Substruck Ltd. were employed by a private client to install 26 nr micropiles for 2 nr extensions to a property in Galway city. We were recommended by two members of the project management team whom we have worked with for many years.
We completed some dynamic probing to confirm the design before works started. The probing rig had to be re-located several times before depths of over 2-3 metres were established. This may indicate a filled site, mostly of boulders, and this was what was in fact the exact nature of the ground.
To achieve the loadings, each micropile had to be provided with a one metre rock socket. The huge advantage to the micropile (or drilled micropile) is that we will always be able to install the pile through any obstacle or boulder whilst remaining within the deviation parameters outlined in the European Standard for Micropiles. Driven piles cannot provide this guarantee. However, grout loss was significant due to the voids but all piles were filled and a head was ensured before simultaneous drill and grouting could continue.
One nr pile was tested to satisfy the design criteria and settlement of 1.2mm and 2.2mm were recorded for SWL=1 and SWL=1.5 respectively.
The builder was very impressed with the hollow bar system and the ease of incorporation into the permanent works. The nut and plate system for load transfer is easy to install and flexible whilst installing reinforcement.