bluuebunny/crossref_metadata_2025 huggingface dataset:
Predictions of block size distribution for quarrying
Authors: Wang H. , Latham J.-P. , Poole A. B.
Published: November 2007

The in situ block size and shape parameters of a rock mass with discontinuities are of signifcance for determining whether an existing or virgin quarry is suitable for armourstone production and for designing an appropriate blast pattern. A method for predicting these parameters is presented in this paper, which includes a detailed discontinuity survey technique and computer determination of the blocks dissected by the discontinuities. The applications of the method to simulated discontinuity data and natural joint data are discussed.
Evaluating the strength and deformability of sandstones
Authors: Dyke C. G. , Dobereiner L.
Published: November 2007

The mineralogy, texture and wave velocity characteristics of a range of sandstones were studied to aid the understanding and prediction of geotechnical properties. From a consideration of volumetric strain variations it is apparent that the weaker rocks display a behaviour markedly different from the stronger rocks. In the weaker rocks, the elastic range is limited to very low stress levels. The sensitivity of the strength and volumetric strain to sample moisture content has also been evaluated and shown to be an important variable in rock deformability behaviour; a decrease in moisture content tends to suppress the onset of dilatancy and microcracking, leading to an increase in peak strength.

Microscopic characteristics, in particular in the areas of grain contact and cementation, were successfully used to explain the strength and deformability behaviour of a wide range of sandstones. Practical index parameters for assessing the strength and deformability of sandstones are outlined. Characterization by S waves shows potential as a complement to the index tests of saturated moisture content and point load for weak and strong sandstones respectively.
Sandstones as geomaterials
Authors: Hawkins A. B. , McConnell B. J.
Published: November 2007

The lithological characteristics and dynamic and static test results are presented for six sandstone types ranging in age from Lower Old Red Sandstone to Triassic. Attention is drawn to the differing geomechanical properties of these sandstones and hence the variation in their suitability as construction geomaterials. Comparisons are made between a number of the static properties of the sandstones and their geomechanical performance.

The paper emphasizes the importance of considering those sandstone properties relevant to particular applications. An indication is given of the suitability of the six examples of sandstones to the main construction geomaterial uses: building stone, armourstone, rip-rap, aggregate sub-base, aggregate dressing and concrete.
A note on undulatory extinction of quartz in granite
Authors: West G.
Published: November 2007

Undulatory extinction of quartz has become important in engineering geology because of its supposed indication of an alkali-silica reactive aggregate. This note reviews the small amount of quantitative data that is available on undulatory extinction of quartz grains in granites and granitic rocks. It is considered that undulatory extinction of quartz occurs as a result of deformation of the rock after its formation and that the greater the cumulative deformation the larger the angle, hence it is a useful indicator of the orogenic history of the rock. Preliminary measurements are reported of the undulatory extinction angle of quartz in some British granites suggesting a field worthy of further study. The note concludes with a discussion of the practical implications of the subject.
J. C. B
ullas
replies:
Authors: Bullas J. C.
Published: November 2007

J. C. B
ullas
replies: I confirm that all the aggregates tested in my Technical Note were crushed rock aggregates, and with hindsight this fact should have been stated in the Note. Because of this, Dr Gribble is correct in his supposition that my proposed new value for
K
of 2800 applies to crushed rock aggregates only. It would seem that the value for
K
of 4000 currently in use was derived from a combination of test results from both crushed rock and natural gravel aggregates.

I would like to thank Dr Gribble for pointing out this omission from my Technical Note.
Radon in the surface waters of southwest England and its bearing on uranium distribution, fault and fracture systems and human health
Authors: Heath M. J.
Published: November 2007

Radon is a natural radioactive gas produced by the decay of uranium and thorium in rocks and soils. High surface radon concentrations are commonly associated with high levels of uranium in underlying rocks. High radon levels can also occur in groundwater, even in rocks with normal crustal uranium concentrations. The discharge of groundwater via faults and fractures can produce radon anomalies unrelated to the distribution of uranium. The surface distribution of radon is therefore influenced by the distribution of uranium and of transport pathways along faults and fractures.

The principal radon isotope (Rn-222, half-life 3.825 days) is capable of migrating significant distances from its source, both as a gas and in solution. In the gaseous form radon can migrate into houses where, in high concentrations, it can represent a health hazard.

The distribution of radon in streams in several areas of southwest England has been investigated. The results show a clear association of high radon levels with the uranium-enriched granite of the region, although this may simply reflect the high fracture permeability of the granite rather than its uranium enrichment with a strong influence of major fracture systems. With regard to radon as a potential health hazard, both source and transport pathways must be identified if high-risk areas are to be located. Surveys of radon in surface waters may provide a useful and speedy technique for the broad identification of such areas.
Methane studies for the Channel Tunnel
Authors: Warren C. D. , Birch G. P. , Bennett A. , Varley P. M.
Published: November 2007

The possibility of encountering dangerous gases during the construction of a tunnel, or in the completed works, needs to be addressed during the investigation and construction stages of a project. The presence of explosive or toxic gases is significant in relation to the health and safety of the workforce and the selection of appropriate plant and equipment to be employed. In recognition of this and the fact that the Channel Tunnel is underlain by coal bearing strata, a detailed desk study was commissioned to review the geological conditions, structure and history of the formations at and below the tunnel horizon. This included information from recent site investigations in the Channel and was supplemented by gas detection surveys conducted within the tunnel workings.
A low-cost dedicated multi-level groundwater sampling system
Authors: Bishop P. K. , Burston M. W. , Tong Chen  , Lerner D. N.
Published: November 2007

An important aspect of any detailed groundwater quality study is determining the vertical distribution of pollutants. This may be achieved by multi-level sampling from purpose designed boreholes. This study describes a relatively inexpensive system of dedicated sampling where gas-driven water samplers (incorporating vibrating wire piezometers) and unsaturated zone gas samplers are installed in conventional plastic water well casing. One important advantage of this system is that all functional units are housed within a protective screen, which offers both protection and improved potential for satisfactory backfilling. Experiments to determine the performance of gas-driven samplers when collecting water contaminated with chlorinated hydrocarbon solvents indicated that quantitatively accurate results are obtained using short lengths of nylon tubing. However, long lengths of nylon tubing introduced significant negative bias in solvent concentrations and it is recommended that a material with lower absorption properties be chosen to collect deep samples. The system was successfully installed on a contaminated industrial site. Significant variations in solvent pollution profiles together with a substantial vertical hydraulic gradient were defined and such hydrochemical and hydraulic information may be simply collected on a routine basis. Such data could not easily be gained from open boreholes, indicating the potential of the dedicated system in groundwater quality investigations.
Defining the catchment of a borehole in an unconsolidated valley aquifer with limited data
Authors: Lerner D. N. , Kumar P. B.
Published: November 2007

Borehole catchments need to be defined for groundwater protection in general and for the control of nitrates in particular. There are rarely enough data to make an accurate definition. The catchment of a borehole which draws from the glacial infill aquifer in a Shropshire valley has been studied, with emphasis on how sensitive the catchment is to variations in hydrological and hydrogeological parameters. The amount and distribution of recharge are the most important controls on the catchment. In this example, 250f the borehole abstraction is derived from valley side recharge, that is runoff from the valley sides which recharges the margins of the aquifer. Thus part of the catchment lies off the aquifer. Despite the limited data available, a zone which probably accounts for about 650f the borehole's abstraction can be defined, which would be sufficient to justify a nitrate control scheme. The complete catchment cannot be accurately defined however and the area covered by the possible range of catchment boundaries is 25% larger than the ‘best’ estimate. Additional field data would be needed to narrow this range significantly.
Assessment of the potential for tectonic fault rupture for high-level nuclear waste repositories
Authors: Swan F. H. , Stepp J. Carl , McGuire Robin K.
Published: November 2007

Active faults that extend to near the Earth's surface may pose a direct threat to the safety of engineered structures. Usually the threat can be mitigated by taking appropriate siting or design actions. Such actions require a thorough understanding of the characteristics and magnitude of the faulting hazard based on detailed field investigations of the site locality and an adequate assessment of the characteristics of past faulting in the site's tectonic regime. An active fault may be defined in purely geological terms as one that has exhibited displacement in the present tectonic regime. However, for engineering considerations an active fault is usually defined in terms of a specified time of most recent movement, or a longer time in which multiple movements have taken place. Deterministic or probabilistic approaches are used to assess faulting hazard for the purpose of engineering design consideration. Support is building for the use of probabilistic procedures alone or combined with deterministic procedures to assess faulting hazard for design of critical facilities.
Flow heterogeneity in a fractured rock: a case study from the Stripa Project
Authors: Holmes D. C.
Published: November 2007

Part of the on-going research effort of the international Stripa Project, based at the Stripa Mine in Sweden, involves a site characterization and validation programme (SCV). This comprises investigation of a block of fractured crystalline rock some 250 × 250 × 100 m in extent penetrated by 12 angled boreholes drilled from tunnels in the mine. The SCV is intended to represent the type of investigation which might occur at a repository site during construction to identify significant flow pathways through the rock mass as well as volumes of ‘good rock’. A staged approach of investigation has been employed in which periods of measurement have alternated with periods of conceptual and mathematical modelling. Predictions have been checked by additional measurements. A variety of single borehole geophysical (radar and seismic), geological mapping, geochemical and hydrogeological (a novel focused packer system) techniques have been employed in the early stages to construct a conceptual model of fracture flow within the rock mass. Mathematical models, based on a fracture-network approach, have been constructed from these data and used to predict fluid flux into the purpose-built boreholes and tunnels. The measured flows, together with transmissivity distribution information derived from inter-borehole hydraulic interference testing, were compared with the predictions and showed good agreement, building confidence in this approach. New models of flux and transport have been developed which incorporate the additional measurements.
An innovative use of groundwater sampling equipment to determine aquifer characteristics in Precambrian basement rocks of Uganda
Authors: Charlesworth D. L. , Howard K. W. F. , Nadon R.
Published: November 2007

Introduction

In many hydrogeological investigations, particularly those involving crystalline basement aquifers in Third World countries, it has not been possible to obtain good data on the aquifer characteristics. This shortcoming arises from a variety of reasons, including the lack of funds to carry out large-scale pumping tests, the lack of suitable boreholes for test pumping and the local lack of availability of appropriate testing equipment.

In a recent study carried out in southwestern Uganda, the Waterra inertial pump, originally designed as a low-cost dedicated sampling device for ground-water monitoring holes, was effectively used in conjunction with pneumatic packers to obtain hydraulic conductivity profiles in both new and existing boreholes.

The work was carried out as part of a research project funded by the International Development Research Centre (IDRC) of Canada and primarily utilized boreholes being drilled as part of a UNICEF/ Government of Uganda rural water supply project.

Background

In 1980, UNICEF and the Government of Uganda undertook an ambitious programme of borehole drilling in rural areas of the country. Using downhole hammer rigs, 115 mm diameter boreholes were drilled through the regolith and into the unweathered Precambrian basement rocks. The regolith was then cased off and the borehole continued to a depth, sometimes in excess of 100 metres, where the drillers thought that a yield of at least 5 l/min would be obtained. Once the drilling was completed the yield was estimated by airlifting and, if adequate, a locally manufactured version of the India Mk II handpump was installed in
The essentials of shallow reflection data processing
Authors: Davies K. J. , King R. F.
Published: November 2007

The aims of processing shallow reflection data are no different from those established for petroleum seismology and the well known methods of this field can on the whole be adopted for high-resolution surveys. The need for rapid and economical processing is being met by the appearance of a range of PC-based packages and results can be obtained from initial data of reasonable quality which are comparable with those normal on the larger scale. This paper surveys the conventional seismic reflection processing sequence and points to some of the particular problems that can arise when it is applied to shallow data.
Surface and hole-to-surface seismic reflection profiles in shallow Coal Measures
Authors: Kragh J. E. , Goulty N. R. , Brabham P. J.
Published: November 2007

Exploration of coal reserves at depths suitable for opencast mining in the UK may benefit from geophysical surveying techniques which can provide information on faulting and the location of old mineworkings. Shallow seismic reflection surveys have been found to be of very limited value for this application, mainly because the nature of the near-surface geology causes the reflection records to be swamped by reverberant refracted arrivals, and commonly groundroll also. Reflections have been observed on such data from interfaces below 100m, typically the maximum depth of interest for opencast mining, but it is doubtful whether such data can be of economic benefit. The technique of hole-to-surface seismic reflection surveys, making use of the boreholes drilled routinely in opencast coal exploration, clearly has much greater potential. Sections have been obtained along two lines of boreholes and show strong reflections from the thicker coal seams in the depth range 30–100m, allowing faults to be clearly imaged.
Abrasivity of Hawkesbury Sandstone (Sydney, Australia) in relation to rock dredging
Authors: Verhoef Peter N. W.
Published: November 2007

During rock cutter dredging for the trench for the Sydney Harbour Tunnel, partially cut in rock of the Hawkesbury Sandstone, tool consumption data were obtained and compared with the wear value
F
developed by Schimazek, and with the cutting and abrasive wear rates as determined by the Newcastle-upon-Tyne cuttability tests. It appears that while the
F
-values correlate well with actual tool consumption, correlations with laboratory cutting and abrasion tests are not always significant.

The
F
-value is obtained from a number of easily measured rock parameters (Brazilian tensile strength, mineralogical composition and grain size.) Use of the
F
-value is considered advantageous compared to laboratory tests which measure the abrasivity of rock directly because it is difficult to perform sufficient abrasivity tests to cover the variability inherent in a rock mass and it is impossible to perform laboratory tests that are truly representative of the actual cutting and abrasion mechanisms operating. Site investigations for rock dredging projects would be improved if systematic determinations of the
F
-values were carried out. This would help to improve the ‘educated guesses’ of tool consumption currently practised during the tendering stages of a dredging project. Accurate prediction, however, will always necessitate a trial dredge excavation to calibrate and to check the appropriateness of the abrasivity parameters chosen.
Acidisation: borehole development and rehabilitation
Authors: Banks D. , Cosgrove T. , Harker D. , Howsam P. , Thatcher J. P.
Published: November 2007

Acidisation is a technique used to improve the performance of boreholes. It is used in the post-construction development of limestone-chalk boreholes and in the post-operation rehabilitation of boreholes clogged by incrustations. The technique has been used widely, but not always with a full appreciation of the processes involved. Acidisation procedures should be designed according to the required effects (e.g. slurry removal, deep penetration of fissures, incrustation removal etc.).

Laboratory studies and test-pumping indicate that the dominant effect of acidisation in newly-drilled Chalk boreholes is to remove drilling slurry, resulting in improvements in both the B, and especially the C, coefficients in the equation

s
=
BQ
+
CQ
2

Caliper logging demonstrates that the greatest effects of acidisation are concentrated in the vicinity of the point of injection, hence acid should be injected in the vicinity of major yielding horizons where known. For a typical public-supply borehole in Chalk, it is believed that the current practice of injecting up to 20 tonnes of concentrated acid is excessive and between a quarter and a half of that amount would probably suffice in many cases. Equivalent molar quantities of dilute acid should be equally satisfactory if ease of handling is advantageous.
Mining-induced earthquakes monitored during pit closure in the Midlothian Coalfield
Authors: Redmayne D. W. , Richards J. A. , Wild P. W.
Published: November 2007

The British Geological Survey installed a seismometer network to monitor earthquakes around Rosslyn Chapel in the Midlothian Coalfield from November 1987 until January 1990. Accurate locations were obtained for 247 events and a close spatial and temporal association with concurrent coal mining, with a rapid decay of earthquake activity following pit closure, was demonstrated, indicating a mining-induced cause. Residual stress from past mining appears to have been an important factor in generating seismicity, and observations indicate that limiting the width of the workings or rate of extraction may significantly reduce or eliminate mining-induced earthquake activity, an extremely desirable prospect which warrants further investigation. A frequency-magnitude analysis indicates a relatively high abundance of small events in this coalfield area. The maximum magnitude of a mining-induced earthquake likely to have been experienced during the life of the coalfield (maximum credible magnitude) was 3.0 M
L
, although an extreme event (maximum possible magnitude) as large as 3.4 M
L
was remotely possible. Significant seismic amplification was observed at Rosslyn Chapel, which is founded on sand and gravel, compared with a nearby bedrock site. As a consequence, relatively small magnitude events caused high, and occasionally damaging, seismic intensities at the chapel. This is likely to be an important effect at similar sites elsewhere.
Modelling the impact of dewatering in the Lower Greensand aquifer, Surrey
Authors: Dottridge J. , Keeble M. R.
Published: November 2007

ARC (Southern) intend to extend and deepen working from two quarries in the Folkestone Formation, near Reigate in Surrey, UK. During the planning process, credible forecasts of the impact of future dewatering strategies are required to reassure the concerns of the Environment Agency, environmentalists and local water users. A hydrogeological and modelling study was carried out to investigate the present groundwater flow in the Lower Greensand aquifer, and to forecast the future pumping rates required to maintain dry excavations, the impact of further dewatering on groundwater levels and quality, and water levels after the end of quarrying. At the site, the Folkestone Formation consists of two discrete sand horizons, separated hydraulically by a clay layer, which supports head differences of 10 m near the quarries. Apart from ARC's recent monitoring of flows and water levels, very limited information on the aquifer was available, but the problem was minimized by careful calibration of the model for the three years with the most data. The results were used to modify working plans to minimize the impact on the surrounding aquifer and to support ARC's application for planning permission to extend the quarries.
Small strain deformation characteristics of two chalks subjected to varying stress conditions
Authors: Talesnick M. L. , Brafman M.
Published: November 2007

The paper presents an attempt to consider the small strain characteristics of two high-porosity chalks from the northern Negev desert in Israel. Special attention was given to anisotropy, nonlinearity and stress regime; compression or tension. A theoretical and experimental framework for considering these aspects is presented and employed. The experimental programme included testing of air-dried hollow cylinder specimens under conditions of uniaxial compression, radial compression and radial tension.

Results of the laboratory testing indicate that the chalks tested display a high degree of anisotropy in the modulus of deformation measured parallel and perpendicular to the direction of sedimentation. The stiffness of the chalks was found to be significantly higher perpendicular to the direction of sedimentation, despite the apparent massive uniform appearance of the intact rock. The chalks displayed significant non-linear stress-strain behaviour, with a strong tendency for the stiffness to decrease as deviator stress is increased. The ratio between material stiffness when subjected to compressive deviatoric stresses in comparison to tensile deviatoric stress was found to be very close to unity.
The effect of large particles on acceptability determination for earthworks compaction
Authors: Winter M. G. , Hólmgeirsdóttir Th. , Suhardi
Published: November 2007

Test procedures for determining the acceptability of fills for earthworks compaction require the removal of particles larger than a predetermined maximum size prior to test. In particular, the use of the Moisture Condition Apparatus requires that stones, defined as particles larger than 20 mm, are removed from the test sample. Many tills contain a significant proportion of such stones. Consequently, the relevance of the results of tests carried out on the remaining, or matrix, material can be questioned. An extensive laboratory test programme has been carried out to determine the effect of oversize particles on the compaction behaviour of soils. The results indicate that the transition from behaviour determined by the matrix to behaviour determined by the stones occurs at approximately 45% to 50tone content. Below this stone content, conventional techniques may be used for determining acceptability for earthworks compaction. However, if the behaviour is determined by the stones, then a series of alternative approaches are recommended for use depending on the nature of the soil and the type of compaction control specified.
The hydraulic conductivity of Singapore Marine Clay at Changi
Authors: Win Bo Myint , Arulrajah A. , Choa V.
Published: November 2007

The hydraulic conductivity of Singapore Marine Clay at Changi was studied by both
in situ
and laboratory methods.
In situ
tests, such as the Cone Penetration Test (CPT), Dilatometer Test (DMT), Self-boring Pressuremeter Test (SBPT) and BAT permeameter test were carried out. Rowe Cells and oedometers were used to determine the horizontal hydraulic conductivity and vertical hydraulic conductivity respectively. Hydraulic conductivity values were found to range between 10
-10
m/s and 10
-9
m/s. Hydraulic conductivity values in the horizontal direction measured from laboratory Rowe Cell tests were found to be about twice the vertical hydraulic conductivity from oedometer tests. Horizontal hydraulic conductivity values measured from Rowe Cell tests were also higher than those measured from BAT and SBPT but about the same order as values obtained from CPTU and DMT. Most hydraulic conductivity values evaluated indirectly from
in situ
dissipation tests were higher than direct measured values from BAT permeameter tests. DMT and CPTU gave the highest horizontal hydraulic conductivity values and SBPT yielded values in between. However CPTU, DMT and SBPT dissipation tests were found to be suitable alternative methods for estimating the hydraulic conductivity of clay. The variation of vertical hydraulic conductivity was characterized by the relationship between void ratio and hydraulic conductivity change index which, based on oedometer results, is only C
kv
=0.3e
0
.
Characterization of freshly quarried and decayed Doulting limestone
Authors: Jones M. S. , Horbury A. , Thompson G. E.
Published: November 2007

Freshly quarried Doulting limestone of Jurassic age differs in terms of mineralogy and porosity compared to the decayed stone of Wells Cathedral, Somerset, UK. Stones from both localities contain allochems including ooids, peloids, extraclasts (reworked Carboniferous limestone) and bioclasts. Sparry calcite cement is present as twinned, syntaxial, overgrowths nucleated onto crinoid ossicles with high Fe content due to extensive burial cementation. The Fe content in specific phases determines the weathering stability of the rock on the building. The decayed stone shows the development of porosity which is parallel to the weathered surface, mobilization of Fe into a hard layer near the surface and incidences of high concentrations of SO
4
2-
, NO
3
-
and Cl
-
. Despite low concentrations of SO
2
present in the atmosphere at the time of the study, the extent of stone decay and composition of crustal deposits implies that SO
2
pollution may have been greater in the past, with stone currently affected by gypsum salts formed during earlier pollution episodes.
Prediction of potential vertical swell of expansive soils using a triaxial stress path cell
Authors: Al-Shamrani Mosleh A. , Al-Mhaidib Abdullah I.
Published: November 2007

Preconstruction treatment or the selection and design of a foundation system both rely on accurate estimates of the potential heave of the supporting expansive soil. The majority of volume change testing of expansive soils has been performed under one-dimensional loading conditions in the oedometer. However, due to differences between laboratory test constraints and field conditions, the amount of volume change measured in various oedometer testing methods may differ dramatically from heave observed in the field.

This paper presents the results of an experimental investigation in which the feasibility of using a stress path triaxial cell for evaluating the vertical swell of expansive soils under multi-dimensional loading conditions was examined. Several series of triaxial swell tests were conducted in which the influence of confinement on the predicted vertical swell was evaluated. The results of these tests were compared with the volume changes observed for samples tested under identical initial conditions in the oedometer. The applicability of the triaxial testing technique was further ascertained by predicting surface heaves observed in an instrumented field test. The triaxial swell tests provided reasonable estimates of the measured field heaves in comparison to the oedometer tests which yielded rather conservative predictions.
Focused packer testing using geophysical tomography and CCTV in a fissured aquifer
Authors: Brown David , Slater Lee D.
Published: November 2007

Double packer testing is a commonly used technique in hydrogeology for assessing vertical spatial variations of permeability in a borehole. In fractured rock systems, spatially continuous fractures are typically major transmissive features that control groundwater flow and solute transport. Efficient, cost-effective packer testing of fractured rock aquifers can be conducted by focusing the packer test on hydraulically conductive zones, defined using borehole geophysical techniques. The combined use of cross-borehole electrical imaging and borehole television (CCTV) as methods for focusing the packer test was applied to a limestone aquifer. CCTV identified features exposed in the borehole whereas Electrical Resistivity Tomography (ERT) revealed their spatial continuity and probable hydraulic significance. Whole borehole pumping tests were conducted to provide a check on the effectiveness of these methods as tools for guiding the packer test. Results from a set of boreholes in a fissured aquifer revealed the transmissivity estimates obtained from the whole borehole pumping test to be close to the sum of transmissivities obtained from focused packer testing of features identified using CCTV and ERT. The hydraulic properties of the aquifer were hence defined whilst avoiding intensive packer testing of the entire length of the boreholes.
Total catchment conditions in relation to the Lincolnshire Limestone in South Lincolnshire
Authors: Rushton K. R. , Tomlinson L. M.
Published: November 2007

Hydrogeological studies of the Lincolnshire Limestone aquifer in south Lincolnshire combined with the development of mathematical models were reported in the 1970s. However, these studies concentrated on the aquifer and did not consider the total catchment conditions of both the groundwater and surface water systems. Greater importance is now placed on understanding total stream and river flows and preparing models which can predict the change in flows due to different abstraction scenarios; this has required a complete review of ‘the catchment’ of the Lincolnshire Limestone and the associated models. This review has led to the development of improved methods of estimating the recharge due to runoff, identifying locations such as inliers of the Lincolnshire Limestone in the river valleys where runoff can enter the aquifer system, improving the representation of wild bores (uncapped overflowing artesian boreholes) and representing leakage through the overlying strata in the east of the study area. These developments now allow the simulation of total river flows, especially low flows. A novel type of diagram has been devised for representing inflows, outflows and changing flow conditions along the streams and rivers.
Numerical techniques in reservoir capacity evaluation
Authors: Sabtan Abdullah
Published: November 2007

Several methods exist for estimating reservoir capacity based on field surveys of reservoir bottom features and the sediment thickness. Recently, the grid method was proposed which reduces the cost by measuring only a few sediment cross sections on selected parts of the reservoir from which the water depths in the remainder can be estimated by interpolation. The objective of the research reported here is to enhance the performance of the grid method by utilizing three additional numerical techniques, namely the Newton and Lagrangian polynomials and the cubic spline. The proposed technique was verified by estimating the known volume of a model dam reservoir in the laboratory. The reservoir volume was successfully evaluated using these numerical methods. It was found that the maximum error using the Newton and Lagrangian methods was 10%, while the maximum error using the cubic spline was as high as 24% and so this method is clearly less applicable. Although the Newton and the Lagrangian methods yield similar results, the latter is preferred as it is easier to use.
Gas permeability changes of rocksalt subjected to thermo-mechanical stresses
Authors: Le Guen C. , Deveughele M. , Billiotte J. , Brulhet J.
Published: November 2007

Permeabilities lower than 10
-17
M
2
cannot be measured using classical methods. To overcome this problem, the pulse decay method may be applied. In this method the evolution of a pressure pulse applied on the upstream side of the sample at 1 = 0 is recorded. An apparatus has been constructed to measure ultra-low permeabilities of rocks under thermo-mechanical stresses; intrinsic permeabilities between 10
-15
and 10
-22
m
2
can be measured.

Several thermo-mechanical tests, including permeability determinations have been carried out on samples from saline lithofacies of the Bresse basin (France). The initial permeabilities are more representative of the condition of the test sample than of the undisturbed state of the formation. Nevertheless, the permeability changes observed during these tests seem to be directly connected to the nature and structure of the material sustains under changes of temperature and stress. During isotropic deformation tests, the response of permeability to pressure varies depending on the specific lithological characteristics of the samples. Deformation tests under deviatoric stress with constant confining pressure and temperature show that, for all the lithofacies, the permeability decreases continuously. This can be attributed to creep deformation of the halite.
Prediction of groundwater table lowering for lignite open-cast mining in a karstic terrain in western Macedonia, Greece
Authors: Kavvadas M. J. , Marinos P. G.
Published: November 2007

Planning for the development of new lignite mines in the Ptolemais basin in western Macedonia, Greece, required the investigation of the hydrogeological characteristics of the adjacent karstic aquifer, since open-cast exploitation involves extensive and sustained groundwater table lowering (up to 260 metres). Review and evaluation of existing hydrological- hydrogeological data, in conjunction with the results of recent measurements, shows that groundwater flow is to the southeast in a single highly transitive karstified marble aquifer. An analytical regional flow model based on the finite element method is developed and used to assess the feasibility of the required groundwater table lowering and its effects on the hydrological budget of lake Vegoritis, nine kilornetres from the mines and in hydraulic continuity with the karstic aquifer. Model predictions show that the required ground water table lowering is not economically feasible at present and that any sustained large-scale dewatering scheme will significantly increase lake losses within a period of one to two years. It is thus concluded that exploitation of the new lignite- bearing horizons should not reach the karstic marbles at the boundary of the basin, but a zone of the relatively impermeable alluvium should be left to act as a seal. This scheme should be combined with partial lowering of the groundwater table to relieve the hydrostatic pressures on the seal, thus increasing the margin of safety against piping and slope failure.
Editorial
Authors: Jones Glyn
Published: November 2007

The responses to the questionnaire sent in February 1993 to the members of the Geological Society covered far more than matters relating to the
QJEG
. No one who knows engineering geologists and hydrogeologists would have expected anything other than a general agreement to differ on many of their individual expectations. And so it proved. The number of hydrogeology papers, their standard, and speed and frequency of publication, all attracted comment, with many strong pleas for the separation of hydrogeology from engineering geology and its inclusion in a dedicated journal. This issue of a Supplement is to a large extent a direct outcome of some of those replies.

While it is not considered opportune at the present time to launch a separate journal, the Council of the Geological Society have agreed to fund one supplement in 1994 to be dedicated to hydrogeology, and a further two supplements in 1995. The members of the Editorial Board have been made fully aware of the concern of many hydrogeologists that publication of papers in their speciality might be restricted to a single annual supplement. We are assured, however, that hydrogeology papers will continue to be published in the
QJEG
so that none would suffer undue delay. Indeed, this approach might well radically speed up publication of papers, which in turn could encourage an increase in the number and quality of manuscript submissions. Ultimately, when sufficient numbers of suitable papers are being regularly received, a new journal might be considered, possibly with its own individual
A re-evaluation of well design procedures
Authors: Parsons S. B.
Published: November 2007

The development of appropriate design procedures for water wells is a subject that has evolved only slowly over the years. Guidelines quoted in most groundwater engineering textbooks are largely empirical and focus on the provision of reliable wells that produce the intended yield with as small a drawdown as possible. The principle of developing designs that minimize the overall cost of the well installation, including the cost of energy used in pumping, is not really addressed. A critical review is presented of established design procedures, and techniques that have been developed for quantifying the energy potentially lost within alternative well designs. Following this review, methods which are more physically realistic and reliable are identified to calculate the key energy loss components of screen upflow losses and partial penetration losses. This, in turn, leads to the development of a way of identifying the costs associated with pumping as a function of the design of the well (most notably the well screen length), which can be used to optimize well design. A comprehensive set of well design guidelines is thereby developed.
The groundwater hydrology of the Manga Grasslands, northeast Nigeria: importance to agricultural development strategy of the area
Authors: Carter R. C.
Published: November 2007

The Manga Grasslands of northern Nigeria/southern Niger form a unique landscape of dunefields and interdunal depressions (playas or oases) within the semi-arid southern Sahel. Little has been written previously about the hydrogeology of the region, despite the importance of water resources to the existing agricultural and evaporite mineral economy. The paper reports on preliminary investigations into the groundwater hydrology of the area and proposes a simple steady-state conceptual model of groundwater recharge and natural outflow. It is concluded that the development of pumped irrigation in the vicinity of the oases would be unwise in view of its likely short- and long-term effects on groundwater levels, and the consequent damage to the existing economy which would result.
Three-dimensional ground movements in the vicinity of a mining activated geological fault
Authors: Phillips K. A. S. , Hellewell E. G.
Published: November 2007

This paper investigates the circumstances and conditions that lead to the activation of a particular geological fault when longwall panel extraction occurs in the vicinity.

Three-dimensional ground movements were observed at survey stations located across a fault as these were being influenced by active mining. The development of ground movements is defined be recording the subsidence, strain and horizontal displacements of the survey stations. The measured ground movements are compared to the predicted
Subsidence Engineer's Handbook
and in-house Subsidence Prediction Program subsidence and strain profiles, and the visual damage evident along the testline. Conclusions are drawn which suggest that surface geology heavily influences the location and magnitude of sustained surface damage.
Analysis of residual subsidence movements in the UK coalfields
Authors: Yao X. L. , Reddish D. J.
Published: November 2007

The importance of residual subsidence in the study of ground movement due to mining is discussed and previous research results are briefly reviewed. On the basis of ten cases investigated within the UK coalfields, the difference between residual subsidence characteristics along longitudinal and transverse lines is studied. Particular attention is paid to the four key positions along the subsidence profile, i.e. the subsidence limit position, the half-subsidence position, the rib-side position and the central position. A case example associated with mining an inclined seam is investigated in detail, showing that different residual subsidence characteristics appear due to mining an inclined seam as opposed to a level seam. Additionally, a prediction model is presented and applied to determine the duration of residual subsidence. The model theoretically indicates the main factors controlling the period of residual subsidence. Finally, an empirical equation, based on data collected within the UK coalfields, for estimating the duration of residual subsidence is put forward with consideration of both depth and geological factors. This is believed to be an important tool for civil engineers to calculate the time span after which no precautions need be taken to protect surface buildings from further damage due to residual subsidence movements.
The influence of petrology and fabric on the engineering properties of concretionary laterite gravel aggregates
Authors: Akpokodje E. G. , Hudec P. P.
Published: November 2007

The probable field performance of concretionary gravel aggregates is difficult to predict in the tropics, mainly due to the lack of understanding of the factors that control their engineering properties. The mineralogy and fabric of commonly used laterite gravel aggregates in Nigeria were studied to assess their influence on the engineering properties. Thin- section studies revealed two characteristic features which greatly influence the physico-mechanical properties: (a) abundant voids and fissures of different sizes and (b) varying degree of iron oxide impregnation. The variations in these characteristics are due to differences in the degree of lateritization. Strong and well developed gravels and pisolites are composed of 65–95 0oethite/hematite and are dominated by small voids. Weak and immature laterite gravels contain much larger pores and greater amounts of quartz and kaolinite. The quartz grains show extensive cracking which futther reduces the mechanical strength of these laterite gravels. The void/fracture-dominated fabric of laterite gravel aggregates is mainly responsible for their unusually high absorption/porosity and relatively low strength. In some laterite gravels, the strength loss on wetting is mainly due to weak cementation and the presence of interstitial clays.
Effect of suction on the strength of rock
Authors: West Graham
Published: November 2007

Some existing experimental data on the uniaxial compressive strength of porous rocks have been re-examined in relation to the suction of the specimens. It is shown that from pF 0 to pF 5 the rock strength is little affected but from pF 5 to pF 7 the strength depends markedly on suction. It is suggested that at low moisture contents, suction contributes to rock strength in a similar way to its well known contribution to soil strength.
Editorial
Authors: West Graham
Published: November 2007

This part of the Quarterly Journal of Engineering Geology contains four long papers. That by James & Little describes the geotechnical properties of sabkha, a salt-flat material that engineering geologists in the Middle East are increasingly being called upon to deal with in the course of civil engineering, particularly in foundation construction. The two papers by MacGregor
et al
. and Pettifer & Fookes deal with rippability and excavatability of rock–matters that are of much practical concern to engineering geologists in both civil engineering and openpit mining. Finally we have the paper by Crimes
et al
. which describes the techniques used to assess aggregate resources in four areas of the UK; this should be of interest to all who are concerned with making the best use of a valuable resource, and reminds us that although it is now eighteen years since the Verney Committee reported on the demand for aggregates in the UK, the subject is still one that continues to occupy the attention of engineering geologists. This paper is illustrated by two satellite images (p 169), and it has been possible to reproduce these in colour to great effect because the authors" organisation has contributed to the cost. We would like to encourage the use of colour illustrations in the
QJEG
where these can be justified on scientific grounds, and the Staff Editor will be pleased to advise prospective authors as to the likely contribution required to the cost.

As I write this Editorial we seem to be experiencing a