A2.2GL3 Geology

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A2.2GL3Geology

• Welcome to the module

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The Module

• Presenters
• Professor Mike Paul (Life Sciences WP3.07)
• Dr Bev Barras (Life Sciences WP 3.06)
• Classes
• Lectures Tuesday 1015-1215
• Practicals Wednesday TBA

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Programme

• Week 1 Introduction to geology
• Week 2 Engineering in rock
• Week 3 Geological maps
• Week 4 Engineering geophysics in SI
• Week 5 Landslides
• Week 6 - NO CLASS (University holiday)
• Week 7 Glacial sediments and landforms

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Assessment

• Examination (2hrs) 65
• Coursework - geological maps 35

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Course Materials

• Powerpoint lectures, handouts, specimen exam
  papers, other paperwork
• Available on the School of Life Sciences website
  www.sls.hw.ac.uk/
• (Link) modules
• (Link) level 2
• Username/password venice/venice
• Module A2.2GL3 Geology

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• Suggested reading
• McLean A.C. C.D.Gribble. 1985. Geology for
  Civil Engineers (2nd ed) George Allen Unwin
• F.G.H.Blyth M.H. de Freitas. 1984. A Geology
  for Civil Engineers (7th ed). Edward Arnold.
• F.G.Bell. 1998. Environmental Geology.
  Blackwell.
• Please note that these are for supplementary
  reading and are not set textbooks

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Part One
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Engineering geology

• What can geology do for me?

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• A site investigation to provide data for design
  should be basically an exercise in engineering
  geology, for if at the very start the geological
  structure of the site is misinterpreted, then any
  subsequent sampling, testing and calculation may
  be so much labour in vain.
• Rudolph Glossop, 8th Rankine Lecture (1968)

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• Geology is the study of the Earth its origin,
  configuration and evolution
• It draws on basic ideas from physics, mechanics,
  chemistry and biology
• It sets these into a spatial context and into a
  time frame

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• Engineering geology is the application of
  geological concepts to problems in civil
  engineering.
• Site appraisal and investigation
• Foundation and excavation design
• Slope stability
• Environmental protection

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• Geology provides a way of thinking about
• The types of material present
• How they are arranged in 3D
• What are their properties
• What processes have operated in the past or at
  the present day

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What do we need to know?
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• How to recognise and interpret rocks, soils and
  landforms
• How to use geological maps
• How to read the ground

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Basic ideas

• Rocks

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Rocks

• Rocks are formed by three processes
• Melting of existing material. This creates
  IGNEOUS rocks.
• Erosion and deposition of particles from existing
  material. This creates SEDIMENTS and SEDIMENTARY
  rocks.
• Heating of existing material without melting.
  This creates METAMORPHIC rocks.

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Igneous rocks

• Igneous rocks are formed by volcanic eruption or
  by solidification underground
• The former are known as extrusive rocks and
  include lavas, volcanic debris flows and ash
• The latter are known as intrusive rocks and occur
  in a variety of underground shapes each with
  different names

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Mount St Helens, 1980
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Typical granite outcrop
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Rubislaw granite quarry, Aberdeen
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Sedimentary rocks

• Sedimentary rocks are composed of separate
  particles held together by cement
• SILICICLASTIC sediments - composed of separate
  silicate particles
• CALCEREOUS sediments - composed of carbonate
  sediments, perhaps formed by biological action
  (limestones eg)

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Quarried sandstone
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Bute House, Charlotte Square Craigleith sandstone
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Sandstone cliffs - Petra, Jordan
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Chalk cliffs - Dover area
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Limestone (ironstone) building - Rockingham,
Northants
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Metamorphic rocks

• These are rocks that are altered mineralogically
  by temperature and/or pressure while still
  remaining solid.
• A very wide variety of such rocks is known, owing
  the the wide variety of possible starting
  materials.

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Mica schist, Loch Rannoch
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Dinorwic slate quarry North Wales
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Basic ideas

• Time

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• Geological time refers to the time elapsed
  since the formation of the Earth - about 4,600
  million years in total
• It can be measured by
• relative dating using fossils
• absolute dating, using the decay rates of various
  natural radioactive isotopes found in rocks

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• Relative dating leads a division into named time
  units identified by the presence of
  characteristic fossils
• For example
• Carboniferous period
• Jurassic period
• The names are historical, based on the type of
  rock, locality or other association

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• There is a hierarchy of units
• Era
• Period
• Stage
• The stage is usually the smallest practicable
  unit, and represents the time over which a
  distinctive species of fossil can be recognised

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• Three points should be noted
• The resulting time periods are very unequal if
  measured in absolute years
• The fossils used to define the time units must be
  common - hence marine shells or similar organisms
  are often used
• Rocks which do not contain fossils must be dated
  indirectly, e.g by their association with other,
  datable rocks

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• The distribution of rock types from the major
  time units across the British Isles is shown on
  this map.
• In a general sense, the oldest rocks are found in
  NW Scotland and the most recent in SE England.

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A SHORT BREAK

• Come back in 10 minutes

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Part Two

• Some applications

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Geology in Ground Investigation
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• If you do not know what you are looking for in a
  site investigation, you are not likely to find
  much of value.
• Rudolph Glossop, 8th Rankine Lecture (1968)

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• Phase 1 desk study and walk-over
• Maps,
• Aerial photos
• Old records
• Site visits

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• Phase 2 main subsurface investigation
• Geophysics (?)
• Boreholes, trial pits
• Sample collection and testing
• Design and calculation

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Shell and auger rig in operation Used to
collect undisturbed samples in soft ground
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Rotary corer in operation. Used to collect
undisturbed samples in hard ground
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Sediment cores from the Sellafield investigations
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A relatively simple seismic survey
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Typical equipment for a large geophysical survey
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Geology in Soil Engineering
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Slope stability

• Stabilisation of active landslides on eroding
  coasts cut into soft sediments

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Holbeck Hall, Scarborough (June 1993)
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The Holbeck Hall slide after remediation (2003)
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Slope stability

• Earthworks failures on old landslides from former
  cold climates

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Slope disturbance due to solifluction
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The Sevenoaks Bypass (A21) following realignment
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Slope stability

• Landslides triggered by exceptional events such
  as severe rainfall.

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Lochearnhead landslide, summer 2004
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Subsidence

• Subsidence arises from underground mining
• coal
• oil-shale
• salt
• limestone
• and from natural solution by groundwater

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Subsidence

• Predicting the amount of subsidence and the
  extent of the affect areas is a fundamental
  engineering geological problem.

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Crown hole above tin workings near Redruth
(Cornwall)
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Subsidence at Ferniehill, Edinburgh - former
limestone workings
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Geology in Rock Engineering
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Damsites

• Require structural integrity against both leakage
  and deformation

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Damsites

• Failures have resulted from
• internal erosion
• foundation movement
• catastrophic overtopping

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Malpasset Dam, Frejus (French Alps)
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Tunnels

• Require stability of the opening against a
  variety of failure modes
• Need to be watertight
• Method of excavation must be considered from
  geological viewpoint

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Gross Glockner Tunnel portal
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Channel Tunnel portal Calais
Sewer tunnel inspection
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Channel Tunnel Rail Link North Downs Tunnel
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Geology in Environmental Protection
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Coastal protection

• Coastal protection is a natural sequel to coastal
  erosion
• It involves an understanding of both geological
  deposits and the present day wind/wave/tidal
  regime

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Palisade to protect toe of eroding cliffs and
thus prevent landsliding
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Groynes to prevent longshore movement of sediment
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Concrete sea wall - note scour in front of wall
footing
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Caged rip-rap to absorb wave energy (made of .?)
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Waste disposal

• The selection and operation of waste disposal
  sites requires knowledge of the geological
  security of the site and of any possible changes
  over the lifetime of the waste.

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CONCLUSIONS
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• Geology is an integral part of civil engineering
• The keys to success are
• Understanding the principles
• Recognising their application to your problem
• Dialogue with specialists

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THE END
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