bluuebunny/crossref_metadata_2025_split huggingface dataset:
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

Abstract
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

Abstract
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

Abstract

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

Abstract
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

Abstract

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

Abstract
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

Abstract
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

Abstract
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

Abstract

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

Abstract

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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract

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

Abstract
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.