The slippery slope

3 August 2018

CampbellReith’s geotechnical team continues to deploy expert knowledge to the field of slope engineering. This is a particularly interesting and challenging subject since it combines geological and geomorphological modelling, geotechnical analyses and extensive engineering judgement, all applied through the fundamental process of ground risk management.

In late 2017 when faced with the challenge of creating a 5m high temporary cut slope within 3m of existing house foundations a ground nailed solution with flexible facing system was developed. Since the site is on an ancient landslip, the scheme incorporated ground nails for both the temporary and permanent works solution creating cost and programme benefits.  A number of additional solutions have been used at the site to manage slope risks including; micro/Pali Radice piling, large dimeter spaced piles, shear keys, drainage improvement and traditional retaining structures.  Additional knowledge on ground conditions gained as the scheme develops is continually fed back into the ground model such that value engineering opportunities are continually realized.

We are near completion of a 12m high reinforced earth highway embankment that straddles a historic landslide.  Engineering solutions deployed to manage slope risks include; extensive ground modelling, lime and cement stabilisation, drainage improvement, a piled tunnel, reinforced earth, erosion protection and pragmatic earthworks management.  The project was feature article in the December 2017 edition of Ground Engineering magazine.

In March our partner Dr Adam Fisher was invited to present at CIRIA’s launch event for their upcoming research project titled ‘Design and Management of Slopes’ hosted at the Institution of Structural Engineers in London. His presentation examined advances in the design and management of engineered slopes over his 24 years in industry and captured projects and experiences in both the UK and Australia.  A copy of the presentation is available under his profile on this web site.

Following from this, our associate Josh Chastney has been invited to present at Ground Engineering’s upcoming conference titled Transport Geotechnics. We are particularly excited by this opportunity since it highlights our work on the North Bexhill Access Road project where solutions have included reinforced earth, controlled modulus columns, ground improvement and drainage improvement.  It‘s a great example of our collaborative approach to slope management since it is a joint presentation with one of our partner organisations Vibro Menard.

Whilst unknown to many, here in the UK we experience several hundred earthquakes each year. Fortunately, the vast majority can’t be detected by humans and do not affect our built environment.  However, we have very strong suspicions that this was not the case in March when following a magnitude 2.8 earthquake on the Richter scale a number of very unfortunate home owners literally lost their back gardens!  A major landslip occurred causing the gardens to slump around 4m down a hillside.  Investigations and design are currently being developed to restore the properties to their former glory and allow the residents to once again sleep easy at night.

Other recent and ongoing commissions that draw upon our slope design and management expertise include a 1km reinforced earth environmental bund, stabilisation of a landslip on the Isle of Wight using lime stabilisation and drainage, an anchored retaining wall in Cornwall, ground nailing for a large highway scheme, temporary works on a motorway scheme, diversion of a water course using gabions/reinforced earth and stabilisation of a chalk cliff face.

On a final note, whilst our geotechnical team members are thoroughly enjoying the current sunshine and hot weather we are all too aware that desiccation cracks that have formed on clay slopes can create major pathways for de-stabilising water pressures once the weather changes. We suspect the phone may well start ringing once the weather changes…

For any queries, questions or comments on slopes please do not hesitate to contact either Adam or Josh in our Redhill office.