- 26 de abril de 2018
Why choose a Bidirectional over a Head-Down Static Loading Test?
The deep foundation scenario over the world is usually the same: A type of foundation is chosen after a careful soil analysis, a project is defined and later executed. In some countries is mandatory to test a percentage of the foundation, in other places is optional and in a few locations the engineers just trust the project and do not do any type of test.
Leaving the cultural differences aside, geotechnical engineers and consultants worldwide know that the best way to determine the load capacity of a pile is running a static loading test.
The Bidirectional test exists since 1981 and is very well accepted in the US, Canada, Brazil, Singapore, China and a few other places but most of countries around the word still performs only the Head-Down test – most part still with kentledge.
The utilization of a top load reaction in a static test appears to be more familiar to lots of engineers but what they don’t know is that the Bidirectional test is safer, more convenient and can reach very high loads.
Why Bidirectional test?
The Bidirectional test consists on the incorporation of one or more expansive interconnected cells are placed on the tip of a metal frame and introduced into the shaft, generally near the pile toe, and concreted together with the pile. The cells are activated hydraulically causing its expansion, pushing the shaft upward and the toe downward. The upward and downward movements can be measured at the level of the cells (bottom and top) with “tell tales” and at the top of the pile with dial gauges.
Since assembly of a reaction system is not required in this type of test and the loads applied are buried, there are significant improvement in terms of safety. And also, with no reaction system there is no cost for transportation, installation, erection of kentledge, anchor or anchor piles.
Types of Pile
Another preferable feature of a bidirectional over a top-down test is that the loads applied are practically unlimited. The load applied is directly related to the number and size of cells used, so with a multiple cell arrangement the test can reach high loads.
Besides that, is not mandatory to perform the test on a test pile like in the case of a top down. After executing the Bidirectional test all the cells and voids are grouted under pressure so the pile remains as a working foundation element.
The test provides the ability to prove whether or not clean-up and removal of debris from the bottom of the shaft has been successful.
Types of pile:
- CFA Pile
- Hollow driving pile (concrete precast)
- Root pile
- Offshore bored pile
- Bored pile
If want know more about the bidirectional test, talk to us. We are specialized in the test and can estar all the world to execute the Bidirectional test.