These works were required after a section of sea wall collapsed during severe storms, undermining a highway, sewer and HV electric cable. The stabilisation works involved supporting composite sections of the rock mass/head with an anchored sprayed concrete panel.
Drilling was carried out by a hydraulic drill and feed beam mounted on a basked carried by a telehandler. Our telehandler mounted hydraulic drill unit was ideally suited to access anchor positions some 6m above the beach level between tides. Two rows of 6m long R32 galvanised soil nails were installed in the head material, and two rows of 2m long rock bolts were installed 1.5m into the bedrock at the base of the slope. The powerful Krupp HB30 hammer unit supplied the power needed to drill in the complex geological formations.
A small pneumatic grout mixer was used to mix OPC and water to 0.4-0.45 ratio grout, and the grout pumped through the hollow bars of the soil nails. Grout was injected into the hole of the rock bolts before installing the solid bar.
Once the grout hardened a steel mesh (A393) was placed over the anchors uniformly across the face of works, and overlain by Maccaferri MacMat R rock netting with erosion protection. The mesh was held in place using 150mm square by 7mm thick galvanised plates, with nuts and washers to suit.
Once the welded mesh was secured to the face of the works, a 150mm thick layer of concrete was sprayed onto the face. Anchors extended beyond the sprayed concrete face to tie into the permanent mass concrete works.