1.
Developing an Operational
Automated Real Time
Tunnel Monitoring System
by
G. H. Tan
SysEng (S) Pte Ltd
K. G. Chua
Wisescan Engineering
Services Pte Ltd

2.
• LTA code of practice allows less than 15mm
movements along the segments
• Tunnel distortion allowable is 1/2000
• Continuously monitors the prisms every 8
hours per day for 7 days a week
• Reliable System up time with financial penalty
imposed for delay or loss of data
• Real time measurement and immediate data
transmission of results
• Immediate alerts if the movement exceeds
70% of allowable movement

3.
Data Transfer Challenges
• No interference of any Radio
Communication channels
• Only IDA approved frequency allowed
• No antenna mast allowed on site
• Limited site access
• First time right in concept design !

4.
Tunnel Monitoring Projects
• Circle Line LTA C825 North,South, East &
West Bound
• SMU site
• Harbor Front LTA C859
• Newton Life Church
• National Library Board
• Deep Tunnel Sewage PUB T06

5.
Excavation
Zone
Working MRT
Tunnels
What is Tunnel Monitoring ?

6.
Instrument setup
inside the MRT tunnel

7.
• Fully Automatic system
• Glass prism as reflectors
• Range 20 to 100m
• Accuracy +/- 1.0mm + 1ppm
• Proven system
• High reliable for continuous
use in Tunnels
Automated Surveying Instrument

8.
GSM Signal Strength variations and these
affect data transmission Quality

9.
B) Data is split into smaller packets. Only the affected Data
Packet is resent only. More robust technique
Data Transmission in Noisy Environment
A) If the data is interrupted, the whole data chuck is resent a
few times. Thus making it inefficient due to the number of
retries. Unpredictable delivery times
Noise Noise
Noise

10.
Transmission Time Consistency with Data
Communication Error Recovery Algorithm

11.
Tunnel movements and SMS Alert

12.
Smarter structural geometric
cross checking algorithms will be
introduced to avoid overloading
and False SMS alerts. The
proposed algorithm will deploy
more 3D numerical checks for the
following: -

13.
Within the same segment
Movements in the 4 prisms shifting
in space
Vertical Movements in the Crown
and Track for vertical loading
Horizontal Movements in the Left
and Right for horizontal loading

14.
Cross-segments
Movements in the prisms along the
same axes in the tunnel
Adjacent Prisms
also move
Crown Prisms
Crown Prisms

15.
Future System Expansion into a
GPRS Network System