T-Value Design Method: A Safe and More Accurate Direction for Working Platforms

Working platforms are important aspects of many construction projects, providing stable and safe working areas. If the platform is being built over particularly loose or weak soils, additional ground treatment may be needed before it is built. Since safety is of the utmost importance, it’s critical that working platforms are designed using proven methods and products to avoid devastating consequences.

Tensar’s design approach for working platforms, the T-Value Method, has proven to be robust, safe and more accurate. It enables engineers to design mechanically stabilized platforms using geogrid that are lower in cost due to the large savings in the volume of fill required compared to other methods. This method allows the benefits of stabilizing geogrids to be incorporated in designs for working platforms. These verifiable designs reduce platform thickness and improve bearing capacity, cutting construction costs by up to 60% and reducing a platform’s carbon footprint by up to 50%.

Validation of the T-Value Design
The T-Value method has been welcomed by the industry. Since its introduction in 2019, the method has been widely used for the design of hundreds of working platforms that have been constructed around the world. Additionally, a number of academic papers  have been published in industry journals, outlining the theory behind the method.

Laboratory Testing: The T-Value design method was developed using finite element analysis (FEA) of granular layers stabilized with geogrid. However, FEA models used in geotechnical design characterize geogrid in terms of its in-air tensile stiffness or strength properties, together with the mechanical characteristics of the soil without geogrid, often measured using triaxial tests.

This can lead to significant under-prediction of stabilization geogrid performance because this depends critically on the mechanical interlock between the aggregate particles and the geogrid apertures. Triaxial testing of the aggregate and geogrid together overcomes this, as it enables the performance of a composite material to be measured.

Field Testing: The T-Value design method has also been tested in the real world, with Tensar teaming up with the University of Saskatchewan in Canada to carry out full-scale plate load tests of a trial section of granular working platform on a clay subgrade.

Testing, using two 20t trucks as a reaction force, was carried out on 0.25m and 0.5m thick granular platforms, on sections with, and without, stabilizing geogrid.

A 1m square plate was used to create a pressure bulb similar in size, and depth, to the one created by the track of a piling rig or crane. This gave a more accurate assessment of ultimate (and safe) bearing capacity of the platform, compared with conventional tests using 0.3m or 0.6m diameter plates.
Download our Research and Development Project Summary here. 

T-Value Design Method Saves on Platform projects
Tensar has integrated the T-Value method into the Tensar+ design software. The Tensar+ Working Platform design tool allows you to model project specific conditions to calculate what a Tensar mechanically stabilized working platform will look like using the T-Value method. Tracked plant as well as outriggers from mobile cranes can be modelled with several pressure distribution options available.

Subgrade strength parameters, groundwater conditions, associated load cases as well as a growing number of different granular fill types can be included. Also, a design proposal, an assessment of available cost, and time and carbon savings can be generated for inclusion in project specific proposals.

Start designing with Tensar+ today to save time, cost, and carbon on your next construction project. Or, get in touch with our team by requesting a free design assessment and discover how Tensar’s geogrid solutions can enhance the performance and value of your working platform design and construction.