Recently, seafloor plate load tests were carried out successfully by Geomil Equipment B.V. in water depths of 40 meters. The tests were required to prove the density (bearing capacity) of the backfill of excavated (dredged) trenches. Plate Load Tests are field test for determining the ultimate bearing capacity of soil and the likely settlement under a given load.
The Underwater Plate Load Test (UPLT) consists of loading a 0.2 m2 steel plate placed at seabed and recording the settlements corresponding to each load increment using the dead weight of a 25 tons MANTA, positioned on the chosen test location. A load cell built in the plate records the applied force, whereas a vertical linear position sensor (LVDT) measures simultaneously the displacement (settlement) of the plate in a stress-controlled condition.
The underwater test load is gradually increased till the plate starts to sink at a rapid rate. The total value of load on the plate in such a stage divided by the area of the steel plate gives the value of the ultimate bearing capacity of soil.
A maximum load of 25 tons can be mobilized on the plate, whereas a displacement of 1000mm can be recorded within an accuracy of 0,1 mm.