1 EOSC433 EOSC433 : Geotechnical Geotechnical Engineering Engineering Practice & Design Practice & Design Lecture 1: Introduction Lecture 1: Introduction 1 of 31 Dr. Erik Eberhardt EOSC 433 (Term 2, 2005/06) Overview Overview 2 of 31 Dr. Erik Eberhardt EOSC 433 (Term 2, 2005/06) Geotechnical 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. This course will examine different principles, approaches, and tools used in geotechnical design. The examples and case histories reviewed will focus primarily on rock engineering problems, although many of the analytical and numerical techniques reviewed are also used in soil engineering design.
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EOSC433: Geotechnical Engineering Practice & Design · Lab – Group Presentations. Term Report/Group Presentations 8 of 31 Dr. Erik Eberhardt EOSC 433 (Term 2, 2005/06) Oral Presentations
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EOSC433EOSC433::
Geotechnical Geotechnical Engineering Engineering
Practice & DesignPractice & Design
Lecture 1: IntroductionLecture 1: Introduction
1 of 31 Dr. Erik Eberhardt EOSC 433 (Term 2, 2005/06)
OverviewOverview
2 of 31 Dr. Erik Eberhardt EOSC 433 (Term 2, 2005/06)
Geotechnical 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.
This course will examine different principles, approaches, and tools used in geotechnical design. The examples and case histories reviewed will focus primarily on rock engineering problems, although many of the analytical and numerical techniques reviewed are also used in soil engineering design.
2
OverviewOverview
3 of 31 Dr. Erik Eberhardt EOSC 433 (Term 2, 2005/06)
What makes it unique is the complexity and uncertainty involved when interacting with the natural geological environment.
Often, field data (e.g. geology, geological structure, rock massproperties, groundwater, etc.) is limited to surface observations and/or limited by inaccessibility, and can never be known completely.
Rock masses are complex systems!
Course OutlineCourse Outline
4 of 31 Dr. Erik Eberhardt EOSC 433 (Term 2, 2005/06)
7 of 31 Dr. Erik Eberhardt EOSC 433 (Term 2, 2005/06)
Week 11: L10 – Rock Support– support vs. reinforcement strategies; ground response curves; support interaction curves.
Lab – RocSupport exercise.
Week 12: L11 – Excavation Methods– blasting; mechanical excavation (TBM); construction and use of empirical design
charts; Matthew’s method.
Lab – Group Presentations.
Week 13: L12 – Instrumentation– monitoring in design; instrumentation types;
data management.
Lab – Group Presentations.
Term Report/Group PresentationsTerm Report/Group Presentations
8 of 31 Dr. Erik Eberhardt EOSC 433 (Term 2, 2005/06)
Oral Presentations of Group Reports
Several groups will be formed, for which a short “consulting” report will be required (<10 pages) based on an analysis performed using any analytical, empirical or numerical method (or combination thereof) as applied to a case history to be assigned.
For example, a distinct-element analysis (e.g. using the program UDEC) of the GjØvik OlympiskeFjellhall/Underground Hockey Cavern in Norway using geometries and material properties obtained from the literature.
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General InformationGeneral Information
9 of 31 Dr. Erik Eberhardt EOSC 433 (Term 2, 2005/06)
Course: EOSC 433
Lectures: Tuesdays from 13:00 to 15:00 (Room 121, EOS Main)Labs: Thursdays from 13:00 to 15:00 (Room 203, EOS Main)
Contact Info – Office: 356 EOS SouthPhone: (604) 827-5573E-mail: [email protected]
Course Web Page –http://www.eos.ubc.ca/courses/eosc433/eosc433.htm
General InformationGeneral Information
10 of 31 Dr. Erik Eberhardt EOSC 433 (Term 2, 2005/06)
Text Book – The textbook (optional) to be used for this course is:
Lecture Notes – PDF’s of these Powerpoint slides will be made available for download via the course web page (hopefully the day before the lecture at the latest).
“Engineering Rock Mechanics - An Introduction to the Principles ” by J.A. Hudson and J.P. Harrison, Elsevier Science: Oxford, 1997.
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Rock as an Engineering MaterialRock as an Engineering Material
11 of 31 Dr. Erik Eberhardt EOSC 433 (Term 2, 2005/06)
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:
· heterogeneous · discontinuous · anisotropic
A common assumption when dealing with the mechanical behaviour of solids is that they are:
· homogeneous · continuous · isotropic
Rock as an Engineering MaterialRock as an Engineering Material
12 of 31 Dr. Erik Eberhardt EOSC 433 (Term 2, 2005/06)
sandstone strengthequal in
all directions
Homogeneous Continuous Isotropic
sandstone
shale
Heterogeneousfault
joints
Discontinuoushighstrength
varies withdirection low
Anisotropic
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Rock as an Engineering MaterialRock as an Engineering Material
13 of 31 Dr. Erik Eberhardt EOSC 433 (Term 2, 2005/06)
Hoek’s GSIClassification
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.
rock mass
intactrock
ground response
fracturedrock
Influence of Geological FactorsInfluence of Geological Factors
14 of 31 Dr. Erik Eberhardt EOSC 433 (Term 2, 2005/06)
We have the intact rock which is itself divided by discontinuitiesto 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.
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.
With all these factors, the geological history has played its part, altering the rock and the applied forces.
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Influence of Geological Factors Influence of Geological Factors –– Intact RockIntact Rock
15 of 31 Dr. Erik Eberhardt EOSC 433 (Term 2, 2005/06)
From this curve, several features of interest are derived:
The most useful description of the mechanical behaviour of intact rock is the complete stress-strain curvein compression.
Lock
ner
et a
l.(1
992)
Influence of Geological Factors Influence of Geological Factors –– Intact RockIntact Rock
16 of 31 Dr. Erik Eberhardt EOSC 433 (Term 2, 2005/06)
high stiffnesshigh strengthvery brittle
medium stiffnessmedium strengthmed. brittleness
low stiffnesslow strength
brittle
low stiffnesslow strength
ductile
Strength, or peak strength, is the maximum stress, usually averaged over a plane, that the rock can sustain. After it is exceeded, the rock may still have some load-carrying capacity, or residual strength.
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Influence of Geological Factors Influence of Geological Factors -- DiscontinuitiesDiscontinuities
17 of 31 Dr. Erik Eberhardt EOSC 433 (Term 2, 2005/06)
Discontinuities such as faults and joints may lead to structurally-controlled instabilities whereby blocks form through the intersection of several joints, which are kinematically free to fall or slide from the excavation periphery as a result of gravity.
Hoe
k et
al.
(199
5)
Influence of Geological Factors Influence of Geological Factors –– In SituIn Situ StressStress
18 of 31 Dr. Erik Eberhardt EOSC 433 (Term 2, 2005/06)
When considering the loading conditions imposed on the rock mass, it must be recognized that an in situ pre-existing state of stress already exists in the rock.
In the case of an underground excavation, such as a mine or tunnel, no new loads are applied but the pre-existing stresses are redistributed.
Total = In Situ + Excavation-Stress Stress Induced Stress
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Influence of Geological Factors Influence of Geological Factors –– In SituIn Situ StressStress
19 of 31 Dr. Erik Eberhardt EOSC 433 (Term 2, 2005/06)
Mar
tin
et a
l.(1
999)
Influence of Geological Factors Influence of Geological Factors –– In SituIn Situ StressStress
20 of 31 Dr. Erik Eberhardt EOSC 433 (Term 2, 2005/06)
Unstable
Stable
Stress PathRelaxationRelaxation
Wedge
In-Situ Stress
σ3
StressStressConcentrationConcentration
σ1
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Influence of Geological Factors Influence of Geological Factors –– GroundwaterGroundwater
21 of 31 Dr. Erik Eberhardt EOSC 433 (Term 2, 2005/06)
Many rocks in their intact state have a very low permeability compared to the duration of the engineering construction, but the main water flow is usually via secondary permeability (e.g. joints). Thus the study of flow in rock masses will generally be a function of the discontinuities, their connectivity and the hydrogeological environment.
A primary concern is when the water is under pressure, which in turn acts to reduce the effective stress and/or induce instabilities. Other aspects, such as groundwater chemistry and the alteration of rock and fracture surfaces by fluid movement may also be of concern.
Influence of Geological Factors Influence of Geological Factors -- TimeTime
22 of 31 Dr. Erik Eberhardt EOSC 433 (Term 2, 2005/06)
Rock as an engineering material may be millions of years old, however our engineering construction and subsequent activities are generally only designed for a century or less.
Thus we have two types of behaviour: the geological processes in which equilibrium will have been established, with current geological activity superimposed; and the rapid engineering process.
The influence of time is also important given such factors as the decrease in rock strength through time, and the effects of creep and relaxation
… the 1991 Randarockslide, Switzerland.
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Rock Engineering DesignRock Engineering Design
23 of 31 Dr. Erik Eberhardt EOSC 433 (Term 2, 2005/06)
Given the large scale of many of these projects, there is considerable economic benefits in designing these structures in the optimalway.
In practice, it quickly becomes evident that one ignores rock mechanics principles and rock engineering experience at considerable physical and financial peril.
24 of 31 Dr. Erik Eberhardt EOSC 433 (Term 2, 2005/06)
Düz
gün
& La
cass
e(2
005)
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Site Investigation & Data CollectionSite Investigation & Data Collection
25 of 31 Dr. Erik Eberhardt EOSC 433 (Term 2, 2005/06)
Rockmassprocesses
geological model
Geophysical investigations
Geological investigations
Will
enbe
rg e
t al
.(2
004)
Site Investigation & Data CollectionSite Investigation & Data Collection
26 of 31 Dr. Erik Eberhardt EOSC 433 (Term 2, 2005/06)
Rockmassprocesses
geological model
Geophysical investigations
Geological investigations
Stabilityanalysis
Controllingmechanism(s)
failure kinematics
Geotechnical monitoring
Willenberg et al. (2004)
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Design MethodologyDesign Methodology
27 of 31 Dr. Erik Eberhardt EOSC 433 (Term 2, 2005/06)
Successful engineering design involves a design process, which is a sequence of events within which design develops logically. Bieniawski(1993) summarized a 10 step methodology for rock engineering design problems, incorporating 6 design principles:
Statement of the problem
Step 1:
Functional requirements and
constraints
Step 2:
performance objectives
Design Principle 1: Clarity of design objectives and functional requirements.
Design MethodologyDesign Methodology
28 of 31 Dr. Erik Eberhardt EOSC 433 (Term 2, 2005/06)
Statement of the problemStep 1:
Functional requirements and constraints
Step 2:
performance objectives
Design Principle 1: Clarity of design objectives and functional requirements.
design variables & design issues
Collection of informationStep 3:geological characterization, rock mass properties, in situstresses, groundwater, etc.