EdlingtonAt ECG, we do like a good landslide! Especially when it happens in a slope which has been previously stable for over 100 years!
Like any of the great detectives seeking to solve a mystery, the clues are often all in the detail and very little in life ever happens by chance.
ECG were commissioned to back-analyse the sudden and unexpected failure of a section of former railway cutting in North Yorkshire in order to determine how and why it happened and to use this understanding as a predictive risk assessment tool along the remaining section of cutting to identify potential areas of future instability.
A detailed conceptual geological model was developed using background research, validated by site investigations which involved restricted access. A numerical geotechnical modelling exercise was then undertaken as part of a sensitivity analysis to further interrogate and critically assess our understanding of the situation.
The assessment concluded that the instability was caused by the interplay between multiple factors including geological bedding controls, drainage characteristics and geometry of the slope together with a progressive degradation of effective stress due to gradual dissipation of negative pore pressures within the soils forming the slope which were established when the cutting was first formed.
The knowledge gained from the assessment was used to identify specific sections of the cutting likely to be at elevated risk of exhibiting future instability based on individual condition.
ECG continues to support the client by maintaining a periodic watching brief over the cutting together with undertaking a long-term monitoring programme using inclinometers and extensionometers to track deformations and soil-strain within ‘at-risk’ sections of the cutting flanks.