mehanika stijena-dostignuća i aktualni problemi - · pdf filerock mechanics-achievements and...

Rock mechanics-achievements and current problems Mehanika stijena-dostignuća i aktualni problemi

Prof. em. Ivan Vrkljan

Faculty of Civil Engineering University of Rijeka President of Croatian Geotechnical Society ISRM Vice President at Large (2011-2015)

Foundation of the ISRM Some of actual rock mechanics and rock

engineering problems - Rock behaviour characterisation - In situ stress and residual stress in intact rock - What is the Strength of a Rock Mass?

Rock mechanics position in Eurocode 7 Polemics in rock mechanics community Expectations of rock mechanics and ISRM Conclusions

Content

Foundation of the ISRM

Geology Engineering geology Rock mechanics

Malpasset, 1958 450 people were killed

Circumstances in which the rock mechanics has been recognized

Critical mass of knowledge about the behavior of rock masses have been reached.

Technologies of excavation and stabilization have begun to significantly affect on the rock engineering and rock mechanics.

The hardline of experts in the field of soil mechanics that rock mechanics should be developed within the soil mechanics.


For rock mechanics recognition, next circumstances are specially important:

Bjerrum, Terzaghi i Casagrande, august, 1957. (ISSMFE officers)


1910-1964: 60 slides were recorded in cuts along the Panama canal. These slides were predominantly controlled by structural

discontinuities. 1936: Karl Terzaghi on the first international conference on Soil

Mechanics and Foundation Engineering in 1936 : ‘The catastrophic slopes of the deepest cut of the Panama Canal showed that we were overstepping the limits of our ability to predict the consequences of our actions ....’

The early 1960s were very important in the development of rock engineering world-wide.


Panama Canal


Müller officially registered the ISRM with the name

„Internationale Gesellschaft für Felsmechanik“ Correspondence between Bjeruma, as Vice ISSMFE President,

shows that Müller registered Society only when Terzaghi gave his consent.

Terzaghi was Müller’s professor and he wanted that new Society to be born with his agreement.

Müller and ISMFE leadership wished that two Societies have a close collaboration.


ISRM Constitutional Meeting, Salzburg, 25 May 1962. Voting.


ISRM Constitutional Meeting, Salzburg, 25 May 1962. Head table with Müller and Pacher


Prof. Josef Stini Engineering geol.

(1993-1958)

Prof. L. Müller Rock mechanics

(1908-1988)

Prof. Karl von Terzaghi Soli mechanics

(1883-1963) It is truly remarkable that the founders of the disciplines of Engineering

geology, Soil mechanics and Rock mechanics - each now represented by International Society were all from Austria.


ISRM 50-years anniversary celebrations

started in October 2011 in Beijing, had a peak during the Eurock2012 in Stockholm, and finish in October 2012 during the 61st Geomechanics

Colloquy in Salzburg, the same city where it was formed in 1962.

The celebrations of the 50th anniversary of the ISRM

ISRM 50th Anniversary Commemorative Book 1962-2012

A number of activities took place during this year of celebrations, among which the publication of the


Salzburg, 2012. Dr Franz Pacher, the only living member of the ISRM founders


Leopold Müller Award

The award is made once every four years in recognition of distinguished contributions to the profession of rock mechanics and rock engineering

Prof. Leopold Müller

Evert Hoek CANADA, 1991

Neville Cook USA, 1995

Herbert Einstein USA 1999

Charles Fairhurst USA, 2003

Ted Brown AUSTRALIA, 2007

Nick Barton UN KINGDOM , 2011

Leopold Müller Award Recipients of the Müller Award

John A. Hudson UN KINGDOM , 2014

John Hudson

John Franklin

• More than 50 Suggested methods have been published • 18 ISRM commission and 3 Joint Technical Committee are active

ISRM Suggested Methods

ISRM achievements of the past 50 years

SUGGESTED METHODS are NOT standards They are explanations of recommended procedures to follow in the various aspects of rock characterisation, testing and monitoring. However, the SMs can be used as standards on a particular project if required, but they are intended more as guidance.



ISRM Suggested Methods are presented with standardized formats, each of which has the following contents: (1) Introduction and history of the suggested method, (2) Scope, (3) Apparatus, (4) Procedure, (5) Calculations, (6) Reporting, (7) Final credits, (8) Acknowledgments, and (9) References.



1981 edited by E.T. Brown Rock characterization, testing & monitoring

Yellow Book

The first collection of the Suggested Methods of the ISRM was edited by Professor Ted Brown and published by Pergamon Press in 1981.



Editors: R. Ulusay and J.A. Hudson. The Complete ISRM Suggested Methods for Rock Characterization, Testing and Monitoring: 1974-2006 40 methods

Blue Book



Free for ISRM members!

Orange Book

Editor, R. Ulusay SMs 2007 – 2014.


21 separate new and upgraded ISRM Sms


Online lecture

The ISRM Online Lecture series was launched in 2013. Every three months, experts in different fields of rock mechanics were invited to give a lecture on a specific topic.



https://www.isrm.net/gca/index.php?id=1190

ISRM ISRM President 2015-2019. Dr. Eda Freitas de Quadros, Brazil

First woman as president of ISRM or ISSMGE in 75 years


The aim of FedIGS The aim of FedIGS is enhance cooperation between international geo-engineering societies.

FedIGS

The three founding sister societies are

1. ISSMGE (International Society for Soil Mechanics and Geotechnical Engineering),

2. IAEG (International Association for Engineering Geology) and

3. ISRM (International Society for Rock Mechanics).

More recently

4. IGS (The International Geosynthetics Society) joined the group

and others are being invited to join.

FedIGS

http://www.iaeg.info/

http://www.issmge.org/en/

http://www.isrm.net/

http://www.geosyntheticssociety.org/

The current position of the FedIGS

FedIGS operates at low level of activity without secretarial assistance and with only 3 JTC’s. (Joint Technical Committee)

JTC1 - Natural Slopes and Landslides JTC2 - Representation of Geo-Engineering Data JTC3 - Education and Training

FedIGS

The historic meeting of the Presidents of the sister Societies in Lisbon where it was decideed in principle FedIGS (2007)

FedIGS

Some of actual rock mechanics and

rock engineering problems

We have a wide range applications to the rock mechanics and the design in rock engineering.

We deal with natural material.

Different behaviour of same rock in different conditions.

Actual problems

We are faced with several problems:

Wide range of applications

• Foundation, • Slope, • Tunnel, • Mine (underground and open pit), • Geothermal energy, • Petroleum engineering, • Waste disposal.

Actual problems

Rock mass is natural material

• Discontinuous • Inhomogeneous • Anisotropic • Not Elastic

acronim: DIANE

Rock is unlike many other artificial materials, like concrete or steel, or soil, mainly due to discontinuous character.

• Pre loaded

Actual problems

We deal with deformed and fractured rock It is important to understand the sequence of fracturing Modeling and design techniques require structural geology information

to be explicitly included in computer model

Rock mechanics and structural geology

Actual problems

Past FUTURE Structural Geology

Interpretation of natural processes that have created the rock structures we see today

Prediction of natural geohazards, such as volcanic eruptions, earthquakes, landslips

Rock Mechanics Interpretation of past engineering practice: past successes, and past failures

Prediction of the rock mass response to engineering perturbations

Hudson 2012, Beijing

Rock mechanics and structural geology subject of interest

Actual problems

Natural fracture Artificial fracture

Rock slabbing and spalling

Actual problems

Different behavior of the same rock around shallow and deep tunnels

Garvity induced failure Failure controlled by rock mass structure

Stress induced failure causing slabbing and spalling, sqeezing

Actual problems

Gravity induced behavior – discontinuity controlled blocks Mechanism: gravity induced failing, sliding or rotating of blocks into the excavation, along discontinuities with potential for local shear failure.

Important parameters:

• number, orientation and distance of discontinuities or degree of fracturing, • waviness, • roughness persistence, • tension and shear strength in general, • strength and deformability of the rock material, • water pressure, • primary stress conditions.

Actual problems

Stress induced behavior Mechanism: the loading of the rock mass due to secondary stresses around the excavation exceeds the rock mass strength.

Important parameters:

deformation and strength parameters of intact rock, discontinuities and rock mass.

Goricki

Actual problems

Squeezing Shear failure mode

Spalling, slabbing High uniaxial stress

Stress induced behavior

σ3=O

Actual problems

Different behavior of the same rocks in the vicinity of the excavation

1- Uniaxial stress

1 2- Traiaxial stress

2 3- Tensile stress

3

Actual problems

Axial strain εax

σax

Ductile

Brittle

Traiaxial test

σ1

σ1

σ3

σ3

σ3

σ3

Deformability and strength in function of the lateral pressure

Confining pressure increasing

σ3= 0

σ3≠0

σ3≠0

σ3≠0

Actual problems

“True” rock behaviour – a primary geomechanics challenge

Rock behaviour characterisation

Geological data collection

Laboratory and in situ testing

Rock mass characterization and classification (Q, RMR, GSI, joint properties, in situ stress, water, …)

Selection of excavation and support alternatives

Numerical methods

Empirical methods

Gravity-driven failure

Stress-driven failure

Excavation and support design

Rock mass behaviour ?




Site characterisation approach for standard geo-engineering projects

Kaiser and Kim, 2008.


Peter Kaiser, Canada

From shallow to deep tunnelling, costly mistakes can be made because the rock behaviour may change and the rock may behave in an unexpected manner. Rock may behave differently when unconfined (near an excavation) or when confined (in the core of a pillar). Hence, it is not sufficient to just provide a geological and a rock mass model; it is necessary to translate the knowledge gained from geological to rock mass and then to rock behaviour models.


Rock behaviour models

Geological model

Rock mass model

Rock behaviour

model

Site characterization

?

Kaiser:

Distinction by failure or behaviour mode is often ignored or even misrepresented by the chosen numerical model. Almost exclusively, the most commonly recognised behaviour modes are related to shear failure; either along block boundaries or through the rock mass. The effects of tensile failure or spalling are rarely anticipated and correctly modelled, and thus not properly described.

Distinction by failure or behaviour mode is very importnt!


Distinction by failure mode

Kaiser:

axial strain εax

σax Before failure After failure

Failure envelopes are smooth forms (linear and nelienaran)

Simultaneously mobilisation of cohesion nad friction

c+ σtanΦ Is this approach correct? Observations show that it IS NOT!

c+= φστ tan

5,0'3'

3'1 1

++=

ciici mσσσσσ

σ

τ (σ1)

(σ3)

Failure criterion Rock behaviour characterisation

p'

q'

1,5% εax

4% εax

7,5% εax 12% εax

0,75% εax

Transition from a cohesive to a

frictional yield mode (Schmertman i Osterberg, 1960.)

the frictional strength component dominates at large strains and high confinement.

the cohesive strength component dominates at low strains and at low confinement (p’)

Bi-linear failure envelope of over-consolidated clays


σ 1/ σ

c

σ3/σc

Tension

Axial splitting

Triaxial state (shear failure)

S-shaped failure criteria

much beter describes the behavior of rock

mass in situ

Intact rock strength

Spalling failure

In situ strength

Deamage threshold


Kaiser, 2008.

tensile type failure shear type failure


Triaxial tests

H-B criterion

Failure criterion of limestone

Faculty of civil engineering Rijeka

0,1 UCS

ACS UCS

σ3

σ1

GSI=50

Spalling limit σ1/ σ3~10

GSI=100 Intact rock


tensile type failure shear type failure

c+= φστ tan

Cohesion + friction

Cohesion than friction

a

cibci sm

++=

σσσσσ

'3'

3'1


Mohr-Coulomb

Hoek & Brown

τ

σ

τ

σ

In more general terms, the fundamental shear strength equation with strain-independent parameters

τ = c +σ ' tanφ is not applicable over the entire confinement range for brittle rocks and thus may be misleading when applied to rock mechanics problems.


Kaiser P.K., 2010, How highly stressed brittle rock failure impacts tunnel design, Eurock-2010-Laussane, Switzerland, p.p. 27-38.

Kaiser:

Barton was interviewed by Vrkljan during Barton's stay in Croatia from 1 to 6 June 2011.

“Conventional continuum modelling with ‘c plus σ’ tan φ’ (linear or non-linear) does not describe rock mass baviour good enough. So all the ‘colour’ in consultants and students appendices showing ‘plastic zones’ are actually better omitted, until a general improvement of method is adopted ‘c than σ’ tan φ’ (degrade cohesion and mobilize friction at different strains)”.


In situ stress and residual Stresses in the Intact Rock

World Stress Map, 2008 (Tectonic scale and regional stresses)

In-situ Rock Stress

In engineering practice, we have little benefit from this map because we operate in a small area (site scale).

Tectonic scale and regional stresses Site scale Excavation scale Borehole/measurement scale Microscopic scale

In-situ Rock Stress

Scale effect on the in-situ stress

Principal stresses are parallel and perpendicular to the free surface.

Principal stresses are locally parallel and perpendicular to the fracture surface.

Geological effect- rock fracture will change the orientation and size of the principal stress

The Influence of a free face Engineering effect- excavation surfaces

Rock mass

Fracture

σ1 σ3

σ1 σ3

In-situ Rock Stress

The Influence of a free face

In-situ Rock Stress

2

3

1 2

3

1


In-situ Rock Stress

Hermosillo, Mexico


In-situ Rock Stress

Cracks in concrete

Carrara marble quarries in Italy

Residual stresses

Finlandia City Hall, Helsinki (2001). The new marble panels clearly bowed in less than 1 year after the old marble panels had been replaced. Almost all of the old panels were bowing concave, however the new panels bow convex! In both cases the marble type was a Carrara marble.

Hudson, 2009

Residual stresses

ZAGREB - Croatia Carrara marble

Residual stresses

What is the Strength of a Rock Mass?

Müller and Pacher, were interviewed the same day when ISRM has been founded on a Salzburg radio station. In the interview, the reporter asks: “Do we know the strength of rock?” Müller replied: “For rock (specimens) tested in the laboratory, yes”.

What is the strength of a rock mass?

Müller: For a rock mass, no. This is what we need to determine. This is why we need an International Society for Rock Mechanics.”


Müller’s central question “What is the strength of a rock mass?”

How far we have come in answering the question?


What is the Strength of a Rock Mass? Progress in answering Müller’s (implicit) question

Vienna-Leopold-Müller Lecture, 2010.

Charles Fairhurst


How to solve problem of discontinuous character of rock mass and scale effects?

Large in-situ test (Plate load teste, large flat Jack test, test chambre)

Back analysis based on observations

Numerical analysis


Discontinuum analysis has been introduced to rock mechanics in 1971. Peter Cundall, then a student of Prof E. Hoek at Imperial College, London presented the paper: “A Computer Model for Simulating Progressive Large Scale Movements in Blocky Rock Systems” Cundall and his colleaguse have cotinued to develop the “discrete element method” for modelling of jointed rock to the present time.

The Synthetic Rock Model (SRM)


The rock mass is assumed to be composed of two principal components:

intact rock a system of joints

Synthetic Rock Model (SRM)

Constitutive behavior of the intact rock should be determined from standard laboratory tests in which the ‘complete stress-strain response’ is observed.

σax

εax


Synthetic Rock Model (SRM)

Rock mass Fracture Representation (DFN) Discrete Fracture Network

Intact Rock Representation

(PFC) Particle Flow Codes

The intact rock is represented in the model by an assembly of circular discs or spheres bonded at the contacts. The joints are introduced into the intact rock model through the Smooth Joint Model (SJM) which allows slip and opening on joint planes.


Comparison of the discontinuum (SRM) and continuum (FLAC) analyses (Fairhurst, 2010)

In the FLAC continuum analysis discontinuous slip along joints This comparison is encouraging. The expectations from SRM are great.

Synthetic Rock Model (SRM) 40,225 discontinuities 330,000 particles 38,656 blocks


Computer methods now allow us to consider virtually many of the rock mechanics questions that have been raised over the last 50 years.

Advances in computer power and disconinuum modelling provide a more rational framework for rock rengineering than current empirical rules.

The critical next step to advance rock machanics and rock engineering is to obtain field-scale data to verifay and improve numerical predictions. Urgent attention should be given to developing cost-effective ways to obtaing such data.

Fairhurst about Synthetic Rock Model (SRM)


Many empirical rules have been develeoped due to complex mechanical behaviour of the rock mass.

An important limitation of empirical rules is that they should not be

used outside the boundaries within which these laws were developed. That is not always respected.

When the better theoretical framework becoming available, we will have to check these rules.

Until then, empirically approach will play an important role in rock

mechanics and rock engineering.

Empirical approach


Bieniawski: RMR-Rock Mass Rating

Barton: Q system; Shear strength of discontinuities Hoek & Brown: Rock mass failure criteria; GSI

Empirical approach


The foundations of the Millau viaduct in France (François Schlosser )

Hoek-Brown failure criteria

Empirical approach


Empirical methods still find wide-spread use today

Olympic games 1994

The worlds largest cavern hall for public use

Height : 25 m Length: 91 m Width: 62 m

Q system, Barton

Empirical methods still find wide-spread use today

Empirical approach


Rock mechanics position in Eurocode 7

2010 The Eurocode 7 or EC7, EN-1997-1:2004 (CEN, 2004), became the Reference Design Code (RDC) for geotechnical design – including rock engineering design – within the European Union (EU).

Eurocode 7

2018-2020 The next version of EC7 will be written between now and 2018, and will then be published in 2018 for adoption in 2020.

EC7 has been also adopted by a number of other countries beyond the EU. On this way it is becoming a key design standard for geotechnical engineering worldwide.

Eurocode 7

Impact of Eurocode 7 worldwide

1980 Agreement between the Commission of the European Communities (CEC) and the International Society for Soil Mechanics and Foundation Engineering (ISSMFE). 1981 ISSMFE established an ad hoc committee for this task. 1987 ISSMFE produced a ‘draft model for Eurocode 7. 1990 Work was transferred to CEN (Comité Européen de Normalisation / European Committee for Standardisation), and in particular CEN’s Technical Committee TC250.

Eurocode 7

Harrison et al, 2015.

EC7 development has been undertaken from the point of view of foundations and retaining structures on and in soils.

Eurocode 7

In EC7 development, ISRM and IAEG have not been formally involved.

It is now widely recognised that EC7 is in many ways inappropriate – and in some circumstances inapplicable – to rock engineering. ISRM Commission on Evolution of Eurocode 7 http://www.isrm.net/gca/?id=1143

Maintenance period was aimed at improving the applicability and ease-of-use of the EC7. Maintenance period started in 2011 and will conclude in 2020 with the publication of a revised version of EC7.

Eurocode 7

Maintenance work programme 2011-2020

Eurocode 7

http://eurocodes.jrc.ec.europa.eu/images/MaintenanceWP

.gif

The Eurocode maintenance work programme

http://eurocodes.jrc.ec.europa.eu/images/MaintenanceWP.gif



2011 CEN/TC250/SC7 established 14 Evolution Groups (EGs) to identify how EC7 could be improved.

John Harrison (Secretary of EG 13)

Andrew Bond (chairman TC250/SC7)

Eurocode 7

Eurocode 7

EG Title Members (Convenor/Secretary) 0 Management and oversight Andrew Bond (Chairman SC7) 1 Anchors Eric Farrell (Ireland) 2 Maintenance and ease-of-use Bernd Schuppener (Germany) 3 Model solutions Trevor Orr (Ireland) 4 Numerical methods Andrew Lees (Cyprus) 5 Reinforced soil Martin Vanicek (Czech Republic) 6 Seismic design Giuseppe Scarpelli (Italy) 7 Pile design Christian Moormann (Germany) 8 Harmonization Andrew Bond (Chairman SC7) 9 Water pressures Norbert Vogt (Germany) 10 Calculation models Christos Vrettos (Germany) 11 Characterization Lovisa Moritz (Sweden)) 12 (Tunnelling) To be decided 13 Rock mechanics John Harrison (UK/Canada) 14 Ground improvement Paolo Croce (Italy)

Eurocode 7

identify deficiencies in EC7 with regard to rock engineering design and construction practice;

bring these deficiencies to the attention of CEN/TC250/SC7 and the other Evolution Groups;

inform the rock mechanics community of the maintenance cycle, in order to ensure that CEN/TC250/SC7 obtains as much practical feedback on the use of EC7 as possible.


Rock mechanics EG 13 tasks

Eurocode 7

Preliminary Workshop at the Eurock 2012 conference in Stockholm, Sweden, Workshop on the “Applicability and application

of Eurocode 7 to rock engineering design” at the Eurock 2014 conference in Vigo, Spain.

Evaluation Group 13 (EG) activity

Andrew Bond (chairman TC50/SC7) Evaluation of Eurocode 7 Delft workshop, 30 Nov-1 Dec 2011

Eurocode 7

SC7's highest priorities for development in next revision of EN 1997

1. Harmonization (Simplify/reduce number of Design Approach; Revise/harmonize NDPs following review of countries' National Annexes)

2. Incorporate recent research results and technical studies (Add/improve guidance on ground water pressures; numerical models; selection of characteristic parameters; use of EN 1997 with EN 1998for seismic design)

3. Sustainability (Remove conservatisms from connection with structural Eurocodes; provide better treatment of consequence/ reliability clases)

4. New part of Eurocode 7 (Reinforced soil, rock mechanics, tunnelling) 5. Simplification of rules (Revise EN 1997-2 to remove material readily

found elsewhere; revise/remove text duplicated scross ENs 1997-1 and 2.

2014 ISRM Commission on the Evolution of Eurocode 7 has been established. The inaugural meeting of the Commission was held in Vigo, Spain during the EUROCK 2014.

Eurocode 7

ISRM activities related to EC7

http://www.isrm.net/gca/?id=1143

http://www.isrm.net/gca/?id=1143

Eurocode 7

Tunnelling in EC7

Geotechnical category 2 Tunnels in hard, non-fractured rock and not subjected to special water tightness or other requirements.

Is there are non-fractured rock?

Schubert: In EC 7 tunnels in general belong to the category 3 structures, requiring detailed investigation and analysis.

Eurocode 7


Limit State Design (LSD)

However, it is not clear that current rock engineering design practice can satisfy this requirement.

EC7 requires designs to adhere to the principles of Limit State Design.

Eurocode 7

Ferrero, A.M., Sofianos, A., Alejano, L.R., 2014, Critical review of Eurocode-7 regarding rock mass characterization. Eurock 2014 Workshop, 26th May, Vigo, Spain, pp.

Rock mass characterization

EC7 does not give details on rock mass characterization and on how the rock discontinuities should be considered in order to quantify the degree of fracturing and anisotropy.

Prescriptive measures Rock mass classification systems

Eurocode 7

Lamas et al, 2014.

Empirical prescriptive measures is allowed in EC7 “ in design situations where calculation models are not available or are not necessary”.

1. Which type of geotechnical structures? 2. Does design by prescriptive measures (classification

systems) can be apply only to EC7 category 1 or also to geotechnical category 2?

Schubert calls for reducing the use of these techniques

Polemics in rock mechanics community

NATM New Austrian Tunnelling Method

Neue Österreichiche Tunnelbaumethode (Neue Österreichiche Tunnelbauweise)


1944 Rabcewicz, idea 1948 Rabcewicz, patent 1956 Venezuela, first use 1963 Birthday of NATM L. Rabcewicz, L. Müller and F. Pacher ("fathers" of the NATM).

Kovári NATM

At the Rabcewicz-Geomechanical Colloquium held in Salzburg in 1993, on the occasion on the thirtieth anniversary of the birth of the NATM, professor K. Kovári criticized the NATM concept.


Prof. Kovári and Prof. Likar, Ljubljana, 2000

Prof. Kalman Kovári, (ETH Zürich), 1993. Lecture given at the Rabcewicz-Geomechanical Colloquium in Salzburg,

Octobre 14, 1993

NATM rests not on an established theoretical foundation, but rather on two

fundamental misconceptions (fundamental error).


1. The rock mass (ground) becomes part of the support structure.

2. NATM theory can optimize the design of the tunnel lining following the so-called Fenner-Pacher ground reaction curve.

Terzaghi Fillunger


The University blamed Fillunger, who then committed suicide by opening the gas jets in the bathroom, with his wife Margarete Gregoritsch 08.03.1937.

It seems that the remaining scientific and professional community observed these events without too much interest.

According to Prof. Gudehus, the polemic between Prof. Kovári and Austrian experts was exceeded only by the well know polemic between Terzaghi and Fillunger, which ended quite tragically.


The rock mass (ground) becomes part of the support structure

Kovári: NATM alone allows the ground to act as a structurally supporting component

“The New Swimming Technique is based on the concept that by activation of uplift

the water becomes a supporting medium”.

Kovári: NATM ignores the achievements of those to whom credit is due for recognizing and clearly formulating this fundamental law of tunnelling: Ritter (1879), Engesser (1882), Wiesmann (1912), Maillart (1923), Mohr (1956).

NATM

TUNNELLING METHOD 1

………………………..

TUNNELLING METHOD 2

TUNNELLING METHOD X


Kovári: According to the official definition of the New Austrian Tunnelling Method, the concept of tunnelling is replaced by the concept of the NATM.

Correct NATM definition according to Kovári

TUNNELLING

TUNNELLING METHOD 1

NATM

………………………..

TUNNELLING METHOD 2

TUNNELLING METHOD X


A critical discussion of the NATM within its own framework of ideas is not possible. Its terms are so ambiguous that they defy close examination. If one considers the NATM as a whole, however, not only is it not free from criticism, it is simply groundless.


Kovári:

Conclusions regarding the NATM edifice of thought

Does the NATM really exist ?

Austrian experts Kovári, (ETH Zürich), 1993

YES NO



50 Anniversary of NATM

ITA-Austria 2012

http://www.austrian-tunnelling.at/download/NATM_Buch.pdf

Austrian Tunnelling Association



Name?


NATM

Sequential Excavation technique

Conventional tunneling method

Barton Hoek Bieniawski Schubert


Barton (Q) and Bieniawski (RMR) Hoek (GSI) Schubert Barton (Q); Bieniawski (RMR); Hoek (GSI)

Palmstrøm Barton (Q)

Palmstrøm

Polemics about classification systems

Palmstrøm Barton


Potential users of the Q-system should carefully study the limitations of this system as well as other classification systems they may want to apply, before taking them into use.

Many of the comments given on the limitations apply also to other classification systems having similar input parameters as Q.

A solution often used in works on rock engineering is to link Q values to other classification systems - or opposite - applying correlation equations. This is a procedure we strongly do not recommend.

Palmstrøm:


“Of more concern to me these days is the absurdity of the algebraic equations linked to GSI (which is only RMR (minus 5?) anyway. I do not believe, nor ever will believe, that one can look at a picture and ‘classify’ a rock mass. The childrens-method of diagram recognition is entirely innapriopriate to the challenges of describing the anisotropic water-bearing medium that we call rock masses”.

Barton (Q) Hoek (GSI)

Barton was interviewed by Vrkljan during Barton's stay in Croatia, June 1 to 6, 2011.

Barton (Q) Hoek (GSI)


Barton: It is time to question this wide-spread method, and the absurdly complex algebra ‘links’ to parameters, that are not actually empirically based.


Are classification systems outdated? ISRM-EUROCK-2013, Wrocław , Poland. Some Remarks On Current Rock Engineering Design Practices ISRM-EUROCK-2012, Stockholm, Sweden.

Schubert Barton; Bieniawski


Selection of parameters, weighting and rating is experience under specific conditions.

Could this experience be used in other conditions?

Classification parameters are universally applied to all rock mass types.

Classification systems

Schubert:


Some classification systems are extended to tunnel design tools by including additional parameters.

Tunnel designs based on such systems necessarily are inaccurate and sometimes even entirely wrong!

This approach does not consider different behavioural modes of the ground and its interaction with excavation and support.

Classification systems and tunnel design

Schubert:


Risk oriented design approaches are becoming more common. The call for engineering approaches to tunnel design and construction continuously spreads. With the current state of the art in engineering and legal as well as insurance issues in mind, abandoning empirical methods, such as classification system should be abandoned as quickly as possible.

Classification systems and tunnel design

Schubert:

Expectations of rock mechanics and ISRM

Rock engineering

Underground structures will be bigger, deeper and will be built in difficult geotechnical conditions

Mining • Open pit deeper than 1000 m • Underground excavations at depths

greater than 3000 m • Oil drilling deeper than 10000 m

Expectations of rock mechanics and ISRM in the next 50 years

Mon Terry, Švicarska

DUSEL - Deep Underground Science and Engineering Laboratory URL - Underground research laboratory


Rock mass characteriztion

Underground laboratories will play a major role in field validation of theoretical development

MODELLING

Discontinuum modeling DEM - Discrete Element Method SRM - Synthetic Rock Mass Model

Coupled Models DECOVALEX Development of Coupled Models and Their Validation Against Experiments Project Chair: J.A. Hudson and


We have great expectations from the:

Randa in the Matter valley – Switzerland May 1991, rockslides of approximately 30 million cubic meters of debris

MONITORING


Monitoring of the in situ behavior of the rock mass is extremely important:

New techniques will accelerate the collection of quality data.

Conclusions

Since ISRM foundation, significant advances have been

made in a number of relevant areas or rock mechanics and rock engineering.

“True” rock behaviour is still a primary geomechanics challenge.

Close interaction with engineering geology is essential for optimum advance.

Developing better methods of characterising the geometry and mechanical properties of the fractures should be the main goal of structural geology.

Geophysical methods promises although are still not as successful as in medicine.

Conclusions

Conclusions

We need more integration of subjects (e.g., fully-coupled numerical modelling that captures all the required variables, parameters and mechanisms).

Underground laboratories will play a major role in field validation of theoretical development.

Neural network ‘intelligent’ computer programs should be used more often.

More integration of science and engineering is necessary.

We need more international co-operation.

Thank you!

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Harrison, J.P.,Alejano, L., Bedi, A., Ferrero, A.M., Lamas, L., Mathier, J-F., Migliazza, R., Olsson, R., Perucho, A., Sofianos, A., Stille, H., Virely D., (2015), Rock engineering design and the evolution of eurocode 7: the critical six years to 2020; ISRM Congress 2015 Proceedings - Int’l Symposium on Rock Mechanics.

Ferrero, A.M., Sofianos, A., Alejano, L.R., (2014), Critical review of Eurocode-7 regarding rock mass characterization. Eurock 2014 Workshop, 26th May, Vigo, Spain.

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Lamas,L.,Perucho, A., Alejano, L., ( 2014), Some key issues regarding application of Eurocode 7 to rock engineering, Eurock 2014 Workshop, 26th May, Vigo, Spain,

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