QuakeLogic Blog Archive

Monitoring Tunnels for Seismic Safety and Risk Management

Highway tunnel interior with structural health monitoring sensors for seismic safety assessment

In short: Tunnels are not automatically safe in earthquakes: liquefaction, slope failure, fault crossings and near-fault pulses damaged or collapsed tunnels in the 1906 San Francisco, 1952 Kern County and 1999 Duzce earthquakes, and the 2012 Sasago ceiling collapse showed components fail even without shaking. Tunnel seismic monitoring with real-time structural health monitoring measures accelerations, displacements and strains in the lining so officials can close a tunnel before it becomes deadly.

Monitoring tunnels for vibrations and deformations is not only critical during the construction phase but also their service life.

In 2012, the Tokyo-bound Sasago Tunnel suffered significant damage when nearly 150 concrete ceiling panels collapsed and crushed three vehicles, including a van carrying six people that caught fire. The deficiencies in mounting components of the ceiling panels were to blame.

But, are tunnels safe during an earthquake?

A common belief that underground structures are safer because they move with the soil, while structures above ground sway back and forth during the earthquakes appears to be misleading. The impact of earthquakes on tunnels can be severe due to ground failures such as liquefaction, strong ground shaking, and fault crossing.

Liquefaction takes place when saturated soft soil deposits loose load-carrying capacity during strong shaking. This phenomenon can cause the ground surrounding tunnels to deform and shift, with potentially severe impacts. The slope instability and fault crossings may also create permanent deformations leading to a collapse of the tunnel.

After the 1906 San Francisco earthquake, the Wrights railway tunnel in southern Santa Cruz mountains was closed for more than a year due to the collapse of approximately 100-m-long part crossing the San Andreas Fault Zone. Another railway tunnel crossing the White Wolf Fault was seriously damaged during the 1952 magnitude 7.5 Kern County earthquake associated with this fault (Kontogianni and Stiros, 2003).

In 1999 a magnitude 7.2 hit the Duzce region in Turkey. Close to the fault rupture, twin highway tunnels on the major highway connecting Ankara to Istanbul were under construction. The tunnels were partially collapsed due to intense pulses of earthquake motion (near-fault effects) as their lines cross the shear zone of the North Anatolian Fault.

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The excavation process during tunnel construction may itself trigger microearthquakes. The vibrations, therefore need to be monitored to identify such seismic activity whether they create any movements or cracks on the tunnel surface. The monitoring vibrations is also needed to estimate the rock formations ahead of the tunnel face to optimize the excavation parameters. Besides, the infrastructure surrounding the tunnel including buildings must be monitored especially in case of construction of new subway (metro) lines.

Structural health monitoring (SHM) system is essential for the seismic resilience of tunnels. A robust real-time SHM system not only allows for assessment of accelerations and deformations (displacements and strains) in tunnel linings but also facilitates the implementation of adaptive risk management. Such a system can assist the officials to make informed and timely decisions to protect people (such as drivers or construction workers) from life-threatening conditions. For example, the highway tunnel can be closed to traffic before any severe consequences take place. Such pro-active actions would not only save lives but also avoid liabilities.

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QuakeLogic is the only company providing cloud-based AI-powered disaster risk management solutions to prevent and reduce human and economic losses risen during and after earthquakes. Our cutting-edge technology platform performs real-time autonomous structural assessments using sensor data and sends rapid notifications after an event with the level of shaking intensity and whether structural integrity is compromised. For tunnels, our platform provides meaningful and easy-to-understand information immediately after an earthquake. This timely and critical information helps the officials to plan their emergency response. We also provide a web-based display where the sensor information can be monitored in real-time. This solution can provide great benefits especially for tunnels under construction phase.

For emergency measures and safety of tunnels, QuakeLogic provides advanced monitoring systems together with real-time and autonomous data analytics.

Key Takeaways

  • In 2012 about 150 concrete ceiling panels fell in Japan's Sasago Tunnel, crushing three vehicles, due to deficient mounting components.
  • The Wrights railway tunnel lost roughly 100 m where it crossed the San Andreas Fault in the 1906 San Francisco earthquake.
  • Twin highway tunnels near Duzce partially collapsed in the 1999 M7.2 earthquake from near-fault pulses on the North Anatolian Fault.
  • Tunnel excavation itself can trigger microearthquakes, so vibrations should be monitored during construction.
  • Real-time SHM of accelerations, displacements and strains enables closing a tunnel to traffic before severe consequences.

Frequently Asked Questions

Are tunnels safe during an earthquake?

Not necessarily. The belief that underground structures are safer because they move with the surrounding soil is misleading. Tunnels can suffer severe damage from liquefaction of saturated soft soils, slope instability, strong shaking and especially fault crossings, where permanent ground deformation can collapse the lining. Historic failures include the Wrights tunnel in 1906, a White Wolf Fault railway tunnel in 1952 and the Duzce highway tunnels in 1999.

Why should tunnels be monitored during construction?

Excavation can itself trigger microearthquakes, and vibration monitoring reveals whether that seismic activity is causing movement or cracking in the tunnel surface. Vibration data also helps estimate rock conditions ahead of the tunnel face to optimize excavation parameters. In addition, surrounding infrastructure such as buildings above a new subway line must be monitored for settlement and vibration effects.

What does a structural health monitoring system measure in a tunnel?

A tunnel structural health monitoring system measures accelerations and deformations, meaning displacements and strains, in the tunnel lining in real time. QuakeLogic's cloud platform processes this sensor data autonomously, reports the shaking intensity after an earthquake, indicates whether structural integrity is compromised, and offers a web display so officials can watch conditions continuously, including during construction.

What happened in the Sasago Tunnel collapse?

In 2012 nearly 150 concrete ceiling panels in Japan's Tokyo-bound Sasago Tunnel collapsed, crushing three vehicles, including a van carrying six people that caught fire. Investigators blamed deficiencies in the components mounting the ceiling panels. The event shows that monitoring tunnels for deformation matters throughout their service life, not only during construction or earthquakes.

How does tunnel seismic monitoring help emergency response?

Real-time tunnel seismic monitoring gives officials immediate, easy-to-understand information after an earthquake about shaking intensity and whether the structure is compromised. With that data they can close a highway tunnel to traffic before severe consequences occur, protect drivers and construction workers, plan emergency response, and avoid liabilities. This adaptive risk management turns the monitoring system into a decision tool rather than a passive record.

Need help with a project? QuakeLogic designs and supplies seismic monitoring, earthquake early warning, structural health monitoring, infrasound, and shake table systems. Browse QuakeLogic products or contact our engineering team with your site, structure, or test requirements.

Bridge Monitoring for Early Damage Detection and Intervention

Highway bridge instrumented with accelerometers and strain gauges for structural health monitoring

In short: Proper bridge monitoring means installing a structural health monitoring (SHM) system of accelerometers, potentiometers, inclinometers, strain gauges, thermocouples and weather stations that reports a bridge's real-time condition and flags changes in performance before they become failures. With about 56,000 structurally deficient US bridges carrying 188 million trips a day, and collapses such as I-35W in Minneapolis and the FIU pedestrian bridge, continuous SHM gives officials the data to intervene early.

There are about 56,000 structurally deficient bridges in the U.S., and these bridges accommodate on average 188 million trips each day according to data from the Federal Highway Administration.

The nation’s transportation infrastructure is aging. More than 200,000 bridges are now more than 50 years old, and many are approaching the end of their design life. Although the seismic construction requirements are aimed to protect the lives of those crossing bridges. The number of bridges that are in such poor condition as to be considered structurally deficient is increasing and posing potential risk.

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Fourteen years ago, the Interstate 35 bridge over the Mississippi River in downtown Minneapolis collapsed. The cars, trucks and even a school bus were driving in bumper-to-bumper traffic across in the evening rush hour. Bridge’s failure plummeted them into the water and onto the rocky river banks. This disaster left a death toll of thirteen and injured 145. The officials were warned that the bridge was structurally deficient due to significant corrosion in its bearings. A federal inspection also rated the bridge structurally deficient, giving it a 50 on a scale of 100 for structural stability.

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In 2018, another horrific bridge collapse occurred in the Florida International University campus in Miami. The failed pedestrian bridge killed six and injured eight people. The bridge was under construction and the errors in the design overestimated how much stress the structure could take.

The question arose about the cause of the collapse of bridges and whether they could have been prevented.

Emergent technologies in sensing, artificial intelligence (AI), and cloud computing are now remedying engineers to construct stronger bridges and also improve bridge maintenance for longer life-span. To provide continuous feedback on the bridge’s structural conditions, sensors supporting structural health monitoring (SHM) systems are being installed into both new and existing bridges.

A robust SHM system, including various sensors and data analytics to monitor the bridge’s real-time integrity, can provide officials and engineers with the knowledge and “peace of mind” that the bridge is performing as expected, and the ability to detect a change in its performance. This knowledge and ability are critical because they are directly responsible for the consequences of failure. To prevent catastrophic collapses, especially the bridges that require significant maintenance, rehabilitation, or replacement can significantly benefit from the SHM system to monitor its elements founds to be in poor condition due to deterioration or damage.

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At QuakeLogic, we provide the most comprehensive SHM system for bridges. We are the only company with a cloud-based, AI-powered technology platform performing autonomous structural assessments using sensor data. Our platform sends rapid notifications with the level of shaking intensity in case of an earthquake and whether the bridge’s integrity is compromised. This system can not only monitor for earthquakes but also utilize data from various sensors such as accelerometers, potentiometers, inclinometers, strain gauges, thermocouples, and weather stations. Our platform sends meaningful and easy-to-understand information. This timely and critical information helps the bridge officials and engineers to give informed decisions and plan their responses appropriately.

Our structural health monitoring platform response matches for the first time the timing of the earthquake impact, which was impossible before. This platform can provide timely information that is needed for an understanding of the performance of a bridge and address problems earlier to improve public safety.

Key Takeaways

  • About 56,000 US bridges are structurally deficient and carry roughly 188 million trips per day, according to FHWA data.
  • More than 200,000 US bridges are over 50 years old and approaching the end of their design life.
  • The I-35W collapse in Minneapolis killed 13 and injured 145 after inspectors rated the bridge 50 out of 100 for structural stability.
  • The 2018 FIU pedestrian bridge collapse in Miami killed six; design errors overestimated the stress the structure could take.
  • SHM systems combine accelerometers, potentiometers, inclinometers, strain gauges, thermocouples and weather stations with cloud AI analytics.

Frequently Asked Questions

What is structural health monitoring for bridges?

Bridge structural health monitoring (SHM) installs sensors on a new or existing bridge and analyzes their data continuously to report the bridge's real-time integrity. Typical sensors are accelerometers, potentiometers, inclinometers, strain gauges, thermocouples and weather stations. The system confirms the bridge is performing as expected and detects changes in performance so engineers can intervene before deterioration leads to failure.

How many bridges in the US are structurally deficient?

According to Federal Highway Administration data cited in the article, about 56,000 US bridges are structurally deficient, and together they carry an average of 188 million trips every day. More than 200,000 bridges are over 50 years old, so the number in poor condition is rising as the transportation infrastructure approaches the end of its design life.

Could the I-35W and FIU bridge collapses have been prevented?

Both collapses had warning signs. The I-35W bridge in Minneapolis was rated structurally deficient with a 50 out of 100 stability score because of significant bearing corrosion before it fell, killing 13 and injuring 145. The FIU pedestrian bridge in Miami failed in 2018 after design errors overestimated its capacity. Continuous SHM data could have exposed abnormal behavior and prompted earlier intervention.

How does an SHM system respond to an earthquake?

QuakeLogic's cloud-based, AI-powered platform performs autonomous structural assessments from sensor data. During an earthquake it sends rapid notifications with the level of shaking intensity and an indication of whether the bridge's integrity is compromised, timed with the event itself. Officials get plain-language information to decide whether to close, inspect or reopen the bridge.

Which sensors are used to monitor a bridge?

A comprehensive bridge monitoring system uses accelerometers for vibration and earthquake response, potentiometers for displacement, inclinometers for tilt, strain gauges for stress in members, thermocouples for temperature effects and weather stations for wind and environmental loads. Combining these data streams in a cloud platform allows the structure's behavior to be assessed continuously rather than only during periodic inspections.

Need help with a project? QuakeLogic designs and supplies seismic monitoring, earthquake early warning, structural health monitoring, infrasound, and shake table systems. Browse QuakeLogic products or contact our engineering team with your site, structure, or test requirements.

Proper Monitoring Provides Early Damage Detection for Dams

Concrete dam with structural health monitoring sensors for early damage detection

In short: Proper structural health monitoring gives early damage detection for dams by continuously measuring their behavior and flagging changes in integrity before failure. At least 1,680 US dams are rated poor or unsatisfactory and average over 50 years old. QuakeLogic's cloud-based, AI-powered platform fuses accelerometer data with potentiometers, strain gauges, thermocouples, weather stations, piezometers and seepage weirs, and sends post-earthquake notifications on shaking intensity and structural condition.

When disaster strikes, we are all at risk! The unprepared ones will get hit the hardest. Today, at least 1,680 dams across the U.S. rated in poor or unsatisfactory conditions. These dams pose potential risks according to the Associated Press article. Without urgent action, aging dams (dams in the U.S. are on average over 50 years old) may not be able to adequately handle the intense rainfall and floods of a changing climate or imminent earthquakes. Because the housing developments are often located nearby these dams, they may fail to protect people.

The significance of structural health monitoring (SHM) for dam safety is widely acknowledged. There are a number of unfortunate examples of failed dams where early signs of deficiencies might have been monitored and detected if a proper SHM system had been in place. A robust SHM system can provide timely information that is needed for an understanding of the performance of a dam. The SHM system, including instrumentation and data analytics, can provide dam owners with the knowledge that a dam is performing as expected, and the ability to detect a change in its integrity. This knowledge and ability are critical for the dam owners because they are directly responsible for the consequences of failure. Because of these reasons, a robust safety monitoring system should be a fundamental part of every dam owners risk management progra

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QuakeLogic provides the most comprehensive structural health monitoring solution for dams. We are the only company with a cloud-based, AI-powered technology platform performing autonomous structural assessments using sensor data. After an earthquake occurs, our platform sends rapid notifications to our users. These notifications include the level of shaking intensity and whether the structural integrity of the dam is compromised. This system not only monitors earthquakes but also utilizes data from various sensors such as potentiometers, strain gauges, thermocouples, weather stations, piezometers and seepage (weirs & flumes).

QuakeLogic’s intelligent structural health monitoring platform generates meaningful and easy-to-understand information. This timely and critical information helps the dam owners to give informed decisions and plan their responses appropriately.

We provide “peace of mind” to dam owners. To learn about our risk management solutions, please contact us at info@quakelogic.net

Key Takeaways

  • At least 1,680 dams across the US are rated in poor or unsatisfactory condition, and US dams average more than 50 years old.
  • Several dam failures showed early signs that a proper SHM system could have detected in time.
  • QuakeLogic's cloud platform performs autonomous, AI-driven structural assessments from sensor data.
  • After an earthquake, owners receive rapid notifications with shaking intensity and whether structural integrity is compromised.
  • Monitored inputs include potentiometers, strain gauges, thermocouples, weather stations, piezometers and seepage weirs and flumes.

Frequently Asked Questions

How many US dams are in poor condition?

At least 1,680 dams across the United States are rated in poor or unsatisfactory condition according to an Associated Press review cited in the article. US dams are on average more than 50 years old, and many have housing developments nearby, so aging structures may not withstand intense rainfall, floods or earthquakes without monitoring and intervention.

How does structural health monitoring detect dam damage early?

Structural health monitoring detects dam damage early by continuously recording instrumentation such as accelerometers, potentiometers, strain gauges, thermocouples, piezometers, weather stations and seepage weirs or flumes, then analyzing the data for changes from expected performance. This gives owners evidence that the dam is behaving normally and the ability to spot a change in integrity before it becomes a failure.

What does a dam owner receive after an earthquake from QuakeLogic's platform?

After an earthquake, QuakeLogic's cloud-based, AI-powered platform sends rapid notifications to users that state the level of shaking intensity at the dam and whether its structural integrity appears compromised. The assessment is generated autonomously from sensor data so owners can make informed decisions and plan their response quickly.

Why should SHM be part of a dam owner's risk management program?

Dam owners are directly responsible for the consequences of failure, so a robust safety monitoring system should be a fundamental part of their risk management program. SHM provides timely information on performance, confirms the dam is operating as expected and detects changes in integrity, which is exactly the information missing in past failures where early deficiencies went unnoticed.

Which sensors besides seismic instruments are used in dam monitoring?

Besides seismic accelerometers, dam monitoring uses potentiometers for displacement, strain gauges for structural strain, thermocouples for temperature, weather stations for environmental context, piezometers for pore water pressure and weirs or flumes for seepage flow. QuakeLogic's platform integrates all of these into one assessment.

Need help with a project? QuakeLogic designs and supplies seismic monitoring, earthquake early warning, structural health monitoring, infrasound, and shake table systems. Browse QuakeLogic products or contact our engineering team with your site, structure, or test requirements.