Lee Tunnel Project Diaphragm Walls London, U.K. Scope of Works: Beckton Overflow Shaft: 1500mm thick diaphragm wall shaft 89m deep approximately 23m internal diameter pre liner wall. 79m deep excavation. Beckton Connection Shaft: 1500mm thick diaphragm wall shaft 92m deep approximately 28m internal diameter pre liner wall. 81m deep excavation Tideway Pumping Shaft: 1800mm thick diaphragm wall shaft 98m deep approximately 40m internal diameter pre liner wall. 82.5m deep excavation Abbey Mills Station Shaft: F 1200mm thick diaphragm wall shaft 84m deep approximately 28m internal diameter pre liner wall. 72m deep excavation. Ab- Abbey Mills Station Shaft:G 1500mm thick diaphragm wall shaft 86m deep approximately 28m internal diameter pre liner wall. 72m deep excavation. Beckton Overflow Shaft Grouting Works: Curtain Grouting - 83nr holes to 11m depth below the dia- phragm wall through reservation tubes Break Out Grout Block - 16m x 8m x 16m block, compromising of 148 boreholes at 1.5m c/c to a depth of 76m. In total 71276m3 C50/60 concrete and 5143 tonnes of rein- forcement steel installed including glass fibre in TBM portals. INTRODUCTION: The Thames Tideway Tunnels programme is a key component of the upgrade of London’s combined sewer system. The first section to be constructed is the Lee Tunnel between the Beckton Sewage Treatment Works and the Abbey Mills Pumping Station. This comprised the construction of five shafts and a 7.2m internal diameter tunnel running 6.9km from Abbey Mills to Beckton. The shafts are some of the largest ever constructed in Europe and range from 20 to 38m finished internal diameter with diaphragm wall depths from 84 to 98m. Each shaft is formed from a reinforced concrete diaphragm wall with a secondary fibre-reinforced concrete lining and conventionally reinforced concrete base slab. MVB, a joint venture of Morgan Sindall, Vinci Construction Grands Projets & Bachy Soletanche delivered the Lee Tunnel project for Thames Water. They worked with Thames Water and their Project Management Team in a collaborative manner under an NEC contract with Mott MacDonald and Morgan Sindall Underground Professional Services as designers. GEOLOGY AND HYDROGEOLOGY The stratigraphy was similar to that encountered under much of east London, comprising a sequence of superficial deposits overlying Tertiary clays, sands and chalk. The chalk (weak limestone of 3 to 6 MPa) was encountered over approximately 50% of each shaft towards the base and was of grade A. The degree of fracturing was variable, but greater near the Thanet Sand interface. Bands and nodules of extremely strong flint were encountered. DIAPHRAGM WALLS DESIGN : The design followed EC2 & EC7 and had to consider an assessment of chalk stiffness, high hoop stresses, large multiple openings and non-axisymmetric loadings. A subgrade reaction programme “Paroi 2”, developed by BSL, was used for the design. Plaxis version 9 was also used to undertake axisymmetric finite element calculations and a Mohr Coulomb soil model without strain hardening used. A608 Five circular diaphragm wall shafts up to 40m in diame- ter with walls up to 98m deep and 1800mm thick CLIENT: Thames Water MAIN CONTRACTOR: Morgan Vinci Bachy JV MAIN CONTRACTOR’S DESIGNERS: Mott MacDonald & Morgan Sindall Underground Professional Services (UnPS) Ltd www.bacsol.co.uk DURATION OF WORKS: 20 months Fig. 1: Hydrofraise Excavation Tool Pumping & Connection Shafts
2
Embed
Lee Tunnel Job Sheet - Bachy Soletanche€¦ · Lee Tunnel Project Diaphragm Walls London, U.K. Scope of Works: Beckton Overflow Shaft: 1500mm thick diaphragm wall shaft 89m deep
This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
Transcript
Lee Tunnel Project
Diaphragm Walls
London, U.K.
Scope of Works: Beckton Overflow Shaft: 1500mm thick diaphragm wall shaft 89m deep approximately 23m internal diameter pre liner wall. 79m deep excavation. Beckton Connection Shaft: 1500mm thick diaphragm wall shaft 92m deep approximately 28m internal diameter pre liner wall. 81m deep excavation Tideway Pumping Shaft: 1800mm thick diaphragm wall shaft 98m deep approximately 40m internal diameter pre liner wall. 82.5m deep excavation Abbey Mills Station Shaft: F 1200mm thick diaphragm wall shaft 84m deep approximately 28m internal diameter pre liner wall. 72m deep excavation. Ab-Abbey Mills Station Shaft:G 1500mm thick diaphragm wall shaft 86m deep approximately 28m internal diameter pre liner wall. 72m deep excavation. Beckton Overflow Shaft Grouting Works: Curtain Grouting - 83nr holes to 11m depth below the dia-phragm wall through reservation tubes Break Out Grout Block - 16m x 8m x 16m block, compromising of 148 boreholes at 1.5m c/c to a depth of 76m. In total 71276m3 C50/60 concrete and 5143 tonnes of rein-forcement steel installed including glass fibre in TBM portals.
INTRODUCTION:
The Thames Tideway Tunnels programme is a key component
of the upgrade of London’s combined sewer system. The first
section to be constructed is the Lee Tunnel between the
Beckton Sewage Treatment Works and the Abbey Mills
Pumping Station.
This comprised the construction of five shafts and a 7.2m
internal diameter tunnel running 6.9km from Abbey Mills to
Beckton. The shafts are some of the largest ever constructed in
Europe and range from 20 to 38m finished internal diameter
with diaphragm wall depths from 84 to 98m. Each shaft is
formed from a reinforced concrete diaphragm wall with a
secondary fibre-reinforced concrete lining and conventionally
reinforced concrete base slab.
MVB, a joint venture of Morgan Sindall, Vinci Construction
Grands Projets & Bachy Soletanche delivered the Lee Tunnel
project for Thames Water. They worked with Thames Water
and their Project Management Team in a collaborative manner
under an NEC contract with Mott MacDonald and Morgan
Sindall Underground Professional Services as designers.
GEOLOGY AND HYDROGEOLOGY
The stratigraphy was similar to that encountered under much of
east London, comprising a sequence of superficial deposits
overlying Tertiary clays, sands and chalk. The chalk (weak
limestone of 3 to 6 MPa) was encountered over approximately
50% of each shaft towards the base and was of grade A. The
degree of fracturing was variable, but greater near the Thanet
Sand interface. Bands and nodules of extremely strong flint
were encountered.
DIAPHRAGM WALLS DESIGN :
The design followed EC2 & EC7 and had to consider an
assessment of chalk stiffness, high hoop stresses, large
multiple openings and non-axisymmetric loadings. A subgrade
reaction programme “Paroi 2”, developed by BSL, was used for
the design. Plaxis version 9 was also used to undertake
axisymmetric finite element calculations and a Mohr Coulomb
soil model without strain hardening used.
A608
Five circular diaphragm wall shafts up to 40m in diame-ter with walls up to 98m deep and 1800mm thick
CLIENT: Thames Water
MAIN CONTRACTOR: Morgan Vinci Bachy JV
MAIN CONTRACTOR’S DESIGNERS: Mott MacDonald & Morgan Sindall Underground
Sustainability √ All spoil from the shafts was removed by marine transport taking around 6000 lorry movements off the roads from the diaphragm walling alone. √ Rather than tankering waste bentonite
offsite the desanding plant included equip-ment capable of reverting it back to its constituent parts so that the water could be re-used or put into the sewage works and the solid powder taken away with the other spoil.
√ A high level of cement replacement by
GGBS was used in the high strength C50/60 concrete.
√ The project was registered with Consid-
erate Contractors Scheme achieving scores of up to 38/40 and liaison meetings took place with local residents.
Fig. 3: Hydrofraise Instrumentation Output
Safety √ Due to the width and depth of the panels a bespoke system of panel covers & edge protec-tion was developed by the site team for all the various stages of construction includ-ing excavation, caging and concreting.