STRATEGIES FOR HANDLING COMPLEX TUNNELING & UNDERGROUND CONSTRUCTION CLAIMS
TERRANCE J. ZICH, PE, PG, CPG: GEOTECHNICAL LEAD
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Course Description/Objectives
• Review tunneling and underground construction techniques with the goal of having a basic understanding of what can go wrong and the causes of damage that can result in claims. • The webinar goal is to broaden the understanding of causes of damage associated with tunneling and underground construction along with the available tools and the benefits of utilizing expert assistance in investigating these losses to assist in determining cause(s) and coverage, if applicable. • Includes a review of case studies in order to provide examples of damage associated with tunneling and underground construction claims.
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Course Description/Objectives
. General Geological & Engineering Concepts . Design Considerations . Tunneling . Other Underground Construction . Claim Considerations/Underwriting Risks . Case Studies . Questions
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1 Geological and Engineering Concepts
•Location, Location, Location • Subways • Sewage systems • Walkways and Roads • Utilities • Storage •Geologic Medium key to Development Considerations •Geologic Complexities present uncertainties •Climate part of Process
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Geological and Engineering Concepts
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Geological and Engineering Concepts
GEOTECHNICAL CONSIDERATIONS:
Soils and Rock Mechanics Definition:
The study of the physical properties of soil, rock and rock masses, especially those properties that affect the behavior of the medium on the ability to bear weight, including such things as mineralogy, water content, density, strength, bedding planes, fractures, faults, etc.
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2 Geological and Engineering Concepts
Soil: •Behavior of soil is a function of the strength of the soil mass, and non-homogeneity of the material e.g. thickness of beds, bedding planes between material; thickness; gradation of material; mineralogy; etc.
Rock: •Behavior of rock is function of the hardness (type of rock), the weathering of the rock and the frequency and type of discontinuities
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Design Considerations
1. Geologic conditions, e.g. Rock or Soil; competency/ density, faults, folds, bedding planes, etc. 2. Groundwater 3. Trapped oil and/or gas 4. Squeezing rocks such as bentonite and anhydrite 5. Dissolving rocks such as limestone and evaporates 6. Adequate testing • The more variable the conditions the more testing required!
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Design Considerations
Groundwater: • Nuisance to cause of failure • Knowledge of location of inflows important • Control is the key
Trapped Oil and Gas: • Potentially catastrophic; control ahead of time
Problematic Soils/Rock • Ground treatment, tunnel liners and other preventive measures
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3 Design Considerations
Site Investigations: •Characterize geologic conditions and hazards •Alignment selection •Geotechnical Engineering Baseline Report •Evaluation of construction methods •Determine preparatory applications
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Short History of Tunneling
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Short History of Tunneling • First tunnels were constructed in the early 1800’s. They were relatively short and typically utilized a locomotive. • 1845 – First tunnel boring machine (TBM) was built, however, funding for the project failed. • 1863 – First urban underground railway was constructed in London. Worked with steam trains (did not utilize TBM). • 1863 – First TBM that tunneled a substantial distance. •19th and 20th century – large advancements in TBM.
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4 The Basics of Tunneling
Tunneling Methods 1. Hand Excavations 2. Drill and Blast 3. Cut and cover 4. Tunnel Boring Machines •Pilot Pipe •AVT Auger Microtunneling •AVN Slurry microtunneling •Excavator/rockheader •Earth Pressure Balance •Hydro/Slurry Shield •Hard rock TBM Shield •Hard Rock TBM Gripper © 2017 Envista Forensics
The Basics of Tunneling
Tunneling projects can result in a wide degree of damage, and as such, having a basic understanding of tunneling construction can be an asset when adjusting a tunneling claim.
Currently, the most common two methods that tunnels are constructed include:
• Cut and Cover (open trench construction) • Tunneling Boring Machine (TBM)
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Tunneling – Cut and Cover
• As the name implies, cut and cover involves the excavation of a trench, erecting the support for the trench, the formation of the tunnel structure and backfilling around the new constructed tunnel. • Up until the successful utilization of the TBM, drilling, blasting along with cut and cover were the main methods for tunnel construction.
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5 Tunneling – Cut and Cover
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Tunneling – Cut and Cover Tunneling Methods
Cut & Cover Projects
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Tunneling – Cut and Cover
While cut and cover can work for the construction of many tunneling projects, it does have its limitations. • Cannot construct using cut and cover through a mountain or under a body of water or under other man-made infrastructure.
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6 Tunneling – Cut and Cover
While cut and cover can work for the construction of many tunneling projects, it does have its limitations.
• Due to the success of subway systems in many large cities coupled with transportation problems, the market for mass transportation is increasing.
• However, due to dense population and/or the existing of extensive infrastructure (roadways, buildings and unities), cut and cover construction is not an option.
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Tunneling – Cut and Cover
While cut and cover can work for the construction of many tunneling projects, it does have its limitations.
• When groundmasses such as rock, dense sands and/or hard clays are encountered, drilling/blasting are the only alternative which can result in increased costs and if not anticipated construction delays.
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Tunneling
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7 Tunneling - TBM
• Many tunnels are being constructed utilizing a tunneling boring machine (TBM) or a combination of a TBM and cut and cover. • A TBM is a machine used to excavate circular shaped tunnels where open trench construction is not an option. • A TBM can tunnel through a wide variety of groundmasses. • A TBM can be operated in relatively close quarters to existing surfaces and sub-surface structures.
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Tunneling - TBM
Drill & Blast Equipment
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Tunneling - TBM
Pilot Bore and Reamer
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8 Tunneling - TBM
AVT auger Micro- tunneling
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Tunneling - TBM Tunneling Methods
AVN slurry Micro- tunneling
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Tunneling - TBM
Roadheader Equipment
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9 Tunneling - TBM
Earth Pressure Balance
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Tunneling - TBM
Large Slurry Machine
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Tunneling - TBM
Hard Rock Single Shield
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10 Tunneling - TBM
Hard Rock Double Shield
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Tunneling - TBM
Hard Rock Gripper Shield
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Tunneling
Selection of Equipment includes but not limited to: • Geologic medium • Site restrictions • Restrictions on use of equipment • Availability of equipment and supplies • Alignments vertical and horizontal • Local knowledge and experience •Costs
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11 Tunneling
Tunnel Liner and Support • Ground treatment • Initial support • Design support • Repair support Systems • Liner Plates • Ribs and Lagging • Shotcrete • Grouting • Rock bolts and reinforcement • Concrete segments
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The Basics of Tunneling - TBM
• Tunneling construction utilizing a TBM requires a launch site and a receiving site. • Sometimes these launch and receiving sites are at ground level
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The Basics of Tunneling - TBM
• Tunneling construction utilizing a TBM requires a launch site and a receiving site. • Sometimes these launch and receiving sites are at ground level. • However, for many TBM projects, a launch pit and receiving pit is required due to topographical restraints.
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12 The Basics of Tunneling – Pit Construction
• Launching and receiving pits are among the first elements to be installed at the beginning of a TBM project. • These often required deep excavations, sometimes multiple stories beneath the ground surface. • In order to retain the soil surrounding a pit, sub- surface perimeter walls are constructed, prior to the excavation of the pit. • This can be done by drilling a series of concrete solider piles or by pouring cast-in-place concrete walls.
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The Basics of Tunneling – Pit Construction
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The Basics of Tunneling – Pit Construction
• Cast-in-place diaphragm walls typically required extensive bracing along the top of the walls.
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13 The Basics of Tunneling – Pit Construction
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The Basics of Tunneling – Pit Construction
• Typically, the launching face, where the TBM starts, consists a steel reinforced concrete wall. • However, TBM’s cannot bore through steel reinforcing, and as such, the reinforcing has to be removed by hand. This is typically referred to as hacking. • Before the concrete and reinforcing can be hacked, the soil pressure on the outside of the wall needs to be redistributed and/or decreased. • This can be done by jet grouting the soils on the outside of the diaphragm wall.
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The Basics of Tunneling – Pit Construction
Jet Grouting Layout • Often referred to as soil improvement, jet grouting is the process where a jet of fluid with high kinetic energy is used to break apart and mix the in-situ soils with a liquid cement slurry so as to form a column of “soil concrete”
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14 The Basics of Tunneling – Pit Construction
• In addition, and in order to monitor water ingress during the hacking process, numerous monitoring holes are installed around the area of the launching ring.
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The Basics of Tunneling – Pit Construction
• In addition, and in order to monitor water ingress during the hacking process, numerous monitoring holes are installed around the area of the launching ring. • The holes are critical for monitoring the presence of water on the outside of the wall and can also provide a location to do additional grouting and monitor grouting pressures
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The Basics of Tunneling – Pit Construction
Hacking of the launching face diaphragm wall
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15 The Basics of Tunneling – Pit Construction
• While reinforce diaphragm walls has historically been a common method used in the construction of the launching pit, due to the time and potential for problems during the hacking process, there is an alternative for the construction of the launching face of the diaphragm wall. • One alternative method is referred to as a “soft eye”.
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The Basics of Tunneling – Pit Construction
• This method utilizes Glass Fiber Reinforced Polymer (GFRP) reinforcement in place of conventionally steel reinforcing. • With the use of GFRP reinforcing, the TBM can directly drill through the D-wall without any hacking and/or removal of reinforcing. • This can greatly decrease the potential for problems associated hacking and steel removal, such as potential wall collapse and water ingress.
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The Basics of Tunneling – Pit Construction
• Once the launching face has been prepared, the TBM can be assembled in preparation for launch.
• A similar process will occur at the receiving pit.
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16 What Can Go Wrong
Due to the vast variation in site conditions including: • Location of site (urban or suburban) • Existing streets and buildings • Location and age of existing utilities • Depth of tunnel • Location of the site relative to water (rivers/lakes) • Site soil conditions/Problematic soils/rock • Groundwater and/or trapped gas and oil
There are a number construction activities that can result in tunneling construction claims
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What Can Go Wrong
In this presentation, we will focus on the following;
• Water egress into and integrity of the launching pit
• Damage to existing streets and buildings
• Damage to existing utilities
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What Can Go Wrong – Launching Pit
• Protection of the launching pit is one of the most important tasks for the successful completion of a TBM project. • TBM costs can vary, but are typically in the range of 20 million dollars (USD). • As such, protection of the launching pit walls from excessive deflection and/or collapse is imperative. • Also, ongoing issues with the launching pit can result in lengthy delays.
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17 What Can Go Wrong – Launching Pit
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What Can Go Wrong – Case Study 1
• Launch pit with classic steel reinforced diaphragm walls. For this reason, hacking of the D-wall was required.
• During hacking, excessive deformation occurred along the bottom of the ring.
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What Can Go Wrong – Case Study 1
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18 What Can Go Wrong – Case Study 1
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What Can Go Wrong – Case Study 1
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What Can Go Wrong – Launching Pit
• Water ingress during the hacking of the diaphragm wall can also be a cause of damage and/or delays. • First, as long as there are ongoing leaks in the diaphragm walls, the launch of the TBM will be delayed. • For this reason, the proper installation of monitoring holes is critical to monitor the presence of water on the outside of the wall. • If the monitoring holes are not well distributed, the presence of water behind the wall can be an ongoing issue resulting in delays.
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19 What Can Go Wrong – Case Study 2
• Again, launch pit with classic steel reinforced diaphragm walls. For this reason, hacking of the D-wall was required.
• During hacking, on two different occasions, water began to leak into the pit.
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What Can Go Wrong – Case Study 2
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What Can Go Wrong – Case Study 2
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20 What Can Go Wrong – Case Study 2
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What Can Go Wrong – Launching Pit
• Water ingress can also result in settlement of property and streets surrounding the launching pit. • Ground water can transport soil from under existing property into the launching pit. • This soil transportation can result in settlement and subsequent damage to streets and/or buildings. • This leads us to another common form of damage during tunneling projects. Settlement to streets, buildings and property.
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What Can Go Wrong – Settlement
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21 What Can Go Wrong – Settlement
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What Can Go Wrong – Settlement
• In most tunneling projects, the ongoing use of nearby streets and building is essential. • For this reason, the elements need to be protected.
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What Can Go Wrong – Settlement
• As previously stated, damage to these elements can be from water ingress into the launching pit, however, settlement damage can also occur after the TBM has been launched. • This can occur from induced ground vibration. • If the TBM is close to an element, these induced ground vibrations can result in direct damage. • However, this induced ground vibration can result in localized consolidation of the soil and subsequent settlement as well. • Some settlement should be expected, however, much can likely be prevented
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22 What Can Go Wrong – Utilities
• The ground beneath most urban areas is filled with utilities. • With the exception of some electrical and telephone, most all utilities are located in the ground. • As such, it is vital that all utilities be identified during the design phase of the tunneling project. • If utilities are impacted, it can result in excessive damage and long delays.
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What Can Go Wrong – Utilities
• Accessing the condition of older utilities, e.g. abandoned utilities, is equally important. • Deteriorated and/or delipidated underground utilities can be highly sensitive to the movement of the TBM. • A sudden collapse of a water/drainage utility can result in settlement and/or sinkholes.
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What Can Go Wrong – Case Study 3
• The TBM had been launched and was progressing. • A sinkhole appeared in the street. • An emergency excavation revealed that a drainage pipe had collapsed and was eroding the soil into the pipe. • The pipe was found to be in a severely deteriorated conditions with many historical cracks. • An emergency excavation was conducted to repair the pipe followed by backfilling and repairing of the street surface.
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23 What Can Go Wrong – Case Study 3
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What Can Go Wrong – Case Study 3
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What Can Go Wrong – Case Study 3
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24 What Can Go Wrong – Case Study 3
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What Can Go Wrong – More?
• These are just a few of the common types of damage that we have seen associated with tunneling projects. • Due to the complexity of tunneling, and the many factors that need to be considered when tunneling with a TBM, there are other causes of damage that can occur. • Cause that was not covered in this presentation was design and/or other construction related deficiencies.
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Tunnel Collapse
Review of some photos of tunnel collapses that are available on an internet search
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25 Tunnel Collapse
Tunnel Collapse during construction changing geology
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Tunnel Collapse
Tunnel Collapse in due to missing anchor bolts
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Tunnel Collapse
Tunnel Collapse in during construction
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26 Tunnel Collapse
Tunnel Collapse during construction improper backfill and rain
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Tunnel Collapse
Tunnel Collapse related to glue used for anchor bolts
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Tunnel Collapse
Tunnel Collapse in during excavation with surface effects
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27 Other Underground Construction
Mining operations Shafts Deep foundations Underground storage caverns Utility Directional Drilling
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Underground Mine Case Study
•High Wall Miner and ADDCAR System Damages •Increase in power indicated jamming of system or fall on the equipment/equipment cameras verified fall •Excavation of equipment/severely damaged •Equipment repaired or replaced as needed •Unanticipated roof fall related to weak cover and water penetration •Mining practices appeared satisfactory and other specific possibilities ruled out
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Underground Mine Case Study
• Recent PT&C/LWG Project – Mine entrance
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28 Underground Mine Case Study
• Recent PT&C/LWG Project – Highwall Miner
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Directional Drilling for Utility Placement
Directional drilling to install utilities below streets and other structures
Image from Terra Trenchless Technologies © 2017 Envista Forensics
Case Studies Summary
1. Faults 2. Weak rocks/soils 3. Odd encounters e.g. boulder, concretions; misc. 4. Water inflows/flooding 5. Gas seeps/explosions 6. Man made features 7. Human errors Stress: Geologic conditions/insufficient studies appear to be number one in cause of failures: includes construction observation and communication
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29 Claim Considerations
• Site Investigation/Geologic medium/ Geotechnical testing • Design considerations • Construction monitoring process/records • Type of Equipment/Selection • Construction and Equipment records • Human factor
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Claim Considerations
• From a Geotechnical Engineering aspects it all starts with the consideration of the geologic and geotechnical conditions and the investigations completed. • However, due the complexities, an available multi- disciplinary team of Geological and Geotechnical Engineers; Geologists; Structural Engineers; Mechanical Engineers; Industrial Engineers and others as provide by Envista as needed, is best expert assistance for determining causes for the tunneling and other subsurface type claims.
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Other Type of Subsurface Investigations
• Sinkhole Claims (Limestone Formations) • Cause and Origin of Retaining Wall Failure/Slope failure • Soil/Groundwater Contamination Issues, Fuel Oil UST Leak • Salt Water Intrusion from Hydro-Fracking on Water Well Quality • Soil movement/subsidence hole (Evaporate Formations) • Duct Bank Damage (Subsurface Collapse) • Collapsible Soils Investigation/effects on Foundation • Shrink/swell clay Investigation so effects on Foundations • General Subsidence Evaluation • Litigation regarding environmental issues such as consequences of pipeline construction; contamination associated with ESA reports; Oil Field Soil Contamination
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30 Thank You! Questions?
Contact: [email protected] [email protected]
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