This project required CAN to design and install a 5000kJ rock catch fence system at the toe of a large sand and talus slope, beneath towering cliffs on the East side of Gibraltar, to protect both the highway and private properties below.

The chosen solution was the Geobrugg RXE-5000. In designing this catch fence, CAN worked closely with Geobrugg in order to ensure that the finished product met the requirements of the specification, but was also buildable in an efficient and cost effective manner.

The catch fence is secured with 75 hollow bar anchors and micro piles, with groups of anchorages encased in reinforced concrete foundations supporting the 7.5m high posts.

The poor ground conditions of weathered sand and rock meant that large amounts of temporary works were required to stabilise the slope above the worksite, in order to safely excavate for the large RC foundation pads and to provide benches for vertical drilling.

It was not an option to use excavator mounted drill rigs on temporary benches due to the limitations on width and allowable bearing pressures, therefore CAN’s custom built slope mounted drill rigs were used to install the inclined anchors.

Utilising quickly installed temporary catch fences, along with existing catch fences as protection, CAN were able to carry out the works safely, protecting the road users below. Additional careful planning kept road closures to a minimum for concrete wagons and craneage.

 

Duration:       10 weeks

Client:            HM Government of Gibraltar

Location:       East Side Catchments, Gibraltar