Geocomposite Explained

Geocomposites are combinations of two or more geosynthetic materials for civil engineering applications that perform multiple geosynthetic functions; the five basic functions are: separation, reinforcement, filtration, drainage, and containment. Such composite materials may enhance technical properties of the soil or the geotechnical structure and minimize application costs.

Geotextile-geonet composites

When a geotextile is used on one or both sides of a geonet, the separation and filtration functions are always satisfied, but the drainage function is vastly improved in comparison to geotextiles by themselves. Such geocomposites are regularly used in intercepting and conveying leachate in landfill liner and cover systems and for conducting vapor or water beneath pond liners of various types.[1] These drainage geocomposites also make effective drains to intercept water in a capillary zone where frost heave or salt migration is a problem. In all cases, the liquid enters through the geotextile and then travels horizontally within the geonet to a suitable exit.

Multi-linear drainage composites

A manufactured product composed of a series of parallel single drainage conduits (like perforated mini-pipes) regularly spaced across the width of the product and sandwiched between two or more geosynthetics (more often geotextiles). They are used for liquid drainage or gas collection while providing a separation and filtration function. Such multi-linear drainage composites are not susceptible to creep in compression or geotextile intrusion when confined in the soil, which means that they maintain their flow capacity over time, even under heavy loads.[2] These drainage geocomposites are regularly used in landfill applications for leachate collection layers and cover systems, and in buildings for sub-slab depressurization systems to collect toxic gases (Radon, VOCs, etc.) and prevent their migration into the building.

Geotextile-geomembrane composites

Geotextiles can be laminated on one or both sides of a geomembrane for a number of purposes. The geotextiles provide increased resistance to puncture, tear propagation, and friction related to sliding, as well as providing tensile strength in and of themselves. Geotextiles are of heavy and are of the nonwoven, needle-punched variety. In such cases the geotextile component acts as a drainage medium, since it can conduct water, leachate or gases away from direct contact with the geomembrane.

Geomembrane-geogrid composites

Some types of Geomembranes and Geogrids are made from the same material, such as high-density polyethylene (HDPE). This commonality in material allows for them to be effectively bonded together, resulting in a composite system that combines the benefits of both components. By integrating Geomembranes with Geogrids, an impervious membrane barrier is created, which offers enhanced strength and friction capabilities. This synergy not only provides superior tensile strength and durability but also improves the overall stability and performance of the system in various engineering applications. Such composite barriers are particularly advantageous in projects requiring robust containment solutions, such as landfill liners, mining operations, and water management systems. The combination of geomembranes and geogrids ensures long-term reliability and efficiency, making them a preferred choice in modern geotechnical and environmental engineering.

Geotextile-geogrid composites

A needle-punched nonwoven geotextile bonded to a geogrid provides in-plane drainage while the geogrid provides tensile reinforcement. Such geotextile-geogrid composites are used for internal drainage of low-permeability backfill soils for reinforced walls and slopes. The synergistic properties of each component enhance the characteristics of the final product.

Geotextile-polymer core composites

A core in the form of a quasi-rigid plastic sheet, it can be extruded or deformed in such a way as to allow very large quantities of liquid to flow within its structure; it thus acts as a drainage core. The core must be protected by a geotextile, acting as a filter and separator, on one or both sides. Various systems are available, each focused on a particular application.

Notes and References

  1. http://www.gseworld.com/products/drainage/geocomposite.html Geonets & Geocomposite Drainage Liners for Erosion Control
  2. https://geosyntheticsmagazine.com/2020/04/01/a-guide-for-specifying-drainage-geocomposites/ A guide for specifying drainage geocomposites
  3. Web site: Wick Drains (Prefabricated Vertical Drains, Vertical Strip Drains) . Hayward Baker . live . https://web.archive.org/web/20151126010008/http://www.haywardbaker.com/WhatWeDo/Techniques/AdditionalServices/WickDrains/default.aspx . 2015-11-26 . 2016-03-03 .
  4. Web site: What Are Wick Drains? . US Wick Drain . live . https://web.archive.org/web/20150311195045/http://www.uswickdrain.com/faqs.html . 2015-03-11 . 2016-03-03 . What Are Wick Drains? Long term consolidation of soft silt and clay often creates serious problems in construction. Ten to twenty years may be required for consolidation of thick compressible layers of soil. This design problem can be overcome by creating closely-spaced artificial vertical drainage paths to which the pore water can flow, thus decreasing the consolidation time to a matter of months. These artificial drainage paths, called wick drains, consist of a central plastic core, which functions as a free-draining water channel, surrounded by a thin geotextile filter jacket. A typical wick drain is approximately 4 inches wide, 1/8 inch thick, and comes in rolls up to 1,000 feet. .