The Government of Gibraltar have embarked upon an ambitious plan to extend and upgrade their current HQ building and Rock Foundations (Gibraltar) Ltd were called upon to provide the ground engineering solution for the project.
As with most projects in the built up areas of Gibraltar access is a real challenge. Using a combination of specialist micro piling rigs we were able to install a total of 151 micro piles, 88 to the lower level works providing a new basement area and 63 to the upper level at existing ground level.
The ground conditions included up to 4m of uncontrolled fill over red sands and then clay with the clay becoming very stiff at around the 10m mark.
The 200mm diameter piles were constructed with augers and a DTH hammer to pass though obstructions and in some cases to provide the design length into the very hard clays at depth. Reinforcement included a full length 60/70mm drill bar tube which was subsequently used to tremmie fill the constructed pile with a C35 grout.
Despite a very tight programme Rock Foundations (Gibraltar) succeeded in completing all of the piling works within the programme period.