Northern Sewerage Project:Lining Selection in a Corrosive Environment
Old Brick Sewers
Long Time Coming
Location
Residential
Section along MPIS
Environmental Concerns
NSP1 Geology
Weathered Silurian along NDS Section 2 (NSP-1)
• Melbourne Formation (Silurian Age)
NSP2 Geology
• New Volcanics (Basalt)
Massive Basalt NIS Section 2 (NSP2)
Long Section NSP1 – NDS 2
Excavation Methods
(photo courtesy of John Holland/Melbourne Water)
• Tunneling (3 TBMs):• EPB 3-meter dia. = 4,700m• EPB 4-meter dia. = 3950m• Main Beam 3-meter dia. = 3190m
Primary and Secondary Support
2400 I.D Test Ring (photo courtesy of John Holland)
• 5 SEGMENTS PLUS A KEY• RIGHT, LEFT AND STRAIGHT
RINGS
Primary and Secondary Support
INITIAL SUPPORT (Rock Bolts)
Final Lining (RCP w/ Sac. Concrete, or FRPP)
1800
R 1500
Heavy Support Light Support
TIMBER BLOCKING
RING BEAM
BACKFILL GROUT
Spatial Constraints
NSP Stage 2 Support Types
Lining Required?
Lining Required?
Lining Required?
Lining Required?
Lining Required?
Lining Required?
Similar Projects
• Singapore DTSS• Pantai Trunk Sewer, Kuala Lumpur• Perth Main Sewer• S1 Sewer, Brisbane• Hallam Valley Main Sewer, Melbourne
Corrosion - Sulphide
Sulphate, SO4
Sulphide, S2-
Hydrogen Sulphide, H2S[aq][aq]
Hydrogen Sulphide, H2S[g][g]
Sulphuric Acid, H2SO4
Moisture on walls
Prevent sulphate reducing to sulphide - add oxygen, nitrate, reduce temperature, BOD, sulphate
Prevent sulphide converting to aqueous hydrogen sulphide - increase pH
Minimise turbulence to prevent hydrogen sulphide in liquid releasing to sewer atmosphere.
Ventilate to prevent hydrogen sulphide converting to sulphuric acid on walls
Liner impervious to sulphuric acid,
Control exits and treat odours.
Investigation
Sulphide and Ventilation
Models
Corrosion of unprotected concrete (>0.5mm/year?)
Durability Reports
Sewer Hydraulics
Minor Surcharge
Should NIS be lined?
Yes
No
Lining Options
S a c r i f i c i a l C o n c r e t eS e c t i o n
P o l y m e r C o n c r e t e
P l a s t i c L i n e dS e g m e n t s
A c i d R e s i s t a n tC o n c r e t e
O N E - P A S S( B G S )
C I P S a c r i f i c i a lC o n c r e t e
A G R U S u r e G r i pG S E S t u d l i n e r / A K S
C a r p i L i n i n g
L i n a b o n d
F l e x i b l eM e m b r a n e L i n e r s
C a s t - i n t o - B a c k f i l l
R C P G R P
E R O C R o s L o k
S e m i - r i g i dL i n e r s
C a s t - i n t o - B a c k f i l l
P l a s t i c L i n e dC o n c r e t e P i p e
K e r a l i n e L i n e dC o n c r e t e P i p e
G l a s s F i b r e R C P w / E p o x y L a m i n a t e
S t e e l P i p e w /E p o x y L i n i n g
F R P P
S t r u c t u r a l P i p e L i n e r
w / B a c k f i l l
T W O - P A S S( B G S + S e c o n d a r y L i n i n g )
F I N A L T U N N E L L I N I N G
Durability
Durability
Durability
Groundwater
Groundwater
Final Lining Selection
• MWC team• industrial catchment• deeper sewer• sedimentary• residential route• groundwater excluded• more $ in BG segments• more sewer drops
• higher risk of H2S corrosion
• required 100% liner• PE sheet
• YVW team• domestic catchment• shallower sewer• basalt• creek valley route• groundwater infiltration• less $ on segments• fewer sewer drops• accepted shaft risk,
avoided tunnel risk • preferred robust liner• GRP pipe
QUESTIONS?
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