2009
Dudley Ward Way, Gibraltar
Government of Gibraltar
CAN Geotechnical Ltd
Golder Associates
Rockfall Protection in Gibraltar High-Capacity Barrier Solution for Critical Road Infrastructure
Rolls of debris mesh being lifted to project site
Raising catch fence posts into position
Using helicopters to lift posts into position
Erecting catch fence posts / drilling anchors
Securing main absorption panels to upper cables and posts
Challenge
Rockfall protection is a fundamental requirement in the design and maintenance of road and railway infrastructure, particularly in regions with steep or unstable slopes. Effective rockfall mitigation systems are essential to ensure public safety, prevent damage to vehicles and property, and maintain the operational reliability of transport networks.
In Gibraltar, the need for robust rockfall protection became urgent following a major incident in February 2002. A large falling rock struck a key roadway on the southeast side of the island, forcing its closure. This route was a vital link within Gibraltar’s transport network, and its loss led to significant disruption. Traffic was diverted through already congested central areas, increasing pressure on infrastructure and causing delays for both commuters and commercial transport.
To address the issue, Golder Associates, acting on behalf of the Government of Gibraltar, conducted a detailed geotechnical investigation. Their objective was to identify the causes of the rockfall, assess ongoing slope stability risks, and develop an effective rockfall mitigation strategy to prevent future incidents and enable the safe reopening of the road.
Solution
Following a comprehensive analysis, Golder Associates designed a multi-layered rockfall protection system to safeguard approximately 500 metres of roadway leading to the Dudley Ward Tunnel. The solution combined several complementary rockfall mitigation measures to maximise safety and performance.
A key element of the design was the extension of a rockfall canopy over the tunnel entrance. This structure provides direct protection by shielding vehicles and infrastructure from falling debris. In addition, passive rockfall catch ditches were excavated into the slope above the road. These ditches act as energy-dissipating features, capturing and containing rocks before they can reach the carriageway.
To further enhance protection, a network of high-capacity rockfall catch fences was installed upslope of the critical area. These barriers serve as a primary interception system, stopping or slowing falling rocks at an early stage and significantly reducing impact energy.
The installation works were carried out by Can Geotechnical and included a total of 200 metres of rockfall protection fencing, divided into multiple sections of 70 metres, 90 metres, and additional lengths. Overlapping fence sections ensured continuous coverage with no gaps in protection. Each fence was designed to achieve a maximum energy absorption capacity of 3000 kJ, reflecting the high-risk environment.
Maccaferri supplied its OM CTR 30/04/A rockfall barriers, each standing 5 metres high and engineered to withstand impacts of up to 3000 kJ. These high-performance rockfall protection systems are among the most robust in the Maccaferri range, which spans from 500 kJ to 5000 kJ solutions. A 3000 kJ barrier is capable of stopping the equivalent energy of a 16.5-tonne lorry travelling at approximately 57 mph, demonstrating the system’s exceptional strength and reliability.
By integrating rockfall canopies, catch ditches, and high-capacity rockfall barriers, the project delivered a comprehensive and resilient rockfall mitigation solution. This approach significantly reduced the risk of future rockfall incidents, enabled the safe reopening of the road, and restored a critical transport link within Gibraltar’s infrastructure network.
Used Products
