Slope & Rockfall Protection

Most hazard slopes need more than one measure. We combine mesh, anchors, nets, barriers and drainage into one scheme, so that each part works at the point in the slope where it is most effective. Hazard mapping, expected block sizes and runout paths set the layout. Where the source cannot be reached, interception and catchment take over from containment at source.

Mesh is hung from crest anchors and left free over the face, so that small blocks and loose debris travel down behind it and settle in a ditch or catchment at the toe. It suits faces where the rock is generally sound and the hazard is frequent small falls. It does not pin the face, so the toe catchment must be sized for the volume the mesh will collect.

The mesh is fixed to the face on a regular grid of anchors and tensioned against it. Loose rock stays where it is rather than moving behind the mesh. Anchor length, spacing and the mesh grade follow the block size and the condition of the rock. Secured drapery is the usual choice where there is little room at the toe for a catchment.

Double-twist hexagonal mesh unravels slowly if a wire is cut, and it accommodates uneven faces. High-strength mesh carries higher loads at the same opening size. Welded mesh panels give a stiff face for shotcrete reinforcement and for the faces of reinforced soil walls. Wire coating, aperture and wire diameter are chosen against the exposure and the expected load.

A hollow bar carries the drill bit and the grout. The hole is drilled and grouted in a single pass, with no separate casing, so the method works in weathered rock, boulder fill and collapsing soils where open holes will not stand. The bar is then the nail or anchor. Pull-out tests on trial anchors confirm the bond before production begins.

Panels of interlaced high-tensile wire rope are laid over the slope and tied to rows of anchors. The net restrains both rock blocks and the soil between them, and its flexibility lets it follow the face. It is used where mesh alone has too little capacity, such as larger blocks and steeper faces. The rope diameter and anchor pattern are set by design.

Where the failure surface is shallow, a rope net anchored beyond it can hold the surface layer in place. It is used on steep cuts in weathered rock and on soil slopes with localised instability. Nets are often combined with a vegetation or erosion layer beneath, so that fine material does not wash out through the openings.

Each ring is wound from several turns of high-tensile wire and linked to four neighbours. The net deforms under impact and spreads the load across many rings. Ring nets are used as the panels of high-energy rockfall barriers and as drapery where blocks are large. Energy capacity depends on the ring type, the support ropes and the brake elements.

A flexible barrier is a net on posts held by ropes and anchors. A falling block stretches the net, and brake elements in the ropes absorb the energy. Barriers are placed across the fall path, either mid-slope or at the toe beside a road or structure. The design height and energy class follow the rockfall analysis. After an event the barrier is inspected and emptied.

Debris flows follow existing channels. A flow barrier spans the channel with a net that retains boulders, timber and mobilised soil, while clear water passes through. The barrier is anchored into stable banks. Sizing follows the expected flow volume and velocity, and the retained material has to be removed after events so that capacity is restored.

Snow-supporting structures are built in the zone where an avalanche starts. They hold the snowpack on the slope so that it cannot accelerate into a slide. The layout, row spacing and structure height follow the snow depth and the slope angle. They are used on mountain roads and at facilities in snow-prone terrain.

After a slip or a rockfall on an operating road, time matters. This is a system chosen for speed of installation, so that the slope can be secured and the carriageway reopened with the least possible disruption. It is a first measure, and a permanent scheme can follow once the site has been investigated.