Pile Load Test –What you must need to know?

These tests are performed out on preliminary piles to confirm the pile design or on working piles as proof load tests. There are basically two types of pile load tests – static and dynamic load tests. Static load tests are generally preferred because they have been conventionally used and also because they are known to replicate the long term sustained load conditions. On the other hand, dynamic pile load test is generally carried out as a supplement to static load tests. The failure mechanism in dynamic load test may different from what in static load test. A recent advancement is a quasi-static load test whereby a controlled explosion in a pressure chamber is used to generate the test load and measurements are made with a load cell and a laser beam.

To carry out pile load test, two types of testing procedures are commonly used named maintained-load (ML) and constant-rate-of-penetration (CRP) tests. The ML method is applicable to compression, tension and lateral road tests, whereas the CRP method is used primarily in compression load tests.The design working load of the pile should be pre-determined where working load is defined as the permissible load for a pile before making space for factors such as negative skin friction, group effects, redundancy etc. In a maintained-load pile load test, the load is applied in increments, each being held until the rate of movement has brought down to a reasonable low value before the next load increment is applied. It is a general practice and used to include a number of loading and unloading cycles in a load test. Such cycles are respectively useful in retrieving the emergence of plastic movements by observing development of residual movement with increase in load.Information on the load transfer mechanism can be retrieved from a Pile load test is the pile is instrumented. In order to ensure optimum results, the pile instrumentation system should be compatible with the objectives of the test. Major aspects include selection; disposition and methods of installation should always be considered carefully.It is very much important that adequate redundancy is maintained to allow for possible damage and malfunctioning of instruments. Wherever possible, isolated measurements should be made using more than one type of equipment to allow cross-checking of results. A knowledge of the proposed construction technique and a preliminary assessment of the expected behaviour of the Pile test will be helpful.