The Importance Of Weight
For standard civil nonwoven geotextiles, the property of Weight (Mass per Unit Area) is reported as a “typical” value. For geosynthetics, a typical value allows manufacturers to report property values that the user can have a 50% confidence level will meet those values.
For civil nonwovens, the tensile strength and hydraulic properties of the fabrics are the critical values. As manufacturing methods improve, less fiber is required to maintain these values. As such, the value of a nonwoven geotextile’s weight in civil applications is of secondary importance. However, for environmental nonwoven geotextiles weight is a critical property.
Environmental Nonwovens In Landfills
Concerns over the long-term performance of sand leachate drainage systems in landfills have led to the use of gravel instead of sand. This requires placing a protection layer between the gravel and geomembrane to ensure the long term integrity of the liner.
The means by which a nonwoven geotextile provides a cushion from point loading of stone is complex. However, the quantity of fibers present is one of the critical components in the protection performance of a needle-punched nonwoven.
M.A.R.V. Weight For Environmental Nonwovens
As a result, weight is reported and specified as a M.A.R.V. (Minimum Average Roll Value) property for environmental applications such as landfills. M.A.R.V. is a middle ground between the absolute minimum value and the typical value. The M.A.R.V. is derived statistically as the typical (mean or average) value less two standard deviations.
Therefore, environmental grade nonwovens require more fiber to produce and are subsequently more expensive than civil nonwovens. Due to the size of public landfills and the type of heavy equipment present at them, environmental nonwovens come in very large and heavy rolls. Often a contractor at a civil jobsite does not have the means to handle such massive rolls.
Outside of public landfill operations, civil nonwovens are the product to use and specify. Should your project require an environmental nonwoven, US Fabrics offers a complete line.