2015
Potishead, Somerset
Avon & Somerset Police
Galliford Try
Tony Gee & Partners
Rockfall Protection and Slope Stabilisation for Quarry-Based Police Training Facility
Pinnacle of rock above the car park
The rock is Carboniferous Limestone of the Black Rock Limestone Subgroup
Extent of proposed meshing works at the pinnacle location
Steelgrid HR mesh during installation
Steelgrid HR 100 PVC secured at the bottom of the slope
Steelgrid HR Link used to connect together adjacent rolls
Challenge
A new police training facility for Avon and Somerset Police, constructed by Galliford Try, was developed at the base of a disused quarry. The gabion-clad building is located on the northern side of the quarry, directly at the toe of a steep, historically quarried rock slope rising approximately 45–50 metres. This presented a significant rockfall hazard and slope stability challenge, particularly given the proximity of critical infrastructure such as the plant room.
Initial geotechnical assessments by Tony Gee and Partners identified instability risks in the slope above the facility. A mitigation design was proposed, incorporating rockfall protection mesh on the upper slope and a rockfall barrier system at the toe. However, once construction commenced, it became evident that there was insufficient space between the slope and the building to install the barrier. This constraint made the original design unfeasible and required a revised slope stabilisation solution that could function effectively within limited space.
Solution
To overcome the site constraints while maintaining robust rockfall protection, a full-height slope stabilisation approach was implemented using Maccaferri engineered systems. The solution combined Maccaferri DT mesh for the upper sections of the slope with Maccaferri Steelgrid HR100 PVC on the lower face, where increased load resistance and durability were required.
The mesh was installed continuously from crest to toe, ensuring comprehensive containment of loose rock. Fixing was achieved using a 12mm steel cable system anchored into competent rock with 2-metre-long threaded bar anchors at 4-metre centres. This configuration provided a secure and durable anchored mesh system capable of restraining unstable material and preventing rockfall.
To ensure the effectiveness of the design, Maccaferri MACRO Studio software was used for advanced geotechnical analysis. The system was designed to accommodate a potential accumulation of up to 1.5 metres of rock debris at the base of the slope. The analysis confirmed that the selected mesh and anchoring arrangement met the required performance criteria for rockfall mitigation.
Additional stabilisation measures were implemented around a prominent rock pinnacle. This included Steelgrid HR100 installed with anchors at approximately 2-metre spacing around the perimeter, connected by a horizontal 12mm cable to enhance structural integrity. Adjacent areas were stabilised using DT mesh with top and bottom fixing cables to ensure continuity.
This engineered solution provides long-term slope stabilisation, prevents the unraveling of loose rock, and eliminates the need for a traditional rockfall barrier. The system’s performance was independently verified by Key GeoSolutions, confirming its suitability for this challenging quarry environment and ensuring the safety of the training facility below.
Used Products
Netting
Maccaferri DT Mesh is a core component of our MacRO rockfall mitigation and natural hazard protection application area. It is one out of a range of meView
