some new developments in rock mechanics research and

Some New Developments in Rock Mechanics Research and Application

Jian Zhao

Wuhan University, 30 October 2014

Research • Micromechanics and critical scale • Rock dynamics and fracturing • Induced seismicity and earthquake Application • Earthquake assessment and rock engineering design • Shale gas, hot rock geothermal, carbon sequestration • Mass mining and rapid excavation

Developments in Rock Mechanics Research and Application

Micromechanics is adopted in all solid mechanics disciplines, it offers better scientific explanation on how materials

behave and fail. Different disciplines focus on different scales.

Micromechanics and Critical Scale

ICAMS, 2013

The scale of micromechanics are varying depending on the approaches, e.g., molecular dynamics (MD), Critical Distance

(CD), and particle flow.

In rock mechanics, Critical Distance (CD) and particle flow are usually adopted.


Micromechanics Research: • Defining Critical Distance for various rocks; • Defining micromechanics constitutive relation; • Proving micromechanics constitutive relation is intrinsic; • Reconstituting macro behaviour of rock material.


Taylor, 2009 EFM

2

0

)(2

σπICK

a =∆

Taylor, 2007 EFM

Constitutive Laws of Micromechanics


Micro trans- and inter-granular fracture model (QB Zhang, PhD 2014)

)()(16

)2

3sin2

)(sin()()2

3cos2

cos3)(()(

)(),(

12I1I

22

2II2II

22

2I2I

1TGd

2IGd

vkvA

vkvAvkvA

vGvG

βββββ +++

=

Zhang and Zhao, 2013 EFM

Micromechanics Numerical Methods and Modelling


Distinct lattice spring model (GF Zhao, PhD 2010)

UDEC with cohesive model (T Kazerani, PhD 2011)

Particle manifold method (L Sun, PhD 2012)

Laboratory Testing and Micromechanics Observation


3D X-ray CT for imaging geomaterials at Monash University’s rock mechanics laboratory (Courtesy of PG Ranjith)

Dynamic behaviour of materials, including rock materials, joints and masses is still relatively less understood, primarily limited by observation means.

Rock Dynamics and Fracturing

Modified after Zhao et al, 1999 TUST

Rock Dynamic Research Roadmap


Observed Rate Dependent Strength of Rock Materials


Zhang and Zhao, 2014 RMRE

I: [10-5, 101] s-1

II: [101, 600] s-1

III: [600, 3000] s-1

Experimental Techniques of Rock Dynamics Testing


Zhang and Zhao, 2014 RMRE

High-speed Digital Image Correlation with SHPB


Photron SA1.1 + macro lens

2''2

''

ZNCC

]),([]),([

]),([]),([

m

M

Mi

M

Mjjim

M

Mi

M

Mjji

M

Mi

M

Mjmjimji

gyxgfyxf

gyxgfyxfC

−−

−×−=

∑ ∑∑ ∑

∑ ∑

−= −=−= −=

−= −=

Zhang and Zhao, 2013 IJRMMS

Triaxially Compressed Hopkinson Bar (TriHB)


Schematic

Numerical simulation

Zhao and Cadoni, 2013 SNF Report

Rock Dynamic Strength Criteria and Micromechanics Model


Sliding wing crack model (Li et al, 2001 IJNAMG)

Intermediate strain rate (Zhao and Li, 2000 IJRMMS) High strain rate (Zhang and Zhao, 2013 IJRMMS)

0.90

1.00

1.10

1.20

0.0 1.0 2.0 3.0 4.0 5.0Normalized strain rate

Nor

mal

ized

str

engt

h

Conf_pressure=20MPaConf_pressure=50MPaConf_pressure=80MPaConf_pressure=110MPaConf_pressure=140MPaConf_pressure=170MPa

2000 IJRMMS

Wave Propagation across Rock Joints and Rock Mass


Experiment

Numerical modelling

Analytical solution XF Deng, PhD 2013

Wu, PhD 2013

Analytical Solutions of Stress Wave Propagation in Rocks

• Virtual wave source method (Li et al, 2010 JGR) • Displacement & stress discontinuity model (Zhu and Zhao, 2011 GJI) • Time-domain recursive method (Li et al, 2012 GJI) • Modified recursive method (Zhu et al, 2012 JAG) • Thin-layer interface model (Li et al, 2013 JAG)


Zhu, PhD 2011

Laboratory Experiments Wave Propagation in Rocks

• Multiple parallel rock fractures • Different fracture spacing and

orientations • Different fracture apertures and filled

materials


Wu, PhD 2013

Numerical Modelling of Stress Wave Propagation in Rocks

• Distinct lattice spring model (Zhu et al, 2011 C&G) • Particle manifold method (Zhao and Sun, 2012 G&G) • UDEC and 3DEC (Deng et al 2012 RMRE, Zhu et al 2013 RMRE)


Zhu, Deng and Zhao, 2011-13 RMRE

Zhao and Sun 2012 G&G

Induced seismicity becomes an increasing concern with energy technologies that involve injection or withdrawal of fluids from deep rocks.

Induced Seismicity and Earthquake

Evans, 2012 Geothermics

Ellsworth, 2013 Science

Research on Induced Seismicity • Energy release and and wave generation during joint

shearing • Effects of joint geometry and roughness on wave

generation • Induced seismicity

due to hydro-fracturing

• Coupling of hydro-thermo-mechanics and seismicity


Ellsworth, 2013 Science

Laboratory Experiments on Induced Seismicity


Wave generation during plate shearing. Wu and Zhao, 2013 EM

Measurements of energy and wave generated and transmitted during rock

fracturing using 3D Hopkinson bar. Zhao, 2009 SNF Proposal

Development of Induced Seismicity Models • Joint shearing – seismicity model • Rock fracturing – seismicity model


Wu and Zhao, 2013 EM

Californian Fault Lab Scale

Goebel and Sammis, 2013 PAG

To be able to assess earthquake potential (by understanding seismic wave generation, propagation and transformation);

To have design methodology for large engineering structures in and on rocks subjected to earthquake and dynamics loads.

Earthquake Assessment and Rock Engineering Design

Deng, PhD 2013

To develop techniques creating desired fracture network for shale gas and HR geothermal system.

Shale Gas, Hot Rock Geothermal, Carbon Sequestration

Zhao, 1994 Geothermics

World’s largest (?) high-pressure, high-temperature testing chamber: sample size 750×750×750 mm, temperature 450 ˚C, σ1≠ σ2≠ σ3= 350 MPa, multiphase flow. Courtesy of PG Ranjith.

To estimate flow in fractured rock masses (and permeability Of rock materials and rock masses) for various fluids, including at super-critical state;

To assess sustainable heat transfer in hot rock geothermal system;

To characterize deep subsurface geology and rock fractures for CO2 confinement.


Courtesy of PG Ranjith

To assess and to manage induced earthquakes in shale gas and deep geothermal system.


Spatial distribution of identified fault planes and hypocenters of induced seismicity at Basel (Mukuhira et al, 2011 GRC).

To develop rock mass characterization system for mass caving mining;

To develop tools for modelling and managing rock mass movement;

To develop better techniques for controlled rock fragmentation.

Mass Mining and Rapid Excavation

Elmo et al, 2013 ASCE IJG

To apply TBM for rapid excavation in mine tunnels that usually are of complex geology and varying grounds.

Mass Mining and Rapid Excavation

Courtesy of AlpTransit

Acknowledgements ZHANG Qianbing, EPFL, Switzerland, helped with preparation. LI Jianchun, CAS, China, reviewed some of the contents. RANJITH PG, Monash U, Australia, provided information and images. Past and current PhD students on rock dynamics in the last 5 years: ZHAO Gaofeng, UNSW, Australia KAZERANI Tohid, Nottingham U, UK ZHU Jianbo, HK PolyU, HK SUN Liang, PetroChina, China DENG Xifei, China Rail Construction, China WU Wei, Stanford U, USA ZHANG Qianbing, EPFL, Switzerland

Developments in Rock Mechanics Research and Application

some new developments in rock mechanics research and

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