UTRE Phase II

Research Activities in Rock

Mechanics/Engineering at CEE/NTU

A/P Zhao Zhiye

Nanyang Centre for Underground Space (NCUS)

School of Civil and Environmental Engineering (CEE)

Nanyang Technological University (NTU)

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Presentation Outline

Research areas

• Rock Dynamics and Protection of Underground Structures

• Advanced Numerical Modelling for Rock Cavern Design

• GIS-based Digital Rock Engineering

• Fire Safety, Evacuation, Social/economic studies

Research Projects

• Jurong rock caverns (JTC)

• Shaft design (I3C/NTU)

• NTU underground space exploration (SEO/NCUS)

• Biogrouting (SUL/MND)

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A/P Low Bak Kong

Rock Mechanics

A/P Zhao Zhiye

Rock Mechanics A/P Yang Yaowen

Instrumentation

Prof Tan Kang Hai

Fire Safety,

Evacuation

A/P Tiong Lee Kong

Risk Modelling

A/P Goh Teck Chee,

Anthony

Rock/Soil Mechanics

Asst/P Wong Ngai Yuen,

Louis

Engineering Geology

Core Members in Rock Engineering, CEE, NTU

Rock Engineering Research Group , CEE, NTU

Prof. Zhao Jian

Advisor to NCUS

Monash Univ, Rock

Mechanics/Eng

Prof. Lu Ming

Director of NTU/JTC I3C

Centre, Rock Eng.

Dr Zhou Yingxin

Senior Principal

Engineer of DSTA

Adjunct A/P of CEE,

Rock Eng

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Rock Dynamic Testing

• 75 mm diameter pressure bars

• 50 mm diameter pressure bars

• Steel, aluminum, PMMA bars

• Granite pressure bars

• High strength cement bars

• Gas gun

• High speed camera

SHPB Test Facilities in NTU

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Rock Dynamic Tests

Joints in rock mass Stress wave propagation in rock mass

Low strain rate Medium strain rate High strain rate

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Development of numerical methods

• 2D discontinuous deformation analysis (DDA)

• 2D/3D numerical manifold method (NMM)

• Reliability based analysis method.

• Rock caverns under blast loads.

• Rock caverns under earthquake loads.

• Rock caverns under coupled fluid/in-situ stress.

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Basic Concept of DDA

Item DDA

Governing Equation

Sub-matrix

11 1 1 112 13

221 22 23 2 2

331 32 33 3 3

1 2 3

n

n

n

n nn n nn n

K K K K d F

K K K K d F

K K K K d F

K K K K d F

6 6

6 1

6 1

ij

i

i

K

d

F

DDA equation of motion

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Basic Concept of DDA

Coupling of FEM/DDA – a nodal based DDA (NDDA)

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Coupling of FEM/DDA – a nodal based DDA (NDDA)

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Coupling of FEM/DDA – a nodal based DDA (NDDA)

Analysis Parameters

Rock

sample

Unit mass (kg/m3) 2600

Young’s modulus (GPa) 10

Poisson ratio 0.25

Friction angle 25˚

Cohesion strength (MPa) 25

Tensile strength (MPa) 12

Rigid plate

Unit mass (kg/m3) 7800

Young’s modulus (GPa) 2000

Poisson ratio 0.25

Friction angle 25˚

Cohesion strength (MPa) 2500

Tensile strength (MPa) 2500

Joint/crack

Friction angle 20˚

Cohesion strength (MPa) 0

Tensile strength (MPa) 0

Control

parameter

Penalty stiffness (GN/m) 4000

Time step size (s) 1×10-5

Max displacement ratio 0.01

SOR factor 1.0

Total analysis time (s) 0.003

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Probabilistic risk assessment of rock caverns

Charts relating limit state safety factor to cavern characteristics

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2D/3D manifold method modelling for jointed rock mass

Slope analysis with 3D NMM

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Numerical modelling of energy absorbing rock bolt

Different energy-absorbing bolts can be modeled

Cone

bolt Durabar

Swellex Garford

Roofex

D-bolt

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Performance comparison of energy-absorbing rockbolts

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.60

5

10

15

20

25

30

Ax

ial

ten

sile

lo

ad (

kN

)

Distance away from the far end of the bolt (m)

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.60

5

10

15

20

25

30

Ax

ial

ten

sile

lo

ad (

kN

)

Distance away from the far end of the bolt (m)

Rebar (fully grouted) D-bolt

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UTRE Phase II

3D NMM modelling

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UTRE Phase II • Blast designs of Jhakri Power House Cavern (Adhikari, 1999)

• Discontinuous Deformation Analysis (2D DDA) simulation

Adhikari, GR., Babu, AR. (1999). “On the application of rock mass

quality for blasting in large underground chambers.” Tunnelling and

Underground Space Technology. Vol. 14, No.3, p.367-375.

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Rock Dynamic Modelling

Development of Key block theory, discontinuous deformation analysis

(DDA), numerical manifold method (NMM)

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Instrumentations and Monitoring

Fibre optic

sensor (FBG)

Piezoceramic

(PZT) sensor

FOS Spectrum Analyzer

PZT Impedance Analyzer

Cycle IV

0

20

40

60

80

100

120

140

0 500 1000 1500 2000

Microstrain

Str

ess (

MP

a)

ESG(60mm)

FBG

0.00035

0.0004

0.00045

0.0005

0.00055

60 70 80 90 100

Frequency (kHz)

Conducta

nce (

S)

Load ratio= 0 Load ratio= 0.33

Load ratio= 0.66 Load ratio= 0.82

Global information

(strain, displacement, etc)

Local information

(damage location

and severity)

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3D GIS for Subsurface Application

Multi-Layered Surfaces and Cavern

Subsurface Geological Modelling and Analysis

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Borehole Information System

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Fire Safety Modelling

XZ

Y

g

Window

Compartment

HRRHeat Transfer

Mass Transfer

XZ

Y

gg

Window

Compartment

HRRHeat Transfer

Mass Transfer

Zone model

Evacuation modeling

• Human behavior

•Tenability condition

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Social, Economic and Environmental Impacts on Use

of Underground Space

• Environmental Impact Analysis (EIA)

• Social and Economic Impacts • Risk Modelling, DAT system (MIT)

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UTRE Phase II Jurong Rock Caverns Project - Basic Facts (Phase 1)

o Built beneath the seabed of Banyan Basin (~120 m).

o Storage capacity of approximately 1.47 million cubic meters

o To store liquid hydrocarbons such as crude oil, condensate and naphtha.

o Save approximately 60 hectares of surface land space.

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UTRE Phase II

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Experimental Studies

Flow tests to establish the permeability of intact rocks and rock joints

Specimen type Gas flow/m2 Water flow/m2 Transient pulse/m2

Intact rock 10-21~10-20 10-14~10-12 10-17~10-18

Open joint N.A. 10-12~10-11 N.A.

Partly-open joint N.A. 10-13~10-11 N.A.

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Schematic of Tunnel Trial Test

Sensor Installation : Before and after shotcreting

in tunnel

Estimated displacements at sensor locations

Total station and FOS displacement at crown of tunnel

Tunnel test: Testing the survivability of the customized FOSs against

shotcreting, and drill-and-blast impact.

Potential instrumentation plan for cavern

monitoring

Instrumentation

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Predicted 3D hydraulic conductivities

Water inflow comparison

(predicted VS measured)

Rock Caverns Seepage Analysis

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2D 3D

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140m wide ,425m long and 165m deep

Numerical Analysis:

Excavation sequence

with UDEC

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Numerical analysis of underground rock excavations

with FLAC3D, UDEC, 3DEC, Rocscience.

Response surface method as a link between

reliability methods and stand-alone numerical

packages, and second-order reliability method.

Probabilistic Analysis of Underground Rock Excavations

accounting for Uncertainty

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Elliptical

Circular Rectangle

Multi-cell

Optimization of vertical access shaft for underground space

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Disadvantages:

1, Large amount of excavation

2, Limitation of access depth

3, Vehicle pollution

Advantages:

1, Easy access

2, Transportation integrity

Alternative 1 Ramp roads

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Disadvantages:

1, Add works of tunnel excavation

2, Limitation of access depth

3, Vehicle pollution

Advantages:

1, Easy access

2, Transportation integrity

3, Reduce amount of excavation

compare with Alt 1

Alternative 2 Ramp roads plus spiral tunnel

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Alternative 3 Ramp roads plus lift

Advantages:

1, Least amount of excavation

2, No limitation of access depth

3, Using conveyor belt to muck

4, Car lift for cargo and small

lift for person during operation

Disadvantages:

Lack of transportation integrity

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BACKGROUND

Utilizing the space in NTU campus in response to the need of its expansion

UNDERGROUND SPACE below NTU Campus – A

Concept Master Planning

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CAVERNS AT

SHALLOW DEPTH

70m below ground level

26m below the deep basement

5 possible shallow cavern

locations

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DEEP CAVERNS

120m below ground level

26m below the shallow cavern

76m from the deep basement

6 possible shallow cavern locations

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Biogrouting for

underground construction

Objectives

• To develop a new grouting material – biogrout and

use it to establish a new construction approach –

biogrouting before excavation – to seal the joints and

strengthen the weak rock in the areas where caverns or

tunnels are to be constructed before excavation.

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Sand grain

Slime bonding

Sand grain

Sand grain

Slime bonding

Sand grain

Scanning Electron Micrograph

(SEM) showing the formation

of Crystals of CaCO3

Bonding of sand

grains by slime

How does it work?

A grouting material made of good microorganisms and other waste

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Application potential

• The project is motivated to solve real construction problems. It

can be used directly into existing projects using existing

grouting systems once biogrout is invented and the related

technologies are fully developed.

Biogrout

Biogrout

Use biogrout for rock joints or concrete repair

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Acknowledgements

• Some of the slides in this presentation are provided by my

colleagues in CEE/NTU, including Tan KH, Low BK, Anthony

Goh, Louis Wong, Lu Ming, Yang YW, Robert Tiong, Chu Jian,

Tan SK, and their researchers.

• local/overseas collaborators in the various projects.

• Financial support from JTC, DSTA, SEO/NCUS (NTU),

I3C(JTC/NTU)

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