High strain static and dynamic load tests are the basic method for measuring pile bearing capacities on the site. Each of them can be used for testing reinforced concrete piles as well as compressed, timber, steel or combined piles. Pile cross-section can be constant or variable along the pile length. While static measurements are considered as most precise, dynamic test loading allows for a free choice of a test pile and determining pile bearing capacity with sufficient engineering precision. The results of such tests may be used in designing provided that the tests are performed on test piles prior to final piling or as as-built measurements.
Static Load Test - SLT) are considered as most precise method for measuring pile bearing capacities. Their results may be used for verifying the calculations models used in the geotechnical design of piles. The results of SLTs performed on test piles, prior to the final piling, may be directly used in designing.
SLTs allow for determining the geotechnical bearing capacity and settlement/uplift of a single pile after time t that has collapsed from the moment of the pile is driven/installed in the ground.
SLTs are measurements of displacement (settlement/uplift) of pile head s loaded with variable load Q. The tests are performed as maintained load tests (MLT). The analysis of the obtained Q-s curve allows for:
• in ultimate limit state (ULS):
- determining the design geotechnical bearing capacity of tested pile Rd (ULS) in the Q-s curve funtion, e.g. in accordance to PN-83/B-02482;
- determining the geotechnical ultimate bearing capacity of pile R, and then determining the design bearing capacity Rd through dividing the ultimate bearing capacity R by the correct safety factor γ, e.g. in accordance to PN-EN 1997-1-1 (EC7);
• in serviceability limit state (SLS), determining total settlement/uplift, both variable and permanent, under the expected service load conditions.
SLTs may be performed as compression and tension tests as well as recurrent tests.
Loads are applied with a hydraulic cylinder mounted between the tested pile and the retaining structure. Based on the cylinder characteristics, pressure measurements allow for determining the load acting on a pile, whereas the digital and/or displacement cells make it possible to continuously monitor the pile head position caused by the applied load.
Aarsleff performs SLTs with max. loads of 4,000kN based on the provisions of
PN-83/B-02482, PN-EN 1997-1, ISSMFE Subcommittee on Filed and Laboratory Testing, Axial Pile Load Test, Suggested Method. ASTM Journal, June 1985, pp. 79-90 or technical specifications included in designs.
