bluuebunny/crossref_metadata_2025 huggingface dataset:
Destructuring and disaggregation of Mercia Mudstone during full-face tunnelling
Authors: Atkinson J.H. , Fookes P.G. , Miglio B.F. , Pettifer G.S.
Published: November 2007

During construction of a tunnel in TriassicMercia Mudstone near Leicester a full face tunnel boring machine did not behave asexpected on the basis of the pre-construction ground investigation. When the machine was operated in open mode the spoil often reduced to a slurry as anticipated. However, when it was operated in closed mode the spoil changed to a plastic clay which clogged the machine. Further investigations were carried out after the tunnel had been constructed. Mineralogical analyses revealed that the Mercia Mudstone formation through which the tunnel was driven contained highly plastic swelling smectite clays which had not been identified in the pre-construction ground investigations. Samples from the tunnel and from elsewhere in the Mercia Mudstone Group were examined in special laboratory tests designed to replicate the conditions during construction. These tests demonstrated that under the influence of the tunnel boring machine in closed mode the spoil could have disaggregated releasing swelling smectite-rich clay. The results of these tests provided explanations for the behaviour of the tunnel boring machine.
Blue clay slope angle in relation to some geological and geotechnical characteristics, Italy.
Authors: Fiorillo Francesco
Published: November 2007

Observation of blue clay slopes outcropping along the Italian peninsula (Apennine foredeep and other inland areas) promptedinvestigation into several factors whichgovern their actual slope angle. Though characterized by good gradient, slope angle may differ from slope to slope, as well as within certain limited areas.

The study attempts to connect structural order (dip strata) and shear strength of the soil to explain slope angle. In many cases it is possible to distinguish (i) slope angle controlled by substratum and, thus, characterized by shear strength higher than the residual condition,and (ii) slope angle controlled by colluvium cover,characterized by shear strength reduced to residual.

Following an infinite slope stability model approach, the above conditions are connected to the half residual friction angle value, ϕ
R
′/2, which splits the slopes intotwo main types: cover-controlled, characterized by β≤ϕ
R
′/2 and completely or in part substratum-controlled, characterized by β>ϕ
R
′/2.

Slope angle distribution, deduced from slope map,can help us to understand the relative role of footslope removal processes and to distinguish slope type, substratum-controlled or colluvium-controlled.

This study cannot embrace all the factors and processes leading to a blue clay slope angle, and local geomorphological processes may complicate the outline proposed, though it does provide a useful first approach.
Rainfall routing to runoff and recharge for regional groundwater resource models
Authors: Heathcote J.A. , Lewis R.T. , Soley R.W.N.
Published: November 2007

The EU Water Framework Directive dictates an integrated approach to surface water and groundwater resource assessment and management. The adequacy of existing groundwater models and surface process models for resource management purposes is reviewed, and is found wanting in areas where both surface water and groundwater flow processes are important. Thus there is a need for appropriate modelling tools to simulate near-surface processes and interface with groundwater models. The basic processes operating between precipitation and groundwater recharge are discussed, with particular consideration of rapid runoff, interflow and ‘runoff recharge’, which can result in delay and translocation of recharge. These processes are translated into an algorithmic scheme defined by only a small number of parameters, based on ideas current in the literature. The resulting scheme is sufficiently flexible to model both outcrop aquifers and those where rapid runoff, interflow and runoff recharge are also important. Calculations can be carried out for simple lumped catchments or on model grids so that the tool can be applied throughout model development as understanding improves, from initial lumped water balances to the generation of distributed stream flow and recharge input files for the MODFLOW groundwater flow code. An important consequence of this approach is that modelled river flows can be compared directly with gauged flows without the need for baseflow separation. The success of the algorithmic scheme is demonstrated by two examples: reproducing the results of an existing model of a limestone aquifer with perforated cover (where runoff recharge is particularly important); and by constructing a new model of a sandstone aquifer with complex top boundary conditions.
Geological-evolutionary model of a gravity-induced slope deformation in the carbonate Central Apennines (Italy)
Authors: Martino S. , Prestininzi A. , Scarascia Mugnozza G.
Published: November 2007

This paper discusses the findings from a study conducted on gravity-induced deformationsoccurring along the SW slope of Mount Nuria linking the village of Pendenza (Rieti, Italy) to the area of San Vittorino, in the alluvial plain of the Velino river, where important infrastructures are present.

The dominantly carbonate composition of the rocks outcropping along the slope, the occurrence of a main spring fed by a regional karst aquifer and the interaction of gravity-induced deformations with buildings and infrastructures resting on the slope or located at its base make the investigated case extremely interesting and reflective of phenomena that are common in similar geological-hydrogeological conditions. Insights from this case and their use for the construction of a ‘geological-evolutionary model’ shed more light on the complex interactions existing between jointed carbonate rocks, seepage, karst dissolution, genesis of gravity-induced deformations and their evolution in space and time, through the analysis of stress-strain conditions withinthe slope. According to the selected methodologicalapproach, data from detailed geological, geomorphological and geomechanical surveys were integrated with those from laboratory tests and from a complex slope monitoring system.

From the results of the study it was possible to: i) refer the investigated phenomena to gravity-induced deformations on the slope scale; ii) build a representative ‘geological-evolutionary model’ and iii) develop an analytical approach to assess the hazard represented by these deformations for local buildings and infrastructures. The identification of different hazard conditions can helpdefine the type and value of possible mitigation efforts.

The investigated case also provided inputs for testing new approaches to the geomechanical characterization of rock masses, to the description of their jointing and to the correlation of their main discontinuities with tectonic and gravity-induced elements.
The use and misuse of CLR 7 acceptance tests for assessment of risks to human health from contaminated land
Authors: Nathanail C. Paul
Published: November 2007

Generic and detailed quantitative assessments of the risks posed to human health from land contamination involve the comparison of representative contaminant concentrations against relevant generic or site-specific assessment criteria respectively. Technical guidance on statistical tests to determine whether contaminant concentrations exceed relevant assessment criteria fails to recognize the effects of sample clustering and heterogeneity in ground conditions on the validity of the test results. Reference to the conceptual model should be made to determine the likely level of contamination to which the critical receptor may be exposed within an averaging area.
Prediction of swelling characteristics of remoulded and compacted expansive soils using free swell index
Authors: Rao A.S. , Phanikumar B.R. , Sharma R.S.
Published: November 2007

Seasonal changes in moisture content result in volume change in expansive soils, which may damage structures founded on them. Evaluation of swelling characteristics of expansive soils, namely, swell potential and swelling pressure, is important for the design of foundations. Many relationships have been suggested for prediction of swell potential and swelling pressure from various index properties such as liquid limit, plasticity index, shrinkage index, activity, clay content, etc., and placement conditions such as initial dry unit weight, initial water content and initial surcharge pressure. Free swell index (FSI) indicates the potential expansiveness of a soil. FSI, being determined on the soil fraction <425 μm sieve like the other index properties of clays, is also an index property of an expansive soil. Hence, it can be used as a parameter in the relationships for swell potential and swelling pressure. This paper proposes relationships for predicting swell potential and swelling pressure of remoulded and compacted expansive soils using FSI and placement conditions. The relationships are based on experimental data for soil samples from 10 different sources.
Deep dry mix ground improvement of a soft peaty clay using blast furnace slag and red gypsum
Authors: Hughes Paul , Glendinning Stephanie
Published: November 2007

The paper describes a field trial using deep
in situ
dry soil mixing to stabilize soft peat deposits beneath the route for the Channel Tunnel Rail Link in the SE of the UK. The aim of this trial was to evaluate whether a ground granulated blast furnace slag (GGBFS)–red gypsum mixture could be used as a replacement for a cement-based binder. Red gypsum is produced as a co-product to the production of the white pigment titanium dioxide. Trial columns were installed adjacent to the main stabilization works. A combination of
in situ
and laboratory testing has shown that the blended binder was as effective as ordinary Portland cement in increasing the strength of the peat. The blended binder columns also displayed similar durability characteristics. Using the alternative binder required no alteration to existing equipment and caused no reduction in production rates. The minerals formed in the samples from the GGBFS–red gypsum columns were of the type formed by pozzolanic reactions and the strength of the GGBFS–red gypsum columns was dependent on achieving a pH of 10.5. The paper recommends that peat samples must be stored in airtight containers prior to initial design mix testing. If required, the pH of the soil–binder mixes should be adjusted (using a small addition of lime) during the treatment process.
A review of ammonium attenuation in soil and groundwater
Authors: Buss S. R. , Herbert A. W. , Morgan P. , Thornton S. F. , Smith J. W. N.
Published: November 2007

Ammonium attenuation in subsoils and groundwater is predominantly due to cation exchange and/or nitrification (biological oxidation) processes. These processes have been little studied in UK formations and this relative lack of information can result in reduced consistency and robustness in the assessment of risks posed by ammonium contamination arising from landfills, effluent soakaways, contaminated sites and other sources. A review of ammonium fate and transport in the subsurface has been completed and guidance developed on the key processes that contribute to attenuation. The amount of relevant literature is small but sufficient to provide indicative ranges of partition coefficients and biological nitrification rates for ammonium in UK subsoils and aquifers. Ammonium attenuation was found to be highly sensitive to the clay mineralogy and pore size of the strata, the availability of oxygen and the chemical composition of the contaminated fluid. The values derived may have application in the initial (screening) phases of risk assessment where the conceptual model for the site under consideration matches that from which the presented data originate.
Theoretical head decay in closed basin aquifers: an insight into fossil groundwater and recharge events in the Andes of northern Chile
Authors: Houston John , Hart Dan
Published: November 2007

Many small to moderate-sized, closed aquifer basins in northern Chile show a groundwater gradient indicating flow despite an apparent lack of recharge under current climatic conditions. An examination of the mechanisms that might produce such flow suggests that the only realistic possibility is head decay from an earlier higher water level caused by ancient recharge. Model studies suggest that for small basins, such recharge must have taken place within the last 1000 years and possibly within the last few hundred years, calling into question whether such resources should be labelled fossil. Recent palaeoclimatic studies of northern Chile show several pluvial periods throughout the Late Pleistocene and Holocene, inaddition to long return period storm events, which continue to the present and which might have led to a series of pulsed flushing events in aquifers. Hence, it is incorrect to label groundwater resources as either fossil or actively recharged, as there is, in reality, a continuum between the two, and all such aquifers require site-specific evaluation and new, more flexible guidelines for development.
Mapping the risk to groundwater resources from farm waste stores in England and Wales
Authors: Armstrong Adrian , Rutter Helen , Gooddy Daren , Lyons Hester
Published: November 2007

Unlined farm waste stores present a potential, but unquantified, risk to groundwater. Field studies of pore water retrieved from beneath active slurry stores indicate that there is a potential for pollutants to be transported down through the unsaturated zone of the aquifer. The highest risk to groundwater is where the water table is shallow, and/or where there is no protection offered to the aquifer by low-permeability soil or drift layers. A preliminary screening tool is presented, which highlights vulnerable areas of aquifer based on the protection offered by superficial layers. Two different approaches were applied, one utilizing soils data and the other making use of superficial geology data. Some of the differences between the approaches are considered, and their influence on the resulting risk assessment are discussed.
Protecting groundwater with oil-retaining pervious pavements: historical perspectives, limitations and recent developments
Authors: Newman Alan P. , Puehmeier Tim , Kwok Vikki , Lam Manfred , Coupe Stephen J. , Shuttleworth Andy , Pratt Christopher J.
Published: November 2007

Pervious pavements are important systems used for source control in Sustainable Drainage Systems (SuDS), which allow water to infiltrate into hard surfaces and then slowly release it either to a drainage outlet or into the ground. They also remove low levels of pollution from the water by filtration and also by biodegradation of hydrocarbons, which are adsorbed to materials within the construction. Following a historical overview of research in this area, this paper describes an experiment that demonstrates the importance of the choice of geotextile in the retention of day-to-day emissions of oil from parked vehicles and the development and initial trials of an oil interceptor system, which has been incorporated within pervious surface construction. The results indicated that in the early years of the life of a pervious pavement the choice of geotextile has a vitally important impact on its oil-retaining role but that, after several years of silting, the choice may become less important. The results also demonstrated that modified direct infiltration pervious pavement systems, constructed on site from traditional materials and geomembrane, can effectively contain very large hydrocarbon spills.
Pesticide pollution of the Triassic Sandstone aquifer of South Yorkshire
Authors: Gooddy D. C. , Stuart M. E. , Lapworth D. J. , Chilton P. J. , Bishop S. , Cachandt G. , Knapp M. , Pearson T.
Published: November 2007

Diffuse pollutants such as pesticides pose a significant threat to groundwater quality. Following the wet autumn and winter of 2000–2001 an upturn in trace pesticide concentrations was detected in blended water drawn from part of the Triassic Sandstone aquifer. A groundwater sampling and monitoring programme was undertaken to assess whether this increase would continue. Over a period of 18 months, 190 groundwater samples were collected from the upper part of the aquifer and analysed for 40 pesticides and for nitrate. A total of 25 pesticides were found of which 16 were detected more than once. Positive pesticide detections were in excess of the EU maximum admissible concentration (MAC) for individual substances of 0.1 μg l
−1
on 33% of occasions. The most commonly detected pesticides generally have higher agricultural application rates and/or relatively greater solubilities. Very high concentrations of mecoprop (up to 7.1 μg l
−1
) were consistently found at two of the sampling sites. Analysis of mecoprop enantiomers suggested more than one source for this contaminant. High concentrations of atrazine (up to 1.4 μg l
−1
) were also detected at three sites and high concentrations of isoproturon (1.2 μg l
−1
) were found where very high mecoprop concentrations were also present. Nitrate concentrations exceed the EU MAC of 11.3 mg l
−1
N at four sites. The spatial and temporal distribution of pesticides obtained from the monitoring network shows no clear trends for prediction of future concentrations. Nitrate-N concentrations and pesticide detections show no clear relationship, suggesting different source, transport or degradation pathways.
Pesticide fate and behaviour in the UK Chalk aquifer, and implications for groundwater quality
Authors: Chilton P.J. , Stuart M.E. , Gooddy D.C. , Williams R.J. , Johnson A.C.
Published: November 2007

Field and laboratory studies have been used to assess the main factors that determine the fate and behaviour of agricultural herbicides in the Chalk aquifer of southern England. Field studies using isoproturon, chlortoluron and atrazine showed that leaching of pesticides from normal agricultural usage produces concentrations in Chalk groundwater of 0.01–1 μg l
−1
for most compounds, which are comparable with the current EU drinking water standard of 0.1 μg l
−1
. Where significantly higher concentrations are found in groundwater (up to three or four orders of magnitude higher), these are associated with localized ‘point’ usage or disposal, often combined with more rapid preferential transport pathways to the water table. Studies of the degradation of isoproturon, mecoprop and atrazine showed that these compounds are significantly more persistent in the Chalk than in soils, with half-lives measured in hundreds rather than tens of days. The observed order of magnitude variation in isoproturon half-lives spatially and with time makes the choice of values for predictive modelling problematic. The implications of the results for the quality at groundwater supply sources are discussed and compared with the situation for nitrate, and uncertainties in knowledge, and therefore the requirements for further work on both transport pathways and pesticide persistence, are reviewed.
Diffuse pollution threats to groundwater: a UK water company perspective
Authors: Knapp M.F.
Published: November 2007

UK Water services companies have a statutory duty to supply water compliant with drinking water quality regulations. Twenty percent of Yorkshire Water's supply is from groundwater. Deteriorating groundwater quality has resulted in closure, blending or treatment of sources. Diffuse pollutants of prime concern are
Cryptosporidium
, nitrate and pesticides. Risk assessments for
Cryptosporidium
lead to closure of spring sources and installation of membrane treatment for groundwater abstracted from a major chalk aquifer. Upward nitrate trends are observed in many aquifers; the concentration of abstracted nitrate is influenced by water-table level and pumping regimes. Government sponsored schemes to control fertilizer applications have reduced nitrate leaching from soil but not yet affected concentrations in deep well abstractions. Potential pesticide contamination from upland bracken removal has been managed by co-operative agreements with land agents. A major sandstone aquifer has been contaminated by amenity and agricultural pesticides. The implications for the water company of diffuse pollution of groundwater are long term resource reduction, less operational flexibility and increased costs. Groundwater monitoring, trend analysis and UK and international experience of cooperative agreements is discussed with reference to the requirement of the Water Framework Directive and associated Groundwater Directive for measures to protect the water environment.
A framework for monitoring regional groundwater quality
Authors: Ward R.S. , Streetly M.J. , Singleton A.J. , Sears R.
Published: November 2007

The attention currently being focused on diffuse pollution has led to an increased recognition of the role of groundwater as a pathway for transporting diffuse pollution to surface waters. Understanding and managing this issue requires a good understanding of the spatial and temporal distribution of diffuse pollution in groundwater. This in turn requires a co-ordinated approach to groundwater monitoring, to obtain accurate and representative data. This paper describes a strategic framework for groundwater quality monitoring that has recently been developed by the Environment Agency of England and Wales. The framework is implemented in three main stages: assessment of drivers and objectives, planning and implementation. The national framework is currently being implemented by a series of detailed regional programmes. These are developed on the basis of catchment-scale groundwater quality monitoring units, which will be broadly consistent with groundwater bodies defined under the European Union (EU) Water Framework Directive. The monitoring network that results from the application of the framework is designed to provide background information on groundwater quality at a catchment scale. Separate monitoring programmes will be required for monitoring pollution associated with individual sites. This paper focuses on the strategic aspects of designing a monitoring network, rather than the technical details of obtaining representative and accurate data from individual sample points, and is illustrated by a case study of the process of design of such a catchment-scale monitoring system.
The terrestrial shallow seismic reflection technique applied to the characterization and assessment of shallow sedimentary environments
Authors: Brabham P.J. , Thomas J. , McDonald R.J.
Published: November 2007

Terrestrial shallow seismic reflection offers great potential in the characterization of shallow sedimentary environments. Experience from the oil industry's standard use of the seismic technique in basin-wide, 3D seismic stratigraphic studies reinforces this point. Unlike the marine environment, where it is relatively easy to record high resolution shallow reflections, land acquisition can be affected by near surface layers that absorb the high frequency signals necessary to resolve thin sub-surface sedimentary layers. The quality of reflection data recorded in shallow terrestrial environments can be difficult to predict without initial field trials. Shallow 2D and 3D reflection data can be improved greatly by the use of appropriate seismic sources, receivers and modern distributed recording systems utilizing many recording channels. UK-based case studies are described at Porth Neigwl; Dinas Dinlle; St Bees and Camlad Valley where the resolution capabilities of the reflection data are of the same magnitude as the thickness of sedimentary units exposed in cliff section or boreholes. At these sites, a fully integrated interpretation framework for sedimentary environments can be determined. A survey at Llanrhidian Marsh, Gower is also described where organic rich surface sediments absorbed the high frequency reflections necessary to image the thin sedimentary units revealed in shallow boreholes.
Coastal cliff recession risk: a simple judgement-based model
Authors: Lee E.M.
Published: November 2007

To predict cliff recession rates, it is necessary to make judgements about the effects of changing environmental conditions and shoreline management practice on the recession process. A simple model is presented that allows judgements to be ordered in a systematic manner. The model can be used to generate single predicted values or a probability distribution of the possible recession rates, as illustrated by an example from the Covehithe cliffs, Suffolk. The output from the probabilistic model can also be used to support risk-based economic evaluation of the benefits of coast protection.
Engineering characterization of estuarine silts
Authors: Long M.
Published: November 2007

Guidance is provided for geotechnical engineers designing civil engineering works in silty soils. A detailed characterization of two estuarine silt sites in Ireland is performed and the soil properties are linked to their geological origin. It was found that these soils are susceptible to densification by conventional and high-quality fixed piston tube sampling and care needs to be taken when using laboratory-derived design parameters, particularly for consolidation and shear strength properties. The 1D consolidation and creep of these silts can be modelled successfully by the well-known Janbu formulation. Settlement predictions from laboratory-derived parameters match measured data reasonably well, but tend to underestimate primary consolidation, consistent with a sampling densification effect. Vane data should be used with caution, as measured strength values may be high, and it seems that more reliable parameters can be derived from cone penetration tests. Conventional techniques for determining soil strength from triaxial tests in silt are inappropriate because of the dilational nature of the material, and more reliable and logical strength estimates can be made from a limiting strain criterion.
Hydrofracturing water boreholes in hard rock aquifers in Scotland
Authors: Cobbing J. , Ó Dochartaigh B.É.
Published: November 2007

Hydrofracturing of new public water supply boreholes in Precambrian crystalline bedrock in Scotland has increased borehole yields by at least one order of magnitude, and made the difference between borehole abandonment and success. In many upland rural areas of the UK, low-productivity aquifers are an important resource for small public water supplies. Where a borehole in low-productivity crystalline rocks proves too low yielding for its designed purpose, hydrofracturing is a cost-effective means of enhancing yield.
The addition of geotechnical properties to a geological classification of coarse-grained alluvium in apediment zone
Authors: Fakher A. , Cheshomi A. , Khamechiyan M.
Published: November 2007

The city of Tehran is founded on Quaternary alluvium, which has been geologically classified by Rieben. The city is located at the foot of the Alborz Mountain Range, which is basically composed of Eocene pyroclastic deposits (green tuff) and other volcanic rocks. The geology and the morphology of the Tehran region is similar to that for other cities located at the foot of mountains. Rieben divided the Tehran alluvia into four categories, identified as A, B, C and D (from oldest to youngest). In the Rieben geological classification system, which is widely used in Iran, the age and general geological characteristics of alluvia are considered, rather than engineering properties. The Rieben and other geological classification systems are described in this paper and geological factors that affect the geotechnical characterization of the Tehran alluvium are discussed. Because of the nature of the Tehran soils, undisturbed samples for laboratory testing are difficult to obtain and the execution of large-scale
in situ
tests is difficult, expensive and not practical for the majority of construction sites. Accordingly, a geological–geotechnical classification system is required to assess the engineering properties of coarse-grained soils for use in small to medium-sized construction projects. To determine the geotechnical properties of the Tehran alluvia, a number of
in situ
tests have been undertaken. The test results have been compared with published research results and the Rieben classification system has been extended to cover geotechnical properties. A similar framework could be used to create local geotechnical–geological classification systems of other coarse alluvia in other locations.
An investigation of primary permeability in strata from a mine in the Eastern Transvaal Coalfield, South Africa
Authors: Bell F.G. , Jermy C.A.
Published: November 2007

Excessive development of methane and water pressures were believed to be a contributory cause of roof fall in a coal mine in the Eastern Transvaal Coalfield. Accordingly, a laboratory investigation of the primary permeability of the strata enclosing the coal seam concerned was undertaken. The principal aim of the investigation was to see if there was a relationship between the various facies of the coal bearing strata and changes in permeability. In this way it may be possible to determine likely zones of pressure build-up.

Permeability testing was carried out on drillholesamples using modified versions of the Ohle cell, the Bernaix cell and the Hoek triaxial cell. The use of the Hoek cell allowed testing to be carried out under different stress conditions. Nitrogen, methane and water were used as the permeating fluids. The liquid equivalent permeability of each sample was determined for the two gases. The permeability tended to decrease with increasing pressure when the two gases were used as the permeating fluid but not when water was used. In addition, the permeability was influenced by the grain size of the material tested and by the direction in which it was tested, that is, along or across the bedding. Hydraulic fracturing occurred in some specimens when tested at high water pressures in divergent flow in the Bernaix cell. An increase in hydrostatic pressure, confining pressure or axial pressure gave rise to a reduction in permeability in triaxial testing, the former giving rise to the greatest and the latter the least decrease. Staged loading showed that the greatest reduction in permeability occurred during initial loading. On cyclic loading the liquid equivalent permeability decreased with increasing applied stress and then increased with subsequent reduction in stress.
Reconnaissance tracer tests in the Triassic sandstone aquifer north of Liverpool, UK
Authors: Streetly H.R. , Hamilton A.C.L. , Betts C. , Tellam J.H. , Herbert A.W.
Published: November 2007

Three tracer tests were carried out by slug injection of fluorescein, amino-G-acid, and bromide at piezometers with 0.4 m long intake zones located 5 m distant from an 80 m deep pumping borehole. The piezometer intake zones were about 2 m (Tests 1 and 2) and 18 m below static water level, and the pumping borehole was sealed using a packer at about 11 m (Tests 1 and 2) and 19 m below static water level. Analytical expressions were used to interpret the data. Test 2 was unsuccessful.

Four pathways were discernible from the Test 1 tracer breakthrough curves. These pathways were interpreted as being due to three dominantly fracture routes and one dominantly intergranular flow route. The earliest (sharp) peak arrived after a few hours, and the last (broad) intergranular flow peak arrived after around 40 hours. Fluorescein was delayed slightly (retardation factor = 1.4) relative to the other tracers. In the deeper Test 3, three pathways were discernible, with concentration peaks at about 9, 25, and 78 hours. Fluorescein was delayed relative to amino-G-acid (retardation factors = 1.25 and 1.5) in the second and third pathways. As with the first test, the last peak was very broad, suggesting a variety of intergranular routes through the rock, and possibly the effect of diffusion.

The tests clearly demonstrate the importance and complexity of fracture flow over short distances in the Triassic sandstones, the complexity of the intergranular flow routes, and that different retardation factors can be associated with different pathways.
Risk assessment of slopes
Authors: Kong W.K.
Published: November 2007

Slopes pose a potential hazard to urban development. The risk analysis of the probability of fatality occurrence (or probability of loss of life) resulting from natural landslide or rockfall is
based on five probability parameters of rain, slope failure/ rockfall, elements at risk, impact significance (i.e. death, injury and property loss) and fatality occurrence. The probability of occurrence and other factors such
as value of life, design lifetime and costs of implementing measures can be used to assess the cost-benefit of the proposed mitigation measures. The cost-benefit analysis demonstrates that from an economical point of view, risks should be reduced until the marginal cost of measures is equal to the marginal benefit to be protected.
Engineering on the precipice: mountain road rehabilitation in the Philippines
Authors: Hart J. , Hearn G. , Chant C.
Published: November 2007

Topography and ground conditions for mountain road engineering within the Central Cordillera of Luzon in the northern Philippines (
Fig. 1
) are some of the most extreme and unstable in the world. The Central Cordillera is a range of mountains that has been emplaced and shaped by rapid uplift, valley incision, slope erosion, and often massive landslides (
Fig. 2
). The Halsema Highway is a 180 km-long,tortuous road that traverses this mountain range and is a vital economic and strategic lifeline to the intensively farmed agricultural mountainous regions of northernLuzon. In 1990 the road suffered extensive loss and damage as a result of a Richter magnitude 7.8 earthquake followed by a succession of typhoons and intense rainstorms. Given the strategic and socio-economicimportance of the highway, the Philippines Government sought international aid to rehabilitate this vital link following the devastation, and feasibility and design studies commenced in late 1996. This paper presents someof the geotechnical investigation carried out for these studies, describing the types of instability and ground conditions affecting the road and the approach adopted to maximize the interpretation of the ground, andto provide geotechnical engineering options for road rehabilitation.
Application of reflection seismology to foundation investigations at A5 Pont Melin Rûg, North Wales
Authors: Nichol D. , Reynolds J.M.
Published: November 2007

A modern road bridge across the Afon Alwen is proposed to replace the existing A5 Pont Melin Rûg, a masonry arch structure built in 1792. However, progress on engineering design has been hampered by problematic ground conditions caused by a previously unrecorded, 40–50 m thick sequence of soft to very soft glaciolacustrine silts (Rûg Silts). The remarkable depth of the Rûg Silts and the need to locate a foundation stratum for the proposed new bridge prompted the application of geophysical techniques. A high-resolution seismic reflection survey was performed to image the subsurface conditions at the proposed bridge site to a depth of 100 m below ground level and provide a comprehensive understanding of the geological profile. The seismic survey successfully delineated the bottom of the Rûg Silts, identified a basal unit of very dense, heterogeneous glaciofluvial gravels and delimited bedrock of Silurian Nantglyn Flags. Subsequently, a single deep borehole confirmed the findings of the geophysical survey and importantly, the investigations proved a possible foundation horizon for the proposed new bridge at a depth of 45.80 m in the basal gravel unit. The seismology provided the largest and most continuous source of geological information across the site and consequently had the greatest influence on the deliberations on foundation selection and optimization. This case history illustrates the benefits of using reflection seismology in areas of complex glacial geology. It also demonstrates the benefits of geophysical investigations to geotechnical assessments of local ground conditions.
A field-based test cell examining clay desiccation in landfill liners
Authors: Philip L.K. , Shimell H. , Hewitt P.J. , Ellard H.T.
Published: November 2007

Desiccation of clays can lead to the development of cracks and this is an important issue for mineral barriers used in lining and capping of landfills. The mechanisms of post-compaction moisture loss in a clay layer are reviewed and the results from a field test cell investigating clay desiccation are presented. A large scale instrumented test cell was constructed comprising a clay layer overlain by a geomembrane. Parts of the test cell were covered with a stone protection layer and parts of the test cell were sloping. Temperatures throughout the clay layer, relative humidity just above the clay, ambient air temperatures and crack patterns and dimensions wereobserved during a 36 day summer period. The amount of cracking was quantified using various crack indices. Cracks in the covered and flat sections were minimal whereas in the sloping uncovered portion cracking was initiated rapidly and then spread until the network of cracks at the surface stabilized and further dryingresulted in crack depth propagation. The geomembrane, exposed to the sun, was found to have a significant heating effect on the soil below. Significant moisture was lost over the entire thickness of the exposed barrier resulting in a modelled flow through the barrier of 19 times the construction value. Immediate covering of the geomembrane was found to greatly reduce the temperature variations, moisture loss and cracking. The results are discussed in the context of current crack theories and implications for landfill design and construction.
The development of a new testing protocol for sulphur compounds in structural backfills
Authors: Czerewko M.A. , Cripps J.C. , Reid J.M. , Duffell C.G.
Published: November 2007

The presence of sulphur compounds in soils and rocks can lead to chemical attack on construction materials such as steel and concrete when these materials are used as backfill to structures. Sulphate attack on concrete is a well-known phenomenon and BRE guidance to some of the causes and prevention measures has been available for some time. However, recent cases of the corrosion of corrugated steel buried structures and thaumasite attack on concrete bridge foundations have highlighted the role played by sulphides such as pyrite. The sulphides can oxidise, producing high sulphate concentrations and acid conditions, which can then attack construction materials. Present methods of assessing corrosion potential tend to concentrate on sulphate and pH, and do not fully address the problem of sulphides.

This paper describes research carried out by TRL Limited and the University of Sheffield for the Highways Agency that aimed to develop better test methods for sulphur compounds in structural backfills. Advances in chemical test methods such as direct determination of sulphur by ICP-AES and novel methods of extraction have been investigated and compared with traditional methods for a range of materials with widely varying sulphur contents and mineralogy. The research led to recommendations for a revised suite of tests for sulphur compounds in structural backfills, appropriate methods of sampling and storage and limiting values for species such as reduced sulphur which are not covered by existing guidance. The research will be implemented by means of revisions to the relevant sections of the Specification for Highway Works and Design Manual for Roads and Bridges.

The paper also aims to highlight the distribution of naturally occurring sulphur species within the UK geological materials. As a result of inadequate sampling, storage and assessment procedures, these sulphur species may cause problems to buried steel and concrete structures.
Application of ground-penetrating radar to investigate the effects of badger setts on slope stability at St Asaph Bypass, North Wales
Authors: Nichol D. , Lenham J.W. , Reynolds J.M.
Published: November 2007

At the St Asaph Bypass, surface cracking developed along the crest of a modern highway cutting, above a cluster of badger setts excavated in the sandy soils of the cutting slope. This prompted concerns about the extent of the underlying tunnel systems and the possible existence of deep cavities lacking surface expression that might cause a potential slope instability problem. The full threat posed to the integrity of the cutting and to the safety of road users remained uncertain. In addition, intrusive investigations were deemed inappropriate and a non-invasive solution to the problem was required.

Ground-penetrating radar was used along a 50 m stretch of the cutting to determine the full extent of the badger setts beneath the surface. The geophysical survey identified 324 m of tunnels and demonstrated that the tunnel network was generally shallow (
c.
0–2 m). Pronounced radar reflections characteristic of air voids were identified in the data and interpreted as the badgers’ access tunnels and living and nursery chambers whereas the more subdued features were interpreted as collapsed and abandoned diggings. This case history illustrates the benefits of using ground-penetrating radar to provide an understanding of slope stability and local ground conditions in areas of environmental sensitivity when non-intrusive investigations are required to provide reassurances in relation to public safety.
The mineralogy and phase equilibrium of Keuper Marl
Authors: Davis Allen George
Published: November 2007

Previously, it has been suggested that the existence of a variable clay mineralogy was responsible for the anomalous engineering behaviour of Keuper Marl. Using x-ray diffraction techniques and chemical analyses, it is shown here that 80 per cent of the samples examined fall in the mineral suite illite-corrensite-carbonates-quartz-hematite, and that there is good evidence that this mineral assemblage has attained phase equilibrium.

Calculation of the true clay mineral content of the samples analysed shows that much of the clay content is aggregated into silt size units, which accounts for the large range of measured Activities.
Classification tests on African red clays and Keuper Marl
Authors: Sherwood Philip Thomas
Published: November 2007

This paper describes the results of soil classification tests carried out on African red clay soils from Kenya and soils from the Keuper Marl formation in England. It shows that in both groups of soils aggregations of clay particles can occur and give rise to anomalous classifications of the soils when they are tested by standard procedures.

The manner in which the particles are cemented together is different for the two groups of soils. In the case of the red clay soils the aggregations give rise to low plasticity values being obtained whereas in the case of the Keuper Marl soils they give rise to low clay contents being obtained when the particle size distribution is determined by sedimentation techniques.

The reason for the aggregation in the red clay soils is shown to be the presence of free iron oxide cementing the particles together. Silica is shown to be the most likely cementing agent in the Keuper Marl soils.

Apart from the aggregation of the Keuper Marl soils there is evidence that non-aggregated clay particles in excess of 0·002 mm diameter are also present. This is an additional reason for anomalous particle size distribution results being obtained for these soils.
Site investigations in coalfields
Authors: Taylor Roy Kenneth
Published: November 2007

The paper primarily considers the diagnosis and evaluation of shallow workings from which coal, ironstone and fireclay have been extracted by underground methods close to outcrop. Instability problems affecting normal structures are mainly attributed to 'room and pillar' workings, and current work on the behaviour of the latter is briefly discussed. The resultant compaction of collapsed strata (goaf) is problematical and evidence is presented which throws doubt on the compaction of 'bell-pit' workings of probable mediaeval age.

Investigation techniques are discussed in detail and attention drawn to the importance of geological structure, particularly faults. Associated 'steps' caused by differential movements are not always fully appreciated. The detailed case histories are taken from the Yorkshire coalfied and consider urban development, re-development and a major road project.

It is concluded that exploration on an areal basis is necessary if all the factors connected with shallow workings and other industrial legacies are to be fully elucidated. In order to rationalize techniques it is advocated that larger investigations should comprise more than one stage. A detailed pre-survey appreciation of the available mining, industrial and geological literature is an integral part of this type of project, and the full co-operation of all the parties involved should stem from this period.
The structure of Keuper Marl
Authors: Davis Allen George
Published: November 2007

Calculation of the true clay-mineral content of samples of Keuper Marl analysed has shown that much of the clay content has been aggregated into silt-size units. This aggregated structure accounts for the large range of measured Activities of the Marl.

A system of structural classification used in pedology will conveniently describe the structural features of the more heavily aggregated, overconsolidated clay soils such as Keuper Marl; some preliminary work with the electron micro-probe analyser supports this method of describing soil structure.

It is suggested that variations in the structure of these sediments indicate varying conditions of deposition and diagenesis, and are related to differences in the magnesium content of the samples analysed.
The microstructure of London Clay
Authors: Tchalenko John Stephen
Published: November 2007

The microstructure of London Clay from several localities and depths was examined in thin section under the polarizing microscope. Except where severely weathered the clay was found to have a strong preferred particle orientation and frequent microscopic discontinuities. These features are compared with those observed in the study of some other clays. The microstructure of an artificially sedimented and consolidated sample of London Clay helps us to understand the origin of the microstructures observed in the natural specimens.
Ground-water conditions in Greater Tehran
Authors: Knill John Lawrence , Jones Kenneth Stuart
Published: November 2007

Tehran is situated on an alluvial plain immediately south of the Alborz Mountains which form an east-west chain stretching across northern Iran. The alluvium is composed of an older, folded group, of probable Pliocene age, which is overlain by flat-lying Quaternary gravels, sands, silts and boulder beds. Recharge from surface streams takes place in the areas underlain by the flat-lying alluvium. The pattern of ground-water flow is related to the sub-surface structure of the alluvium. Chemical data are presented which indicate that extensive surface recharge takes place below the city. The ground-water balance is discussed and it is concluded that, at present, there is a balance between inflow and abstraction.