PURPOSE OF BI-DIRECTIONAL STATIC LOAD TEST
Osterberg self-balancing test (or O-cell test, bi-directional static load test) is a new static load test technology for pile invented and commercialized by an American Professor Jorj Osterberg.
METHOD OF BI-DIRECTIONAL STATIC LOAD TEST
Bi-directional static load test is actual static load test.
Bi-directional static load test uses pile’s skin friction and end bearing for reaction system.
The hydraulic jack assembly is cast in the pile instead of at the top of the pile as normal static load test. Hydraulic jacks are welded between two bearing steel plates and attached to steel cage, positioning of hydraulic jack assembly is determined based on soil data. The main aim of positioning the assembly will be to equalize the bi-directional forces in the pile (skin friction of above segment and skin friction of below segment with end bearing)
Bi-directional static load test measures movement in the top and bottom of jack, not at pile top as normal static load test.
In single-level bidirectional static load test:
In multi-level bidirectional static load test:
Each segment is then mobilized separately, and the multiple results from the same pile are combined to access the overall pile performance
- ASTM D1143/ D1143M-07 “Standard Test Methods for Deep Foundations Under Static Axial Compressive Load”