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Download Rock Engineering Practice  Design -   Tunnels Deep Tunnels –– Importance of GeologyImportance of Geology Weak rock under high stresses may lead to squeezing ground conditions, which may result

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  • Rock EngineeringRock EngineeringPractice & DesignPractice & Design

    Lecture 1: Lecture 1: IntroductionIntroductionIntroductionIntroduction

    1 of 30 Erik Eberhardt UBC Geological Engineering ISRM Edition

  • Authors Note:Authors Note:The lecture slides provided here are taken from the course Geotechnical Engineering Practice, which is part of the 4th year Geological Engineering program at the University of British Columbia (V C d ) Th k i i d (Vancouver, Canada). The course covers rock engineering and geotechnical design methodologies, building on those already taken by the students covering Introductory Rock Mechanics and Advanced Rock Mechanics Rock Mechanics.

    Although the slides have been modified in part to add context, they of course are missing the detailed narrative that accompanies any l l d h h l lecture. It is also recognized that these lectures summarize, reproduce and build on the work of others for which gratitude is extended. Where possible, efforts have been made to acknowledge th v ri us s urc s ith list f r f r nc s b in pr vid d t th the various sources, with a list of references being provided at the end of each lecture.

    Errors, omissions, comments, etc., can be forwarded to the

    2 of 30 Erik Eberhardt UBC Geological Engineering ISRM Edition

    Errors, omissions, comments, etc., can be forwarded to the author at: erik@eos.ubc.ca

  • Course OverviewCourse OverviewThis course will examine different principles, approaches, and tools used in geotechnical design. The examples and

    hi t i i d ill f case histories reviewed will focus primarily on rock engineering problems, although many of the analytical and numerical techniques reviewed are also numerical techniques reviewed are also used in other areas of engineering.

    Rock engineering design has largely evolved from different disciplines of applied mechanics. It is a truly interdisciplinary subject, with applications in geology and geophysics, mining, petroleum and geotechnical engineering.

    3 of 30 Erik Eberhardt UBC Geological Engineering ISRM Edition

  • Course OverviewCourse OverviewWhat makes geotechnical engineering unique is the complexity and What makes geotechnical engineering unique is the complexity and uncertainty involved when interacting with the natural geological environment.

    Rock masses are complex systems!

    Often, field data (e.g. geology, geological structure, rock mass properties, groundwater, etc.) is limited to surface observations and/or

    4 of 30 Erik Eberhardt UBC Geological Engineering ISRM Edition

    properties, groundwater, etc.) is limited to surface observations and/or limited by inaccessibility, and can never be known completely.

  • Deep TunnelsDeep Tunnels

    Gotthard Base-Tunnel (CH)

    Cost = $7 billion (and counting)Time to build = 12+ yearsLength = 57 km Length = 57 km Sedrun shaft = 800 m Distance between parallel tubes = 40 m Excavated material = 24 million tonnes

    0) e

    t al

    .(20

    00

    5 of 30 Erik Eberhardt UBC Geological Engineering ISRM Edition

    Loew

  • Deep Tunnels Deep Tunnels Importance of GeologyImportance of Geology

    Weak rock under high stresses may lead to squeezing ground conditions, which may result in damage/failure to the ground support system or require the costly re-excavation system, or require the costly re excavation of the tunnel section.

    al.

    (200

    0)Lo

    ew e

    t

    In strong brittle rock, high stress conditions may lead to rockbursting (the sudden release of stored strain energy). Bursts manifest themselves through

    6 of 30 Erik Eberhardt UBC Geological Engineering ISRM Edition

    strain energy). Bursts manifest themselves through the sudden ejection of rock into the excavation.

  • Deep Open PitsDeep Open PitsChuquicamata (Chile)

    Classification = open pit copper mine.Pit size = 4,500m long, 3,540m widePit depth = 800m (1100m by 2014)Pit depth = 800m (1100m by 2014)Production = 650,000 metric tons/yearOre grade = 1.1% Cu

    7 of 30 Erik Eberhardt UBC Geological Engineering ISRM Edition

  • Deep Open Pits Deep Open Pits -- Complex Complex InteractionsInteractionsFinsch Mine, South Africa

    (Flores & Karzulovic, 2002)

    Numerous mining operations are considering the move to underground in order to mine deeper resources h it th i d when open pits near their end.

    However, our body of practical knowledge related to the impacts of underground mining on the surface

    i t i li it d i t d i environment is limited, introducing economic risks to the mine and safety risks to mine personnel.

    P l b S th Af i

    8 of 30 Erik Eberhardt UBC Geological Engineering ISRM Edition

    Palabora, South Africa(Moss et al., 2006)

  • Hydroelectric ProjectsHydroelectric Projects

    )et

    al.

    (200

    4)Th

    uro

    e

    Nathpa Jhakri Hydroelectric Project (India)

    Estimated cost = $2 billionDam = 60.5 m concrete gravity damCapacity = 1500 MWConstruction = began in 1993 (was to take 5 years) Status = 4 units running 2 still to be completed

    9 of 30 Erik Eberhardt UBC Geological Engineering ISRM Edition

    Status = 4 units running, 2 still to be completedBoasts = largest & longest headrace tunnel in India

  • Hydroelectric Hydroelectric Projects Projects Rock Mass InteractionsRock Mass InteractionsWE WE

    Creepingrock mass4000

    M.a.s.l.

    SatlujH

    Typical majorrock slide (Fig.2)

    Foliation (quartz-mica-schists and related

    Stress

    3000

    2000

    UPHILLDeformation ofrock mass undercompression / tensionstress

    h

    Tunnel

    ated rock types)field

    2000

    1000

    Spallingof rock materialand shotcrete

    Bucklingof steel ribs

    Sheardeformation

    field

    11,5 m

    0 m1000200030004000 1000

    04)

    Cracks inshotcrete lining

    Foliation (quartz DOWNHILL

    11,5

    m

    ro e

    t al

    .(20

    0

    10 of 30 Erik Eberhardt UBC Geological Engineering ISRM Edition

    tz-mica-schist)

    DOWNHILL

    Thur

  • Rock as an Engineering MaterialRock as an Engineering Material

    A common assumption when dealing with the mechanical behaviour of solids is that they are:that they are:

    homogeneous continuous isotropic

    However rocks are much more complex

    isotropic

    However, rocks are much more complex than this and their physical and mechanical properties vary according to scale As a solid material rock is often: scale. As a solid material, rock is often:

    heterogeneous discontinuous anisotropic

    11 of 30 Erik Eberhardt UBC Geological Engineering ISRM Edition

    anisotropic

  • Rock as an Engineering MaterialRock as an Engineering Material

    sandstone strength

    Homogeneous Continuous Isotropic

    sandstoneequal in

    all directions

    Heterogeneous Discontinuous Anisotropicshale

    Heterogeneousfault

    Discontinuoushighstrength

    varies withdirection low

    Anisotropic

    sandstone joints

    12 of 30 Erik Eberhardt UBC Geological Engineering ISRM Edition

  • Rock as an Engineering MaterialRock as an Engineering MaterialTh k f t th t di ti i h k i i f th The key factor that distinguishes rock engineering from other engineering-based disciplines is the application of mechanics on a large scale to a pre-stressed, naturally occurring material.

    Hoeks GSIClassification intact

    rock

    rock mass ground response

    fractured

    13 of 30 Erik Eberhardt UBC Geological Engineering ISRM Edition

    fracturedrock

  • Influence of Geological FactorsInfluence of Geological Factors

    In the context of the mechanics problem, we should consider the material and the forces involved. As such, five primary geological factors can be viewed as influencing a rock mass.

    We have the intact rock which is itself divided by discontinuitiesto form the rock mass structure. to form the rock mass structure.

    We find then the rock is already subjected to an in situ stress.

    Superimposed on this are the influence of pore fluid/water flow and time.

    With all these factors, the geological history has played its part, altering the rock and the applied forces.

    14 of 30 Erik Eberhardt UBC Geological Engineering ISRM Edition

    g pp

  • Influence of Geological Factors Influence of Geological Factors Intact RockIntact Rock

    The most useful description of the mechanical behaviour of intact rock

    992)

    is the complete stress-strain curvein compression.

    ner

    et a

    l.(1

    9

    From this curve, several features of interest are derived:

    Lock

    n

    derived:

    deformation moduli (E, ) brittle fracture parameters Da

    mag

    e,

    AE

    cohesion Relative C

    al.(

    1999

    )

    brittle fracture parameters peak strength criteria the post-peak behaviour

    Cum

    ulat

    ive

    D

    damage

    Cohesion

    erha

    rdt

    et a

    l

    15 of 30 Erik Eberhardt UBC Geological Engineering ISRM Edition

    Normalized Stress (/cd) Ebe

  • Influence of Geological Factors Influence of Geological Factors Intact RockIntact Rock

    7)

    Strength, or peak strength, is the maximum stress, usually averaged over a plane, that the rock can sustain. After

    arri

    son

    (199

    7

    it is exceeded, the rock may still have some load-carrying capacity, or residual strength.

    Hud

    s

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