Landslides can have significant impacts on roads, causing closures, infrastructure damage, and disrupting transportation networks. The extent of these effects depends on factors like landslide size, speed, terrain, and soil conditions. Economic consequences include delays and increased expenses for businesses due to altered transportation routes. Safety risks abound as landslides can occur with little warning, posing threats to individuals on the roads. Beyond immediate concerns, landslides contribute to environmental consequences such as soil erosion and alterations to landscapes, affecting ecosystems and water quality in the affected areas. In the face of escalating climate-induced challenges, the demand for innovative solutions to repair landslide-affected roads has become more urgent than ever.
In this context, a landslide-prone road in Shropshire is undergoing repair work on a retaining wall. The challenging task involves addressing complex geological and topographical issues at Jigger’s Bank in Coalbrookdale, a vital route to the Ironbridge Gorge World Heritage Site. The 26-week repair program, initiated by Telford and Wrekin Council, is addressing foundational issues and is being executed by the principal contractor Balfour Beatty Living Places, along with ground anchor specialist Vertical Technologies and various subcontractors.
Scope of Work
The detailed inspections of the wall revealed that its northern section had deteriorated more than expected with further voids and collapsed areas identified. These are being repaired with further stabilisation work to make the structure safe for construction.
The project encompasses the partial reconstruction of collapsed wall sections and the installation of over 100 10m-long galvanized steel ground anchors. Commencing repair work on a 160m-long section in September, the contractors are now focusing on installing anchors to fortify the retaining wall.
How is the repair work being executed?
Site Clearing and Preparation:
The repair project initiated by meticulously clearing vegetation and a substantial earth embankment at Jigger’s Bank’s northern end. This process aimed to establish a stable foundation for subsequent repair activities, ensuring a solid base for the project.
Temporary Track Establishment:
Recognizing the necessity for unimpeded access, a temporary track was set up. This track not only facilitated the movement of heavy machinery but also played a crucial role in providing full access to the retaining wall, a key element for the success of the repair work, emphasizing the importance of logistical planning.
Detailed Inspections:
Thorough inspections of the retaining wall were conducted, revealing unforeseen deterioration in the northern section. This detailed assessment identified voids and collapsed areas, guiding subsequent decision-making for additional stabilization measures and underscoring the significance of a comprehensive initial analysis.
Sprayed Concrete Application:
A 50mm thick layer of sprayed concrete is being applied to enhance the structural integrity of the wall. This protective coating serves as a crucial preparatory step, ensuring a stable surface for the installation of rock anchors and emphasizing the proactive measures taken to fortify the structure.
Rock Anchor Installation:
Strategically cored holes in the retaining wall allow for the insertion of rock anchors into the underlying bedrock. This fundamental process stabilizes the structure, preventing future landslides by providing robust anchoring points, showcasing a methodical approach to structural reinforcement.
Ground Anchor Installation:
Over 100 galvanized steel ground anchors, each 10 meters in length, are being installed to add an extra layer of structural reinforcement. Tailored to address the geological challenges of the area, this method emphasizes a comprehensive approach to fortifying the retaining wall against potential instability.
Continuous Monitoring and Adjustments:
Due to complex geology and site topography, ongoing monitoring is integral to the repair process. This dynamic approach allows for real-time adjustments, acknowledging unforeseen challenges and ensuring adaptability to evolving conditions, highlighting the importance of flexibility in the project.
Unexpected Challenges and Stabilization Efforts
Detailed inspections revealed greater deterioration in the wall’s northern section than anticipated, leading to additional voids and collapsed areas. Councillor Lee Carter acknowledges the complexity of the project, emphasizing the need for adjustments as new sections of the structure are uncovered. A temporary ramp was constructed to address challenges posed by the wall’s location, facilitating the positioning of heavy machinery and equipment.
Councillor Lee Carter said: “We can finally see what we are really dealing with now the site has been cleared and the wall properly exposed. “We always knew this would be a complex project with adjustments needed as we progress and unearth more sections of the structure,” he added.
The position of the wall itself has presented challenges and the contactors had built a temporary ramp allowing heavy machinery and equipment to even get into the right position.
Project Timeline and Budget
While confident about delivering the project on time and within budget, the council remains aware of potential curveballs due to the area’s complex geology and site topography. The repair initiative is funded through the highway capital program as part of the council’s ‘Pride in Our Community’ program.
Historical Landslides and Geological Context
Jigger’s Bank has faced previous landslide closures in 2013 and 2015, attributed to the region’s known instability. A geomorphological mapping report from 2009 highlighted upslope back scars and mid-slope lobes, indicative of the area’s vulnerability. The presence of a quarry and small local block failures was noted, emphasizing translational slopes. The British Geological Survey records over 20 landslides in the wider Ironbridge Gorge area, attributing the occurrences to the late Carboniferous and Silurian age rocks prone to landsliding.
The valley sides, rising steeply from 40m at river level to over 140m on the plateau above, contribute to the geological challenges. The current repair work aims to mitigate these challenges and ensure the long-term stability of Jigger’s Bank.
Conclusion:
The ongoing repair work on Jigger’s Bank stands as a testament to a proactive response to the complex geological challenges inherent in the region. This initiative not only aims to fortify the retaining wall but also represents a crucial step in ensuring the long-term stability of Jigger’s Bank, a vital route to the Ironbridge Gorge World Heritage Site.
Source: geplus.co.uk,bbc.com