Geotechnical Investigation and Design – Roade Cutting

Challenge

We were commissioned to undertake geotechnical investigation and design of slope stabilisation works at a 100m long section of Roade Cutting near Northampton. Roade Cutting is located at a critical position on the West Coast Mainline and the condition of earthwork had been assessed as poor. The objective was to improve the condition of the earthwork to enable Network Rail to classify it as “Serviceable and Low Risk”. The main site constraints included the designation of the site as a SSSI due to the local geology, limited slope and lineside access, thick vegetation, loose, unstable slopes.

Solution

A comprehensive desk study and preliminary ecological appraisal was undertaken to identify geotechnical, environmental, ecological and archaeological constraints that might impact the proposed works and to inform a conceptual geological model. We designed, specified and supervised a ground investigation comprising four exploratory boreholes with monitoring installations and five trial pits to target geotechnical risks, the results of which were interpretatively reported to inform the design of remedial solutions. We completed kinematic analysis of rock outcrops and slope stability analysis of the soil slopes. These calculations were used to inform an options appraisal. Four detailed options were presented to the client and Network Rail and the preferred solution was selected. We designed slope stabilisation measures comprising soil nails and an active structural mesh facing and developed the design through the Network Rail approvals process. To mitigate the constraint of lineside access, and to avoid periodic closing of the West Coast Mainline, the design was tailored for a construction sequence from the slope crest.

We completed a roped access condition inspection of the SSSI prior to works on behalf of Natural England. We provided construction support throughout the construction phase and managed verification, and cost saving solutions including shortening of the soil nails where suitable, through testing.

Benefit

We worked successfully with the client ensuring that design and construction of the slope stabilisation works was achieved on schedule and under budget. This enabled the condition of the cutting to be upgraded to the target standard.

Want to know more?

Email James Howard if you would like to know more.



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