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Planning, Design and Construction of Underground Infrastructure in Singapore
Ow Chun Nam Director, Land Transport Authority
• Underground Infrastructure in Singapore
• Challenges • Site Investigation
• Deep Excavation
• Bored Tunnelling
• Conclusions
Planning, Design and Construction of Underground Infrastructure
Rail Network Expansion by 2030
RTS Link Between Singapore and Johor
• Singapore to Kuala Lumpur
• 315km, 90mins travelling time
• Operational in 2020
• Possibly part underground
High Speed Rail Link
Major Underground Road Tunnels
CTE: North Tunnel: 0.7 km; South Tunnel: 1.7 km; Opened: 21 Sep 1991
Fort Canning Tunnel: 0.35 km; Opened 16 Jan 2007
KPE: Total tunnel length: 9km; Opened 26 Oct 2007 and 20 Sep 2008
Woodsville Interchange: Total tunnel length: 0.69km; Opened 28 Jan 2012
MCE Tunnel : 3.5km to be opened at end 2013
Singapore Underground Road System: underground road tunnels
North South Expressway Tunnel and Semi Tunnel : 12.3 km to be completed around 2020
Transmission Cable Tunnel Route Overview
MARYMOUNT
THOMSON PIE
GAMBAS
SEMBAWANG
MANDAI
NS Tunnel
EW Tunnel
AYER RAJAH
NORTH
BUONA VISTA
HOLLAND
DUNEARN
RANGOON
MAY ROAD
INTERFACE
KALLANG
AIRPORT ROAD
TAGORE
ANG MO KIO
PAYA LEBAR
JIP Tunnel
BENOI
PIONEER
PESEK
WEST JURONG
ISLAND
• Underground Infrastructure in Singapore
• Challenges • Site Investigation
• Deep Excavation
• Bored Tunnelling
• Conclusions
Planning, Design and Construction of Underground Infrastructure
• To provide sufficient ground and ground water data • for a proper description of essential ground properties/
behaviour to plan the most appropriate construction method; and
• for a reliable assessment of characteristic values of ground parameters to achieve a safe and cost-effective design
• Continuous process for entire duration of project
Objectives of Site Investigation
• Boreholes too widely spaced
• To have more boreholes – practical problems
Challenges – Boreholes Spacing
Challenges – MRT Tunnel
Tunnel Alignment
41m
65m
56m 58m
Potential JTC 2nd Link Immersed Tunnel
PUB – NIPE Tunnel DTSS Phase 2 (Future) Upper/Lower Limits
1.6km 3.2km 0.4km
PROPOSED JURONG ISLAND – PIONEER TRANSMISSION CABLE TUNNEL
Challenges – Tunnelling under Water Bodies
BH-169 (GL-49m)
ABH-216 (GL-49m)
ABH-214 (GL-36m)
Tender stage : 4 Boreholes
▼Approximate Level of Rock Head
Ground LevelRL 102.7m BH-214
FILL
N=0
M
N=0
F2
N=1~12
F1
N=7~19
G-V
N=41~86
G-I, II
N=76~100
G-III
R=20~80%
G-I,II
R=90~100%
E
N=9
G-III
N=54~67
ABH-215 (GL-66m)
• Tender Design
• Rock head level = 70.5m as per GIBR
• Diaphragm wall depth = 32m
• Shotcrete & rockbolt for lower shaft (in G-III/G-II)
Challenges – Variable Rockhead
Deep shaft ~60m depth
• Tender Stage Borehole = 4 nos
• 1st Stage Add Borehole = 5 nos
• 2nd Stage Add borehole = 10 nos
ABH-D-01 (GL-57m)
ABH-D-05 (GL-42m)
BH-169 (GL-49m)
ABH-216 (GL-49m)
ABH-D-08 (GL-31m)
ABH-D-06 (GL-42m)
ABH-215 (GL-66m)
ABH-D-04 (GL-67m)
ABH-D-07 (GL-62m)
ABH-D-02 (GL-43m)
ABH-D-03 (GL-69m)
Option-2 7m move
ABH-D-09 (GL-57m)
ABH-D-10 (GL-62m)
ABH-D-11 (GL-49.5m)
ABH-214 (GL-36m)
ABH-D-12 (No Rock head)
ABH-D-13 (GL-45m)
ABH-D-14 (GL-65m)
ABH-D-15 (GL-54m)
• From additional SI
• Rock head level (G-III) is much
deeper than original
• Max difference in rock head
level (G-III) is 25m
• Alternative construction
method is needed due to new
geological information
Challenges – Variable Rockhead
Challenges – Variable Rockhead
Option 1 – To relocate shaft
7m
Challenges – Variable Rockhead
Option 2 – Original location with redesigned shaft
GIBR Rockhead Level
Commonly used methods • Electrical resistivity
• Seismic refraction
• Seismic reflection
• Surface wave method
• Geo-tomography
Geophysical Survey
More efficient and accurate methods are required
to determine
• rock levels
• depth of piles
to minimise risk of underground construction in
urban areas
Challenges
• Underground Infrastructure in Singapore
• Challenges
• Site Investigation
• Deep Excavation
• Bored Tunnelling
• Conclusions
Planning, Design and Construction of Underground Infrastructure
Challenges
Deep Excavations in Soft Clay without Ground Treatment
Deep Excavations in Soft Clay with Ground Treatment
Ground Treatment
Typical Station Excavation Depth
Deep Excavation – Bras Basah Station
Singapore Art Museum
Cathedral of the Good Shepherd
Bras Basah Rd
B1 Level
B2 Level
B3 Level
B4 Level
B5 Level
Connection SMU
Reflection Pool
Deep Excavation – Bras Basah Station
Deep Excavation – Bencoolen Station
Subway
NAFA Campus 1 NAFA Campus 2
Bayview Hotel
Plaza By The Park
SMU
NAFA Campus 1
Slide 26
Bra
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asah
R
oad
Ho
tel
Re
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ezvo
us
Strand Hotel
Be
nco
ole
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Ho
use
Hotel 81
Ho
tel
Be
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ole
n
Somerset Bencoolen
Manulife Centre
Bayview Hotel
NAFA Campus 2
New Dev’t. NAFA Campus 1
Pri
nse
p L
ink
Subway link to SMU
Project Challenges
1. Built-up corridor
-- close proximity to existing buildings
-- very deep station box (43m below ground)
-- thick layer of hard ground (boulders)
-- restricted working hours due to stakeholders requests
2. Pedestrian walkway & vehicular access to buildings to be maintained at all times
Space Furniture
C936 Bencoolen Station SM
U
Bayview Hotel
NAFA Campus 2
New Dev’t.
Station Footprint
Station Excavation – DTL3
CROSS SECTION
BENCOOLEN STREET
43.
2m
Need for Horizontal Grouting
Top tunnel in Marine Clay Bottom tunnel in OA
Existing Tunnels
Future Tunnels
Existing Piles / Barrettes
Transfer Beams and Barrettes for Underpinning
Cable Tunnel – Deep Shafts Utility building (above ground)
Shaft (~60m)
Adit
Tunnel enlargement
Cable tunnel
Soil/Rock Interface
Deep Shaft – Rock Fissure Grouting
• Underground Infrastructure in Singapore
• Challenges • Site Investigation
• Deep Excavation
• Bored Tunnelling
• Conclusions
Planning, Design and Construction of Underground Infrastructure
• Phase 1/2 MRT Construction in 1980s: Greathead Shield with hydraulic backhoe excavator or roadheaders / 1 EPBM / 1 TBM
• Compressed air used extensively
• Grouting done through the segments
Construction Methods
Greathead Shield EPBM (C301)
• NEL: 14 EPBMs (2 Dual Modes), 2 Open Face TBMs
• Face pressure and stability by controlling the extrusion of the spoil through the screw conveyor and the advancement of the machine
• Automatic tail void grouting
Construction Methods
EPBM (C705) EPBM (C706) EPBM (C710)
• Circle Line: 19 EPBM, 8 Slurry TBMs
• Scanners / belt weighing experimented and adopted subsequently
• Slurry TBM used for sections with granite
Construction Methods
Slurry TBM (C854) Slurry Treatment Plant EPBM (C823)
• DTL1: 3 EPBMs
• DTL2: 10 EPBMs + 9 Slurry TBMs
• DTL3: 19 TBMs
Construction Methods
EPBM (C902) Slurry TBM (C915) EPBM (C917)
• Expansion of underground rail system constrained by tight time schedule
• Significant number of TBMs required over a short period of time
• TBM manufacturing and delivering lead time critical
• Client procurement an effective way to manage this
• Possible cost savings from direct procurement from the TBM manufacturers
• Procurement of TBMs restricted to areas with homogeneous soil such as Old Alluvium
• Bulk procured 10 nos Downtown Line Stage 3 TBMs – Novated to successful civil contractors
TBM Bulk Procurement
10m
20m
30m
40m
50m
60m
70m
Deep Tunnels
Underpasses & Shopping Malls
MRT System
Cable Tunnel
Common Services Tunnel
Deep Tunnel Sewerage System
Underground Expressways
Sewers & Gas Pipes
Source : The Straits Times, 11 Feb 12
• Specifications beefed up
• 19 inch disc cutters introduced
• 2 x double compartment manlock required
• Probe drills permanently mounted
• Front midget drill provided
TBM Specifications
Permanently Mounted Drills
Page 39
TBM Front Drilling
Tunnelling through Tight Curves
75m radius curve
Tunnelling through Tight Curves
• Major underground facilities to be built in Singapore
• Challenges to the industry
• New methods and technologies to address the challenges
Conclusions
THANK YOU
MRT Network in Singapore by 2020
• To match the design of soil improvement methods to
• the groutability of the ground encountered
• the targeted engineering property of soil to be improved
• To have minimum disturbance to surrounding structures
• To develop new method and technology, e.g. horizontal grouting techniques
Challenges