MGC2004

REAL TIME MONITORING

SYSTEMS FOR TUNNEL &

DEEP EXCAVATION PROJECTS

Dr Ng Tiong GuanGeoEng Consultants

Dr Tan Guan HongSysEng (S) Pte Ltd

MALAYSIAN GEOTECHNICAL CONFERENCE 2004 16 – 18 March 2004

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Outline of Presentation

Introduction

Requirement for continuous monitoring

Automated Tunnel Monitoring System

Case History 1

Real-time eMonitoring System

Case History 2

Concluding Remarks

Is there a need?

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Introduction

In urban areas, construction and basement excavation near to existing structures & services are inevitable.

Due to higher demand and better market value, developments near to existing MRT stations/tunnels are popular.

In the construction of new MRT line and interchange, expansion of existing facility often need to be carried beside operating MRT station/tunnel.

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Deep excavation very near to

existing buildings & services

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Deep excavation

near to existing MRT

station.

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Expansion of existing siding tunnel to

accommodate future MRT line.

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For development near to existing MRT structures, stringent controls are specified in CPRP.

Including allowable movement & requirement for Continuous Monitoring…

CODE OF PRACTICE FOR RAILWAY PROTECTION, LTA

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Table 12.1 Allowable Limits for Rapid Transit Systems Structure and Track

Type of MRT structure

Bored tunnel, cut-and-cover tunnel, station

and viaduct

Total movement in any direction

< 15mm

Differential movement

in any plane

15mm or 1:1000

whichever is lesser

Code of Practice for Railway Protection

Clause 12.1.1 Structural and Track Limits

“The design and construction of development or building works within the railway protection zone shall satisfy the requirements of Table 12.1…”

Required if predicted cumulative movement of rapid transit systems structure due to all

construction activities within the railway protection zone exceeds 5mm

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Automated Tunnel

Monitoring System

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Semi-automated system with manual data retrieval and manual alert system

Fully automated system with automatic data retrieval and SMS alert system

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Typical Set-up of Automated Tunnel

Monitoring System

Glass prism as reflectors

Range 20 to 100mAccuracy +/- 1.0mm + 1ppm

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Smart SMS Alert System

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Case History 1:

2-level basement excavation within Railway Protection Zone

Case History 1

Wall Type B

Wall Type C

Existing

Church

2-level

Basement

Existing

MRT Tunnels

Case History for Automated Tunnel Monitoring System

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Case History for Automated Tunnel Monitoring System

MGC2004Finite Element Modelling

Automated Tunnel Monitoring System Deployed

• A total of 27 rings of the south bound tunnel was monitored.

• Each ring contained 4 prism targets.

• The spacing of the monitored rings was typically 5m apart.

• The tunnel was monitored 3 cycles/day.

• The results were sent to contractor, consultants and authorities immediately, upon automatic processing, through e-mail.

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Case History for Automated Tunnel Monitoring System

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Real Time eMonitoring

System

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Real Time eMonitoring System

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Comparison between GSM & GPRS

System GSM GPRS (General Packet Radio Service)

Speed 9600 bps 32,000 bps

Connection By demand through dial-up

Always on

Bandwidth Occupied full bandwidth even

without data transfer

Occupied bandwidth only during data

transfer

Cost Depend on connection time

Depend on amount of data send

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Case History 2:

Deep excavation project for cut-and-cover tunnel

MGC2004CCL2 LTA Contract 821 Kim Chuan Depot

Eastern Ramp

Sheet pile wall with 2-3

layers of horizontal strutting

Approx. 800m

Case History for Real Time eMonitoring System

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Case History 2:

Plan & Typical Section

19m deep excavation with 5

layers of compound struts

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Real-time eMonitoring System Deployed

40 nos or 15% of the total no of struts were instrumented/monitored.

10 nos or 25% of the instrumented struts are monitored by VW load cell.

Total 100 channels of VW strain measurement.

Monitoring frequency every 10min.

The results were sent to central server and eMS web-site.

SMS alert to contractor and consultants when measured strut force exceeding 70% of design value

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Case History for Real Time eMonitoring System

MGC2004VW Load Cell

Case History for Real Time eMonitoring System

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VW Strain Gauges

Case History for Real Time eMonitoring System

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Solar Powered eMonitoring Data

Logger

Case History for Real Time eMonitoring System

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Average Axial Force in Level 1 Strut 21-A

-100

0

100

200

300

400

500

600

700

800

900

14-N

ov

15-N

ov

16-N

ov

17-N

ov

18-N

ov

19-N

ov

20-N

ov

21-N

ov

22-N

ov

23-N

ov

24-N

ov

25-N

ov

26-N

ov

27-N

ov

28-N

ov

29-N

ov

30-N

ov

01-D

ec

02-D

ec

03-D

ec

04-D

ec

05-D

ec

06-D

ec

07-D

ec

Date

Forc

e (

kN

)

S21-1-A Trigger Design Allow able

Average Axial Force in Level 1 Strut 21-B

-100

0

100

200

300

400

500

600

700

800

900

14-N

ov

15-N

ov

16-N

ov

17-N

ov

18-N

ov

19-N

ov

20-N

ov

21-N

ov

22-N

ov

23-N

ov

24-N

ov

25-N

ov

26-N

ov

27-N

ov

28-N

ov

29-N

ov

30-N

ov

01-D

ec

02-D

ec

03-D

ec

04-D

ec

05-D

ec

06-D

ec

07-D

ec

Date

Forc

e (

kN

)

S21-1-B Trigger Design Allow able

Preload

Excavation to next level

Preload

Excavation to next level

Case History for Real Time eMonitoring System

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SMS Alert

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CONCLUDING

REMARKS

Is There a Need for Continuous Monitoring…?

Tunnelling Affects Roads

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Tunnelling Affects Roads

Tunnelling Affects Buildings

This Can Happen in 24 hours ! Reported in

Front Page of Straits Times

Glassgow Road Sumitomo

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Failure of Shaft Excavation Causes Road Settlement

Excavation Failure Causes Road and Building Subsidence

PREVENTION IS CHEAPER AND BETTER THAN

CURE

CONCLUSION…

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THANK YOU

MALAYSIAN GEOTECHNICAL CONFERENCE 2004 16 – 18 March 2004