H.J. Reeves

Initial geological considerations before installing ground source heat pump systems

Abstract The performance of an open- or closed-loop ground source heat pump system depends on local geological conditions. It is important that these are determined as accurately as possible when designing a system, to maximize efficiency and minimize installation costs. Factors that need to be considered are surface temperature, subsurface temperatures down to 100–200 m, thermal conductivities and diffusivities of the soil and rock layers, groundwater levels and flows, and aquifer properties. In addition, rock strength is a critical factor in determining the excavation or drilling method required at a site and the associated costs. The key to determining all of these factors is an accurate conceptual site-scale model of the ground conditions (soils, geology, thermogeology, engineering geology and hydrogeology). The British Geological Survey has used the modern digital geological mapping of the UK as a base onto which appropriate attributes can be assigned. As a result it is possible to generate regional maps of surface and subsurface temperatures, rock strength and depth to water. This information can be used by designers, planners and installers of ground source heat pump systems. The use of appropriate geological factors will assist in creating a system that meets the heating or cooling load of the building without unnecessary overengineering.

Engineering Geology for Tomorrow’s Cities

This book and the accompanying CD-ROM provide a statement of our knowledge and understanding of engineering geology as applied to the urban environment at the start of the 21st century. In particular, this volume demonstrates that: * working standards originally developed nationally are becoming internationalized; * risk assessment, rather than just assessment of hazards, is driving decision-making; * geo-environmental change, whether climatically or anthropogenically driven, is becoming better understood; * greater use of underground space is being made; * the relentless advance of information technology is providing new opportunities for engineering geologists to interpret and visualize the subsurface. This book shows that in developed and developing countries alike, engineering geolgists are increasingly exchanging ideas and learning from each other in a genuine two-way process. These ideas will contribute significantly to the sustainable development of both new and long-established urban environments world-wide.

The role of stress history on the flow of fluids through fractures

Abstract Understanding flow along fractures and faults is of importance to the performance assessment (PA) of a geological disposal facility (GDF) for radioactive waste. Flow can occur along pre-existing fractures in the host-rock or along fractures created during the construction of the GDF within the excavation damage zone (EDZ). The complex fracture network will have a range of orientations and will exist within a complex stress regime. Critical stress theory suggests that fractures close to localized shear failure are critically stressed and therefore most conductive to fluid flow. Analysis of fault geometry and stress conditions at Sellafield has revealed that no features were found to be, or even close to being, classified as critically stressed, despite some being conductive. In order to understand the underlying reasons why non-critically stressed fractures were conductive a series of laboratory experiments were performed. A bespoke angled shear rig (ASR) was built in order to study the relationship between fluid flow (water and gas) through a fracture surface as a function of normal load. Fluid flow reduced with an increase in normal load, as expected. During unloading considerable hysteresis was seen in flow and shear stress. Fracture flow was only partially recovered for water injection, whereas gas flow increased remarkably during unloading. The ratio of shear stress to normal stress seems to control the fluid flow properties during the unloading stage of the experiment demonstrating its significance in fracture flow. The exhumation of the Sellafield area during the Palaeogene-Neogene resulted in considerable stress relaxation and in fractures becoming non-critically stressed. The hysteresis in shear stress during uplift has resulted in faults remaining, or becoming, conductive. The field and laboratory observations illustrate that understanding the stress-history of a fractured rock mass is essential, and a mere understanding of the current stress regime is insufficient to estimate the flow characteristics of present-day fractures.

Methodology for creating national engineering geological maps of the UK

In the United Kingdom (UK) geological maps traditionally have been attributed with lithostratigraphical map units. However, without significant supplementary information, these maps can be only of limited use for planning and engineering works. During the middle part of the 20th century, as development of the science of engineering geology began to accelerate, engineering geological maps started to appear in various forms and at various scales to meet the challenge of making geological maps more suited to land-use planning, engineering design, building, construction and maintenance. Today, engineering geological maps are routinely used at various scales as part of the engineering planning, design and construction process. However, until recently there had been no comprehensive, readily available engineering geological map of the UK to provide the broad context for ground investigation. This paper describes the recently published (2011) 1:1 000 000 scale engineering geology superficial and bedrock maps of the UK. It describes the methodologies adopted for their creation and outlines their potential uses, limitations and future applications. Supplementary material: Engineering Geology (Bedrock) Map of the United Kingdom, Engineering Geology (Superficial) Map of the United Kingdom and Extended Key for the Engineering Geology Maps of the United Kingdom are available at http://www.geolsoc.org.uk/SUP18528.

A GIS for the planning of electrical earthing

When creating an electrical earth for a transformer with vertically driven earthing rods, problems can arise either because the ground is too hard or because the ground is too resistive to achieve the required earthing resistance. To assist in the planning of earthing installations a geographic information system (GIS) layer has been created. In its simplest form it consists of a colour coded map that indicates the most likely earthing installation: a single vertically driven rod (indicated by dark green); multiple vertically driven rods (indicated by light green); a horizontal trench, where a rod installation is unlikely (indicated by yellow); for difficult ground, a specialist installation (i.e. drilling; indicated by red). However, the GIS can be interrogated to provide site-specific information such as site conditions, likely depth of installation and quantity of earthing materials required. The GIS was created from a spatial model constructed from soil, superficial and bedrock geology that has been attributed with engineering strength and resistivity values. Calculations of expected earthing rod resistance, rod or trench length, and all possible combinations of ground conditions have been compared with the ‘likely’ conditions required for each of the four proposed installation scenarios to generate the GIS layer. The analysis has been applied to the electrical network distribution regions of Western Power Distribution, in the English Midlands, and UK Power Networks, which covers East Anglia, London and the SE of England. Because the spatial model that underlies the GIS has been constructed from national databases the analyses can be extended to other regions of the UK.

Two hundred years of engineering geology

On 31 March 2007, a meeting entitled ‘Engineering Geology Through the Centuries’ was held at Keyworth in Nottingham. The meeting was convened jointly by the Engineering Group of the Geological Society of London (GSL) and the Yorkshire Geological Society, and formed part of the celebration of the bicentenary of the GSL. The meeting focused on the lives and achievements of a number of British engineering geologists who have made outstanding contributions to their profession and to science. The meeting formed part of the Societys ‘Local Heroes’ initiative for the bicentenary. The set of papers in this issue of the Quaternary Journal of Engineering Geology and Hydrogeology celebrates the contribution over the last 200 years by scientists and practitioners who have influenced the development of engineering geology or whose work has been particularly important to related aspects of human history. In addition to papers on the individuals discussed at the meeting, papers are included that discuss the development of engineering geology, historically and in the context of education and training. Engineering geology has been an important scientific sub-discipline for as long as people have sought to build and construct their living environment. If nothing else, people soon learnt where buildings could be built safely and where poor foundation conditions or the presence of geohazards meant that unacceptable risks were present. However, engineering geology came to greater prominence with the flowering of geology as a major science in the early 19th century, a time that saw the founding of the GSL in 1807. Of course, there have been many other influential engineering geologists in addition to those discussed in this collection of papers and the paper by Turner addresses some of these, as do accounts such as that on North America by Kiersch (1991). For the Keyworth meeting, the editors set out …

William Smith and the development of engineering geology in England

William Smith started his career in a world where much was known of geological matters and, with the publication of Huttons Theory of the Earth, knowledge was being tempered by understanding. His early training as a surveyor gave him the skills of accurate observation and recording together with a geographically wide experience that enabled him to recognize that strata could be ordered, and outcrops correlated, by the fossils that they contained. He first recorded this new concept in 1797 and used it to create the worlds first geological map (of the area around Bath) in 1799 and the first geological map of England and Wales in 1815. The national map was not only geologically detailed and accurate but also showed collieries, mines, canals and reclaimed land. Smiths intention was for it to show where to look for (and not look for) minerals. Thus, his recognition of ordered correlatable strata, his creation of the first geological map, his expertise in draining land, stabilizing landslides and planning canal routes amply demonstrates his ability to create, and apply, the 3D geological model that is a prime requisite in modern engineering geological practice. Therefore, he should be regarded as the first engineering geologist of the modern world. This paper will demonstrate the validity of this assertion.

An Ontology of Soil Properties and Processes

Assessing the Underworld (ATU) is a large interdisciplinary UK research project, which addresses challenges in integrated inter-asset maintenance. As assets on the surface of the ground (e.g. roads or pavements) and those buried under it (e.g. pipes and cables) are supported by the ground, the properties and processes of soil affect the performance of these assets to a significant degree. In order to make integrated decisions, it is necessary to combine the knowledge and expertise in multiple areas, such as roads, soil, buried assets, sensing, etc. This requires an underpinning knowledge model, in the form of an ontology. Within this context, we present a new ontology for describing soil properties (e.g. soil strength) and processes (e.g. soil compaction), as well as how they affect each other. This ontology can be used to express how the ground affects and is affected by assets buried under the ground or on the ground surface. The ontology is written in OWL 2 and openly available from the University of Leeds data repository: http://doi.org/10.5518/54.

URBAN GEOLOGY: INTEGRATING SURFACE AND SUB-SURFACE GEOSCIENTIFIC INFORMATION FOR DEVELOPMENT NEEDS

The British Geological Survey (BGS) operates an urban geoscience programme that aims to provide up-to-date information on ground-related issues for the towns and cities of the UK. Research in the major conurbations of Manchester, Swansea and Glasgow is demonstrating the value of integrating surface geological mapping with sub-surface geoscientific information through the use of three-dimensional models. This approach provides a more holistic view of the near-surface environment and provides a means of identifying potential problems and opportunities at an early stage in any proposed development. If implemented over a wider area, it could assist in designing site investigation strategies and reduce costs by ensuring a more focused approach to strategic planning.

Integration of Geohazards into Urban and Land-Use Planning. Towards a Landslide Directive. The EuroGeoSurveys Questionnaire

Exposure to hazards is expected to increase in Europe, due to rapid population growth in urban areas and the escalation of urbanization throughout many countries. In the framework of the European Geological Surveys (EGS), the Earth Observation and Geohazards Expert Group (EOEG) has carried out a survey based enquiry regarding the integration of geohazards (earthquakes, volcanoes, landslides, ground subsidence, floods and others) into urban and land-use planning. Responses from 19 European countries and 5 regions reveal heterogeneous policies across national borders. 17% of the countries have not yet implemented any legal measures to integrate geohazards into urban and land-use plans and half of the participating countries have no official methodological guides to construct geohazard maps. Additionally, there is a scarce knowledge about real social impacts of geohazards and resulting disasters in many of the countries, although they have a significant impact on their national economies. This overview stresses the need for a common legislative framework and homogenization of the national legislations as well as mutual guidelines which adopt the principles applicable to the management of geohazards and explain the process to be followed in the production of hazard documentation. This is especially relevant in case of landslide and subsidence hazards; although those are of great importance in Europe, there are no common guidelines and practices similar to Directive 2007/60/EC on the assessment and management of flood risk. Based on their expertise, EuroGeoSurveys (EGS) have the potential to coordinate this activity in European geohazard guidelines and to promote the interaction among stakeholders.