As part of the design philosophy for this marine piling project Rock Foundations (Gibraltar) undertook to drive a steel tube through the sand and silts that make up the upper layers of the sea bed, down through the clays and into the marl/limestone in order to conduct appropriate tests ahead of the large construction programme that was to follow.
The only location available to carry out such a test that would give indicative information regarding the ground conditions for the proposed projects was from the quay side in between the cafes and bars of the Ocean Village Marina Complex.
As the equipment used to perform the required driving test, the 5009 Silent Hammer, was in excess of 50t a great deal of planning was required by the Rock Foundations (Gibraltar) Engineers and logistics teams.
Protective measures were put in place to allow the rig to track to the test location without causing any damage or disruption to the neighbouring commercial properties. Once in position the rig was set up and commenced driving the 180mm steel tube from the quay side.
As predicted the drive through the upper layers met with little or no resistance. Once in the stiffer clays the resistance began to build up increasing dramatically as the tube began penetrating the marl clay. Refusal occurred a short distance into these hard materials.
The test confirmed that a driven solution for the Marine piles in this instance would not be the best solution. This discovery allowed valuable time for the engineering teams to provide a preliminary design for a cased drilled solution which proved to be a successful option.