Engineering geology maps of the UK

School and university students of geology, engineering geology and geotechnical engineering generally have less knowledge of engineering geological conditions than those who have had experience of hands-on research or practice. In the UK, the number of geology, geoscience and earth science departments has reduced over the past 25 years. Engineering geology has a very weak academic base and geology is taught less to civil engineering students than previously

The mineralogy and fabric of 'Brickearths' in Kent, UK and their relationship to engineering behaviour

Mineralogical and petrographical investigation of two loessic brickearth profiles from Ospringe and Pegwell Bay in north Kent, UK have differentiated two types of brickearth fabric that can be correlated with different engineering behaviour. Both sequences comprise metastable (collapsing) calcareous brickearth, overlain by non collapsing ‘non-calcareous’ brickearth. This study has demonstrated that the two types of brickearth are discretely different sedimentary units, with different primary sedimentary characteristics and an erosional junction between the two units. A palaeosol is developed on the calcareous brickearth, and is associated with the formation of rhizolithic calcrete indicating an arid or semi-arid environment. No evidence has been found for decalcification being responsible for the fabric of the upper ‘non-calcareous’ brickearth. Optically-stimulated dates lend further support for the calcareous and ‘non-calcareous’ brickearth horizons being of different age or origins. The calcareous brickearth is metastable in that it undergoes rapid collapse settlement when wetted under applied stresses. It is characterised by an open-packed arrangement of clay-coated, silt-sized quartz particles and pelletised aggregate grains (peds) of compacted silt and clay, supported by an interped matrix of loosely packed, silt/fine-grained sand, in which the grains are held in place by a skeletal framework of illuviated clay. The illuviated clay forms bridges and pillars separating and binding the dispersed component silt/sand grains. There is little direct grain-to-grain contact and the resultant fabric has a very high voids ratio. Any applied load is largely supported by these delicate clay bridge and pillar microfabrics. Collapse of this brickearth fabric can be explained by a sequence of processes involving: (1) dispersion and disruption of the grain-bridging clay on saturation, leading to initial rapid collapse of the loose packed inter-ped silt/sand; (2) rearrangement and closer stacking of the compact aggregate silt/clay peds; (3) with increasing stress further consolidation may result from deformation and break up of the peds as they collapse into the inter-ped regions. Smectite is a significant component of the clay assemblage and will swell on wetting, further encouraging disruption and breaking of the clay bonds. In contrast, the ‘non-calcareous’ brickearth already possesses a close-packed and interlocking arrangement of silt/sand grains with only limited scope for further consolidation under load. Minor authigenic calcite and dolomite may also form meniscus cements between silt grains. These have either acted as ‘‘scaffolds’’ on which illuviated clay has subsequently been deposited or have encrusted earlier formed grain-bridging clay. In either case, the carbonate cements may help to reinforce the clay bridge fabrics. However, these carbonate features are a relatively minor feature and not an essential component of the collapsible brickearth fabric. Cryoturbation and micromorphological features indicate that the calcareous brickearth fabric has probably been developed through periglacial freeze–thaw processes. Freezing could have produced the compact silt/clay aggregates and an open porous soil framework containing significant inter-ped void space. Silt and clay were remobilised and translocated deeper into the soil profile by water percolating through the active layer of the sediment profile during thawing cycles, to form the loosed packed inter-ped silt matrix and grain-bridging meniscus clay fabrics. In contrast, the upper ‘non-calcareous’ brickearth may represent a head or solifluction deposit. Mass movement during solifluction will have destroyed any delicate grain-bridging clay microfabrics that may have been present in this material

The structure and operation of the BGS National Geotechnical Properties Database. Version 2

The main part of this report describes the development history, structure and content of the BGS National Geotechnical Properties Database, with a final section describing planned future developments to enhance ease of access to, and promote wider use of, the database information for a variety of applications. The National Geotechnical Properties Database primarily holds geotechnical information extracted from site investigation records provided by clients, consultants and contractors, and from field and, secondarily, from laboratory test results carried out by the British Geological Survey. Information held within the database includes locations to British National Grid Coordinates; borehole, core and in situ test data; sample data; and a range of laboratory index, mechanical properties and chemical test data on soils, rocks and water. The database tables and fields are designed to be compatible with data supplied in the Association of Geotechnical and Geoenvironmental Specialists (AGS) industry standard digital transfer format, enabling rapid addition of data electronically, in addition to manual entry of analogue legacy data. This information forms the basis for the geotechnical attribution of the 2D and 3D digital geological models and underpins BGS core and commissioned engineering geology research. It also provides an important information resource for external customers and internal/external enquiries. The role of Geotechnical Database Manager has been undertaken by Suzanne Self since 2000

Field observations and laboratory test results on tills in the Nairn-Inverness area of NE Scotland

The report describes the field observations, sampling and geotechnical laboratory results on selected Scottish till sections in the Nairn-Cawdor area, Inverness-shire, Scotland. The first part of the report introduces the project and the context of this particular work. This is followed in Part 2 by an account of the sampling and testing methods undertaken for both geotechnical characterisation in the laboratory and micromorphology analyses. Part 3 provides an account of the location details of the logged and sampled exposures and descriptions of the lithological sequences at each site. Part 4 presents details and results of the characterisation tests (particle size analyses) undertaken on the collected geotechnical samples. The results of micromorphological analyses undertaken on thin sections prepared from ‘undisturbed’ samples acquired from this study are being described in a separate report

Spike Train Processing By A Silicon Neuromorph: The Role Of Sublinear Summation In Dendrites

this paper. 3 Result

Functional relationship between nucleus isthmi and tectum in teleosts: Synchrony but no topography

Abstract Neural activity in the optic tectum was compared with activity in the nucleus isthmi (NI) of both goldfish and sunfish with the aim of understanding how the two brain structures interact to process visual information. The two species yielded very similar results. Superficial tectum responds reliably to visual stimulation with topographically organized receptive fields; deep tectum and NI respond to stimulation throughout the field of the contralateral eye and habituate rapidly. Bursts of large-amplitude spiking in NI occur spontaneously and in response to contralateral visual stimulation. These NI bursts correlate with activity bursts across the tectal lobe on the same side, especially in the deeper layers. NI bursts may also synchronize with spiking activity in deep tectum. Trains of small-amplitude spikes in NI can be elicited by both ipsilateral and contralateral stimulation, but are not reflected in tectal activity. Simultaneous recordings from two sites in one NI were almost identical, suggesting that NI operates as a functional unit, broadcasting the same message across the ipsilateral tectal lobe