bluuebunny/crossref_metadata_2025_split huggingface dataset:
Discussion of papers in this issue
Authors: Sims I. 
Published: November 2007

The potential for alkali-reactivity of an aggregate and its actual reactivity as seen in practice can often be detected by a detailed petrographic examination where the standard chemical and physical tests provide ambiguous results.
French (this volume) comments that the standard mortar bar tests (ASTM-C227-71) may not always lead to accurate diagnosis of the likely performance of an aggregate. In practice, misunderstandings often arise over the application of the test to carbonate or impure carbonate aggregates or to other rocks lacking the specifically alkali-silica reactive minerals. Problems in interpretation also arise where the mortar bar results show progressive expansions that are close to or below the failure criteria suggested by ASTM C227-71. Silicate rocks showing slow expansion rates are now recognized, including Gillott's (1975) Type III reactions and marginal results of the mortar bar test cannot therefore be regarded as unimportant. The consideration of both these problems can be greatly assisted by petrographic examination which may allow proper diagnosis of the type of reaction that is likely to occur even though the rate may not be predictable.
Sometimes a petrographic examination identifies the principal cause of deterioration or failure of concrete. In one British example, unreinforced concrete bases were subject to cracking, and alkali-silica reactivity was established by petrographic analysis as the major mechanism involved (Fig. 1A and B). The coarse aggregate was an inert limestone, the cement was a high-alkali variety, and the sand was mostly quartz except for alkali-reactive chert which occurred in the coarsest sand fraction. The
The hydrogeochemistry of the Jurassic limestones in Gloucestershire, England
Authors: Morgan-Jones M. , Eggboro M. D. 
Published: November 2007

Summary
This study is a review of the major and minor chemical constituents in groundwater in the Jurassic limestones of Gloucestershire, England. Particular emphasis has been placed on the identification of hydrogeochemical processes.

Groundwaters in the limestones of the Great Oolite Series and the Inferior Oolite Series, where they are unconfined, are of the Ca, HCO
3
type. In areas where both limestone series are confined beneath clays there is a gradual change in the chemistry to a Na, HCO
3
type. Deep within the confined limestones, particularly in the Great Oolite series, an Na, Cl component has been identified. Natural heavy metal concentrations are generally very low except where old pipework has influenced the Pb or Zn content.

Significant down-dip chemical changes in terms of redox conditions, pH, dissolved oxygen content, ion-exchange and the concentrations of minor constituents are exhibited by groundwaters in the limestones of both series. An oxidation-reduction zone has been defined in each limestone unit. In the Inferior Oolite the zone occurs some 8 km down-gradient from the onset of confined conditions. In the Great Oolite a similar zone occurs 1–2 km into the confined area. The delay in the onset of reducing conditions in the Inferior Oolite is tentatively attributed to leakage of Great Oolite water through the intervening Fullers Earth.
The development and geotechnical problems of sabkha, with preliminary experiments on the static penetration resistance of cemented sands
Authors: Akili W. , Torrance J. K. 
Published: November 2007

Summary
The sedimentary and evaporative environment that has prevailed on the southern shores of the Arabian (Persian) Gulf region, has produced salt encrusted flat areas known as ‘sabkha’, along the coast and in some nearby depressions.
In this paper the morphology, development, mineralogy and hydrology of coastal sabkhas have been briefly reviewed. Geotechnical properties and problems associated with sabkha deposits have been described.
The authors' general view of sabkha as cemented and uncemented layers of varying thickness and properties has been confirmed by a limited field study in terms of pits and boreholes carried out near Dhahran, Saudi Arabia. Calcium carbonate and more recent diagenetic minerals such as gyp-sum serve as the primary cementing agents.
Laboratory experiments aimed at simulating the development of cementation in sabkha material, by chemically precipitating calcium carbonate and calcium sulphate within pluviated sand samples, have shown that marked increase in static penetration resistance is exhibited with the addition of 2-5% precipitate (by weight of sand) as compared to uncemented sands. The results also demonstrate the potential advantages of using static cone pentrometers in the field to assess the strength and layering of sabkha.
Discussion on ‘Geotechnical, mineralogical and chemical interrelationships in weathering profiles of an over-consolidated clay’ by D. J. Russell and A. Parker
Authors: Robinson D. 
Published: November 2007

D. Robinson writes: The authors have clearly demonstrated in their Fig. 3
a
the change in shape of the illite basal 10 Å reflection with depth in a weathering profile of the Oxford Clay. They attributed this change to a decrease in crystallinity caused by weathering which results in a progressive loss of interlayer potassium and leads to an increased shoulder on the low 2θ side of the 10 Å peak. Quantification of the shape factor, as the authors suggest, has been widely attempted in clay mineral studies. In the examples quoted (Gill
et al.
1977; Weaver 1960) the ratio of the peak-minus-background intensity at 10 Å to that at 10.5 Å is utilized in the examination of crystallinity changes through diagenesis into low-grade metamorphism. This ratio therefore is a measure of the similarity to an ideal 10 Å peak rather than reflecting the importance of the 11 Å
d
-spacing as in the shape-factor chosen by the authors.

The changes demonstrated in peak-shape, however, could also be caused by the presence of varying proportions of random mixed-layer components in the illite (Thorez 1975). The authors will be aware that there are various pretreatment methods that allow the recognition and semi-quantification of interlayer components (Hower & Mowatt 1966; Weaver 1956). It may be that the various geotechnical parameters could be better understood if there is a varying proportion of interlayer component in the illite, especially if it is of a swelling character.
It is obvious that the authors have many more data
An analysis of secondary toppling rock failures—the stress redistribution method
Authors: Evans R. S. 
Published: November 2007

Summary

Following the terminology of
Goodman & Bray (1976)
, several examples of secondary toppling failures are presented. Six possible failure mechanisms are considered; bearing capacity failure or differential settlement due to weathering and creep with associated stress redistribution are concluded to be the most likely failure mechanisms; however, the former is not supported by field evidence. The differential settlement mechanism involves stress relaxation in the basal softer rocks (claystones) whereby the overburden load is redistributed to the fresher materials, thus reducing the amount of differential settlement likely to occur. The lateral constraints provided by horizontal stresses may temporarily inhibit this mechanism.
A building site on cambered ground at Radstock, Avon
Authors: Hawkins A. B. , Privett K. D. 
Published: November 2007

Summary
This paper gives details of the foundation problems at a housing development on a 4–7° slope of Blue Lias limestone, overlying Rhaetic and Keuper Marl.
Cambering in the past has produced extension gulls with cavities up to 1 m wide and zones of disturbance over 5 m wide. These structures were not visible on the surface or on the aerial photographs and presented unforeseen problems when discovered in foundation trenches. Extensive site checks have been undertaken, the foundations for each building plot being inspected by one of the authors.
A simple classification of the extension gulls on this site, based on the mode of opening along joint and bedding surfaces and any subsequent collapse or infilling, is presented. The overall stability of the hillside is discussed with reference to the residual strength of the Rhaetic, which here is a highly plastic, montmorillonitic horizon containing well marked shear planes.
The presence of the gulls necessitated several changes of the site layout in an attempt to avoid the most highly disturbed ground. The developer suffered a 150ss in the proposed number of units.
Dalton By-pass: site investigation in an area of abandoned haematite mine workings
Authors: Arrowsmith E. J. , Rankilor P. R. 
Published: November 2007

Summary
The choice of the public for a route for the Dalton By-pass lay through an extensive area of well-worked and abandoned haematite mine workings. The geology of the area and the method of mining are described, and the reasons are given for the selection of the preferred route.
The problems associated with the route are discussed, together with the detailed planning necessary to organize an extensive complex site investigation, involving almost 700 boreholes in a roadway length of 4½ km. A typical cutting is examined in some detail to illustrate the contractual and technical problems connected with the required excavation of a cutting slope directly over a major iron ore sop; these problems include the removal and treatment of the water-filled collapse cone over the rubble-filled cavern left by the ore extraction. The relative costing of an elevated structure and an embankment founded on collapsed workings are discussed.
Some engineering conclusions are drawn from the site investigation regarding the suitablty of embankment fill, the rate of settlement of embankments on alluvium, and the stability of a rock slope.
Mesozoic and Tertiary argillaceous units: distribution and composition
Authors: Sellwood B. W. , Sladen C. P. 
Published: November 2007

Summary
The generalized distribution and mineralogy of major Mesozoic and Cenozoic mud formations in England can be illustrated using isopach maps and composite cross-sections.
Burial diagenesis has only affected the clay minerals in the deeper parts of the Wessex-Weald area onshore. Early diagenetic clay minerals are only significant in the Triassic where sepiolite, palygorskite and corrensite formed in strongly saline environments. Authigenic clays formed sporadically in the Jurassic, Lower Cretaceous and Tertiary when smectite formed by halmrolytic alteration of mafic volcanic ashes.
For most of the Mesozoic and Cenozoic the clay mineralogy reflects weathering in the source areas.
The engineering properties of mudrocks
Authors: Cripps J. C. , Taylor R. K. 
Published: November 2007

Summary
The ‘rock’ and ‘soil-like’ properties of British mudrocks are shown to be influenced by: (a) their lithology; (b) their geological history of loading (especially during exhumation); (c) the type and method of testing; and (d) the degree of weathering. In particular, unloading and weathering leads ultimately to a normally-consolidated clay of much the same undrained shear strength, irrespective of age and origin of the parent material.
For this reason, the engineering properties of the unweathered mudrocks are illustrated separately in terms of classification indices, undrained and effective shear strengths and deformability in relation to geological age.
Thermal conductivities of mudrocks in the United Kingdoms
Authors: Bloomer J. R. 
Published: November 2007

Summary
Any prediction of sub-surface temperatures, or evaluation of heat flow from measured temperatures, requires knowledge of the thermal conductivities of the rocks in the area under consideration. An accurate evaluation of the thermal conductivity of mudstones is particularly important, not only because of their widespread occurrence in sedimentary basins but also because of their relatively high insulating effect.
The difficulties in making thermal conductivity measurements of mudstones and the methods used are briefly discussed.
A simple expression for a relationship between thermal conductivity, density and lithology is derived from physical considerations and verified by experiment. The importance of this relationship for geothermal studies in uncored wells is discussed (mudstone sections are rarely cored in commercial holes).

Finally, a table of values of thermal conductivities of mudstones, of Triassic to Pleistocene age, from the Hampshire and Lincolnshire basins and from the Moray Firth, are presented. These values range from l.2 Wm
-1
K
-1
for the Pleistocene clays in the Moray Firth to 2.3 Wm
-1
K
-1
for the Keuper Marl in the Hampshire Basin.
Shallow foundations on London Clay
Authors: Johnson P. B. 
Published: November 2007

Summary
The drought period of 1975-76 was a stark reminder to the construction industry of the potential risks involved in placing shallow foundations on those clay sub-soils which are susceptible to the phenomena of swelling and shrinkage. Many of these clays are encountered in SE England and a fairly large outcrop of London Clay occurs in the Fareham area of Hampshire. A considerable number of foundation problems exist in this area and eight case histories are reviewed in this paper, with particular emphasis on the effect of trees and vegetation on soil moisture content. Four of these cases deal with damage to existing properties and four are concerned with new development. This study reinforces the view that piles may well provide the best technical solution for foundation construction in problem areas such as this.
The influence of shrinkage cracks on pore-water pressures within a clay embankment
Authors: Anderson M. G. , Hubbard M. G. , Kneale P. E. 
Published: November 2007

Summary
For slope stability estimations, the soil pore-water conditions need to be accurately specified. The influence of cracks in clay was previously observed significantly to modify soil water response. In this study shrinkage cracks were monitored in a clay embankment where the soil water response to precipitation had been shown to be more rapid than the clay micro-permeability would predict. The cracks were shown to increase the hydraulic conductivity of the clay at all times of the year and to be the cause of the rapid soil water potential responses monitored. X-ray examinations of closed crack sites indicated that fractures at these sites formerly extended to greater depths.
Chloride ion concentrations as an aid to estimating recharge to the Woburn Sands
Authors: Irving W. M. 
Published: November 2007

Summary
On the N side of the London basin the principal representative of the Lower Greensand is the Woburn Sands, which outcrops in Bedfordshire and Cambridgeshire.
Where the outcrop is covered with till, recharging waters contain higher concentrations of chloride than those recharged in drift-free areas. This is considered to be due to higher evapotranspiration rates where the soil is underlain by boulder clay. Indirect recharge from influent streams and mixing with old saline waters also cause localized increases in chloride concentrations.
Average, annual, natural direct recharge for till-free areas, calculated from average annual rainfall and average chloride concentrations in the recharge and rain waters, agrees closely with published figures calculated using Penman and Grind-ley's equations. Approximate values for recharge through boulder clay are calculated in this way and the merits and limitations of this method for estimating recharge are discussed. The amount of indirect recharge from influent streams is also estimated.
Least-squares fitting of the linear Mohr envelope
Authors: Lisle R. J. , Strom C. S. 
Published: November 2007

Introduction
Mohr's hypothesis proposes that when shear failure along a plane takes place, the normal stress σ and the shear stress τ acting on that plane have a characteristic functional relationship. This function relating τ and σ, it is proposed, depends on the material and can be represented on the στ plane by a line defining the critical values of α and τ for shear failure.
In practice this critical line is constructed tangen-tially to Mohr circles representing different combinations of principal stresses applied to specimens of a particular material and is therefore referred to as the Mohr envelope.

For some materials a straight Mohr envelope with the equation τ =
c
+ μσ appears from the results of triaxial testing. Furthermore in the routine testing of some materials (e.g. soils) a straight line envelope is sometimes assumed a priori. In such tests small deviations of the Mohr circles from the envelope are attributed to errors and a best-fitting straight line is used to obtain the parameters (μ,
c
) necessary to characterize the properties of the material.

We describe here a procedure for calculating a best-fitting straight Mohr envelope from data consisting of the applied principal stresses (i.e. from the Mohr circles).
The concept of best-fit used

The criterion used for selecting the envelope of best fit is illustrated in Fig. 1. By means of a least-squares fit we represent the Mohr envelope by a straight line τ =
c
+ μσ- subject to the condition that
S
Hydrogeological conditions in the Middle East
Authors: Burdon D. J. 
Published: November 2007

Summary
The geology of Middle East is summarized under the subheadings: Precambrian basement, epicontinental sediments, geosynclinal and shelf deposits, Tertiary volcanics and Quaternary cover. The main tectonic episodes including epeirogenic movements, rifting and the Tertiary orogeny, are reviewed.
The imposition of hydrometeorolocal and climatic conditions upon the regional geology provides the setting for the hydrogeological discussion. Five factors which influence infiltration to aquifers under conditions of low precipitation and high potential evaportranspiration are discussed.
The predominance of fossil groundwater is the most striking hydrogeological phenomenon occurring on a regional scale in the Middle East. Its mode of formation during the pluvials is outlined and the isotopic evidence is reviewed. The main physical and chemical characteristics of fossil ground-waters are described.

It is conservatively estimated that some 65 000 km
3
of good- to medium-quality groundwater are stored in the great artesian basins of the Near East. These fossil ground-waters are a non-renewable natural resource. Current annual abstraction is, as yet, a small percentage of the total reserves but economic factors rather than the volume of reserves will determine the ultimate extent of their exploitation.

The renewable groundwater resources of the Middle East tend, by comparison, to be of local rather than regional significance. Some originate outside the Middle East, coming in as surface flows in the Nile and Tigris-Euphrates and infiltrating into the sediments in and adjacent to the flood plains.
Other renewable resources accumulate within the region where high precipitation and mountainous relief are associated. Such areas include the Djebel Akhdar of Cyrenacia, the Tertiary fold mountains from the Taurus through the Zagros to the Oman ranges, and the volcanic and basement highlands of Yemen, Asir and Ethiopa. Locally, in areas of lower precipitation, lenses of recent fresh groundwater float on regional more saline groundwater. In some areas subsurface flows towards and through wadi systems are also of importance.
Hydrogeology of the Great Nubian Sandstone basin, Egypt
Authors: Shata A. A. 
Published: November 2007

Summary
In Egypt, the strata of major hydrogeological interest are composed of a sandstone complex ranging from Cambrian to Upper Cretaceous in age. This sandstone complex, commonly known as the Nubian Sandstone, has a thickness varying from less than 500 m to more than 3000 m and rests directly on Precambrian basement.
This simple picture is complicated by a number of major structural fault and fold axes which traverse the region in a north-easterly direction. The sandstones reach their max-imum development in the Ain Dalla basin, a downthrown structural block SW of Bahariya oasis. Basement features exercise a dominant control on the structural and sedimentological form of the sandstone complex.
In spite of the structural complications, the Nubian sand-stone, underlying an extensive area of Egypt, probably con-stitutes a single hydrogeological system to the W of the Gulf of Suez. To the E, on the Sinai peninsula, a second system may exist with some connection to the main western system in the N.
The main western system, which extends into Libya and Sudan, comprises a multi-layered artesian basin where huge groundwater storage reserves were accumulated, principally during the pluvials of the Quaternary.
The carbonate rocks overlying the Nubian Sandstone complex display karst features locally and are recharged by upwards leakage from the underlying major aquifer.

Large-scale development of the Nubian Sandstone aquifer in Egypt has been under consideration since 1960. Latest proposals for the New Valley development project involve exploitation at the annual rate of 156.2 × l0
6
m
3
at El-Kharga, 509.2 at
Texture changes in crushed basalt road base
Authors: Wylde L. J. 
Published: November 2007

Summary
The internal texture of undisturbed samples of granular road base has been studied by microscope examination of pet-rological thin sections prepared from samples impregnated with epoxy resin. The study of compacted crushed basalt road base materials subjected to repeated loading from traffic and in laboratory tests, showed that the -75 μm particles become rearranged to give local accumulations of finer particles. A ‘Texture Factor’ (TF), assessed by a point counting method, was developed to quantitatively describe and follow such changes in the internal texture. The TF increases progressively with repeated loading and the increase is more rapid at higher moisture contents. The TF in road pavements is highest near the surface and a possible relationship between TF and existing pavement condition is described. Possible applications of TF measurements on existing roads to problems of material durability and pavement performance are discussed.
Discussion on ‘The development and geotechnical problems of sabkha, with preliminary experiments on the static penetration resistance of cemented sands’ by W. Akili & J. K. Torrance
Authors: Martin P. L. 
Published: November 2007

Drs Akili & Torrance are to be congratulated on a timely and interesting paper.
Over the past decade there has been a considerable involvement of British consulting engineers and contractors in the Middle East generally and in the Gulf area in particular, and as a result a fairly large volume of experience has been gained on Middle East engineering construction, much of which is concerned with sabkhas. However, the vast majority of this experience is not yet published and, indeed, may never be so, as it is often buried quite deeply in the files of clients and clients' contractors or engineers.
Nevertheless, there has been a reasonable amount of engineering geology, geotechnical information published in the British and, to a certain extent, the Continental technical press and the authors may be interested to have their attention drawn to the following list of references which, although by no means exhaustive, gives an indication of the range and scope of recent publications on this side of the Atlantic.