bluuebunny/crossref_metadata_2025 huggingface dataset:
A method of reducing the cement content of two stabilized Niger delta soils
Authors: Akpokodje E. G.
Published: November 2007

Cement is an effective agent in stabilizing the fine grained Niger delta soils to provide base course material for roads. The amount of cement required to stabilize the clays/silty clays and the uniformly graded medium to fine sand can be reduced by as much as 50 0f the two soil types are mixed in equal proportions (1:1 ratio) before cement stabilization.
Problems in the recognition of seawater intrusion by chemical means: an example of apparent chemical equivalence
Authors: Tellam J. H. , Lloyd J. W.
Published: November 2007

The determination of the origin of saline groundwaters is sometimes crucial for the successful exploitation of an aquifer system. Although hydrochemical methods provide a direct approach to the problem, modification of intruding water can often give rise to interpretational difficulties. By means of a case history from the Permo-Triassic sandstone aquifer of the Widnes-Manchester area, the problems encountered are illustrated. The major ion chemistries of (a) saline waters originating from upconing of deep old saline water and (b) saline groundwaters resulting from recent intrusion are compared using computer modelling techniques with a third group of waters of unknown provenance. It is concluded that in some cases an apparent chemical equivalence, in which the same chemical product can arise through more than one set of processes, can occur; in such cases major ion analyses alone are not of use in determining groundwater origins. Explicit discussion of equivalence problems has rarely been undertaken in the hydrochemical literature, and the results presented have implications beyond saline intrusion studies.
Creating a geological database for planning tunnels under London
Authors: Rosenbaum M. S. , Warren C. D.
Published: November 2007

The creation in 1972 of a simple computer database for Greater London has enabled rapid assessment of geological conditions to be carried out. The use of the database for an appraisal of tunnelling conditions for potential underground road and rail routes is described. In terms of computer technology, the system described uses well established techniques but the ground investigation examples draw attention to the merits of employing database management and surface analysis software libraries.
Discussion on ‘Completely weathered granite—soil or rock?’ by M. D. Howat
Authors: Gamon T. I.
Published: November 2007

T. I. G
amon
writes: The ‘completely weathered granite’ studied by
Howat (1985)
represents a transitional stage in the weathering sequence between fresh granite and residual soil. It has been recommended that the term ‘completely’ be superseded by the term ‘extremely’ (
Dearman 1984
), as the weathering processs at this stage is far from complete. Continued weathering results in a collapse of the soil skeleton with a loss of microfabric and continued discolouration of the material to a characteristic dark reddish brown. It is likely that the finer textured material and the discoloration observed in the mass structure is the residual soil picking out relict discontinuities.

Whilst the depth of weathering can extend to 100 m, the depth of the interface between the rock and soil zones, the weathering front (
Mabbutt 1961
), is generally at a depth of 30 to 40 m in the Hong Kong Granite. Below the weathering front the visible signs of weathering are generally concentrated parallel to existing discontinuities. A typical weathering profile for the Hong Kong Granite is illustrated in (Fig. 1) (
Gamon & Finn 1984
).

To compare the data obtained from several different boreholes, in which the weathering front has been encountered at different depths, it is more useful to plot the data against depth ratio rather than depth. The depth ratio is defined as the ratio of depth of the SPT test or dry density determination to the depth of the weathering front.

The relationship between SPT ‘N value and depth ratio (Fig. 2) is
Stabilization of boulders at a hillslope site in Hong Kong
Authors: Grigg P. V. , Wong K. M.
Published: November 2007

In Hong Kong, there is a high incidence of surface boulders on hillside slopes. Recently attention has been focused on the neutralization of these boulders where they may affect downslope developments. A study to assess and stabilize a boulder field adjacent to one site is described and discussed. The study considered the mode of development of the boulder field, development of a boulder stabilization philosophy, undertaking of a ground survey, and design of the various stabilization measures.
A simple approach to the estimation of soil compaction parameters
Authors: Al-Khafaji A. N.
Published: November 2007

In this paper the role of Atterberg limits and clay content on parameters of soil compaction is examined. The effect of both Atterberg limits and clay content on Proctor maximum dry density and optimum moisture content are determined quantitatively. Using curve fitting techniques empirical equations are derived and charts are prepared.

From these charts it is possible to estimate the potential optimum moisture content and maximum dry density for standard Proctor compaction from the knowledge of both liquid limit and clay content and less accurately from the knowledge of liquid limit only. The chart shown in
Fig. 8
is used when only liquid limit is known and the chart in
Fig. 13
is used when both liquid limit and clay content are known.
The use of stochastic models in the assessment of a geological database
Authors: Rosenbaum M. S.
Published: November 2007

The most appropriate method of assessing ground investigation information will depend on the nature of the investigation and the character and quantity of data. There are significant advantages to collecting such data in a quantified form since computer-based databases can then be established, facilitating their rapid assessment. Methods of assessing an engineering geological database are described. Particular attention is paid to the use of stochastic models for analysis, which are applicable to data whose distribution can be described in terms of a random function.
Cause and significance of heave at Llandough Hospital, Cardiff—a case history of ground floor heave due to gypsum growth
Authors: Hawkins A. B. , Pinches G. M.
Published: November 2007

Inspection of some roof areas at Llandough Hospital, Cardiff indicated that the brick walls had moved outward at eaves level. A level survey of the ground floor showed approximately 60 mm of arching. The paper describes the structure, the site investigation to assess the cause of the damage and geochemical and microbiological tests on the black calcareous pyritic mudstones of the underlying Westbury Formation. The paper concludes that the heave was caused by volume change related to the growth of gypsum.
Migration of landfill gas and its control by grouting—a case history
Authors: Raybould J. G. , Anderson D. J.
Published: November 2007

Methane gas detected in and around properties in a residential area of St Helens could have originated from one of several sources: gas distribution mains, faulty sewers, shallow coal seams and a nearby landfill site. Investigations eliminated some of these, and a landfill source was eventually confirmed by radiocarbon dating. Drilling, together with the records of an abandoned opencast prospect, showed that the gas was migrating through ancient shallow coal workings, possibly reaching the surface via a fault zone. Temporary remedial works were carried out to ventilate the mine workings in the residential area. The permanent remedy consisted of grouting the workings along the boundary of the landfill site to prevent further lateral migration, together with on-site methane ventilation.
Computer analysis of lithostratigraphic data derived from geotechnical records
Authors: Day R. B. , Tucker E. V. , Wood L. A.
Published: November 2007

The database GEOSHARE is used to demonstrate some practical applications of a geotechnical database and illustrate the potential benefits of establishing a national computer database of site investigation records. GEOSHARE is an easy to use (menu driven) system in which data of only a purely factual nature is stored. The data storage system is designed to accommodate the complete range of site investigation records in forms that are merely transcripts of the originals. Flexible report and graphic display procedures are described. Three geological case studies are discussed to demonstrate the value of computer analysis of the stored data to the engineer.
Discussion on ‘Mire morphology and the properties and behaviour of some British and foreign peats’ by N. B. Hobbs
Authors: Burwash A. L. , Weisner W. R.
Published: November 2007

The writers would like to touch briefly on some recent North American development in peat classification and testing. In 1979, the American Society for Testing and Materials (ASTM), formed a sub-committee on peats and organic soils. Its mandate was to develop standards for geotechnical, energy and horticultural purposes. One of the committee's first tasks was to develop a method for distinguishing peats from other organic soils. Their conclusion was that an organic soil should not be called a peat unless its organic content was 75% or greater.

The next logical step in the process was to develop a geotechnical classification system for peats (as they are defined above). In 1984 the writers developed a simple system of descriptions and engineering correlations. To date several North American organizations have used the system and provided their comments. Comments from overseas are also welcome at any time. Steps in the descriptive process are determination of:

organic content

degree of humification by the Von Post method

basic fibre details.

No botanical knowledge is required to use the system. Simple descriptions such as black, amorphous peat (H
6
) or brown nonwoody fine fibrous peat (H
2
), result.

Although it is recognized that morphology is an important aspect of the engineering properties of peatlands, only certain aspects have been incorporated into a simplistic classification system. Based on our experience, only on rare occasions would an ecologist be consulted to examine a peat profile for engineering applications. It is agreed, however, that engineers need to acquire additional skills in
Road construction on soft and compressible soils
Authors: Evans N.
Published: November 2007

The aim of the meeting was to identify the problems and solutions of road construction on soft and compressible soils, to show where these soil types are likely to be encountered, and to describe some recent experience of road construction on these materials.
The use of the geotechnical database ‘Geoshare’ for site investigation data management
Authors: Raper J. F. , Wainwright D. E.
Published: November 2007

A geotechnical database called Geoshare has been developed at Queen Mary College to act as a comprehensive data management tool for site investigation data (Wood
et al.
1982). It is capable of storing and searching ‘free format’ geotechnical records, and is designed to handle all aspects of data management in a site investigation project, from the input of the records to the analysis of the retrieved information. The application of Geoshare to the reconstruction of a superficial deposit stratigraphy is demonstrated, showing the use of the retrieval facilities as applied to borehole data collected in the site investigation for a trunk road scheme in S. Wales. The problems of poor borehole/trial pit log descriptions are dicusssed in the light of the use of Geoshare, and a software compatible terminological format for log descriptions is suggested, adapted from an engineering based revision of British Standard 5930 (1981).
Cave dams of the Guanyan System, Guangxi, China
Authors: Smart P. L. , Waltham A. C.
Published: November 2007

With well over 1 million km
2
of carbonate rocks exposed at the surface, and a history of exploitation spanning in excess of 2000 years, the Chinese probably have more experience than any other people in developing the water resources of carbonate aquifers. Interestingly, many of the smaller scale projects are carried out by local farmers and co-operatives, with little recourse to the advice of professional engineers and hydrologists, although even in large regional schemes, much local expertise and labour is involved (see for example Hegtkcar 1976). While recently some of the Chinese work on karst hydrology has become available in the west (Song 1981; Song
et al
1983; Yuan 1981, ) much of the practical experience resulting from these local and small scale developments remains unpublished even in China. We were therefore very fortunate to be able to examine the engineering works associated with the Guanyan cave system, just south of Guilin, Guangxi Province, SE China, during a recent joint venture with the Institute of Karst Research, Ministry of Geology, Guilin.

The Guanyan (Crown Cave) system is developed in a sequence of relatively pure, predominantly finegrained limestones and dolomites over 2600 m thick, and ranging from Devonian to Carboniferous in age (Yuan 1980). These are folded into thrust faulted, NW-SE-trending folds, but dips are generally less than 30°. The underlying impermeable shales, siltstones and sandstones form a mountainous terrain rising to 1400 m above sea-level east of the limestone, and provide the headwaters for streams feeding into the caves (Fig.
The design of a high pressure and temperature oedometer
Authors: Rosenbaum M. S. , Clarke B. A.
Published: November 2007

The design is described of a high pressure and temperature oedometer capable of simulating the migration of waste fluids through argillaceous sediments. Innovatory features are the methods of controlling the pressure and flow rate of the pore fluids, the hardfacing of the piston and cylinder containing the specimen and the provision of dynamic sealing which is stable at elevated temperatures and pressures over long periods of time.
Pyritic shale heave in the Lower Lias at Barry, Glamorgan
Authors: Wilson E. J.
Published: November 2007

This brief technical note describes a case history of pyritic shale heave discovered in an old underfloor fill of quarry waste composed of Lower Lias shales, at Barry, Glamorgan.
Discussion on ‘Electrical conductivity and saline concentrations in arid land groundwaters’ by J. C. Doornkamp & H. A. M. Ibrahim
Authors: Walton N. R. G.
Published: November 2007

N. R. G. W
alton
writes: Doornkamp & Ibrahim's brief article, suggesting the use of simple electrical conductivity measurements instead of the more difficult and time-consuming chemical analyses for major troublesome anions such as chloride and sulphate, appears of interest to those in the engineering profession who would prefer a simple ‘EC-fix‘ type solution to salinity problems in both construction and irrigation engineering.

However, the article lacks fundamental credibility to groundwater scientists both in its presentation of obviously erroneous data and in its simplicity of approach to groundwater chemistry—a subject which the authors appear to discover for the first time when posing the key question for future research: ‘which environmental parameters control the specific relationships between electrical conductivity and the ionic concentrations of selected salts?’

Firstly, the axes of the graphs shown in Fig. 1 are obviously incorrectly labelled, since although middle-eastern groundwater is salty, it is not so salty as to be found on graphs from 0 to 200 000 micromhos/cm in stepsof 40 000! Dividing these figures by l00 would make them suitable for UK groundwaters, but middle-east ground water would fit better by dividing only by 10, giving an EC scale of 0 to 20 000 micromhos/cm.

The difficulty now comes in trying to sort out what has gone wrong with the anion axes, since these are also both patently absurd. Dividing the sulphate axis by 10 appears to give reasonable results, so that a Bahrain groundwater with EC = 10 000 would give SO
4
= 12 m
J. C. Doornkamp and Hani A. M. Ibrahim reply:
Authors: Doornkamp J. C. , Ibrahim Hani A. M.
Published: November 2007

J. C. D
oornkamp
and H
ani
A. M. I
brahim
reply: We are grateful to Mr Walton for his interest in our short communication, which we hoped would stimulate (rather than provoke) a debate on the gross differences shown up by our generalized representation of data from three parts of the Middle East. Mr Walton clearly agrees that local controls on actual values are both many and varied. It is of further interest that he too was able to use a linear relationship between EC and Cl, SO
4
, etc. in his work on Qatar.

We have re-examined the axes on the graphs shown in Fig. 1 and can only comment as follows. The EC axis is controlled, in the range shown, by the very high values recorded in Bahrain (see Doornkamp
et al.
1980 as quoted in our paper). The Egyptian data do not reach such extremes, though some high values from Sabkha areas are included. The units used on the graphs are controlled by the data for the Nile delta as received from the Egyptian Groundwater Research Institute. We have checked and the graphs are faithful to those data. We have also checked the conversions we used for the Bahrain and Port Said data and they still fit the graphs. Furthermore, if we check EC = 10 000 on the SO
4
graph then it conforms almost precisely to what Mr Walton wants, i.e. SO
4
= 12 m eq/1 (more easily checked as EC = 100 000 giving SO
4
= 120 m eq/1).
Groundwater abstraction—construction, operation and maintenance: an international overview
Authors: Stoner R. F. , Bakiewicz W.
Published: November 2007

The rapid expansion of groundwater abstraction over the last forty years is outlined and the reasons for the varying degrees of success of groundwater projects, both for irrigation and water supply, are reviewed, highlighting some of the problem areas. Despite the current pause in groundwater development, opportunities still exist for expansion, particularly in the fields of rural water supply, pollution control and water quality. Recent improvements and current practices in investigation techniques, drilling, design, materials and pumps are summarized. The changing nature of the work and the training of its practitioners are discussed, leading to the conclusion that one of the most positive improvements is better training and greater expertise in groundwater, throughout the world. This aspect is emphasized by the high standard of the numerous technical publications concerned with groundwater. A description of the interaction between the roles of engineers and geologists stresses the value of interdisciplinary cooperation and the sharing of responsibilities.
Slope instability in a profile of weathered norite
Authors: Dobie M. J. D.
Published: November 2007

On Christmas Day 1982, a combination of heavy rain and a broken water supply pipe resulted in significant mass movement on a hillside in the Bukit Gombak area of Singapore. Subsequent investigations revealed a sliding mass of about 50000 m
3
, approximately 100 m from crest to toe in plan with a height of 22 m. Average slope angle was about 12°. Ground conditions consisted of fill overlying residual soil derived from the underlying norite bedrock. This resulted in a situation where heavy rainfall caused rapid rises in ground water levels followed by very slow dissipation. Mass movements occurred when water levels in the slope rose above a certain value. From observations and local knowledge of the area, it was concluded that the mass movements had been taking place over many years previously and were still continuing. The geometry of the actual failure surface was not established, however analyses of a number of possible slip surfaces indicated an average ø’ of less than 18°. Two ring shear tests on samples of residual soil from the slope gave values of ø
r
’ a little below 15°. Thus, although the data measured are limited, these results suggest that the stability of the slope was controlled by residual strength. Furthermore, the case history demonstrates how permeability distribution within a slope can have a major influence on its stability.
Soil properties and pavement performance in the Niger Delta
Authors: Arumala J. O. , Akpokodje E. G.
Published: November 2007

The pavement conditions of roads in the Niger Delta and the geotechnical properties of the soil materials used in constructing them were studied in an attempt to find permanent solutions to the recurrent widespread pavement failures in the region. The most severe surface deformations, pavement cracking and failures occur in the seasonally flooded fresh/salt water swamps because of the high water table, poor drainage and the very fine-grained (> 70 0.000000ines) silty clays/clays used. It is suggested that a pavement design consisting of well compacted, subgrade/sub-base, cement stabilized base course, paved shoulders and good drainage would ensure good performance and avoid the expensive haulage of better base materials from long distances.
The application of shape descriptor analysis to the study of aggregate wear
Authors: Latham J.-P. , Poole A. B.
Published: November 2007

Two identical samples of fresh rock aggregate have been artificially abraded in two rotating mills. Two subsamples consisting of 16 pieces from each mill were traced throughout 90 h of gentle abrasion and were examined at various stages. The examination used a video camera to capture data from outlines of silhouettes of the 16 pieces. Maximum projections were analysed using Fourier and Fractal methods to produce shape descriptor values which monitored shape, texture and roughness at different stages of the abrasion process. Full accounts of the methods employed are reported. Random projections were analysed in less detail. Reproducibility of the textural descriptors between the two subsamples is good when examined by maximum and by random projections, the latter method showing more scatter.

The objectivity and speed of these methods of shape quantification have already been exploited in other disciplines, but this study appears to be the first time they have been used to assess the performance of aggregates and more specifically, armourstone used in coastal protection works. The results are discussed in this context.
Civil engineering difficulties in the karst of China
Authors: Waltham A. C. , Smart P. L.
Published: November 2007

Karst landscapes, developed by solutional erosion of massive limestones, are characterized by underground drainage and the development of closed depressions. In tropical areas, with high solution rates, long uninterrupted periods of erosion and a lack of glacial planation, the expansion and deepening of these closed depressions creates a rugged relief dominated by either conical hills or steeper-sided towers. The form of the cones and towers is a function of both the carbonate lithology and the erosional history; the towers develop only in massive, mechanically strong, compact limestones where erosional planation and tectonic uplift have kept pace over a long period of time (
Smart et al 1986
).

These karst landscapes are characteristic of huge areas of southern China, largely in the provinces of Guangxi and Guizhou (Fig. 1) and the spectacular scenery of the limestone has often been represented in classical Chinese painting. They are now also becoming a major tourist attraction, with Guilin, in Guangxi, frequently visited by Westerners. These terrains do, however, pose serious difficulties to the civil engineer.

Where relief is not great, or where rates of uplift have been low, corridors of flatter ground have often been created by lateral planation at the water table. These corridors may be lithologically or structurally controlled, and form obvious routes through the karst.

Where the relief is higher and the regional water table is not intersected, coalescence of the depressions to form flatter ground is rare, and road and rail development is more problematic. In order to avoid excessive and
Limestone weathering: its engineering significance and a proposed classification scheme
Authors: Fookes P. G. , Hawkins A. B.
Published: November 2007

As a foundation material, limestone differs from other rocks in that voids may be found at almost any depth within the rock mass. They may result directly from solution weathering near the surface and along discontinuities, or as specific cave systems at depths related to present or past ground water levels.

The paper reviews the processes involved in the weathering by solution of the crystalline limestones, typically of Palaeozoic age. It offers a tentative, simple engineering classification of the solution features characteristic of limestones; and presents case histories to illustrate some of the problems which may be encountered during construction in areas of limestone bedrock.
Rock weathering in engineering time
Authors: Fookes P. G. , Gourley C. S. , Ohikere C.
Published: November 2007

The paper attempts a comprehensive review of
in situ
weathering of rock used in civil engineering construction. It also presents some new data on weathered rock from Britain which have been used to develop a proposed tentative Rock Durability Indicator scheme. This is based on simple engineering tests to help assess the potential performance of the rock in service.

It is concluded that weathering in geological time can have significant influence, under certain circumstances, on the durability of aggregate or stone in-service. Durability is defined as the rock material's ability to resist degradation during its working life and is considered to be dependent on a number of parameters; viz. the original stage of weathering of the rock mass; the degree of imposed stressing during winning, production, placing and service; the climatic; topographical and hydrological environments in-service.

The production and construction procedures can have an important influence on the mechanical strength of the material. Physical weathering processes and imposed loading generally have the most significant effect on deterioration but chemical weathering could be of significance in-service, especially in hot, wet climates.

No one engineering test can be used as an absolute predictor of performance. Combinations of common mechanical and physical tests such as water absorption, specific gravity, point load strength, modified AIV and magnesium sulphate soundness can be used in various combinations to help assess potential durability. For a more complete evaluation, environmental factors such as the climate, topography and hydrological regimes need to be taken into account.
Coal Measures mudrocks: composition, classification and weathering processes
Authors: Taylor R. K.
Published: November 2007

British Coal Measures mudrocks are dominantly non-marine, mature sediments with a high average clay minerals content of over 75%. A geological classification based on quartz content does not differentiate the dominant durable mudrocks from the non-durable types and overconsolidated clays in the formation. A uniaxial compressive strength greater than 3.6MN/m
2
with a three cycle slake durability value of over 60% is suggested as an appropriate division between durable and non-durable mudrocks of this age. Physical breakdown, which acts as a control on chemical weathering triggered by pyrite oxidation, is considered to be governed by incidence of sedimentary structures, slaking and expandable mixed-layer clay content.

Shear strength reduction during post-glacial weathering can be significant. A tentative fully weathered effective stress peak strength for the weakest mudrocks and clays is deduced to be φ′ = 22°(
c
′ = 0). Colliery tip investigations indicate that chemical weathering effects on the shear strength of the mudrocks are small. A diagenetic rank factor applies both to peak shear strength and slake durability of mudrocks excavated from UK coal mines.
Rock mass discontinuities in theory, practice and reality
Authors: Cripps J. C.
Published: November 2007

The meeting was opened by Dr. R. K. Taylor, Chairman of the Engineering Group.

J. A. Hudson
(Imperial College, London) pointed out in a paper on ‘Discontinuities and excavation design in rock engineering’ that early studies of rock behaviour had centred on intact rock. He went on to outline the information about discontinuities in terms of orientation, frequency and persistence which are required for the design of excavations and associated rock support systems.

The reaction of rock mass to applied stress and the transmission of stress and water through rock masses are modified by the presence of discontinuities. For a particular rock mass, provided sufficient is known about the properties of both the rock itself and the discontinuities, the deformability, permeability, joint frequency and orientation,
in situ
stress and strength can all be estimated theoretically. However, since deriving solutions for real rock masses is a very complex operation, rock engineering tends to be a mixture of theory and empiricism. This may be adequate for situations for which there are accepted practices, but when dealing with new applications, for example radioactive waste disposal or geothermal energy exploitation, design must be based on a clear understanding of fundamental rock mass principles.

It is important to appreciate that engineering work may have the effect of changing the behaviour of the rock mass and although some aspects have received a great deal of attention there has been little work done on others, for instance the relationship between water flow and weathering; an important factor
Faults near Hinkley Point Nuclear Power Station
Authors: Skipp B. O.
Published: November 2007

The Central Electricity Generating Board are seeking licence and planning approval to build a Pressurized Water Reactor just to the west of the existing Advanced Gas-Cooled Reactor at Hinkley Point, Somerset. As part of a seismic hazard evaluation both regional and local geology have had to be studied in detail.

The site is located in a complex structural setting at the eastern end of the North Somerset coastal fault belt. Detailed field mapping was carried out on the foreshore from just east of Hinkley Point to just west of Watchet with the purpose of identifying structural style, sequence of faulting and approximate age of the last movement. When assessing the seismotectonics of the region it was necessary to study the degree of middle and late stage Tertiary inversion prominent in southern England, less evident in the immediate vicinity of Hinkley Point.

Of especial interest is the north-west-south-east trending Watchet-Cothelstone-Hatch Fault and its relationship to the east-west trending faults passing close to Hinkley Point.

The Watchet Fault truncates the main east-west trending faults in the foreshore inducing a marked drag towards the fault plane, thus this phase of movement on the north-west trending fault is younger than the generally vertical displacements associated with the east-west trending faults. Examination of gypsum slickensides shows that the influence of the later movement of the north-west trending fault on reactivation of the east-west trending faults, did not extend beyond 350 m east from the main fault plane.

The fault plane of the Watchet Fault is
The use of Portland Stone rock armour in coastal protection and sea defence works
Authors: Clark A. R.
Published: November 2007

The Portlandian sequence comprises a variety of lithologies. some of which have traditionally been used as building stones since Roman times. The geology and engineering properties of the Portlandian building stones are presented and compared with the published acceptance limits for use of rock armour in marine works. A review of the historical use and performance of Portland rock in nineteenth century breakwaters in Dorset indicates that the rock performs adequately. Details are given of the selection and use of rock armour from the Isle of Portland in recent coast protection and sea defence works and details of the rock performance are presented.
Aspects of geotextile-wrapped well screen design—an experimental investigation
Authors: Kennedy R. A. , Lloyd J. W. , Howley J. A.
Published: November 2007

Geotextile screens are increasingly being used as a wrapping on a base pipe for the screening of fine aquifer materials. This is due to the ease with which they may be installed and specified. They are a relatively recent development and the hydraulic efficiency associated with their use as abstraction screens has not yet been quantified.

In this study, the efficiency has been tested using a physical well model and a variety of commercially available textiles. The purpose of the programme was to compare the hydraulic efficiency of various geotextile fabrics screening differing aquifer materials. In addition the requirements of the open area of the casing of the screens were also examined. The results of the tests indicate that geotextiles must be matched to aquifer material on the basis of hydraulic efficiency. It is clear that the presence of aquifer particles reduces the permeability of any screen and this is also true in the case of geotextile-wrapped screens. The extent of this reduction varies between geotextiles and appears to be a function of their structure. On the basis of the test results, recommendations may be made for geotextile selection. Geotextile screens appear to be particularly suited to the screening of fine unconsolidated aquifers if the correct fabric is selected. Losses incurred from the screening of other coarser aquifers also appear to be negligible. Too conservative a filter criterion may result in unnecessary well losses. The open area of casing used as part of geotextile screens installed in fine sands may be as low as 300025; without incurring significant losses.
The location of aquifers in crystalline rocks and alluvium in Northern Nigeria using combined electromagnetic and resistivity techniques
Authors: Hazell J. R. T. , Cratchley C. R. , Preston A. M.
Published: November 2007

The tenfold increase in borehole siting in Northern Nigeria during the last few years has resulted in an increase in the use of electromagnetic (EM) methods and a corresponding decrease in the more traditional but less cost effective resistivity methods. The role of geophysics in exploration is optimally in combination with direct geological observation. Two types of aquifer which are amenable to geophysical investigation in the Nigerian environment are weathered, jointed crystalline rocks and alluvium.

Location of joints and associated narrow zones of deep weathering in crystalline terrain is best achieved by EM techniques with resistivity backup where needed. Resistivity alone does not always reveal such features. Location of shallow aquifers in alluvium is amenable to a combination of EM and resistivity techniques. However, the complexities of alluvial and underlying Quaternary sedimentation necessitate extensive computer modelling of both sets of data in order to optimize the field techniques and interpretation methods. In particular the use of selected combinations of intercoil spacings to estimate maximum thicknesses of aquifers shows some promise.
Changing storage beneath a stationary water table—an anomaly of certain humified peats
Authors: Brown J. M. B. , Ingram H. A. P.
Published: November 2007

Abstract

Previously published seepage tube test results for well-humified peats at Dun Moss showed anomalous water transmission properties only partially explained by non-Darcian behaviour found in permeameter tests. In a new suite of seepage tube recovery tests it was found that the shape of the recovery curve varied with the time taken to establish the initial displacement. This variation, which is not associated with any movement of the water table, suggests that these peats possess a pressure-sensitive storage property consistent with the elastic behaviour of a wide range of aquifer materials of current interest to hydrogeologists. This interpretation is supported by comparison with the hydrogeological ‘slug test’ and by results from a special ‘re-fill’ variant of a recovery slug test. In these tests the water level was observed to decline spontaneously while below the equilibrium level, an effect explicable only by exchanges to storage.
Some geological and engineering characteristics of lodgement tills from the Vale of St Albans, Hertfordshire
Authors: Little J. A. , Atkinson J. H.
Published: November 2007

This paper gives the results of mineralogical and engineering classification tests and one-dimensional consolidation and swelling tests on undisturbed and reconstituted samples of a number of different lodgement tills from the Vale of St Albans in Hertfordshire. These tills are presumed to be of Anglian age and mark the approximate southernmost Quaternary ice advance in the area. They are interbedded with fluvioglacial sands and gravels which were deposited on the proglacial fringe of a retreating ice mass, and other sands and gravels which are associated with a former course of the Thames in the Vale. In mineralogical tests the tills were found to contain crystalline calcite; this could lead to cementing in undisturbed samples which would be broken down during preparation of reconstituted samples.

The results of oedometer tests show little evidence of compression or consolidation anisotropy in clast fabric orientated, undisturbed samples. Differences in the compression and swelling characteristics of undisturbed and reconstituted samples attributable to calcite cementing were observed, particularly at the lowest consolidation pressures during initial loading. Differences in permeability between the undisturbed and reconstituted samples were also found to be greatest at the lowest consolidation pressures during initial loading. Examination of the swelling characteristics revealed a marked threshold effect shown by significant variations in the swelling index associated with changes from loading to unloading and from swelling to reloading.
Seismic refraction profiling of rockhead in the Coal Measures of northern England
Authors: Brabham P. J. , Goulty N. R.
Published: November 2007

The seismic refraction method using compressional waves has been used in site investigation for many years to locate rockhead. Results from several surveys in northern England, where Quaternary glacial drift overlies Coal Measures, show that shear waves exhibit a large positive contrast in seismic velocity between overburden and bedrock, whereas the ranges of seismic velocity of compressional waves in overburden and bedrock are not clearly separated. Consequently, shear wave velocity is a more reliable indicator of lithology, and seismic refraction profiling using shear waves may be a better technique for estimating the depth of rockhead.

Unusually low compressional wave velocities have been measured over abandoned mine workings. If this is a subsidence effect, it may prove useful for locating old mine workings.
The investigation of toppling slope failures in welded ash flow tuff at Glennies Creek Dam, New South Wales
Authors: Woodward R. C.
Published: November 2007

The Glennies Creek Dam spillway was designed as an unlined rock cutting in welded tuff 700 m long with a bedwidth of 37 m, a maximum cut height of 40 m and right-and left-hand side slopes of 3 in 1 and 2 in 1, respectively. Toppling failures in the 3 in 1 right-hand spillway batter occurred during construction. In order to maintain rockfill production, that part of the right-hand batter affected by the failures was battered back from 3 in 1 to a slope of 1 in 1; involving 33 000 m
3
of additional excavation.

Geological investigations concluded that toppling became possible due to the removal of the column toe support due to plane sliding movements on joints dipping towards the cut at 24°. These sliding movements were caused by immediately adjacent heavy quarry blasting which reduced the available joint friction angle from the peak value of 38° to the residual value of 25°. An essential step in the analysis of slope stability is the identification of slopes susceptible to toppling. The application of standard methods of toppling analysis to slopes which are not susceptible to toppling even though it may be kinematically possible will result in unnecessarily conservative slope designs.
Characteristics of the Permian and Triassic aquifers of south-west Scotland
Authors: Robins N. S. , Buckley D. K.
Published: November 2007

Strata from the Permian and Triassic supergroups form a series of deep sedimentary basins and associated outliers in south-west Scotland. The strata are mostly water-bearing and form valuable local aquifers which are exploited for public and private supply. Secondary permeability provided by joint surfaces, bedding planes and other features is an important component of most of the aquifers. However the development is not universal; at some sites the intergranular permeability is dominant and at others both secondary permeability and intergranular permeability are lacking. Geophysical borehole logging is used to examine the secondary permeability.
Shear strength and consolidation characteristics of Obhor sabkha, Saudi Arabia
Authors: Hossain D. , Ali K. M.
Published: November 2007

The shear strength and consolidation characteristics of the subsoil of Obhor sabkha (north of Jeddah, Saudi Arabia) are critically reviewed. The problems of assessment and the practical implications are discussed.

Aging, desiccation, cementation and groundwater table changes appear to have contributed to the observed variation in the properties of the lightly overconsolidated soft grey, sensitive, silty clay covering the landward two-thirds of the sabkha. The overconsolidation of the underlying stiff, brown, sandy silty clay is considered to be due to desiccation and erosion followed by a rise in sea-level during the last transgression of the Red Sea.

Field vane tests sometimes show locally high undrained shear strength in the soft clay due to interference by large gypsum crystals or marine shells, both of which also cause difficulty in sampling and specimen preparation. The nature and the thickness of the uppermost soil units, the position of groundwater table and the chemical nature of the environment in the different parts of the sabkha are shown to be an important consideration influencing the selection of appropriate types of foundation and any requirements for soil improvement.
Diversion of faulting by hills
Authors: Berrill J. B.
Published: November 2007

An earlier analysis showed that fault rupture may be deflected around a heavy building founded on a sedimentary layer directly over a strike-slip fault. In this note the analysis is extended to the case of a sloping sedimentary hillside overlying a vertical fault in basement rock. Here, too, it is found that the presence of the hillside may cause the fault surface to be deflected from the vertical, in a downhill direction, as it nears the ground surface. The amount of deflection depends principally on the steepness of the slope, but also on the horizontal distance of the fault from the toe of the slope.
Microseismic techniques for monitoring incipient hazardous collapse conditions above abandoned limestone mines
Authors: Miller A. , Richards J. A. , McCann D. M. , Browittt C. W. A. , Jackson P. D.
Published: November 2007

The progressive collapse of abandoned limestone mines over many decades has led to problems of general subsidence and crown-hole formation in parts of the West Midlands. The substantial size and extent of the voids makes the cost of infilling all of the mines prohibitively expensive, at least in the short term. One option is to monitor the workings to identify active areas and assess the rate of collapse. This would provide government and local authorities with additional criteria for establishing priorities for remedial action. Monitoring of the condition of the mines is made difficult by their general inaccessibility, but it was thought that the detection of microseismic energy associated with rock failures and roof-falls might provide a useful method of remote monitoring.

This paper summarizes a series of studies designed to develop and field test a method of monitoring microseismic events and discriminating them from the many other seismic sources. Experiments involving simulated roof-falls in an accessible (air-filled) mine indicated that the most detectable source of seismic energy is generated by debris impacting on the mine floor, rather than by stress-induced rock failure. Consequently, the energy is in a lower frequency range (around 10 to 300 Hz), than was at first anticipated.

Trials using both continuous and triggered recording, with a variety of transducers, installation techniques and network configurations, provided useful information regarding optimum network design for the discrimination of roof-falls. On the basis of these findings a seismic network was successfully implemented to monitor roof-falls during a mine infill trial. Finally, an experimental network of instruments in boreholes at a water-filled mine demonstrated, by means of artificial seismic sources, that the technique can also be applied to flooded, inaccessible mines.
A revision of the description and classification of weathered granite and its application to granites in Korea
Authors: Lee S. G. , de Freitas M. H.
Published: November 2007

This paper reviews commonly occurring difficulties associated with the description and classification of granite and proposes revised schemes for this purpose. The schemes can be applied to granitic material and granitic masses, the revised scheme for describing the latter incorporating the new criteria of volumetric percentage of weathering grades to define weathering zones. Examples are provided of the application of these revised schemes to granites in Korea.
The relative density of geologically aged, British fine and fine-medium sands
Authors: Barton M. E. , Palmer S. N.
Published: November 2007

Values of relative density (
D
r
) have been measured on 20 samples of uneemented, virtually matrix-free, fine and fine-medium quartzose sands ranging in age from Recent to Jurassic. For all except Recent and younger Pleistocene sands, which were impregnated
in situ
, the
in situ
dry density (ρ
d
) was measured on intact, block samples. A single method was used for
ρ
d
min (Kolbuszewski's tilting method) and three methods for ρ
d max
: namely the vibrating hammer procedures of Kolbuszewski, B. S. 1377 Test 14 and slow pouring.

A general trend of increasing
D
r
with geological age was given by all the methods used for determining ρ
d max
. Even with the Kolbuszewski method, values of
D
r
> 100% were obtained on some of the sands: a maximum of 1120eing recorded on the Grantham Sand of Jurassic age. Values of
D
r
using the B.S. 1377 procedure ranged between 23 and 57 0.000000or the Recent and Pleistocene sands and between 90 and 122 0.000000or the Tertiary and Mesozoic sands. The ease of the slow pouring method for ρ
d max
recommends it as a potentially useful diagnostic test to determine the degree of locking in geologically aged sands.
Soluble salt damage to thin bituminous road and runway surfaces
Authors: Obika B. , Freer-Hewish R. J. , Fookes P. G.
Published: November 2007

The paper reviews current knowledge of damage by soluble salts to thin bituminous highway and runway surfacings in warm climates. It critically examines the various recommended maximum salt limits for materials in highway construction and reviews preventative and remedial practices.

The study included a laboratory simulation of salt damage using climatic cabinets to identify the cause of salt damage to thin bituminous surfacing of a runway in the West Indies.

The work shows the importance of linking relationships and influences of geology, hydrogeology and construction practice with material and salt types, migration and crystallization pressures, crystal properties, hydration/dehydration and climate in order to prevent damage occurring.