This photographic article considers the habit and mineralogy of gypsum crystals from a glacial till deposit and Jurassic rock strata in Northamptonshire (UK). The crystals display excellent examples of fish-tail and swallow-tail twinning as well as unusual features such as deformed twin planes, clay inclusions and ripple-like textures.
Gypsum in the Oadby Member Glacial Till
Coarse selenite (prismatic/well-formed gypsum) crystals, up to 100mm in length, are present within the Oadby Member glacial till exposed within a quarry local to the Weldon area of Northamptonshire, UK. Gypsum crystals from this area range in size from 5mm to 150mm (typically 30-50mm) and are generally colourless to light grey.… Read the rest
Thaumasite Damage to M5 Bridge Foundation Concrete
This month’s issue of New Civil Engineer (May 2016), the magazine of the Institution of Civil Engineers, features the long-term remedial works to the concrete foundations of overbridges along the M5 in southern England, UK, as a result of thaumasite damage.
In the article, titled “Concrete Concern – Long term rescue effort underway for M5 bridges with crumbling foundations”, Dave Parker (of NCE) discusses the background to the UK thaumasite problem, the extent of damaged bridges and the on-going remedial programme. The full article can be found on the NCE website by clicking here.… Read the rest
This photographic feature discusses the gypsum nodules that can be found at Whitmore Bay, Barry, Wales, UK. Whitmore Bay is a popular sandy beach on the South Wales (UK) coastline. In the west of Whitmore Bay, the cliff sections expose red-brown mudstones and siltstones of the Triassic Branscombe Mudstone Formation (Mercia Mudstone Group, formerly known as the Keuper Marl).
Whitmore Bay, Barry. Copyright Gareth James (Creative Commons Licence)
Within the sub-horizontal mudstones and siltstones are white to pinkish brown gypsum nodules, some of which have dissolved leaving hollows or voids, others have been partially replaced by calcite.… Read the rest
Brian Hawkins (HM Geotechnics) and Tom St John (University of Bristol) have published a paper on the presence of sulfur-species in glacial tills (boulder clays) and the implications for engineering and construction. The authors consider a case study of road construction (A10) in an area underlain by glacial till in Hertfordshire, UK.
The paper, titled “Engineering significance of sulfur/sulfate in glacial tills” follows prior discussion of the A10 case study by Hawkins (2013):
Hawkins, A.B. (2013). Some engineering geological effects of drought: examples from the UK. Bulletin of Engineering Geology and the Environment.… Read the rest
Czerewko and Cross (AECOM) have published a paper on the use of a granular construction interface to separate road pavements from underlying pyritic subgrade. The authors consider case studies and the implications for road construction where such an interface has and has not been used.
The paper, titled “Benefits of a granular interface over pyritic subgrades” follows a prior case history publication by M. Czerewko on the construction of the A46, whereby pyritic subgrade extended over much of the road scheme:
Czerewko, M.A., Cross, S.A., Dimelow, P.G., and Saadvandi, A. (2011). Assessment of pyritic Lower Lias mudrocks for earthworks.… Read the rest
Paul Beetham (Loughborough University), Tom Dijkstra (BGS), Neil Dixon (Loughborough University), Paul Fleming (Loughborough University), Robert Hutchison (Opus) and John Bateman (Independent consultant) have published a review paper on the application of lime stabilisation in UK earthworks.
The paper, titled “Lime stabilisation for earthworks: a UK perspective” considers the chemistry of the lime stabilisation process and the implications of the minimum mellowing period and air voids. The role of sulfate swelling in lime stabilised materials and how the risk of the this may be reduced is also discussed. The full abstract from the ICE Proceedings: Ground Improvement is shown below.… Read the rest