Terms & Conditions:

LIMITATIONS - Use of this software and any related written materials or related technical support (individually and collectively the 'Technology') is expressly conditioned upon execution by the User of a Software and Technology License Agreement with Tensar International Corporation (TIC). The unauthorized use hereof is strictly prohibited. This Technology should be used only by an experienced and duly licensed professional engineer. TIC advises the User that this Technology is necessarily general in nature, and that soil and water conditions, earth pressures, bearing capacity, global stability, the nature of backfill, differential settlement, loading conditions and other environmental and site conditions above and below the surface are all site-specific and vary widely. Accordingly, in developing any final design and construction, certain design parameters and information other than or different from that suggested in this Technology, as well as certain assumptions, judgments, inspections, tests and/or analyses, must necessarily be established and then taken into account by the User in the final design and construction. Furthermore, this Technology incorporates the specific performance characteristics of certain approved Tensar geogrids and is only to be used with such approved Tensar geogrids.
USER INFORMATION – User understands and agrees that the Program is a web cloud-based service and that User is required to provide information about itself in order to gain access to the Program. Tensar International records, collects, stores and uses the identity of User and other User personal and project information for Tensar International’s own business use (including for marketing and sales purpose). Such User information is not sold or intentionally provided to third parties for their use; however, Tensar International does not guarantee that the user information will be kept confidential or that a third party will not devise a means to access such information.

Tire Pressure

It is assumed in the Giroud-Han analysis that the contact pressure on the pavement is equal to the tire pressure. In the United States, the tire pressure for a standard highway truck is 80 psi (approximately 550 kPa), and this is used by default in the program. However, modern haul vehicles are often characterized by axle loads higher than the standard 18 kips and also have higher tire pressures, in some cases up to 100 psi or greater. The user may wish to consider using a higher tire pressure than the 80 psi default value used in SpectraPave4TM Software.

Axle Load

An Equivalent Single Axle Load (ESAL) is 18 kips and this value is used by default in the program. However, modern haul vehicles often have axle loads of 20 kips or even higher. The user may wish to consider using a higher axle load than the 18 kip default value used in SpectraPave4TM Software.

Axle Passes (each)

Axle passes equals the number of vehicle passes multiplied by the number of axles per vehicle. Thus, 400 passes of a 3-axle dump truck would represent 1,200 axle passes. For computational purposes, each axle is presumed to carry the same load, or (conservatively), the load of the heaviest axle. For a typical haul road or working platform this may be around 1,200 or so, but for permanent pavements, it may be nearer 10,000 or even greater.

Maximum Rut Depth

Rut depth describes the maximum surface deformation for an unpaved road or access platform required to maintain serviceability. For working platforms and permanent unsurfaced pavements, 1.5 inches (40 mm) is normally appropriate, while for temporary haul roads, a maximum rut depth of 3 inches (75 mm) is more common.

Aggregate Fill CBR (%)

The Aggregate Fill CBR is the parameter used to describe the strength of the unbound aggregate following placement and compaction on top of the proposed subgrade. It should be appreciated that for soft subgrade conditions, this value may be significantly less than the value determined from a laboratory test on the same material. However, independent testing undertaken by the US Army Corps of Engineers (USACE) has shown that this phenomenon is far less likely to be exhibited when a Tensar Geogrid is placed at the interface between the aggregate fill and underlying subgrade. In the Giroud-Han method, a maximum ratio of 5.0 is assumed for the moduli of the aggregate fill and subgrade materials (Esb/Esg). While this is sensible for unreinforced pavements and those reinforced by geotextiles and other geogrids, the USACE has shown that this may be a conservative approach for pavements reinforced with Tensar Geogrids.

Design Subgrade CBR (%)

The required thickness of granular material calculated using SpectraPave4TM Software is very sensitive to the magnitude of the subgrade strength. Caution should be exercised to ensure that the value used in the analysis is representative of the conditions likely to be experienced in situ during the life of the pavement; freeze/thaw activities and seasonal variations in moisture content, for example, should be considered when selecting an appropriate design parameter. Correlations for CBR based on various other soil parameters are available in the chart below.

Unreinforced

The reinforcing benefit provided by a geosynthetic is a function of its material properties: aperture size and stability, rib shape, rib thickness and its junction efficiency. For TensarTM TX Geogrid, these are included within the program

Minimum Overlap

Overlap 3 ft. (0.9m) for CBR ≤ 1
Overlap 1 ft. (0.3m) for CBR ≥ 4
Interpolate between