bluuebunny/crossref_metadata_2025 huggingface dataset:
Classification tests on African red clays and Keuper Marl
Authors: Davis A. G. , Birch N. , Chandler R. J.
Published: November 2007

From
A. G. DAVIS, N. BIRCH & R. J. CHANDLER:

The author has produced some useful data on the influence of aggregation on the index properties of red clays and Keuper Marl, in particular confirming that the apparently silty nature of Keuper Marl results from the aggregation of clay-mineral particles. We would however like to take up some points made by the author with reference to Keuper Marl.

One point on which we wish to comment is the assumption made by the author that in determining the liquid limit, further mechanical working beyond the 10 minutes specified in B.S. 1377 did not increase the liquid limit. This occurred in spite of an apparent increase in the measured clay-size fraction. The author further assumed that prolonged pre-treatment mixing was sufficient to break down all aggregations, leaving some of the clay-mineral fraction having particle diameters larger than 0–002 mm.

In Fig. 1 we show the variation of liquid limit with mixing time for two similar marl samples. Mixing was carried out in a Hobart paddle mixer which could take a sample of about 1/8 cu ft. It is seen that the liquid limit increased appreciably above that obtained using the B.S. 1377 method. Clearly for this particular marl the liquid limit increases with further working, though we hesitate, in view of the variable nature of Keuper Marl, to state that this will be the case for all marls. We do however question the use of the greaseworker as a substitute for mechanical working
Classification tests on African red clays and Keuper Marl
Authors: Sherwood P. T.
Published: November 2007

AUTHOR'S REPLY:

Davis, Birch & Chandler raise a number of points which I shall deal with in order of importance:

(1) They state that, “they see no reason to depart from the B.S. procedures for index [plasticity] tests on Keuper Marl”, and elsewhere they quote a sentence of my paper out of context which may leave the reader with the impression that I think that B.S. plasticity test results on Keuper Marl soils give anomalous results.

In fact, I fully agree that there is no reason to depart from B.S. procedure for the plasticity tests on Keuper Marl; I have never suggested otherwise, either in my paper or elsewhere.

My paper shows that the aggregations of particles in Keuper Marl are broken down by the mixing procedure specified in B.S. 1377 (i.e. 10 minutes' working with palette knives on a glass plate) and that consequently the results obtained are the ultimate values. Evidence for the B.S. results being the ultimate values is provided by:

(a) Table 3 of my paper which shows that the liquid limit reaches its ultimate value after ten minutes' mixing;

(b) the fact that the plasticity data obtained by B.S. procedure correlates well with the clay content obtained by mineralogical analysis (Fig. 2 of my paper);

(c) the correlations between liquid limit and other soil properties listed in the fifth paragraph of the comments of Davis
et al.

(2) Figure 1 of the comments by Davis
et al.
shows that for the particular marl studied by
Classification tests on African red clays and Keuper Marl
Authors: Coleman J. D.
Published: November 2007

From
J. D. COLEMAN:

I write to support and amplify the conclusions (p. 54) of this author concerning the fabric of African red clays and Keuper Marl. It is clear that:

(1) The properties of undisturbed engineering soils may differ from those of a simple mixture having the same composition as the soil.

(2) The differences may arise because the mineral grains in the soil are not in random positions, but have a structure within the soil resulting from the sedimentation, chemical and stress history.

(3) The structure may be physically stable, or preserved in the soil by cementing agents derived from the chemical history. Crystalline cements may be detected optically or by x-rays, but fine amorphous cements may be detected by a chemical/mineralogical mismatch as shown by Sherwood for Keuper Marl.

(4) Sherwood has also shown that where cementing agents are present, the normal soil classification tests may give misleading results, and research based on soil chemistry may be needed.

May I add that research based on soil physics leads to similar structural conclusions for African red clays. Thus, their reflexion spectrum has been used (Coleman 1965) to show that the colouring agent (disordered alpha ferric oxide in one instance) is present mainly as a particle coating, and moisture-sorption studies suggest that the coating is porous, so that the soils may have a moisture content in the field as high as 30 per cent.

J. D. Coleman

Soil Physics Laboratory, Department of Civil Engineering, The City University, London e c
Site investigations in coalfields—the problem of shallow mine workings
Authors: Short A. G.
Published: November 2007

From
A. G. SHORT:

I congratulate the author on his paper and his outline of the methods of investigating old, shallow workings. This is one of the most difficult parts of any investigation, and it is one where laboratory testing and theory cannot be relied upon. The successful evaluation of a site underlain by workings must be dependent on a knowledge of the geology of the area and methods of working, boreholes, excavations, powers of observation and considerable experience in this work.

The author indicated a maximum depth of bell-pits in the order of 40 ft. In his book on Derbyshire, Farey(1811) gives an interesting description of this type of working and quotes 10 yd as a maximum depth. This is almost certainly an understatement, and Pilkington (1789) stated that it was usual not to descend lower than 18 yd.

Electrical-resistivity methods of survey can give a reasonable degree of success under certain site conditions. I have a slide of the iso-resistivity lines produced from a survey where the existence of an adit was proved. Negative results, however, cannot be interpreted as indicating undisturbed ground or the absence of old workings. Reference was made to the site in Doncaster which was underlain by old galleries in the Bunter Sandstone at shallow depth. Access was obtained to the galleries and a full survey carried out.

A. G. Short 26 Abercrombie Street, Chesterfield, Derbyshire, Farey (1811) gives an interesting description of this type of working and quotes 10 yd as a maximum
Mechanism of the alkali-carbonate rock reaction
Authors: Gillott J. E. , Swenson E. G.
Published: November 2007

This paper reviews the main hypotheses proposed for the alkali-carbonate rock reaction, and presents evidence supporting the mechanism advanced by this laboratory. The latter postulates that the alkali-expansivity of certain carbonate rocks containing dolomite is due to a wetting of previously unwetted clay minerals; the wetting is made possible by the de-dolomitization reaction which produces access channels for moisture.

The new evidence consists of (a) no volume change of pure dolomite crystals immersed in 2M NaOH for 4 months; (b) the decreasing expansion of solid plus liquid of rock powders in 2M NaOH with increasing particle size of pure dolomite, using a dilatometer technique; (c) the observation from scanning electron micrographs of alkali-reactive and non-reactive rocks that much of the clay constituent appears to be distributed close to the dolomite rhombs, thus accounting more readily for the idea that dedolomitization opens up channels for moisture to gain access to the clay; and (d) a detailed study of some 50 carbonate rocks from the highly calcitic to the highly dolomitic with special emphasis on petrographic examinations and their correlations with results of laboratory performance.
Influence of boundary effects on the packing and porosity of granular materials
Authors: Lees Geoffrey
Published: November 2007

External boundaries, i.e. the walls of containers, and internal boundaries, for example, reinforcement bars, exert an influence on the packing and hence porosity of granular particles. Many attempts, both theoretically and practically based, have been made to establish correction factors for this influence so that the porosity of a material in one container could be predicted from its known porosity in a different container. The limitations of such approaches are discussed and the general conclusion reached that although these methods may be of use for containers and particles of certain shape and for circumstances where the particle size does not approach the size of the container, they are not universally applicable to containers and particles of all shapes or to cases where the aggregate size approaches the size of the container.

The consequent conclusion is made that where it is desired to know the porosity in a given container, for example where such knowledge is a pre-requisite for design of an aggregate grading, there may be no alternative to making the porosity determination in a container of the size and shape in which it is intended the aggregate should ultimately be placed.
The influence of tectonics on the geotechnical properties of Calabrian rocks and the mapping of slope instability using aerial photographs
Authors: Burton Alfred Norman
Published: November 2007

The Calabrian peninsula is undergoing rapid degradation at the present time by erosion and landsliding. These phenomena are aggravated by the reduced strength of many of the rock formations forming the peninsula, resulting from Alpine tectonic movements. Maps showing landslides and related features were prepared, with the aid of aerial photographs, in conjunction with the geological re-mapping of the peninsula at a scale of 1 : 25 000.
Studies of inter-particle void characteristics
Authors: Lees Geoffrey
Published: November 2007

A method is described for studying certain characteristics of the voids contained within a mass of aggregate particles. Measurements have been made on void cells dissected from single size aggregate systems of a variety of particle shapes in dense and loose packings. The measurements refer to the critical ratio of occupation and the critical ratio of entrance. From these measurements occupation size distribution curves and entrance size distribution curves can be drawn, analogous to particle size distribution curves. The application of the results to the problem of the design of aggregate gradings to minimum or controlled void content, by pre-mixing or filtration techniques, and of the related problem of segregation of mixed aggregates is discussed.
Some
in-situ
permeability tests in sands
Authors: James Peter Michael
Published: November 2007

1. The site

The construction of a new head barrage for the Muda Irrigation Project, in northwest Malaya, involved knowledge of the
in-situ
permeability of adjacent alluvial sands, in order to determine the extent of sheet pile cut-off needed on one side of the structure.

Figure 1 shows the geological conditions at the site extending from the proposed structure, through the river diversion to the permeability test site.

This profile was determined from a number of earlier boreholes and a seismic traverse made during the initial site investigation of the area. The layer of coarse sands with fine gravel seen on the figure was of particular interest in the test. Figure 2 shows the particlesize distribution of both this layer and the overlying layer of fine sands and clayey silty sands. The clays with sand lenses underlying the coarse granular layer were taken as an impermeable base.

Three 'wells' were used for the permeability tests. These are marked on Fig. 1 as kl, k2, k3. The spacing between kl and k2 was 38 ft and between k2 and k3, 54 ft. The wells were sunk in line and at right angles to the flow of the river.

2. Method of testing

The three permability test wells, each 6 inches in dia., were terminated in the clays below the coarse granular layer. Four-inch internal dia. p.v.c, tubing was inserted inside the cased holes down to the clay stratum and the casing was withdrawn. The bottom 20 ft of the tubes had
Geological Society Engineering Group Working Party report on the logging of rock cores for engineering purposes
Authors: Knill J. L. , Cratchley C. R. , Early K. R. , Gallois R. W. , Humphreys J. D. , Newbery J. , Price D. G. , Thurrell R. G.
Published: November 2007

1. Introduction

1.1.
general

Many engineering geologists devote a significant proportion of their time to the logging of boreholes and, specifically, to the interpretation of rock cores in engineering terms. A variety of techniques have been devised for logging such cores but in the United Kingdom the systems which have been adopted are often inadequate in relation to modern requirements. The Code of Practice for Site Investigations (C.P. 2001 1957, 94) provides a minimal statement on the methods of preparing logs from borings; no specific advice is given on rock core description. It is apparent, also, that the maximum potential yield of data from many boreholes is not attained and, in consequence, the benefit from drilling not fully realized.

1.2.
purpose

This Working Party of the Engineering Group of the Geological Society of London was set up with the objective of recommending methods which can be used in the logging of rotary cored boreholes sunk primarily for civil engineering purposes. It was agreed that the report should deal with the description of cores, and methods of handling and storage; only aspects of the drilling technique and programme relevant to the appreciation of the ground conditions would be included. Detailed consideration of drilling, in-situ testing and borehole inspection methods would be omitted.

1.3.
application

The Report is intended to provide a review of the information which can be obtained from borehole cores and guidance as to the manner in which this information can be recorded. The Report has not the authority
Solifluction on low-angled slopes in Northamptonshire
Authors: Chandler Richard John
Published: November 2007

(Weeks 1969)
has described a number of sites where slip surfaces have been encountered on slopes where the angle is less than the angle of ultimate stability against land sliding. The purpose of this note is to report two sites in Northamptonshire where slip surfaces have been observed on similarly low-angle slopes, and to suggest a possible mechanism for their formation.

Reference to
Fig. 1
shows that the two exposures are both at the 'feather edge' of cambered slopes of the Inferior Oolite (in this instance the Northampton Sand), overlying Upper Lias Clay. In both cases the Northampton Sand forms a structureless rubble, the junction with the Lias clay being about an inch above a slicken-sided slip surface of considerable extent. The slip surfaces are ascribed to solifluction movements.

The first site
(A in Fig. 1)
, at Wellingborough [SP 903 693] was a temporary section in a cutting slope which exposed a slip surface that could be traced for nearly 150 ft parallel to its strike. The second site, (B), a road improvement scheme at Isham [SP 881 745], provided a section aligned obliquely to the direction of greatest slope. This section is shown in
Fig. 2
. The down-slope extent of the Northampton Sand rubble was marked by a topographical feature where the slope increased from 4 to 6°, and where the slip surface ran out to ground level.

In each case there is some evidence that the slip surface may be somewhat undulatory, though in general
Some engineering experiences in tropical soils
Authors: Dixon Hugh Hume , Robertson Robert Hugh Stannus
Published: November 2007

The paper deals with some engineering aspects of residual soils in the tropics including experience of halloysitic soils during the construction of the Ruiru Dam in Kenya and the more detailed studies of residual soils carried out during the construction of the Sasumua Dam. Such soils, as compacted, have an unusually low dry density and high optimum moisture content but high shear strength. Engineering properties are apparently inconsistent with the index properties; moreover, standard control tests show marked variations.

Mineralogical studies can explain some of these apparent irregularities. Water is bound to the halloysite crystals and the measured proportion of bound water varies according to the treatment in the test method. Further, the grading as determined by hydrometer tests varies markedly according to the dispersing agent used. The halloysite particles are collected in robust silt-sized clusters imparting to the soil a high shear strength and many of the properties of a granular material.
Engineering geology in the investigation and construction of the Batang Padang hydro-electric scheme, Malaysia
Authors: Newbery John
Published: November 2007

The Batang Padang hydro-electric scheme in West Malaysia is located in an area of tropically-weathered granite. Major factors in the siting, design and construction of the engineering structures, which include three dams, twelve miles of tunnel and a power station 900 ft underground, were the nature of the residual soil mantle and the structure of the underlying rock.

Site investigation included over 10 000 ft of cored borings carried out in two stages. The first stage confirmed that there were no major geological impediments to the scheme and enabled basic design concepts to be established. Stage two obtained data for detailed design of the dams and tunnels. Principally because of the presence of deep weathering, earth-fill dams were the most economic and suitable. As the pressure tunnels were located mainly in competent granite with tight joints, unlined designs were chosen.

Exploration of the power station site was deferred until excavation of the tailrace tunnel permitted an exploratory adit to be constructed. The investigation included measurements of elastic modulus, strain measurements in drillholes from which were computed the
in situ
stresses in the rock, and a discontinuity survey. Laboratory tests were made on cores. The results confirmed that the cavern would be excavated in intact rock suitable for permanent support by bolts, gunite and mesh.

During construction it was possible to evaluate the success of the site investigation. Overall rock tightness led to a major reduction in the scale of grouting. Intact rock in the power station proved ‘defective’ in that it resulted in exfoliation of the cavern walls necessitating more extensive guniting than expected. A major geological problem proved to be tunnelling through residual soil below the water table. This led to flow slides necessitating tunnel diversions.
Geological education for undergraduate civil engineers
Authors: Cawsey David Charles , Francis Christopher Michael George
Published: November 2007

Problems exist in the teaching of geology to undergraduate civil engineers. These may be attributed not only to the inherent nature of the subject material but also to the attitude of qualified civil engineers. The scepticism expressed by some civil engineers is ascribed to the partial replacement of geology by soil mechanics, the specialist nature of geotechnical work within the construction industry, the non-quantitative nature of geology, and the lack of geologists employed in civil engineering.

Difficulties are experienced in teaching because of the limited time available and the necessity for students to acquire enough basic knowledge to enable them to appreciate the applications of the science to civil engineering.

An outline teaching schedule is suggested that allows for some 'pure' geology as well as engineering geology. Field work, project work and reference to case histories are important if the student is to appreciate the relevance of the subject material. With this treatment geology may be a unifying as opposed to a peripheral subject in civil engineering courses.
The influence of weathering on the microstructure of Keuper Marl
Authors: Barden Laing , Sides Geoffrey
Published: November 2007

Problems exist in the teaching of geology to undergraduate civil engineers. These may be attributed not only to the inherent nature of the subject material but also to the attitude of qualified civil engineers. The scepticism expressed by some civil engineers is ascribed to the partial replacement of geology by soil mechanics, the specialist nature of geotechnical work within the construction industry, the non-quantitative nature of geology, and the lack of geologists employed in civil engineering.

Difficulties are experienced in teaching because of the limited time available and the necessity for students to acquire enough basic knowledge to enable them to appreciate the applications of the science to civil engineering.

An outline teaching schedule is suggested that allows for some 'pure' geology as well as engineering geology. Field work, project work and reference to case histories are important if the student is to appreciate the relevance of the subject material. With this treatment geology may be a unifying as opposed to a peripheral subject in civil engineering courses.
The Nag's Head Landslips, Cullompton By-Pass, Devon
Authors: Sherrell Frederick William
Published: November 2007

The paper describes a deep cutting in Upper Carboniferous rocks, and examines the sequence and extent of the landslips which subsequently affected it. The causes of the landslips are considered and discussed in relation to the geological and hydrogeological conditions which obtain in the cutting. The hydrogeological investigation, from which the final remedial measures were designed, suggests that where the groundwater conditions may constitute a major part of the geotechnical aspect of the design of future cuttings in similar rocks, a full understanding of their aquifer characteristics is of great importance.
An investigation of the aquifer potential of the Fell Sandstone of Northumberland
Authors: Hodgson Albert Vivian , Gardiner Michael David
Published: November 2007

The results of this preliminary investigation indicate that the Fell Sandstone is the best aquifer in Northumberland, and that the groundwater potential is largely undeveloped.

The formation has an outcrop of 118 square miles (305 km
2
), of which 65 square miles (168 km
2
) are drift free. The attractive qualities of the sandstone are the friable, granular nature, the good sorting and the commonly occurring fissures and joints. The storage capacity of the formation is of the order of 10
12
Imperial gallons (4·55 × 10
12
litres). Analysis of precipitation data and water balance calculations suggest an average recharge of between 40 and 70 mgd, (182 × 10
6
l/d–319 × 10
6
1/d). Determinations of porosity and laboratory permeability give mean values of 13·8 percent and 6·4gpd/ft
2
, (314 1/d/m
2
) respectively; the transmissibility could be considerably greater than the mean value of 5300 gpd/ft (7900 1/d/m) calculated by pumping the existing boreholes. The results of chemical analyses show that the water quality is good.

There seems little doubt that further water supplies required for commercial development on Tweedside and in south-east Northumberland could be developed from the Fell Sandstone aquifer. Proposals for the economic development and future study of the aquifer are outlined.
The classification for engineering purposes of tills from moraines and associated landforms
Authors: McGown Alan
Published: November 2007

This paper makes a critical review of some of the many previous attempts at identifying and classifying tills from morainicand associated landforms and comments on the deficiencies of these as a basis for an engineering classification system. A new approach to the classification of till is suggested, which it is claimed, is suitable for both engineering and some geological purposes. This new system is then applied to a number of tills from the West Highlands of Scotland and some reported gradings of tills from other countries.
Geological Society Working Party Report on The logging of rock cores for engineering purposes
Authors: Broch J. A. , Broch E. , Walton G.
Published: November 2007

Dear Sir,

We have some suggestions regarding the report of the Working Party on Rock Core Logging. The logarithmic scales for both strength and bedding plane spacing are welcome. Do, however, the arguments in favour of the proposed strength classification outweigh the practical advantages of a system based on equal divisions, when only slight modifications would be required for sub-divisions evenly spaced on a logarithmic scale?

Use of adjectives such as weak, strong, close or wide can also lead to difficulties. The relationship between terms such as ‘moderately weak’ and ‘moderately strong’ may not be immediately obvious. When setting up a system for rock quality classification based on both strength and fracture spacing (Franklin, Broch and Walton, 1971) some of these difficulties are overcome. A common nomenclature (low, high etc.) was used for both axes and also for rock quality (Figure 1), terms such as ‘low strength’ and ‘low fracture’ spacing replacing terms such as ‘weak’, ‘thin’ and ‘close’. There is little to be gained by differently classifying the spacing of joints, bedding planes or other types of structural discontinuity.

Attention is drawn to the ‘point load test’ as an alternative to the ‘uniaxial test’ for strength classification. Results for the two types of test are closely correlated. The point load test, however, uses portable field apparatus and requires no specimen preparation.
The engineering geologist in project reconnaissance and feasibility studies
Authors: Edwards Rowland John Graham
Published: November 2007

The purpose of reconnaissance and feasibility studies is examined together with the part played by the engineering geologist. His functions, activities and output are then considered under five main headings: Providing a project outline (reconnaissance); description of the project area; plan of fieldwork; site information; and project analysis and report. An illustrative example of the use of terrain evaluation is included.

The necessity for accuracy, simplicity and relevance in all phases of the work is emphasized. It is suggested that the contribution of the engineering geologist is often undervalued or even neglected. The reason for this is occasionally ignorance of the contribution that he can make but it is more frequently the result of poor communication, and/or co-ordination between the individuals or groups involved in such studies.
Management of underground water resources
Authors: Jones Glyn Parry
Published: November 2007

The choice of water management practice depends partly on normal commercial exploitation and partly on its position as a life-essential. The underground “resource” that is to be managed includes potable and non-potable waters whether they be in “temporary” or “permanent” storage, and consideration needs to be given to the use of non-potable aquifers for waste disposal purposes. Acceptance of management as the promotion of optimum regional welfare requires its introduction in the development of a water resources system at an early a stage as possible. The management scheme should give consideration to a wide range of user requirements and meet such demands from a number of devices at its disposal. Optimum performance will be obtained from widespread modification of the hydrological cycle by the integrated use of surface and subsurface resources. This requires a thorough understanding of all aspects of the cycle, and the degree of mutual interdependence of the components is illustrated. Examples of a variety of management schemes are briefly described and serve to show the significant role played by hydrogeology in the design of these schemes. Water-resources management is dependent on specialist hydrological advice, but the status and career opportunities for scientists in this field have yet to achieve parity with those of engineers, and until such time as this is achieved then interdisciplinary study will remain desirable but not realizable.
Buried channels
Authors: Early K. R.
Published: November 2007

This discussion deals with buried channels as a factor in reservoir feasibility and is introduced by a broad classification of buried channels. Firstly, buried channels are by definition abandoned erosional features and, along the channels, one can expect to find coarsely granular bed-load stream deposits or, in the case of glacially eroded channels, similar deposits arising from sub-glacial drainage or a pre-glacial river. Because buried channels are seldom without this feature they nearly always pose a leakage problem beneath the dam or from the reservoir perimeter, if they are so placed. Naturally the leakage problem depends upon connection of the permeable channel fill with the reservoir. If the valley is covered by an extensive impermeable deposit fully spanning the rock channel, the buried channel may not after all be a problem, but very careful investigation of the impermeable layer is essential. Channels in the current bedrock surface filled with Pleistocene/Recent deposits are usually related in some way to present topography and a thorough knowledge of the local drainage conditions and geology makes it possible at least to suspect their presence, if not to have a close idea as to where they are, and of the order of their depth. There is another category, less frequently encountered, of ‘fossil buried channels’ where a bedrock surface related to another geological Era is involved, and an unconformity has been brought close to the present surface by crustal movements and erosion. These are illustrated in England and Wales by Triassic wadis which are more
Author's Reply:
Authors: Tate T. K. , Robertson A. S. , Gray D. A.
Published: November 2007

The authors welcome Dr Wurzel's contribution concerning radioactive tracers and look forward to reading the paper he is preparing on their use in crystalline rocks in Rhodesia. A guide book on “Nuclear Well Logging in Hydrology”, shortly to be published by the International Atomic Energy Agency in association with the International Hydrological Decade, with which one of us (DAG) is associated, reviews the techniques comprehensively. However, the author's paper was concerned with the recognition of fissure flow using non-radiometric techniques which are of general application and do not suffer from the somewhat restrictive attitude of some territories to the use of radio tracers in water supply wells, even in the small quantities which are necessary; this has been recognised as a problem in the U.S.A. where a brine injector was developed as an alternative (Scott Keys 1968). The technical advantages of a tracer free from density effects are fully recognised both at high and low velocities, especially at the low end, near the diffusion rate. One of us has been associated with the United Kingdom Atomic Energy Authority in the development of a prototype, single-point radio tracer injection probe for use in boreholes (Anon. 1968). Severe calibration problems were encountered which resulted in part from the density effect, although Scott Keys (1967) commented that such effects may not be significant. Certainly other errors may be more significant, including those due to the position of the injector in relation to the centre of the borehole, to variations in borehole diameter and
Preliminary sources of site information for roads in Britain
Authors: Dumbleton Michael John , West Graham
Published: November 2007

The published Report (LR403) reviews sources of information on ground conditions in Britain, and points out some of the road-engineering applications to which they may be put. Sources include geological, soil, land-use, topographical and hydrographic maps and publications, mine records, information obtainable from official bodies and local engineering works, air photographs, and site inspection. The availability of these sources of information and their interpretation and application to site investigations for roads are described.

The information that they provide can be useful at all stages of planning, design, construction and service, but is likely to be of most value if obtained at an early stage in the planning of a road project. Information is particularly important for route location and the early recognition of situations offering particular engineering difficulties, and for the planning and interpretation of the detailed site investigation.

The information is available at low cost compared with that obtained by direct subsurface exploration, and at an earlier date, and its use can allow more economical site investigations to be planned.
Investigations of the landslide at Walton's Wood, Staffordshire
Authors: Early Kenneth Reginald , Skempton Alec Westley
Published: November 2007

Field and laboratory investigations of the Walton's Wood landslide led, for the first time, to the determination of the residual strength of a clay by (1) tests on natural slip surfaces, (2) reversal shear tests on previously unsheared specimens, and (3) stability calculations. The shear strengths determined by all three methods were practically identical, and could be represented by the parameters cr′ = 0, r′ = 14°. The strength of the clay in its ‘fully-softened’ or ‘critical’ state was approximately c′ = 0, ′' = 20°. The much lower residual strength is due to the development of a continuous slip surface at large displacements and re-orientation of clay particles along the slip surface.

The landslide had probably been initiated by the erosion of an ice-marginal drainage channel during a retreat stage of the Last (Weichselian) Glaciation. The consequent oversteepening of the hillside, in mudstones of the Upper Coal Measures, led to landslips and rapid weathering, so that eventually the slope became blanketed by a thick layer of colluvium inclined at an angle of about 11° to the horizontal. Final equilibrium had not yet been attained when, in 1961, construction of a motorway embankment began on the old landslide. Failure of the partially built embankment occurred. A description is given of the remedial measures which enabled the motorway to be completed at this locality in November 1963. Typical index properties of the clay in the landslide mass are:
w
= 29, LL = 57, PL = 27, clay fraction = 70 per cent. The predominant clay mineral is kaolinite.
Wearing-course aggregates in Northern Ireland
Authors: Cameron Ian Burnett
Published: November 2007

The Institute of Geological Sciences in Belfast and the Northern Ireland Ministry of Development have been active in the search for a wearing-course aggregate which will give results consistently above the Ministry of Transport specifications for Polished Stone Value. Two promising sources of natural aggregate are being investigated. Results of tests on samples from the Co. Antrim bauxite deposits indicate that this may well be suitable for road surfacing after calcining.
The effects of soil structure on the engineering behaviour of a sensitive clay
Authors: Jarrett Peter Malcolm
Published: November 2007

In this paper various facets of the microstructure of a quick clay are described. The manner in which the microstructure affects the practical engineering behaviour is also indicated with special reference to slope stability and settlement problems.
Subsidence problems in route design and construction
Authors: Malkin Alexander Bernard , Wood John Charles
Published: November 2007

The paper reviews the main causes of ground subsidence as it affects route design and construction in the United Kingdom. Investigation techniques and remedial measures are discussed in relation to both natural and mining subsidence. In addition to the common occurrence of subsidence problems in the coalfields, emphasis is placed on their presence elsewhere in the country. Natural subsidence problems are associated mainly with carbonate and saliferous rocks but mining activity has taken place at various times at numerous geological horizons for a variety of minerals. Future mining activity is likely to involve fewer minerals but will still be dominated by the coal industry. Experience has shown that the conflicting interests of route planners and mineral operators can usually be resolved by negotiation, accompanied in some cases by compensation.
Road materials and quarrying
Authors: Fish Brian Griffith
Published: November 2007

1. Introduction

Insofar as quarrying has any public image it tends to be associated with the
Dartmoor
concept of a criminal swinging a 14 pound sledge-hammer; there is in southeast England the other image of rapacious gravel scratchers digging up people's gardens when they're not looking.

Because of this general lack of understanding it is perhaps useful in a paper of this kind to define
quarrying
in more scientific and precise terms. In the Institute of Quarrying it is defined briefly as the extraction of surface minerals and their processing for the market. Thus although the popular concept of
breaking ground
is correct, it is only half the story. For by far the most complex and technical side of the industry is the preparation of end products for distribution. Moreover, a wide variety of materials is involved, including the range of igneous rocks, limestone, chalk, sandstone and sand and gravel, the latter including sea-dredged material. From these are produced the end products, ranging from fill as the most unsophisticated, through lean-mix and cement stabilized bases, to tar- and bitumen-bound base courses and asphalt wearing courses; also concrete for rigid pavements and for structures ancillary to the road itself.

It is important to realise that, in this country, the quarrying industry itself produces and distributes these end products. Indeed so complete is the vertical integration in some cases that a company may also lay the end products and complete the operation. Thus the industry is a very close partner in road
The morphology of degraded landslide slopes in South West Dorset
Authors: Brunsden Denys , Jones David K. C.
Published: November 2007

Geomorphological techniques, including morphological mapping and profiling have been used to investigate the distribution of old landslides on the southern slopes of the Char valley in West Dorset. It is shown that these field techniques provide data which can be usefully employed to precede and supplement geotechnical investigations. The spatial pattern of landslide morphology is described and a tentative chronology suggested. The survey reveals a similar, although more extensive and complete, pattern of landslide degradation to that reported for slides on London Clay and the Lias Clay of the East Midlands.
Periglacial mudslides in Vestspitsbergen and their bearing on the origin of fossil ‘solifluction’ shears in low angled clay slopes
Authors: Chandler Richard John
Published: November 2007

Data are presented concerning mudflows of very silty material occurring on slopes in the range 8½° to 12°. In the stress range within which these flows (or more properly slides) occurred the angle of shearing resistance was at least 36°, so that for movement to have been initiated on slopes less steep than about 16°–18° slope stability analyses require that substantial artesian pore pressures should exist. Both electrical and standpipe piezometer observations confirmed the existence of artesian pressures in this slope, though the pressures at the time of observation were not quite high enough to cause further mudflow movement. This observation is consistent with stability analyses carried out using the measured soil strengths.

The significance of these observations is discussed in the context of the shear surfaces that have recently been reported from low angle clay slopes in midland and southern England.
The role of rock mechanics in the reconnaissance of rock foundations
Authors: Londe Pierre
Published: November 2007

1. Introduction

The geologist and the engineer are both faced with specific difficulties when they attempt to forecast the behaviour of a large rock mass. All the difficulties come from the fact that a rock mass is always crossed by a number of joints, or cracks, or fractures, or shear faults. In addition, these discontinuities are often open due to stress relief near the free surface of the mass. Knowledge of the mechanics of a discontinuous medium is still new and so rock testing cannot be considered to have any rigorous theoretical basis and, despite the considerable increase in the number and diversity of tests made over recent years, progress has been rather uncoordinated. Some trends, however, are noticeable in the approach used by practitioners, mainly dam designers. In the past the engineer or the geologist faced with the decision of building or not building a dam on a given rock site was asked to guess its future behaviour. There was a temptation to display a gift of divination. More and more engineers however refuse to gamble or to make believe that they are especially gifted and instead they use rock mechanics. In other words, the time has come when not only experts are consulted but the rock itself.

2. Geological description

Validity of tests
. The rock mass takes the form of an assemblage of blocks with a very low void ratio (Fig. 1). The surfaces of separation are called
major discontinuities
to distinguish them from fine
Analysis of the stability of rock slopes
Authors: Londe Pierre
Published: November 2007

1. Introduction

T
HE PROBLEMS
entailed by the stability of rock slopes are among the most difficult with which the profession is faced. Yet they are not exclusively academic, as amply evidenced by disasters such as the Malpasset Dam abutment failure and the Vajont rock slide.

Owing to the scale effect, strength properties vary generally with specimen size, and little or nothing is known about the laws governing this variation. Fortunately, however, there is practically no scale effect when the residual shear strength of a continuous layer of soft material is considered. This is the case of fault gouge or sedimentary clayey joints which are responsible for most failures of natural rock slopes. In view of this, and in the present state of knowledge, only rock slopes with surfaces of separation of large extension can be satisfactorily analyzed for stability.

A three dimensional method of analysis of such slopes has been worked out. The principle of the method will be described first and then a few examples will be given of its application to dam abutments. It is obvious that the process is perfectly valid for rock slopes other than dam abutments provided there exist large surfaces of separation.

2. The principle of three-dimensional analysis

Assumptions
. The stability of the slope is analyzed in terms of the stability of a given rock volume (Fig. 1). The internal faces of the volume are plane: the surface (
O
,
B
,
C
) or plane P
1
; the surface (
O
,
C
,
A
) or plane P
2
; the surface
Structure of a red clay soil from Nyeri, Kenya
Authors: Smart Peter
Published: November 2007

A red soil from Nyeri has a well developed crumb (erde) structure. Electron microscopy shows the crumbs to comprise mainly small clay plates and smaller, 50 Å, iron oxide particles. The iron oxide particles tend to aggregate with each other; otherwise the particles are mixed randomly. The observations help to explain the moisture holding and compaction characteristics of the soil.
Groundwater recharge in the Lower Greensand of the London Basin—results of tritium and carbon-14 determinations
Authors: Mather John David , Gray David Alfred , Allen Raymond Alfred , Smith Douglas Brian
Published: November 2007

Groundwater derived from the Lower Greensand of the London Basin has been ‘dated’ by the use of tritium and carbon-14 techniques. The data indicate that replenishment from the northern outcrop is feasible but that movement from the southern outcrop is extremely slow and possibly restricted.
Effects of non-linearity on the prediction of settlements of foundations on rock
Authors: Hobbs Noel Bambury
Published: November 2007

Many rocks exhibit non-linear deformation characteristics, but nevertheless are regarded as linear when estimating settlements. The results of a plate test on Bunter Sandstone are examined taking account of the non-linear nature of the rock. A method of estimating the settlement of large structures is outlined, using a 60 ft diameter reactor foundation as an example as cases on non-linear rocks can only be considered on a numerical basis. The errors incurred in treating non-linear rocks as linear and in extrapolating from plate loading tests are discussed.
Fissure patterns and slope failures in till at Hurlford, Ayrshire
Authors: McGown Alan , Saldivar-Sali Arthur , Radwarn Amr M.
Published: November 2007

The present investigations have shown that the till at Hurlford, Ayrshire, is fissured and that a very definite fissure pattern exists. The nature of the fissures and influence of weathering, overburden pressures and stress release have been established and new scalar property classification especially designed for tills have been successfully employed.

A close relationship between fissure fabric, slope stability and directional shear strength characteristics has been found and the mechanism of slope failure at Hurlford has been identified to be the opening and softening of fissures in the till.

The three-dimensional shear strength anisotropy of the Hurlford soil has been shown to be outside of the bounds of applicability of conventional sample size—shear strength relationships which assume random fissure patterns in clays.
Mapping major joints in the Lower Oxford Clay using terrestrial photogrammetry
Authors: Moore J. F. A.
Published: November 2007

A prominent structural feature of the Lower Oxford Clay near Peterborough is formed by a series of near vertical joints traversing the full height of excavations up to 25 m deep and extending for at least several hundred metres in a north-south direction. The orientations and spacing of these joints were determined by means of a series of stereophotographs taken at intervals from the same three points, as a face was excavated. Using machine contour plots derived from the stereopairs a three-dimensional model was constructed to demonstrate the joint disposition. Although some bifurcation of joints occurs the average spacing is about 8–10 m. A similar, nearly orthogonal, set of joints is also present but less well-developed.
A review of the geological factors influencing the mechanical properties of road surface aggregates
Authors: Hartley Alan
Published: November 2007

Investigation of the mechanical properties of road surfacing aggregates and particularly of the polishing characteristics has occupied many researchers in recent years. The influence of geological factors on these properties has however not received the same prominence in the literature as the engineering aspects. This paper has been written with a view to gathering together the salient features of the less publicised work.

After reviewing the general requirements of road surfaces the term “roadstone durability” is introduced in the context of surfacing aggregates and the various geological factors likely to influence the roadstone durability are indicated. The influence of petrography upon the strength and the resistance to stripping, abrasion and polishing of roadstones is described together with methods used to assess their potential performance.

Shortage of high quality surfacing materials has resulted in the development of artificial aggregates and some aspects of this work are described.
Possible applications of photogeology to the study of rock mechanics
Authors: Norman John Wakelin , Huntington Jonathan Fordham
Published: November 2007

Photogeology may provide useful general information in some spheres of rock mechanics, particularly in the very earliest stages of an investigation before ground is broken. Possible aspects for study are hydrogeology, major fracture systems, broad changes in rock character, structure and regional stress, soil mapping and natural slope failures. Much research is still needed in some of these fields, and suggestions for this are given.

Some types of detailed ground based rock mechanics research would be helped by using the methods of ground photogrammetry, and by photogeological interpretation of ground stereoscopic photographs.