|This project required two micropile supported ground beams for a rear and side extension to a property in Douglas. The design included for extension of the ground beam beneath the rear elevation of the orginal building. This would act as a cantilever and provide for increased point loads due to the new open plan layout.
22 nr Ischebeck micropiles were designed and constructed to carry loads of up to 150kN. The tendon of this micropile acts as a sacrificial drilling rod, load bearing element and injection point all in one. They are designed so that the high capacity steel hollow bar carries the majority of the load. The grout or drilling fluid suspension acts as a casing, preventing collapse of the borehole whilst also providing buckling protection for the bar through ground improvement and the geotechnical bond at the grout/soil interface. Two nr were tested by an independent specialist to 225kN.
A 500mm wide * 400mm thick RC ground beam was constructed over the micropiles, with load transfer via a 200*200*20mm steel plate fixed to the hollow bar with proprietary locking nuts. Reinforcement consisted of 2 nr longitudinal H20 at the bottom and 2 nr H10 at the top with 300mm*300mm 10mm Links @ 300mm centres.