A new apparatus for determining the shrinkage limit of clay soils

A new apparatus for the determination of shrinkage limit is described. Two versions have been produced: a manually operated prototype ‘version1' followed by an automated version named SHRINKiT. Test results using the former for British and overseas clay soils are described and comparisons made with the British Standards preferred method. A further set of test results is described for SHRINKiT. However, it was not possible to compare these with the BS 1377 method owing to the introduction of a ban on the use of mercury in the British Geological Survey's geotechnical laboratories. The new method is set in the context of the huge cost of shrink/swell-related subsidence damage in Britain and the relative disuse of both BS 1377 methods for shrinkage limit, for reasons of safety. The shrinkage behaviour of different soils types and sample states is discussed, in addition to the advantages and disadvantages of the new method

Slope dynamics project report : Holderness Coast - Aldbrough, drilling & instrumentation, 2012-2015

This report is a published product of an ongoing study by the British Geological Survey (BGS) of the coastal change at Aldbrough on the Holderness coast, East Riding of Yorkshire, UK. The test site at Aldbrough has been selected as one of the BGS Landslide Observatories because it is representative of the high rates of coastal recession along this stretch of the east coast. The Aldbrough Landslide Observatory is operated under the BGS ‘Slope Dynamics’ task within the BGS’s ‘Landslide’ project of the ‘Shallow Geohazards and Risk’ team. As well as providing new insights with respect to the volumetric rates of recession and the near surface processes, it is a focus for the trialling of new surface and subsurface monitoring technologies. The establishment of the Aldbrough observatory and the initial research findings are reported in a series of reports in addition to this report. These are: Hobbs, P. R. N., Jones, L. D., Kirkham, M. P., Pennington, C. V. L., Jenkins, G. O., Dashwood, C., Haslam, E. P., Freeborough, K. A. and Lawley, R. S. (2013) Slope Dynamics Project Report: Holderness Coast – Aldbrough: Survey & Monitoring, 2001 - 2013 British Geological Survey, Open Report No. OR/11/063. Hobbs, P.R.N., Kirkham, M.P. & Morgan, D.J.R. (2016) Geotechnical laboratory testing of glacial deposits from Aldbrough, Phase 2 boreholes. British Geological Survey, Open Report No. OR/15/056. Whilst this report is focused on the drilling and instrumentation programme, it should be read in conjunction with the reports listed above, which provide further details on survey and monitoring, and the geotechnical properties of the underlying geology. A series of reports will follow presenting the updated drilling and instrumentation reports, and their publication will be announced through the BGS project web page. Readers of these reports will probably also be interested in the context for this research, which can be found in: Hobbs, P.R.N., Pennington, C.V.L., Pearson, S.G., Jones, L.D., Foster, C., Lee, J.R., Gibson, A. (2008) Slope Dynamics Project Report: the Norfolk Coast (2000-2006). British Geological Survey, Open Report No. OR/08/018

Shrinkage limit test results and interpretation for clay soils

The shrinkage limit is one of the Atterberg limits and is a fundamental geotechnical parameter used to assess the settlement of engineering soils containing clays, yet is rarely tested for as part of ground investigation. This paper describes shrinkage limit test results on a variety of soils from Britain and overseas obtained using an improved laboratory testing procedure developed at the British Geological Survey (BGS). The co-relationships with the other Atterberg limits and with density are explored. In particular, the coincidence of the shrinkage limit with the water content at the peak bulk density achieved in the test is examined. The shrinkage behaviour for undisturbed and remoulded states and a 3-way relationship between water content, density and suction are demonstrated. Some tropical residual and highly smectitic soils show a very wide range of shrinkage behaviour, albeit for a small dataset, when compared with the larger dataset of temperate soils tested. Consideration is given to limitations of the new and existing test methods

Coastal landslide monitoring at Aldbrough, East Riding of Yorkshire, UK.

The paper describes results to date of an ongoing monitoring study of coastal ‘soft cliff’ recession at the British Geological Survey (BGS)’s ‘Coastal Landslide Observatory’ (CLO) on the east coast of England at Aldbrough, East Riding of Yorkshire, UK. The cliffed site, part of the 50 km long Holderness coast, consists of glacial deposits, and is one of the most rapidly eroding coastlines in Europe. This rapid rate of erosion provides an ideal opportunity for observation and process understanding because it facilitates the collection of data over periods of time encompassing significant new landslide events at the same location. The results of two approaches are reported: firstly terrestrial LiDAR surveying (TLS) and secondly the installation of instrumented boreholes. The aim of the research is to combine these to investigate the role of landslides and their pre-conditioning factors and the influence of geology, geotechnics, topography and environmental factors on cliff recession. To date, an average recession rate of 1.8 m per year and a maximum rate of 3.4 m per year have been recorded for the site. The establishment of the CLO and its conceptual geological / geotechnical model are described in a related article (Hobbs et al. 2019a)

Slope dynamics project report : Holderness Coast - Aldbrough, survey & monitoring, 2001-2013

This report is a published product of an ongoing study by the British Geological Survey (BGS) of the coastal change at Aldbrough on the Holderness coast, East Riding of Yorkshire, UK. The test site at Aldbrough has been selected as one of the BGS Landslide Observatories because it is representative of the high rates of coastal recession along this stretch of the east coast. The Aldbrough Landslide Observatory is operated under the BGS ‘Slope Dynamics’ task within the BGS’s ‘Landslide’ project of the ‘Shallow Geohazards and Risk’ team. As well as providing new insights with respect to the volumetric rates of recession and the near surface processes, it is a focus for the trialling of new surface and subsurface monitoring technologies. The establishment of the Aldbrough observatory and the initial research findings are reported in a series of reports in addition to this report. These are: Hobbs, P.R.N., Jones, L.D., & Kirkham, M.P. (2015) Slope Dynamics project report: Holderness Coast – Aldbrough: Drilling & Instrumentation, 2012-2015. British Geological Survey, Internal Report No IR/15/001. Hobbs, P.R.N., Kirkham, M.P. & Morgan, D.J.R. (2016) Geotechnical laboratory testing of glacial deposits from Aldbrough, Phase 2 boreholes. British Geological Survey, Open Report No. OR/15/056. Whilst this report is focused on the survey and monitoring programme, it should be read in conjunction with the reports listed above, which provide further details on drilling and instrumentation and the geotechnical properties of the underlying geology. A series of reports will follow presenting the updated survey and monitoring reports, and their publication will be announced through the BGS project web page. Readers of these reports will probably also be interested in the context for this research, which can be found in: Hobbs, P.R.N., Pennington, C.V.L., Pearson, S.G., Jones, L.D., Foster, C., Lee, J.R., Gibson, A. (2008) Slope Dynamics Project Report: the Norfolk Coast (2000-2006). British Geological Survey, Open Report No. OR/08/018

The Cholecystectomy As A Day Case (CAAD) Score: A Validated Score of Preoperative Predictors of Successful Day-Case Cholecystectomy Using the CholeS Data Set

Background Day-case surgery is associated with significant patient and cost benefits. However, only 43% of cholecystectomy patients are discharged home the same day. One hypothesis is day-case cholecystectomy rates, defined as patients discharged the same day as their operation, may be improved by better assessment of patients using standard preoperative variables. Methods Data were extracted from a prospectively collected data set of cholecystectomy patients from 166 UK and Irish hospitals (CholeS). Cholecystectomies performed as elective procedures were divided into main (75%) and validation (25%) data sets. Preoperative predictors were identified, and a risk score of failed day case was devised using multivariate logistic regression. Receiver operating curve analysis was used to validate the score in the validation data set. Results Of the 7426 elective cholecystectomies performed, 49% of these were discharged home the same day. Same-day discharge following cholecystectomy was less likely with older patients (OR 0.18, 95% CI 0.15–0.23), higher ASA scores (OR 0.19, 95% CI 0.15–0.23), complicated cholelithiasis (OR 0.38, 95% CI 0.31 to 0.48), male gender (OR 0.66, 95% CI 0.58–0.74), previous acute gallstone-related admissions (OR 0.54, 95% CI 0.48–0.60) and preoperative endoscopic intervention (OR 0.40, 95% CI 0.34–0.47). The CAAD score was developed using these variables. When applied to the validation subgroup, a CAAD score of ≤5 was associated with 80.8% successful day-case cholecystectomy compared with 19.2% associated with a CAAD score >5 (p < 0.001). Conclusions The CAAD score which utilises data readily available from clinic letters and electronic sources can predict same-day discharges following cholecystectomy

Establishment of a coastal landslide observatory at Aldbrough, East Riding of Yorkshire, UK

The paper describes the establishment of the British Geological Survey (BGS)’s field-based ‘Coastal Landslide Observatory’, designed for the study of coastal ‘soft cliff’ recession on the east coast of England at Aldbrough, East Riding of Yorkshire. The cliffed site is part of the 50 km long Holderness coast which is one of the most rapidly eroding coastlines in Europe. The site features a 16–17 m high sea-cliff formed by Late Devensian (18–13 ka) glacial deposits dominated by tills. The aim of the research is to investigate the role of landslides and their pre-conditioning factors, including geology, geotechnics and topography, in cliff recession with a view to developing coastal landslide forecasting capability. Two research approaches are encompassed in the observatory: firstly, terrestrial LiDAR surveying, from 2001 to present, to create digital elevation models of the cliff and, secondly, installation of instrumented boreholes from 2012. The design, methods, conceptual ground model, implementation of the observatory and geotechnical laboratory test results are described in this article. The interpretation of results and the final ground model are presented in a related article in this volume