The Round House

Client

Cormac Solutions / Cornwall County Council

Location

Looe, Cornwall

Value

£32,000

These works comprised the stabilisation of a landslide at Round House in West Looe, Cornwall. Works included:

  • Vegetation removal
  • Descaling
  • Rock bolting/dowelling
  • Meshing
  • Reinstatement

Vegetation removal and descaling works were carried out using a rototrack machine for ease of access. Operatives were required to wear safety harnesses while working at height. Trees with a girth up to 200mm were removed and a controlled removal of loose rocks and rubble was carried out. The voids in the existing wall of the Round House were packed with mortar filled sandbags.

The rock bolting/soil nailing works were completed using the rototrack machine fitted with a man cage. Our operatives used a lightweight pneumatic drilling mast and rock drill mounted on a sliding beam to install 113 2m long rock bolts and 11 3m long soil nails. The feed beam was mounted on the 360° MEWP to allow it to reach the top of the embankment. Soil nails were drilled with air flush and back-grouted through the hollow bar. Rockbolt holes were filled with grout before inserting the bar.

Before inserting the bar, rockbolt holes were filled with a 52.2n OPC grout and water at a ratio of 0.45, to achieve 30N strength within seven days.

On completion of the drilling works, a layer of erosion protection/rock netting was fixed over the slope over an area of approximately 300 sq. metres. The Maccaferri MacMat R was placed in vertical strips and held in place with 150mm square galvanised plates placed over the dowel bar and hollow bar heads, and secured by a permanent galvanised nut and washer. The vertical joints were secured using stainless steel hog rings placed by a pneumatic clipping tool. The top and bottom edges were then secured using 16mm galvanised wire ropes, terminating at the outermost anchorages. The wire ropes were tensioned using permanent galvanised turnbuckles before the mesh was folded over the cable and clipped in place.

Drainage ducts were installed vertically fixed behind the rock netting to channel rainwater away from the slope discharging into the highway drainage at the foot of the slope.

Access to carry out the remediation works was from the existing highway with partial possession to ensure minimal disruption to traffic and residents. All works were completed ahead of schedule.