Bi-Directional Static Load Testing

BDSLT with the GRL-Cell

The GRL-Cell is a high capacity device installed within a deep foundation to statically load test the foundation. As the GRL-Cell is pressurized, it loads the foundation element in two directions. The portion of the foundation element above the cell location is pushed upward against its shaft resistance. At the same time, the foundation element below the cell location is pushed downward against its shaft resistance as well as against the toe bearing or “base resistance.” Shaft and toe movements as well as embedded strain gage instrumentation are monitored for each applied load. An estimated top load movement curve is constructed from the measured shaft resistance load-movement and base resistance load-movement responses. 

Bi-Directional Static Load Test Benefits include:

• High capacity static load test method for drilled shafts, bored piles, barrettes, and ACIP/CFA piles.
• Separates soil/rock resistance and movement data for shaft and toe. 
• Determines magnitude of the mobilized shaft and toe resistances. 
• Embedded strain gauges within the foundation determine the soil/rock resistance distribution along the foundation length for optimizing the foundation design. 
• Not restricted by structural or geotechnical limit of load frame, reaction beams, or reaction piles.

Bi-Directional Load Testing is standardized by ASTM D8169 – Standard Test Methods for deep foundations under Bi-Directional Static Axial Compressive Load.