Screw Pile Testing Update for Innovative Hybrid Footing

Originally published in SAFE Structural And Foundation Engineering Newsletter (Issue 203 Dec 2024), this is a field trial update for our project Innovative Hybrid Footing for Light-Weight Structures in Expansive Soils.

By Biju Balakrishnan, Principle Structural Engineer, INTRAX Consulting Engineers

Last month, a comprehensive screw pile testing program was successfully completed to assess their effectiveness in resisting tension during ground heave scenarios.

Conducted over eight weeks at a test site in Koo Wee Rup, near Pakenham, the program was made possible thanks to the generosity of ACSEV’s past president, Len Dalziel, who provided both the land and essential equipment, power, and tools.

A temporary office facilitated on-site operations, and extensive soil testing was conducted to characterize the ground conditions. Thanks to in-kind contributions from Hardcore Geotech, which supplied equipment and labour. Various in situ and laboratory tests were performed, including Standard Penetration Tests (SPT), Cone Penetration Tests (CPT), shrink-swell analysis, suction tests, and triaxial tests.

Based on the detailed soil profile, screw piles were installed at depths of 2.4, 3.3, 4.2, and 5.8 meters. A total of 28 test piles and 34 reaction piles were installed using hydraulic drive motors, with installation torques recorded using a calibrated Torque Hub. To ensure accuracy, a 48-hour period allowed the soil to mobilize its strength before testing. The piles were subjected to both compression and tension tests in accordance with AS 2159. Load and
deflection data were collected using advanced data loggers, calibrated string potentiometers for deflection measurements, and load cells for applied forces.

Volunteers from ACSEV and FFSV provided invaluable in-kind support throughout the testing phase. The tests were conducted under the expert supervision of Prof. Pat Rajeev by Dr. Aruna Karunaratne, Biju Balakrishnan (FIEAust CPEng), and Dr. Sri Srisangeerthanan. This collaborative effort has yielded significant data to better understand screw pile behaviour in tension and compression, enhancing engineering solutions for challenging ground conditions.