Osterberg load test

Osterberg (1984) developed a method that reduces the cost of conducting high capacity static load tests, in particular for the drilled shafts, as shown in Figure 11.6. Once the concrete is in place, the operator pumps hydraulic fluid into the jack and keeps track of both pressure and volume. The jack expands and pushes up on the shaft. A dial gauge measures this movement, from which a plot of side friction capacity versus axial movement can be obtained. The devise also includes a telltale rod that extends from the bottom of the pancake jack to the ground surface. It measures the downward movement at the bottom, and thus produces a plot of toe-bearing pressure versus axial movement. 

Osterberg, J.O. 1984. A new simplified method for load testing drilled shafts. Foundation drilling. Association of drilled shaft contractors. Dallas. 

Drilled shaft Side and end All Load test (Osterberg, 1989)... 

Osterberg, J. O. 1989. New Load Cell Testing Device Proc. 14th Annual Conference, Deep Foundations Institute, Vol. 1, pp. 17-28. 

---