CML CASE STUDY

Geotechnical Rock Slope Assessment at Matlock Tunnel Portals

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Client: CML

Service Delivered: Rope Access Rock Slope Assessment & Geotechnical Remedial Options Appraisal
Location: Matlock, Derbyshire – Tunnel Portal Sites
Project: Matlock Holt Tunnel Portal Rock Cuttings

Background

Network Rail tasked CML with confirming the resilience of multiple rock slope cuttings near Matlock Bath railway station and identifying options for future remedial work.

GeoAccess carried out detailed rock slope assessments across three tunnel portal sites:

Matlock Holt
High Tor North & South
Willersley

The goal was to assess slope stability, record geotechnical data, and provide remediation recommendations to enhance the long-term safety and resilience of these high-risk assets.

Geotechnical Rock Slope Assessment at Matlock Tunnel Portals

Method

GeoAccess conducted bespoke geotechnical inspections over five consecutive nightshifts.

The site team included:

An IRATA Level 1 Earthworks Examiner
An IRATA Level 3 Supervisor
CML support staff including a COSS-qualified Site Supervisor and operatives

CML operatives carried out vegetation clearance and light scaling works in advance, improving visibility for assessment.

Using rope access techniques, the GeoAccess team traversed each rock face to gather data, including:

Slope geometry & azimuth
Discontinuity details
Groundwater evidence
General geological observations & photographic records

The resulting Geotechnical Options Reports combined geological mapping and rock cutting examinations with failure mechanism analysis, frequency estimates, and likely failure sizes. Recommendations included active and passive remedial options, considering slope geometry, cess constraints, and long-term maintenance requirements.

Innovations & Solutions

Pre-site desk studies incorporating topographical, geological, and cess geometry data improved efficiency and targeted on-site inspections.
Rope access methods enabled detailed observation of high and complex rock faces that were otherwise inaccessible.
Combined approach of vegetation clearance, mapping, and slope data collection ensured comprehensive reporting for remedial planning.

Results & Conclusion

Site works completed in just five nightshifts
Comprehensive Geotechnical Options Reports delivered within two weeks
Provided CML and Network Rail with clear recommendations on slope resilience and remedial measures
Enhanced understanding of failure mechanisms, ensuring proactive asset management

Through this project, GeoAccess demonstrated its ability to deliver fast, safe, and detailed geotechnical rock slope inspections, helping CML and Network Rail plan effective remediation strategies for tunnel portal cuttings in a cost-efficient and timely manner.