new geonumerics in rock engineering · 2015. 5. 12. · iit kharagpur uniaxial loading: rock sample...

Geonumerics in Rock Engineering

Dr. Debasis DebProfessor

Department of Mining Engineering

IIT Kharagpur – 721 302

E-mail: [email protected], [email protected]

mailto:[email protected]

mailto:[email protected]

IIT Kharagpur

Research Interests

Rock Mechanics

Ground Control

Mine Design

Analytical and numerical methods in design of geo-structures

Extended Finite Element Methods in bolt mechanics and support design

Mesh-free numerical methods in geomechanics

Professor Debasis Deb 2

IIT Kharagpur

Structural Defects in Rocks

Fault in RockFolds in Rock

Jointed Rock Mass


IIT Kharagpur

Rock Failure


Frost wedging in joints, fastest

movement and rock can become air born, results in talus

A bedding or joint plane in a

rock slope

IIT Kharagpur

Stability Analysis of Underground Mine


Shaft X-cut to-183 mRL ore drive

Shaft X-cut to -230 mRL ore drive

Decline X-cut to -243 mRL ore drive

Sectional view of the ore body

Ore body and shafts inside the solid model

IIT Kharagpur

Model: Stope Pillars in a Moderate to Hard Rocks


Stopes, crown, trough and rib pillars

Zoomed view of ore body

Shaft

Solid model of the study area

IIT Kharagpur

A Snap Shot of Stress Pattern


Major principal stress around the stoping area

IIT Kharagpur

Stability Analysis of Open Stopes in Hard Rocks


A schematic diagram of

sub-level open stope

ANSYS Solid Model having

multiple ore bodies

Trough Pillar

Draw Point

IIT Kharagpur

Model: Open Stopes in Hard Rocks


Top

rocks/soil

Ore body

Abandoned

surface mine

162 m

230 m

219 m

Top

rocks/soil

Ore body

Abandoned

surface mine

162 m

230 m

219 m

Chromite ore

Sub grade

ore

Sepentinite

Gabbro

+30 mRL

0 mRL

-30 mRL

-130 mRL

Chromite ore

Sub grade

ore

Sepentinite

Gabbro

+30 mRL

0 mRL

-30 mRL

-130 mRL

-60 mRL

-90 mRL

The In-situ Model Different Ore/Rock Types

IIT Kharagpur

The Stope/Excavation Model


Trough

Trough drive

10m Rib pillar

Trough pillar

0 mRL

-30 mRL

Trough

Trough drive

10m Rib pillar

Trough pillar

0 mRL

-30 mRL

Finite element mesh of stopes

IIT Kharagpur

Stress Distribution


C

D

D’

C’

Tensile

zone

C

D

D’

C’

Tensile

zone

Minor Principal Stress distribution

-0.8000

-0.6000

-0.4000

-0.2000

0.0000

0.2000

0.4000

-150 -100 -50 0 50 100 150

Distance from mid of pillar(m)

Min

imu

m p

rin

cip

al str

ess(M

Pa)

Middle of pillar

Stress along C-C’

at 0 mRL

Stress along D-D’

at -30 mRL

-0.8000

-0.6000

-0.4000

-0.2000

0.0000

0.2000

0.4000

-150 -100 -50 0 50 100 150

Distance from mid of pillar(m)

Min

imu

m p

rin

cip

al str

ess(M

Pa)

Middle of pillar

Stress along C-C’

at 0 mRL

Stress along D-D’

at -30 mRL

Minor principal stress distribution at 0 mRL and -30 mRL across the rib pillar

IIT Kharagpur

Weak and Gently Dipping Ore Body


Longitudinal model section

Plan of the region showing

geotechnical borehole locations

Enlarged view of raise and rib pillar located from 4th level to 2nd level.

IIT Kharagpur

3D Solid and Mesh Model


Figure 19. 3D model showing ore body, HW, FW and loading conditions

IIT Kharagpur

Sequence of Excavation


Backfilled Backfilled

Stope 1Stope 2

Rib pillar

New slice


Stope 1Stope 2

Rib pillar

New slice


Rib pillar


Rib pillar

New slice

Stope-1 Stope-2


Rib pillar


Rib pillar

New slice

Stope-1 Stope-2


Stope 1 Stope 2


Stope 1 Stope 2


Stope 1 Stope 2


Stope 3 Stope 4


Stope 1 Stope 2


Stope 3 Stope 4

Figure 20b. Stage 1 of mining activities Figure 20c. Stage 2 of mining activities

IIT Kharagpur

Principal Stress around the Stoping Area


Mining stage-3 Mining stage-4

Mining stage-1 Mining stage-2

IIT Kharagpur

Future Directions and Developments

Numerical Modelling in Geotechnical Engineering

o Numerical Analysis of Jointed Rock Mass

o Numerical Analysis of Reinforcement

o Mesh-free Methods for Dynamic Fracture Process


IIT Kharagpur

Numerical Methods for Jointed Rock Mass

Continuum methodso Finite Difference Method (FDM)

o Finite Element Method (FEM)

o Boundary Element Method (BEM)

o Smoothed Particle Hydrodynamics (SPH)

Discontinuum methodsDiscrete Element Method (DEM)

Discrete Fracture Network (DFN) methods

Hybrid continuum/discontinuum modelsHybrid FEM-DEM

Hybrid SPH-FEM


IIT Kharagpur

Uniaxial Loading: Rock Sample with a Joint

Analytical solution:


n

Joint

plane

n

Joint

plane

-140

-120

-100

-80

-60

-40

-20

0

0 10 20 30 40 50 60 70 80 90

Maxim

um

diffe

rntia

l str

ess

1-

3 (M

Pa)

Angle, (deg)

Analytical

XFEM

fracture strength of

rock

Slip of joint plane

Analytical Model X-FEM Model

single joint plane in rock sample Analytical solution and X-FEM results

3

1 3

2 tan

1 tan cot sin 2

j j

j

c

IIT Kharagpur

A Joint Plane Intersecting a Tunnel


A

Joint plane

Enhanced node

0.00

0.05

0.10

0.15

0.20

0.25

0.30

1.0 1.5 2.0 2.5 3.0 3.5 4.0Distance along the joint plane ( )

Analytical solution

XFEM-solution

/ nτ σ

/r a

The variation of the ratio along the joint plane

IIT Kharagpur

Performance Analysis of Reinforcement:Fully Grouted Rock Bolts


Block building using rock bolts Highway slope

Drilling process for installing bolt

Tunnel in Rock Mass Reinforced

IIT Kharagpur

Bolt Mechanism


Axial load

Shear load

Anchor length

Bolt

Nut

Face plate

ResinRebar

Nut with hemispherical seating

Face plate

Thread bar

Cement grout

Axial load

Shear load

Anchor lengthPickup length

Neutral point

Bolt

Excavation Face

Axial load

Shear load

Anchor lengthPickup length

Neutral point

Bolt

Excavation Face

Conventional wisdom on load distribution along a bolt

Recent concept of load distribution along a bolt

Rebar type rock bolt Threaded type rock bolt

IIT Kharagpur

Direct Shear Test


0

5

10

15

20

25

30

35

0 5 10 15 20 25 30 35

Sh

ear

forc

e o

n join

t (k

N)

Shear displacement (mm)

Experimental result (Spang & Egger, 1990)

Simulation result (Spang & Egger, 1990)

Proposed doubly enriched finite elements result

joint

bolt

n

A maximum shear load of 31.4 kN, 30 kN and 31.25 kN are obtained from experimental, simulation and proposed DEFE method for shear displacement of 20 mm, 12.5 mm and 18.9 mm respectively.

IIT Kharagpur

Mesh Free Methods for Dynamic Fracture: Smoothed Particle Hydrodynamics (SPH)

Failure under uniaxial Compression:

Tensile Failure:


0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

2

0

0.5

1

1.5

2

2.5

3

3.5

0

2

4

6

8

10

12

14

16

x 106

0

0.5

1

1.5

Associative Law Non-associative Law

Maximum Tensile Stress

Effective Plastic Strain

IIT Kharagpur

Slope Failure Analysis



0

2

4

6

8


0

1

2

3

4


0

5

10

15

x 10-3Bench Width = 6 m Bench Width = 8 m

Bench Width = 10 m

IIT Kharagpur

Failure of Jointed Rocks


0

0.5

1

1.5

2

2.5

x 10-3

0

0.2

0.4

0.6

0.8

1

x 10-3

Accumulated plastic strain in the presence of multiple intersecting joint planes

Accumulated plastic strain in the presence of single joint plane

Wedge failure in jointed rock mass after rectangular opening

IIT Kharagpur

Rock Blasting

Without joint plane

With joint plane


IIT Kharagpur

Digital Image Correlation: Data acquisition System


UTM

Rock sample

Web camera

Magnetic

camera stand

Upper platen of UTM

Visualization and

recording system

Speckled face

Load cell

Computer

Data

logger

Camera

Upper

platen

Lower platen

IIT Kharagpur

Thank you


new geonumerics in rock engineering · 2015. 5. 12. · iit kharagpur uniaxial loading: rock sample...

Documents