A Tambew internal jack with concreting tube access slots
The internally-jacked pile test was first publicised by JO Osterberg who patented in some countries certain aspects of the jack that he was using, which has become known as the Osterberg cell – a registered name.
Detailed information about the Tambew method of internally-jacked pile testing can be read in the following documents.
1. Internally Jacked Pile Tests – General Method Statement. Click here to access.
2. Internally Jacked Pile Tests – Special Method Statement for [jobname]. Click here to access.
The use of internal jacking does not affect the standard specification for doing the test. This can therefore be the one most commonly used in South Africa: SANS 0120:Part 2 Section F – 1983 Piling, Clause 7.4 British Procedure. This requires the load to be imposed in increments of 25% of working load (WL) up to WL, then unloaded, then loaded in increments of 25% of WL up to 150% of WL. At each increment the load is held constant until the rate of settlement is <0.2mm per hour, or for 24 hours, whichever comes first. For piles in clay soils this test can take a full week to do.
An alternative specification is the “Quick Load Test Method” of ASTM D1143 “Standard Test Method for Pile Under Static Axial Compressive Load”, which can be completed in one day.
The service of determining further information about the mechanics of the pile behaviour by using Strain Rods is available for internally jacked tests – as for all other concrete piles. See LOAD TRANSFER TO SOIL on page LOAD TESTING for more information about Strain Rods.
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