Counter-weight for Pile load test

Pile foundation is required for many heavy structures like multi-storey buildings or bridges.  Sometime engineers request the contractor to conduct pile load test to check the strength of the pile.   It is done by applying the force through a jack to the test pile.  To balance the force we need counter weight, usually in the form of concrete blocks stacked over a platform (Figure 1).  Other alternative is to use adjacent piles connected to the test pile by welding them to steel I beam.

My idea is instead of using concrete blocks we use FRP (Fibre Reinforced Plastic) containers filled with water.   The advantage is they are much lighter and can be easily stacked without the use of heavy lifting equipment.  We place them layer by layer and once a layer is formed we fill the containers of that layer with water before proceeding to the next layer.  After the test we can drain the water and store the containers for the next test.  Note that their light weight makes it easy to transport and to store them.

Since the unit weight of water is less than that of concrete we need more volume of water to produce the same counter weight.  This means we need more space.  However since the pile test is performed before the upper or super structure's construction commences, space should not be a problem.

Figure 1 Concrete blocks for counter weight in pile load test

Figure 2 Water filled FRP containers as counter weight in pile load test