Some problems on underground works for Hanoi metro projects
HANOI PEOPLE'S COMMITTEE
HANOI METROPOLITAN RAIL TRANSPORT PROJECT BOARD (HRB)
LUU Xuan Hung, Ph.D PHAM Quoc Thai, Ph.D
Hanoi, 29 February 2008
Content
Part I. Introduction to the Hanoi Metro Projects.
Part II. Some problems on underground construction for Hanoi metro projects.
Part III. Some solutions proposed for
application.
Part I. Introduction to the Hanoi Metro Projects.
• General planning of Hanoi capital until the year 2020
• Line 1: Nhon-Hanoi railway station (Phase 1)
• Line 2 :Tu Liem/Nam Thang Long-Thuong Dinh (Phase 1)
• Construction method
Ministry of Transport proposed to build 8 urban rail transport lines, forming the main axes of the public transport network in Hanoi:
-Yen Vien - Ngoc Hoi (25 km) -Ha Noi - Ha Dong (15 km)
-Bac Co - Hanoi Station - Voi Phuc - Nhon (16 km)
-Hanoi - Noi Bai Airport (25 km) -Daewoo - Trung Kinh - Hoa Lac (32 km)
-Giap Bat - Southern Thang Long (19 km)
-Buoi - Dong Anh - Soc Son (24 km)
-Co Bi - Gia Lam - Kim No (26 km)
General planning of Hanoi capital until the year 2020 (Decision No. 108/1998/QD-TTg dated 20/06/1998)
Line 1: Nhon-Hanoi railway station
Option V1A
L=12.5 km, mainly integrated at segregation. Total 15 stations – U/G section 2.9 km, 4 stations
– Elevated section 9.6 km, 11 stations
Viaduct U/G
VĐ2 Intersection VĐ3
Intersection Crossing
National Railway
Hanoi station
0
Nhon Depot
12,5 km
Line 2 :Tu Liem/Nam Thang Long-Thuong Dinh
Tu Liem/Nam Thang Long -Thuong Dinh Line length:
17.2km Underground section: 14 km.
Underground section goes under ancient quarter and city center.
Construction method
3000 8000 2000 3000 W
For the underground section, the station could be excavated by cut and cover method, and TBM could be used to excavate a tunnel between stations.
Part II
Some problems on underground construction for Hanoi metro projects
- Various existing structures in the vicinity, on ground surface - Unknown obstacles in the ground and public utilities relocation - Flooding and land subsidence
- Difficult geological condition (heterogeneity) - Planning for the use of underground space - Constraints of alignment
- Tunnel depth (for twin or single tunnel) - Construction site and access difficulties
- Traffic congestion by cut and cover method
Various existing
structures in the vicinity, on ground surface
Line 2 Line 1
Sensitivity of structures (building in ancient quarter, railroad, Hanoi station...) to ground settlements
Railway
Line 2
Ancient quarter Hanoi
Railway station
Unknown obstacles in the ground and public utilities relocation
• Existing state of public utilities has not been investigated and listed.
• Presence of frequently
unknown obstacles and the public utilities relocation
causes specific difficulties for urban tunnelling (space for relocation in some
stations)
Flooding and
Subsidence Areas Along UMRT Line 2 Corridor
Flooding and Subsidence
- Usually flooding due to rains at certain areas in the city, primarily as a result of poor and insufficient drainage system.
- Land subsidence is a growing issue, as excessive ground water extraction continues as alternative water supply sources have not been developed yet.
Difficult geological condition (heterogeneity)
• From ground to about 10m depth, the geological condition changing with weak geological formations (clayey mud, clay with sandy clay- plastic solid to semi solid, clayey sand,
clayey silt, sandy clay-plastic solid to semi solid), and lenses.
The underground stations will be built through these layers.
• In the deep layers, there are aquifers (fine sand, medium sand and alluvial clayey silty sand), the steady water source supplied by Red river. It is difficult to dewater and drain by pumping system. The underground section is mainly located in these layers.
Planning for the use of underground space
• There are not plan for underground space use in Hanoi.
• Underground station and the tunnel depth design have some difficulty, example the interconnection between Line 1
(extension) and Line 2 in Hang Bai-Tran Hung Dao crossroads.
Line 1
Line 2 High building (with
underground floors) Line 1 (Extension) Line 2
Commercial center in the stations
Constraints of alignment
• Selection of both horizontal and vertical alignment generally meets with constraints. (curve at Kim Ma-Nui Truc, Giang Vo- Cat Linh, Kim Ma-Nui Truc, Phan Dinh Phung-Hang Giay…)
• Land acquisition costs would be very high and the foundations of the existing buildings would create complications during
construction.
Ministry of Health building
Tunnel depth (for twin, single tunnel)
-For Line 1, we can use twin or single tunnel.
-The Line 2, vertical twin tunnel is suitable for ancient quarter section and horizontal twin tunnel for the Hoang Hoa Tham street section.
-Considering the Overall cost, safety of construction, schedule of construction, station dimensions, geological condition..
Traffic congestion by cut and cover method
3000 8000 2000 3000 W
The streets are narrow and the traffic land is reduced It causes the traffic congestion
Construction site and access difficulties
Launching Shaft for TBM
Ngoc Khanh Car Parking, Opposite to Daewoo Hotel Lieu Giai
Road
Kim Ma Road
Selecting places of attack (launching shaft, access to TBM), place for mud and lining segments stock and the point of
going underground
Point of Going underground
Thu Le Zoo/Park
Daewoo Hotel
Point of Going U/G
Kim Ma Str.
Lieu Giai Road
Part III. Some solutions proposed for application
Design step
• Detailed geotechnical investigation
• Detailed investigation of public utilities and relocation method design
• Impacts on underground water level and land subsidence
• Solutions to minimize damages to the adjacent existing buildings
• Detailed study and analysis of risk management
• Study of integrated underground space plan Construction step
• TBM method : Slurry TBM, EPB TBM, or Mix shield TBM
• Good tunnelling practice, Monitoring during the construction
• Ground treatment measures
• Traffic management solutions
Investigation and design
• Detailed geotechnical investigation: Laboratory tests (physical parameters, groundwater chemistry, direct shear box tests, oedometer, consolidation tests, triaxial tests CU+U…) and site
investigation (SPT, permeability tests Lefranc or Lugeon, pumping tests, piezometers for reconstruction of the hydrogeological
regime..), distance between the boreholes could be 100 m.
• Detailed investigation of public utilities and relocation method design.
- Drawings (at least scale 1/500) showing the existing main Public Utilities (P.U.) must be prepared for the Metro Line corridor. The location, the type, the depth or height, the dimension of those utilities will be given.
- Main utilities along and across the alignment such as the gas lines, high voltage electric cables, water supply, water drains, canals,
sewerage, telephone and optic fiber lines must be suitably
relocated for each station site (space for relocation around station).
• Study of integrated underground space plan for effective underground space use for every field.
Risk management
• Land subsidence must be analyzed by considering the weak local geological structure, existing groundwater exploitation, loss of groundwater during the construction phase
• Solutions to minimize damages to the adjacent existing buildings due to tunneling-induced ground settlements include: Settlement prediction; Monitoring; Protective works; Defects surveys; and Repairs
• Risk management procedures should be provided for to cover all the possible risks and to prepare measures to deal with that risks including corresponding cost estimate
The TBM method
(Slurry TBM, EPB TBM, or Mix shield TBM)
• TBM method could permit of safe and economic tunnelling in soft ground under urban conditions
• For the Line 1, in loose or medium dense sand, a Slurry TBM has more advantages
• Mix Shield TBM is the most suitable for excavating the Line 2 bored tunnels
Tunnelling practice and Monitoring
• Good tunnelling practice (including continuous working,
erecting linings immediately after excavation and providing
tight control of the tunnelling process to reduce the magnitude of settlement);
• At-source measures (including all actions taken from within the tunnel during its construction to reduce the magnitude of ground movements generated at source, such as face
stability, backfill grouting at shield tail, etc.)
• Monitoring: Settlement, displacement of hole during
excavation, convergence of tunnel, deformation of lining, ground stress and ground displacement around lining...
• Structural measures (to reduce the impact of ground movements by increasing the capacity of a building or
structure, typically including underpinning or jacking/shoring).
• Traffic management solutions
Ground treatment measures
• Anchors, grouting (jet grouting, compensation grouting, compaction grouting…), and also some solutions of
presupport and preconfinement (advance grouting, grouted body, face reinforcement, pipes umbrella over the roof…);
cut off walls, dewatering and drainage…
With some problems and the solutions presented above, the tight cooperation between the stakeholders (project owner,
consultants, contractors and relevant units) is important to carry out safe and
economic tunnelling operations
Thank you for your
attention!
Reference
• Hanoi Authority for Tram and Public Transport Development Management (HATD), 2006. Hanoi Pilot LRT Line - Feasibility Study Report, Hanoi, November 2006.
• Japan International Cooperation Agency (JICA), Hanoi People's Committee (HPC), 2006. The Comprehensive Urban
Development Program in Hanoi Capital City (HAIDEP). Draft Final Report - Prefeasibility Study B: The UMRT 2 Line. Almec Co.,
Nippon Koei Co. Ltd., Yachiyo Engineering Co. Hanoi, November 2006.
• Vu Quyet Thang , 2008. Underground water and land subsidence in Hanoi ancient quarter.
• Nguyen Duc Toan and Luu Xuan Hung, 2007. Hanoi Metro Pilot Line Project: Some aspects of risk management and subsidence.
Seminar of ITA and ITST on Tunnelling.
• Kovari K., Ramoni M. 2004. Urban tunnelling in soft ground using TBM's. Key note lecture at International Congress on Mechanized Tunnelling: Challenging Case Histories. Politecnico di Torino, Italy - 16-19 November 2004.
