Shorncliffe Soil Stabilisation – StrataWeb®

Overlooking Moreton Bay in the seaside suburb of Shorncliffe, the newly built Cliff Street Park Look Out connects Eagle Terrace and the coastal pathway below with steps to allow access down the steep embankment. During construction, it was determined that the batter stretching 75 meters each side of the staircase was started to fail. The landscape design required 200mm of topsoil plus 100mm of mulch to be placed on the slopes to allow vegetation regrowth, but the steep 1 in 2 slope meant reinforcement was needed to prevent the topsoil from eroding onto the path and into the sea below.

DESIGN

The slope area to be stabilised ran approximately 150m along the leading edge of the upper pathway and lookout area, dropping up to 16m down the slope, with the design solution having to work around existing trees, the staircase, as well as some stormwater pits on the slope. StrataWeb SW445 – 200mm was selected as the preferred solution to provide the reinforcement to the topsoil layers.

The proximity of the new lookout and carpark area to the batter meant there was not enough room to secure the StrataWeb using a traditional anchor trench and stretch it down the slope. Instead, the design used Platipus Anchors to secure the StrataWeb tendons, with each tendon being connected to the anchors at the crest of the slope.

In some areas, StrataGrid was to be placed to give added stabilisation to the soil surface below the StrataGrid. Once placed, the 200mm high geocells would be filled with topsoil and mulch, then covered with a biodegradable layer of jute matting to protect young plants while they establish.

INSTALLATION

The gradient and surface of the slope was smoothed out as much as possible to allow optimum contact between the StrataWeb and the lower soil surface. Cirtex provided onsite assistance with the Platipus Anchor installation and testing, as well as initial installation of the StrataWeb geocells.

Once secured at the top of the slope, StrataWeb is simply stretched evenly down the batter, with each tendon clipped in place and the anchor pins installed through the StrataWeb.

StrataWeb provided surface erosion protection and a planting zone on a steep slope within an environmentally sensitive area. Without it, it’s likely that all newly added topsoil would have eroded onto the footpath and into the ocean within the next rain event. Now, visitors and residents can enjoy the view and walk around Shorncliffe’s beautiful coastline.

The StrataWeb system provided the following benefits to the project:

• Stabilises soil on steep slopes up to 60°
• Can be incorporated into various designs using different securing methods
• The collapsible panels mean cost-effective transport to site