Kevin Privett

... 2). At Inglesbatch and Whiteway, in an area where the spur slopes are be~tween 4 and 8 the apparent mapped thickness is over 60 m ... Where the strata have been exposed in the White-way area, the beds have been observed to have no obvious orientation in the lower part of ...

The construction of port Solent Marina involved the removal. of alluvial silt to expose a Iayer of reworked chalk which acted as the foundation for a land reclamation project utilizing 564,000m3 of Ports Down chalk as fill, up to 5m thick. In order to prevent deterioration of the reworked chalk and to continue working throughout the winter with the minimal of delay, a "thick layer" compaction specification was developed to preserve the lump structure of the chalk and avoid instability. Following a literature search on the use of chalk as fill, initial site trials were used to develop a specification for 450mm and 500mm thick layers. Construction was monitored by chalk classification tests, in-situ density tests, trial pitting and full-sized foundation Ioading tests, one of which involved cycling of the groundwater Ievel. Careful methods of working produced a successful fill which could support a foundation pressure of 167kPa with less than 10mm settlement. Settlement of the underlying natural ground was shown to be virtually complete by the end of the filling operation. No measurable effects of groundwater movement were detected.

Up to 9 × 106 l of light non-aqueous-phase liquid (LNAPL) is present in a 400 m-wide zone in the Permo-Triassic sandstone 30 m below a working industrial site. Remediation by skimmer wells failed to meet the expectations of the regulatory authorities. A detailed study has concluded that this form of remediation is not possible in this formation.Initial estimates of the volume of LNAPL in the sandstone had been made by applying the concept of correcting for an ‘exaggerated thickness’ in the wells and multiplying by the porosity. Regulatory requirements were to remove most, preferably all, of the LNAPL. Site observations and measurements from high-quality core samples showed that the fine pores of the rock obey the capillary characteristic model. This was derived some 50 years ago in the oil production industry but has, in the opinion of the author, not been fully appreciated by the contaminated groundwater remediation sector in the UK. The model has been used to make a more reliable ...

The Fuller's Earth formation is an overcon-solidated, jointed, randomly Assured, calcareous mudstone with some thin to medium, jointed argillaceous limestone bands. South of Bath, the formation contains the commercial (montmorillonite rich) Fuller's Earth bed. This Paper reviews the effect of the proportion of calcite present on the moisture content, Atterberg limits, particle size, and residual shear strength. Attention is drawn to the importance of appreciating that the calcite percentage and the clay mineralogy are both likely to change with time as a result of weathering processes. This will affect the stability of natural slopes and man-made cuttings, excavations, etc. La formation de terre à foulon est un limon compact calcaire surconsolidé jointé et fissuré au hasard qui contient des bandes de chaux argillacée jointées d'épaisseur faible ou modérée. Au sud de Bath la formation comprend la couche de terre à foulon commerciale qui est riche en montmorillonite. L&#39...

This thesis presents the results of research undertaken in the south Cotswolds. Emphasis is placed on the engineering geological aspects of planning and construction on hillslopes, many of which have been superficially disturbed by cambering and landslipping. Special attention is paid to the geotechnical properties of the mudstone/clay horizons of the Fuller’s Earth and the Rhaetic, with emphasis on a study of the residual shear strength parameters. During the examination of numerous gulls in the Blue Lias at Radstock, a simple classification scheme was devised for the various extension styles produced in the interbedded limestone and clay sequence. The engineering significance of these phenomena is discussed. At Radstock cambering has taken place over the Rhaetic, especially the highly plastic Cotham Beds; these horizons have been investigated at this and other localities. Superficial structures are not well depicted on conventional geological maps. An attempt is made to determine to what extent they may be identified by engineering geomorphological mapping. Only disturbances which rupture the ground surface are clearly discernible and hence reliably depicted by this type of mapping; moreover it is shown that land use can obscure evidence of past instability. Engineering geomorphological mapping has been used as a preliminary study in the realignment of the A46 north of Bath. The proposed routes are discussed and some of the potential problems highlighted. It is demonstrated that false colour infra-red photography can be of considerable use in helping to identify areas of ground disturbance. A study of the geotechnical properties of the Fuller’s Earth shows an increase in “clay fraction”, expanding lattice clay minerals, plasticity and oxidation as weathering proceeds, with a corresponding drop in shear strength, bulk unit weight and calcite percentage. The presence of thin limestone bands modifies this profile. Calcite is found to have a significant effect on the plasticity of the Fuller’s Earth. The use of the Bromhead ring shear apparatus to determine residual strength has enabled many samples to be tested at normal loads up to 600 kPa; a number of advantages over the conventional shear box are discussed. The parameter φ’r is found to be stress dependent and as a result previously published correlations with other data are critically assessed and the choice of φ’r in engineering practice is considered.

The UK has a long history of quarrying and many disused sites were simply abandoned. Increased population pressure and awareness of environmental issues has resulted in two main changes: quarries can be valuable assets for redevelopment, and those not redeveloped are rehabilitated to become part of the landscape once again. This paper outlines some of the after uses for quarries in the UK including large multi-use projects such as combined new townships and flood prevention schemes. Landfilling has long been carried out in former quarries, originally in an uncontrolled manner but latterly with regard to environmental protection using engineered containment systems. A summary of the methods used to line steep quarry slopes is presented. Although such methods have been in use for more that 10 years, many are still considered novel because there is little research data on aspects such as liner strain leading to reduced effectiveness. The various factors involved in determining any site as suitable for landfilling are well known. Former quarry sites have additional factors relating to the design and serviceability of the lining system on steep slopes. A consideration of all factors is necessary and where several potential site options are available, the use of software screening tools is advocated. QRisk is a geotechnical risk assessment tool for safety and financial risks resulting from slope instability. The use of GIS is a powerful tool for managing spatial data and building target plans based on weighting of various factors affecting sensitivity of receptors such as groundwater.

Introduction The papers in this session of the conference concentrate on some of the processes described by the Theme Lecturer, Professor Hutchinson, and the engineering properties of the materials. Engineering implications are referred to in the papers but are included in this session because the process/properties element is stressed. This report is intended to provide a brief introduction to the session papers and all references are to papers in this conference. The term “periglacial” is sometimes restricted to geomorphological processes where freeze-thaw is the dominant action but the definition generally is widened to include all those processes, and their landforms, taking place in cold climated outside the margins of an ice sheet and so encompasses everything that is not directly glacial. This conference has used this wider definition and thus deposits such as laminated glacial lake sediments (Bell and Coultard) are included in this session. Table 1 illustrated the range of features that could be considered, many of which are discussed to varying degress in the papers. TABLE 1: List of periglacial features/processes. LARGE-SCALE LANDSLIPS SOLIFLUCTION, MUDFLOWS, SHEARS ASYMMETRIC VALLEYS FROST CREEP CAMBERS, VALLEY BULGES ICE WEDGES POLYGONS FROST HEAVE, INVOLUTIONS FROST MOUNDS, PINGOS FROST SHATTERING LOESS DEPOSITION LAMINATED LAKE DEPOSITS CHEMICAL OF CaCO3 SLOPE PROCESSES The various processes involved in the formation and modification of slopes, either in their natural condition, or if modified by some engineering works. Is is not surprising then, that the majority of papers submitted to this session concern periglacial slope processes.

Port Solent is a waterside development of a 36 hectare site at the north end of Portsmouth Harbour occupying what used to be the shallow, impounded Paulsgrove Lake and surrounding derelict land (SU635052). The existing lake level was lowered and approximately 310000 m3 of accumulated silt and other unsuitable material were removed. This exposed a formation of reworked (probably soliflucted) chalk overlying deeply frost-shattered, structureless chalk, becoming more structured with depth. Groundwater was artesian and it was only the cohesive fraction of this material which prevented instability. A total of 2.2 km of in situ concrete retaining wall was constructed and approximately 600 000 m3 of imported fill placed to a maximum thickness of 5 m for land reclamation behind the wall. Chalk from the nearby Ports Down Hills was chosen as the fill material, from quarries at Warren Farm (SU603072), Downend (SU601066) and Paulsgrove (SU635066). An experimental excavation and embankment were used to formulate the method of working and supported by initial site trials a compaction specification was developed for 450 mm and 600 mm thick layers of chalk (Privett 1990). This ‘reduced effort’ compaction specification preserved the lump structure of the chalk and was designed to allow placing of chalk in adverse conditions where more severe compaction requirements would have caused problems of instability. The chalk was successfully placed on the relatively soft formation with artesian groundwater and throughout the winter season, sometimes in shallow standing water. The integrity of the chalk fill was monitored by

Mr D. N. Holt, Chairman of the Engineering Group, welcomed the large audience to the Meeting, designed to promote the interchange of ideas between Clay Mineralogists, Engineering Geologists and Geotechnical Engineers. Nine papers were presented and discussed: Engineering geology of clay minerals: swelling, shrinking and mudrock breakdown by Dr R. K. Taylor of University of Durham who introduced the theme of the Meeting. Argillaceous sediments make up about 60% of the geological column, clay minerals accounting for about two-thirds of the constituents of over-consolidated clays and mudrocks. In North America, expansive clays are regarded as the principal hazard, whilst in southeast England shrinkage of heavy clays is the main geotechnical problem. Expansive clays are rarer in the older rocks, and in the UK there are virtually none below the Silurian. After summarizing the structure of clay minerals Dr Taylor discussed problems caused by expanding seat earths and roof seams in coal mines. Formation waters are generally saline, creating Na-montmorillonite which is more expansive than the Ca variety, exacerbating the problems. Swelling is divided into mechanical or physicochemical in origin; a mechanical origin is more common in soil mechanics problems, clay minerals may not be involved. Samples recovered from depth with high KQ values may swell in a total stress oedometer because of high suctions generated by stress release on sampling. In long-term excavations mechanical and physicochemical swelling can take place. The swelling process of clays is a function of absorbed water; there is strongly bonded water near the surface of

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.

... The Engineering Group is greatly honoured that Professor John Hutchinson has agreed to give this Glossop Lecture. It is entitled 'Reading the Ground: Morphology and Geology in Site Appraisal'. I am sure that we are all going ...

Clay from the Fuller's Earth formation is shown to contain mainly illite, kaolinite and calcite, in contrast to the Fuller's Earth Bed in which montmorillonite is the main clay mineral. A negative correlation has been demonstrated between the calcite content and the plasticity as measured by the Atterberg limits. Fresh samples from the Fuller's Earth Bed have a higher plasticity than those of the fuller's earth clay with similar calcite percentages, due to the relative increases in the expanding lattice clay mineral. Weathering of the fuller's earth clay typically reduces the calcite content and increases the percentage of montmorillonite, resulting in a higher plasticity.

Abstract BS 5930 offers little assistance to engineers wishing to use residual strength parameters in slope stability analysis. It wrongly suggests the ring shear gives lower parameters than the shear box. BS 5930 does not mention the fact that the residual strength is stress dependent, hence the failure envelope is curved and the parameters must be assessed using an appropriate effective normal stress. For this reason the correlation charts relating ϕ′R to plasticity index or clay content need replacing with a series of charts in which these properties are plotted against ϕ′R values obtained at a number of effective normal stress loadings. Even then such correlations should be treated with caution.

Establishing appropriate lines of evidence enables us to resolve the challenges faced in engineering geological practice. When considering the lines of evidence used to derive a conceptual site model (CSM), three interlocking themes are: (1) multi-disciplinary working, (2) knowledge and experience and (3) lessons from the past. This is explored through case histories. There may be no standard approach and conventional engineering geological skills are not always sufficient; as during the decommissioning of cryogenic gas storage tanks at Canvey Island. Alternatively, there may be reservations about using a standard approach; which led to the unconventional use of chalk fill at Port Solent Marina. In the case of a major oil leak into the Permo-Triassic aquifer, understanding the basic science of the problem explained why the original CSM was too simplistic and informed a change of remedial strategy. Obtaining permits for an underground gas storage facility on a landslide complex on the Isle of Portland required numerous lines of evidence to assess the stability of the slope. Furthermore, new lines of evidence can be added to old data sets as technology develops, such as the use of LiDAR in mapping Cotswolds landslides.

Establishing appropriate lines of evidence enables us to resolve the challenges faced in engineering geological practice. When considering the lines of evidence used to derive a conceptual site model (CSM), three interlocking themes are: (1) multi-disciplinary working, (2) knowledge and experience and (3) lessons from the past. This is explored through case histories. There may be no standard approach and conventional engineering geological skills are not always sufficient; as during the decommissioning of cryogenic gas storage tanks at Canvey Island. Alternatively, there may be reservations about using a standard approach; which led to the unconventional use of chalk fill at Port Solent Marina. In the case of a major oil leak into the Permo-Triassic aquifer, understanding the basic science of the problem explained why the original CSM was too simplistic and informed a change of remedial strategy. Obtaining permits for an underground gas storage facility on a landslide complex on the Isle of Portland required numerous lines of evidence to assess the stability of the slope. Furthermore, new lines of evidence can be added to old data sets as technology develops, such as the use of LiDAR in mapping Cotswolds landslides.

Careful testing has shown that
similar results can be obtained using
the Bromhead ring shear apparatus
and the conventional reversal shear
box.
Extended testing has confirmed
that residual failure envelopes are
curved and that the curvature is most
pronounced below about 2OOkPa
effective normal stress and in soils
with a high clay fraction. Two new
terms are introduced, Complete
Failure Envelope and Lowest Residual
Strength.
The importance of acquiring data
relevant to the correct overburden
pressures is emphasised; for a
shallow slide of 1-2m the phi'r may be 9°
higher than for a deep slide, with a
high effective normal stress. Thus an
appropriate figure should be read
from the residual friction coefficient
or from a straight line approximation
over a selected normal stress range,
preferably from the Complete Failure
Envelope.
Correlation charts relating residual
strength to clay fraction and/or
plasticity index are only meaningful if
the points have been established at
the same effective normal stress, and
also if this stress level is relevant to
the problem being considered.

Up to 9 million litres of light non-aqueous phase liquid (LNAPL) is present in a 400m wide zone in the Permo-Triassic sandstone 30m below a working industrial site. Remediation by skimmer wells failed to meet the expectations of the regulatory authorities. A detailed study has concluded that this form of remediation is not possible in this formation. Initial estimates of the volume of LNAPL in the sandstone had been made by applying the concept of correcting for an 'exaggerated thickness' in the wells and multiplying by the porosity. Regulatory requirements were to remove most, preferably all, of the LNAPL. Site observations and measurements from high-quality core samples showed that the fine pores of the rock obey the capillary characteristic model. This was derived some 50 years ago in the oil production industry but has, in the opinion of the author, not been fully appreciated by the contaminated groundwater remediation sector in the UK. The model has been used to make a more reliable estimate of LNAPL volume and to demonstrate to the regulatory authorities the processes involved and how these control the ability to clean the site. The concept of 'apparent volume' is introduced as an overall measure of apparent thickness in the site-wide monitoring borehole network. Apparent volume is shown to be broadly negatively correlated with groundwater level fluctuations and so the measure of changes in apparent thickness is not a sound basis for regulatory compliance.  It was found that LNAPL thickness in wells is less than the thickness of the contaminated zone in the sandstone and, importantly, the degree of saturation is no more than 30%.  This leads to a reduction in effective permeability of two orders of magnitude (from the fully saturated condition) which has serious implications for remediation.  Most of the LNAPL is immobile and so pumping is ineffective; it does not reduce the volume of aquifer impacted nor does it have any significant effect on reducing the source zone for dissolved phase generation, the size of any dissolved phase plume or the longevity of such a plume.

Environmental geology is a relatively new discipline which has developed out of engineering geology (the geology related to civil engineering) and includes, amongst other things, aspects of the behaviour of materials and the ground, hydrology, hydrogeology, geochemistry, environmental science, the mobility and fate of contaminants in the ground.  The new environmental geologist is one of the partners in a multi-disciplinary team which is necessary for talking modern problems.

The most common way of dealing with contaminated land is through the planning system, when a site is re-developed.  There is a Government initiative to favour the re-development of brownfield sites rather than the development of greenfield ones.  Often they are derelict sites which have been abandoned by industry and still contain the legacy of their industrial past.  Typically, an organisation such as the Black Country Development Corporation or the Welsh Development Agency will rehabilitate an entire area, build new roads and provide sites to attract industry and commerce to the region.

The environmental geologist has to find out what hazards remain and how these are best dealt with in order to make the new development safe and to ensure wider environmental protection.  For example, the redevelopment of a scrap yard  will involve the cleanup of the ground which is of immediate concern to the new owner and occupiers but it may also remove accumulations of mobile contaminants that may be leaching into the rivers or groundwater, such as oil or fuel from old vehicles or more toxic chemicals such as polychlorinated biphenyls (PCBs) from old transformers. 

To be able to do this efficiently requires a knowledge of what went on , and where, during the history of a site – the past is the key to the present.

Now that the problems of contaminated land are being recognised more fully, the remediation of sites is not confined solely to when (and if) they are re-developed.  Abandoned metal and coal mines, where pyrite has been exposed and allowed to oxidise, pose a threat to the environment from ferruginous, acidic discharges when the mines flood.  On-going industrial concerns like oil depots are renowned for leaking pipes and underground tanks.  It is becoming more common to investigate contamination at working as well as closed sites.  This poses extra challenges for the investigating team.  Indeed, there is a new section of the Environmental Protection Act 1990 which is about to become law and requires local authorities to take action on contaminated land.

This thesis presents the results of research undertaken in the south Cotswolds.  Emphasis is placed on the engineering geological aspects of planning and construction on hillslopes, many of which have been superficially disturbed by cambering and landslipping.  Special attention is paid to the geotechnical properties of the mudstone/clay horizons of the Fuller’s Earth and the Rhaetic, with emphasis on a study of the residual shear strength parameters.

During the examination of numerous gulls in the Blue Lias at Radstock, a simple classification scheme was devised for the various extension styles produced in the interbedded limestone and clay sequence.  The engineering significance of these phenomena is discussed.  At Radstock cambering has taken place over the Rhaetic, especially the highly plastic Cotham Beds; these horizons have been investigated at this and other localities.

Superficial structures are not well depicted on conventional geological maps.  An attempt is made to determine to what extent they may be identified by engineering geomorphological mapping.  Only disturbances which rupture the ground surface are clearly discernible and hence reliably depicted by this type of mapping; moreover it is shown that land use can obscure evidence of past instability.

Engineering geomorphological mapping has been used as a preliminary study in the realignment of the A46 north of Bath.  The proposed routes are discussed and some of the potential problems highlighted.

It is demonstrated that false colour infra-red photography can be of considerable use in helping to identify areas of ground disturbance.

A study of the geotechnical properties of the Fuller’s Earth shows an increase in “clay fraction”, expanding lattice clay minerals, plasticity and oxidation as weathering proceeds, with a corresponding drop in shear strength, bulk unit weight and calcite percentage.  The presence of thin limestone bands modifies this profile.  Calcite is found to have a significant effect on the plasticity of the Fuller’s Earth.

The use of the Bromhead ring shear apparatus to determine residual strength has enabled many samples to be tested at normal loads up to 600 kPa; a number of advantages over the conventional shear box are discussed.  The parameter φ’r is found to be stress dependent and as a result previously published correlations with other data are critically assessed and the choice of φ’r in engineering practice is considered.

The construction of port Solent Marina involved the removal. of alluvial silt to expose a Iayer of reworked chalk which acted as the foundation for a land reclamation project utilizing 564,000m3 of Ports Down chalk as fill, up to 5m thick. In order to prevent deterioration of the reworked chalk and to continue working throughout the winter with the minimal of delay, a "thick layer" compaction specification was developed to preserve the lump structure of the chalk and avoid instability. Following a literature search on the use of chalk as fill, initial site trials were used to develop a specification for 450mm and 500mm thick layers. Construction was monitored by chalk classification tests, in-situ density tests, trial pitting and full-sized foundation Ioading tests, one of which involved cycling of the groundwater Ievel. Careful methods of working produced a successful fill which could support a foundation pressure of 167kPa with less than 10mm settlement. Settlement of the underlying natural ground was shown to be virtually complete by the end of the filling operation. No measurable effects of groundwater movement were detected.

Mining can have a wide range of impacts on the physical, social and economic environments and it has become an essential requirement for new projects to fully investigate these prior to commencement of operation. Environmental Baseline Assessments (EBAs) characterise the existing environment in and around the mine site. Traditionally, EBAs have not been risk based. However, the concepts involved can be readily placed within a tiered, risk-based framework, which ensures the correct data is gathered. Using examples from Africa, the Middle East and the UK the concept of a Risk Based Environmental Baseline Assessment (RBEBA) is introduced. This approach offers the advantage of enabling benchrnark environmental information to be gathered within a framework which allows future changes to be scientifically judged. The approach considers the sources of potential contaminants, how the contaminants will move along pathways, and which receptors are at risk. The methodology described is one which can be adopted at all mine sites, in all geologic settings.

United States law, both fedearl and state, requires environmental assessments of certain industrial establishments prior to closure or transfer to a new owner.  If a site is to be reclaimed it is the current owners responsibility to prove to the satisfaction of the authorities that it is clean. One of four major phases of study that must be undertaken is the Remedial Investigation Feasibility Study which includes gathering site data and assessing the feasibility of different remedial actions. For sites that are on the Superfund list there are rigorous procedures defined by the United States EPA.  The investigation work for a large site may take years to complete and cost several million dollars.  Site assessments for property transfers are on a much lower scale (but can lead to the discovery of contamination sufficient to place the site on the Superfund list). There are no detailed guidelins and current practice has evolved a three tier level of assessments necessary to address the issue of how much investigation is enough.  These three levels are the Screening Phase, Environmental Assessment and In Depth Environmental Assessment.  Given the ever increasing environmental liabilities, it is vital that Environmental Assessments are carried out by suitably qualified professionals to very high standards of care, compared to more traditional forms of site investigation.

The UK has a long history of quarrying and many disused sites were simply abandoned. Increased population pressure and awareness of environmental issues has resulted in two main changes: quarries can be valuable assets for redevelopment, and those not redeveloped are rehabilitated to become part of the landscape once again. This paper outlines some of the after uses for quarries in the UK including large multi-use projects such as combined new townships and flood prevention schemes. Landfilling has long been carried out in former quarries, originally in an uncontrolled manner but latterly with regard to environmental protection using engineered containment systems. A summary of the methods used to line steep quarry slopes is presented. Although such methods have been in use for more that 10 years, many are still considered novel because there is little research data on aspects such as liner strain leading to reduced effectiveness. The various factors involved in determining any site as suitable for landfilling are well known. Former quarry sites have additional factors relating to the design and serviceability of the lining system on steep slopes. A consideration of all factors is necessary and where several potential site options are available, the use of software screening tools is advocated. QRisk is a geotechnical risk assessment tool for safety and financial risks resulting from slope instability. The use of GIS is a powerful tool for managing spatial data and building target plans based on weighting of various factors affecting sensitivity of receptors such as groundwater.