The St Astier Blog – all the latest news on our specialist repair schemes and related activities brought to you with a hefty dose of insight into the inner workings of our humble company.
Earth Anchor Retaining Wall Repair
The above mass stone retaining wall in Penrith had been suffering from long term on-going movement as a result of root growth from the line of mature trees behind. Although the retaining wall remained generally plumb, it had been pushed outwards at low level. A series of vertical cracks, corresponding with the location of the trees was evident and it was thought that significantly increased loading was being generated when the trees were in full leaf. Furthermore, a build-up of pore water pressure and a lack of suitable drainage was also believed to be compounding the problem.
As there were no existing drains present a Platipus ‘active' Plati-Drain system was specified to simultaneously provide resisting and draining capability. A total of 28 diamond core holes were created in line with the established design angle at each anchor location in the wall to facilitate installation. Each of the lightweight Platipus S08 corrosion resistant earth anchors were then installed to a design length of 6m via a machine excavator with driving rod attachment. Providing a theoretical 40kN per anchor or 22 kN per m run of wall each unit was matched with a 6m length of Plati-Drain to facilitate discrete drainage.
Load bearing bronze plates, with a hemispherical washer to accommodate the angle of earth anchor installation, were fitted and ancillary works including the raking out and re-pointing of the wall with lime based mortar (NHL 5.0) was completed.