Investigating Ground Engineering Risks Related to Cambered Strata

Southern Testing engineers visit local outcrops for training in identification of cambered strata, overcoming related ground engineering problems that affect developments across parts of the country.

Continuing Southern Testing’s commitment to developing the technical skills of our talented engineers, prior to the Covid-19 Pandemic, we conducted an in-house training course on the topic of cambered strata and the associated geotechnical and ground engineering risks. This course is part of our graduate training scheme, which is accredited by the Geological Society of London in terms of helping our staff progress towards Chartered status (Chartered Geologist CGeol, or Chartered Scientist CSci).

Cambering is a geological process leading to the formation of inclined/rotated strata around valleys, and the presence of gulls/fissures within the ground. Cambering generally occurs where a layer of brittle rock – sometimes termed the ‘cap rock’ – overlies softer, more malleable rock or soil, and where a river has created a valley. During periglacial conditions, weathering processes lead to the gradual mass movement and rotation of blocks of the cap rock towards the centre of the valley.

A ‘Gull’ is a fissure formed within the cap rock, between the rotated blocks. Gulls may be loosely filled with superficial soils, and may have voids present at depth.
Topics covered within this training course included:

  • Development of geological cambering
  • Identification of geological and geomorphological conditions that could indicate the presence of cambering within an area
  • Assessment of geotechnical and ground engineering problems related to cambering, and their solutions.
  • Development of Conceptual Geological Models and Conceptual Engineering Geological Models (Ground Models) for cambered strata.

The course was run in-house by one of our Chartered Geologists, and included a field trip to observe cambering in- situ around the South East. Key geological field skills were discussed and developed, including creation of ‘scanline’ surveys and cross-sections, to create Conceptual Engineering Geological Ground Models.

We also discussed what common engineering problems are related to cambered strata, including formation of sinkholes and other collapses, as well as what investigation techniques are available for assessing the risk to a site. Based on this, a range of potential solutions to help overcome the hazards presented by cambered strata were reviewed.

Southern Testing Laboratories have a long history of investigating cambered strata around the UK, and in particular within the south-east. Using our extensive project database, we are able provide our Clients with robust engineering assessments of the impact of cambered strata on foundations, highways, soakaways and drainage, as well as offering advice on solutions to sinkhole collapses when they occur or are foreseeable.

The initial means of assessment is thorough a Desk Study, which will help to identify the potential for cambered strata (and other hazards that may be affecting the site). From there, if necessary, we can recommend a targeted site investigation, and undertake it using our in-house fleet of ground investigation equipment and highly trained staff.

If you’ve got a development on a site where cambering could be a problem we’d love to hear from you.

Please get in touch at enquiries@southerntesting.co.uk, or call us on 01342 333100.

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Southern Testing are continuing to work through the Coronavirus (COVID-19) emergency, including carrying out site work where it is safe to do so.

The Government have given express support to the Construction sector and have issued specific guidance for working on site. The Construction Leadership Council have also issued guidance.

We have revised our travelling and working practices to ensure that our staff are protected, and to meet the particular requirements of the guidance as well as our own risk assessments. The guidance and our working practices are under constant review.

Most site investigation work can be undertaken safely under the current restrictions.

We are committed to helping all our clients, old and new, during this difficult time. Should you have any site investigation requirements, or wish to discuss a particular project, please do not hesitate to contact us.