stable when the sand fill is dense, and it does not undergo volume changes with time, ie, settlements. Fine-grained fills stabilised with cement or polymer have also been used in geotextile containment units for marine applications however, this is a new, emerging development and is not discussed further in this chapter. 

Three types of geotextile containment units are used in marine engineering, differentiated on the basis of shape and volume geotextile bags, geotextile tubes and geotextile containers (Fig. 20.2). 

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.

One technique to improve the stability of breakwaters and containment dykes con-stmcted on soft foundations is to use geotextile reinforcement across the base of the stmcture (Fig. 20.19). This basal reinforcement technique has been used successfully for many years in the onshore construction of embankments on soft foundation soils, and is discussed in detail in chapter Geotextiles used in reinforcing foundations. Because of its cost—benefits, this technique has also been used in marine engineering structures over the past 20 years. 

Geotextiles have been used in marine engineering applications for 60 years and are currently considered standard practise. Over the years they have demonstrated their abUity to fulfil different functions in many demanding marine environments. Today, geotextiles are used in marine engineering applications aU over the world. 

The use of geotextile filters in marine engineering structures is standard practise. Their performance criteria for this application have developed over 40 years and are currently well-founded and well-understood. Geotextile filters must be chosen on the basis of meeting specific mechanical, hydraulic and durability criteria for them to perform successfully as filters in marine structures. They must also be installed properly to perform. 

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