TN 6.22-7200 Stormtech Subgrade Performance February
TN 6.22-7200 Stormtech Subgrade Performance February.pdf
TN 6.22-7200 Stormtech Subgrade Performance.
StormTech chambers, as buried arch structures, concentrate overburden loads at the chamber feet and spaces between rows of chambers. A foundation layer of crushed stone under the feet of the chambers is used to partially disperse these concentrated loads to an appropriate bearing pressure on the subgrade. It is the responsibility of the consulting engineer to determine the foundation stone depth for the specific chamber application based on the overburden loads and allowable subgrade bearing capacity.
StormTech provides Minimum Foundation Depth tables in the chamber Design Manuals from which a system designer may compute the required depth of foundation stone based on cover height above the system and allowable bearing pressure of the subgrade as determined by the consulting engineer.
The Minimum Foundation Depth tables are based on a simplified assessment of foundation pressures which may not be appropriate for all site conditions.
Additionally, the design tables are for common spacings between chamber rows. Specific chamber applications may utilize row spacings not covered by the tables. Thus, the design tables do not constitute foundation designs for all design conditions.
Loading scenarios are analyzed showing a typical cross-section of a StormTech System. Actual and conceptual load effects are tested and diagrammed.
Subgrade performance considerations of bearing capacity, settlement and subgrade saturation is meant to assist geotechnical designers in evaluating some of the unique characteristics of StormTech. Minimum foundation depth tables with equations are included.
This Technical Note discusses foundation performance limits for StormTech and explains how bearing pressures and loaded area below a StormTech bed may be calculated per ASTM F2787. It is intended to support consulting engineers in determining site-specific allowable bearing pressures and as a resource for system designers in selecting proper foundation stone depths for all configurations of cover height and chamber row spacing.