TUNNEL CONSTRUCTION (CONSTRUCTION ENGINEERING)
Submitted By: RABIU WASIU ADESOYE. Department of Civil Engineering University of Ibadan.
Department of Civil Engineering, Faculty of Technol echnology ogy,, University of Ibadan.
Lecturer in Charge: Engr. (Mrs.) J. O. Oladejo
INTRODUCTION DEFINITIONS A Road Tunnel is defined as enclosed roadways with vehicle access that is restricted to portals regardless regardless of type of the structure or method of construction1.
USES Tunnels are used for highwa highway y traffic, railroads, and subways; to transport water, sewage, oil, and gas; to divert rivers around dam sites while the dam is being built; and for military and civil-defense purposes.
Plate 1: 50 km Channel Tunnel between UK and France under Construction. Source: Pierre Jean Pompee, Channel Tunnel Construction Construction
MAJOR TUNNELS OF THE WORLD NAME OF OF TUNNEL
LOCATION
LENGTH OF OF TUNNEL
USE US E OF TUN TUNNE NELL
Laerdal Tunnel
Norway
24.5 km
Vehicular
Saint Gotthard
Switzerland
16.3 km
Vehicular
Arlberg
Austria
14.0 km
Vehicular
Seikan
Japan
54.0 km
Railroad
Channel Tunnel
UK - France
50 km
Railroad
Qinling (1 & 2)
China
19 km
Railroad
DESIGN CRITERIA
SHAPES There are three shapes of highway highway tunnels: 1.
Circular Tunnels
2.
Rectangular Tunnels
3.
Horseshoe/ Curvilinear Tunnels.
The shape of the tunnel depends on the mode of construction and the ground conditions. Circular Tunnels, Tunnels, for instance are usually constructed using either
Tunnel Boring Machine Method (TBM) or by Drill and Blast Method. Rectangular Tunnels are usually constructed constructed by the Cut and Cover Cover
method, by the immersed immersed method, or by the jacked jacked box tunneling. Tunnels are usually constructed by the Horseshoe Configuration Tunnels drill and blast in method, method , or the Sequential Seq uential Excava Excavation tion Method (SEM), also known as the t he New Austrian Tunneling Tunneling Method (NATM) (NATM)
ALIGNMENTS Tunnel should be designed in accordance with the The Road Tunnel respective manual for Geometric Design, e.g. the AASHTO Geometric Code, Nigerian Highway Highway Manual etc. t he road should be designed to cater for all The width and size of the kinds of vehicles in the Geometric Code, according to the class of highway highway it represents (i.e. Federal or State S tate Highway). Highway). The Alignment of the Tunnel must be consistent with the
alignment of the roadway leading to it. like the sight distances, The Alignment must consider factors like minimum turning radius and design speeds in its design. Except for maintenance reasons, two way roads should be
discouraged in in a single tube t ube of tunnel, tu nnel, for safety safety reasons. Cyclist use of tunnels should be discouraged discouraged Pedestrian and Cyclist except except a special passage is designed d esigned for them.
TUNNELLING DESIGN METHODOLOGIES The processes involved involved in the design of a tunnel are defined as follows: i. Define the functional requirements, including the design life l ife and durability requirements. ii.Carry out the necessary geologic, geotechnical and geohydrological ii.Carry investigations and analyses. iii.Conduct environmental, cultural and iii.Conduct and institutional institu tional studies to access how they impact the design and construction of the tunnel.
iv.Perform iv.Perf orm tunnel type studies to determine the most appropriate method of tunnel construction.
TUNNELLING DESIGN METHODOLOGIES v.
Establ Establish ish the design design criteria criteria and perfo perform rm the the design design of the variou variouss tunnel elements. The initial and final support systems and the lining should be designed, considering the ground conditions co nditions and the proposed method of construction.
vi. Establ Establish ish tunnel tunnel Align Alignmen ment, t, Profi Profile le and Cros Crosss Sectio Section. n.
vii. vii. Deter Determin mine e potenti potential al modes modes of failur failure. e. viii. Prepare Prepare project documents including construction plans, specifications, schedules, estimates, estimates, and Geotechnical Baseline Reports (G.B.R)
Geological Profile and Description of Works for Channel Tunnel between UK and France. Tunnel slope slope is between 0.2% and 1.1%, often found at 0.6% at U.K Side, and 1.1% at the France side.
GROUNDWATER CONTROL - Building a dry tunnel is a primary concern for for tunnel construction, as a dry tunnel provides a safer, safer, friendlier fr iendlier environment, while significantly reducing operation operation and maintenance costs. - Based on the advanced waterproofing waterproofing technologies today today, the International Tunneling Association (ITA) recommends the following infiltration criteria: ALLOWABLE INFILTRATION INFILTRATION Tunnels ≤ 0.002gal/sq. ft/day Underground Public Space ≤ 0.001gal/sq. ft/day
In addition, no dripping or visible leakage is allowed in the structure.
GROUNDWATER CONTROL There are two basic types of waterproofing systems: drained (open) and undrained (closed). Open waterproofing system system allows groundwater inflow into the tunnel drainage system. The tunnel vault area is equipped with a waterproofing system system that forms an umbrella-like protection that drains seeping water into a prepared drainage system located at the bottom of the tunnel sidewalls and in the tunnel invert. It is usually used in rock tunnels where infiltration rates are usually low. Closed Waterproofing system extend around the entire tunnel perimeter, and thus exclude water from entering into the tunnel drainage. The linings are thus designed to cater for hydrostatic pressure. It is used in permeable soils where groundwater discharge into the tunnel would be significant, and its discharge would lower the water table and probably cause settlements.
INVESTIGATIONS Several investigations are required at the preliminary, design and construction phases of a tunnel project. The processes are highlighted below: Collection and Review of Available Information Information for a general general knowledge of the area (Existing Topographical, hydrological, Geological, Geotechnical, Seismic, Environmental, Zoning etc) Topographic and Aerial Photographs Reconnaissance and Preliminary Survey Sur veyss Water Water Well Logs Flood Insurance Maps Hydrographic Surveys Utility Surveys (especially in cities) Identification of Underground Structures and Obstacles •
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Structure Preconstruction Survey Geologic Mapping Subsurface Investigations Test Borings and Sampling Sampling Sampling - Overburde Overburden n Soils Soils Sampling – Sampling – Rock Core Soil and Rock Identification and Classification Classi fication In - situ Tests ests Geophysical Tests Seismic Wave Propagation Laboratory Laborator y Tests Tests Groundwater Investigation Pumping Pumpi ng Tests Tests
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TUNNELLING CONSTRUCTION METHODOLOGIES METHODOLOGIES
TUNNELLING CONSTRUCTION METHODOLOGIES (a) Cut and Cover System. (b) Pipe Jacking System (Micro Tunneling). (c) Shield Tunneling Tunneling (TBM). (d) New Austrian Tunneling Method (NATM). (e) Immersed-Tube Tunneling System.
CUT AND COVER METHOD
Sequence of Construction (Stages 1 to 3)
CUT AND COVER METHOD
Sequence of Construction (Stages 4 to 6)
CUT AND COVER METHOD Advantages: • Economy Economy for for shallow depths (4 - 10 m) and for shorter shorter applications. • Un-sophisticated Un-sophisticated labor and equipment required. different conditions. • Adaptability to different • Simple structural & geotechnical analyses required. • Safe environment (ventilation and fire hazard). Disadvantages: • Possible disturbances to existing facilities. Practical limitations of depth. • Practical • Unsuitability under buildings or water.
SOIL GROUTING
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Grouting is the process of filling gaps using mortar. In Tunnel Tunnel Construction, gaps gaps in the soil needs to be filled using mortar to prevent the collapse or sinking of the ground and the tunnel. The process of soil grouting is shown below:
Soil Grouting Techniques
Jet Grouting: Soil Replacement Process
Soil Grouting Techniques
Slurry Wall Concept
(b) Pipe Jacking System (Micro Tunneling)
Schematic Representation
Tunnel Construction Construct ion
Preparation of Driving Shaft
Jacking Pipes Using Hydraulic Jacks 23
Guidance and Positioning Using Laser-Guided Steering System
Tunnel Construction Construct ion
Laser Guide & Control Monitor
Screen Capture
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Tunnel Construction Construct ion
MTBM Break Through
Extraction of MTBM 25
MTBM - Shields Shields of Differen Differentt Sizes Sizes
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MTBM - Differ Different ent Shapes Shapes of Cuttin Cutting g Heads
Dirt cutter head (clay (clay and silty sand)
Sand shelves
Carbide cutter head (soft to medium hard rock) 27
Pipe Jacking System (Micro Tunneling) Advantages: • • • • • • •
Suitability for almost all types of soil. Large depths with unlimited lengths of drive. High levels of accuracy and safety. Wide choice of pipe and joint materials. High construction rates. Reduced manpower requirements. Reduced environmental disturbance.
Disadvantages: • • •
Sophisticated equipment and highly skilled labor. Inability to make rapid changes in line or level. Very expensive corrective actions, if required.
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(c) Shield Tunneling (TBM) (TB M)
Cutter Head
Tunnel Tube
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Support Fluid Circulation System System
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Construction Sequence
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Shield Tunneling (TBM) Advantages: • • •
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Suitability for almost all types of soil. Suitability for wide tunnels (highway, railway, etc.). Large depths ( > 10 m), with unlimited lengths of drive. Reducing environmental disturbance and utilities diversions.
Disadvantages: • • • •
Sophisticated equipment and highly skilled labor. Inability to make rapid rapid changes in i n line or level. Very expensive corrective actions, if required. Difficult structural structural and geotechnical analyses reqd. 33
(d) NATM Construction Sequence
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New Austrian Tunneling Method Advantages: • •
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Best alternative for non-circular roadway tunnels. Suitability for almost all stable to strong ground types, including rock. Suitability for a variety of soil conditions. Small thickness of tunnel lining, reducing the amount of excavation. Economy and speed of construction.
Disadvantages: • • •
Highly skilled workers workers and expert engineers. Safety measures for shotcrete application. Ground water freezing and/or soil strengthening (in case of water-bearing water-bearing cohesion-less soil).
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(e) Immersed-Tube Tunneling System
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(e) Immersed-T Immerse d-Tube ube Tunneling unneling System Construction Sequence: 1. Dredging the trench in river or sea bottom. 2. Prefabrication Prefabrication of tunnel sections, and sealing ends with bulkheads. 3. Floating the sections to the tunnel trench. 4. Lowering the sections to seabed. 5. Joining the sections together underwater. 6. Removing the temporary bulkheads. 7. Backfilling the trench.
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Immersed-Tube Tunneling System System Advantages: •
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Economy (most economical alternative for any type of underwater tunnel crossing). High construction rates (particularly for steel tube tunnels). Wide variety of different conditions.
Disadvantages: • • •
Casting basin (for concrete box tunnels). Highly skilled and experienced experienced workers. workers. Safety measures for underwater construction. 38
Other Necessary Features •
Lighting
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Aeration and Ventilation
References •
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American Association of State Highway & Transportation Transportation Officials Technical Committee for Tunnels (T – 20). Taylor and Francis Group, Handbook of Highway Highway Engineering, 2006.
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Design Highway Manual, Federal Republic of Nigeria, 2006
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Jean Pierre Pompee, Channels Tunnel Construction.
Thank you
