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How might we inspect the Deep Tunnel Sewerage System without the need for man entry, in order to assess the condition within the tunnel?
Challenge Owners
Background
PUB is responsible for managing Singapore's water cycle, which includes the crucial process of reclaiming used water into NEWater, a major source of water supply. To achieve water sustainability, it is integral to collect and convey used water to our Water Reclamation Plants (WRPs). Deep Tunnel Sewerage System (DTSS) is a mega underground used water superhighway which centralises the collection of used water to the water reclamation plants entirely via gravity. The DTSS has been designed and constructed to last 100 years, with a length of 48km for DTSS Phase 1, diameters of 3.3 - 6m and depths of 18 - 50m.
To enter the DTSS, there are a total of 38 shafts, with 22 of them being direct shafts situated directly above the tunnel. These direct shafts are interspersed with 16 other offset shafts which are typically 30 - 50m away from the tunnel. The diameters of shafts range between 1.8m to 7m (typically about 3m).
As a preventive measure, PUB is keen to regularly inspect the physical condition of the DTSS’ corrosion protection lining (CPL) and the structural integrity of the tunnel. Currently, PUB faces challenges in carrying out routine inspection of the DTSS due to the lack of cost-effective technologies locally that can be used to inspect the entire length of DTSS tunnel safely (i.e. without man entering the DTSS tunnel).
Current Practice
Ad-hoc inspections on some of the tunnel stretches have been carried out by civil contractors working near the DTSS, using large-size floating CCTV pontoons. These inspections are costly and are done to fulfil PUB's sewer protection requirement for pre- and post-construction CCTV surveys. On average, one to two ad-hoc inspections are carried out annually. However, it is not practical to expand the use of existing floating CCTV pontoons to cover the entire tunnel due to the high cost and difficulty of launching them into the tunnel. This operation requires the use of a heavy lifting crane to remove the concrete cover of the tunnel shaft. Additionally, the floating CCTV pontoons are unable to traverse long distances because the pontoons are limited by the length of the tether cable.
We are seeking remotely operated or autonomous unmanned vehicles that can navigate and inspect the Deep Tunnel Sewerage System (DTSS) tunnel to provide imagery or recordings of the tunnel interior without requiring human entry.
To eliminate the need for human entry, the solution must either be adaptable to the different configurations of the tunnel shaft (i.e., able to be deployed from both direct and offset shafts) or travel longer distances. Additionally, it must be easy to launch (without the need for deployment of heavy machinery) and able to withstand the diverse and harsh conditions in the tunnels, such as different types of water flow conditions, high air flow speeds, and corrosive environments, and be intrinsically safe.
If successful, this solution will enable PUB to develop a method for routine inspection of the DTSS tunnel. This is crucial for ensuring its structural soundness and maintaining water sustainability in Singapore.
In addition to routine inspections, if the solution can stream real-time video from within DTSS, PUB will be able to conduct thorough real-time inspections of tunnel conditions in the event of urgent damage scenarios, such as damage from nearby construction activities or explosions. Furthermore, the solution could be developed to be multi-functional such as performing measurements within the tunnel.
A. Operation Requirements
1. The distance to be covered during inspection will depend on whether the solution can be deployed and retrieved via direct shaft, indirect shaft, or both. Please refer to the information below to determine the distance required to be covered during the unmanned operation.
a. The maximum distance between direct shafts is approximately 6km.
b. The maximum distance between adjacent shafts is approximately 2.85km.
c. The shafts have a vertical distance of 18 - 50m.
d. The adit tunnels have a horizontal distance of 30 - 50m.
e. The adit tunnels are typically dry and connects to the top of the main tunnel, which are located 0.5 - 1m from the bottom of the main tunnel. Some adit tunnels have steps cascading into the main tunnel.
2. The solution can comprise of multiple components and tools to launch and retrieve the main inspection module, as long as it does not require any handling by human personnel within the shafts and tunnel.
3. There are two types of removable openings for accessing the DTSS shafts: the cast iron sewerage manhole frameset and the removable concrete slab structure. The cast iron sewerage manhole has a diameter of 900mm and is preferred option for the deployment and retrieval of the solution. The concrete slab structure requires the use of heavy lifting equipment to be removed.
4. The operation or failure of the solution should not inflict any damage to the CPL or structure of the tunnel at any time.
B. Tunnel Conditions
The accumulation of used water flowing downstream of the tunnel creates diverse conditions within the DTSS tunnel. Ideally, the solution should be adaptable to all types of conditions within the tunnels. However, we are open to having multiple solutions tailored to perform in selected conditions, especially if the solution is more cost-effective. The known conditions include:
1. Varied water levels in the tunnel, ranging from 0.5m (in upstream sections) to 5m (in the downstream sections).
2. The design water flow inside DTSS tunnel has a velocity ranging from greater than 0.9m/s to less than 3m/s. Mean velocity in dry weather is 2.1m/s.
3. Lateral inflows from the soffit of the tunnel can cause waterfall-like features obstruct the navigation path.
4. The water flows at the downstream section of the tunnel are known to be turbulent. Lateral inflows might occur suddenly and cause localised turbulence.
5. The wind speed in DTSS tunnel should be similar to the water flow speed when the manhole is closed. When the manhole is open, the wind speed near the manhole opening can reach speeds of up to 14m/s.
6. Silt deposits accumulate under the flowing water.
7. Water droplets are present in the air within the tunnel.
8. The environment is unilluminated and GPS-denied.
C. System Requirements
The solution shall be equipped with the following:
1. 360° view and high-resolution (HD) cameras that can capture clear imagery and video footage while withstanding turbulent conditions and water splashes.
2. Data communication systems, either wired or wireless, that can function across the distance to be covered during the inspection and in a GPS-denied environment.
3. Suitable illumination devices to ensure clear video footages are recorded during the deployment.
4. Odometer or other positioning tools that can provide the accurate location and distance travelled.
5. Components that comply with intrinsic safety requirements.
6. Tether cable that is neutral buoyant and of sufficient length, for solutions that require a tether cable.
D. ‘Good-to-have’ features
The following ‘good-to-have’ features are not mandatory but can be useful for our operations:
1. Real-time inspection video footage.
2. Water flow and level measurement.
3. Gas pressure, flow and level measurement.
4. Circumferential laser profiling capable of detecting minor cracks (given Code of Practice stipulate allowable crack width not more than 0.1mm).
5. Underwater sonar imaging to detect sedimentation.
A. Limitations of trialled technologies
1. Floating CCTV pontoon
a. The pontoon cannot float in the tunnel sections with low flows.
b. The pontoon can only be launched into DTSS tunnel via direct shafts and requires the lifting of the concrete slab to access the shaft due to its large size.
c. The maximum tethered distance that the pontoon can cover is 3 km, and only in the downstream direction.
2. Drones
a. A drone prototype developed for an R&D project was able to fly in both upstream and downstream directions. However, the following challenges were encountered:
B. Other possible technologies that were considered
1. Smart floating balls or buoys
a. There are commercially available smart floating balls or buoys with video capabilities that can inspect small diameter sewers. However, this solution is currently not feasible for DTSS because there are no methods to retrieve the balls or buoys without avoiding human entry into DTSS tunnel.
2. Autonomous drones
a. Autonomous drones have the advantage of being able to operate in complete darkness, without GPS and radio communication. However, these drone solutions are not proven to have the ability to be launched and retrieved autonomously via the shafts and adit tunnels.
A. Routine Inspection of the Deep Tunnel Sewerage System Tunnel
Kelvin needs to inspect the Deep Tunnel Sewerage System (DTSS) to assess its physical condition and structural integrity, specifically the corrosion protection lining (CPL). However, it's not safe for him to do the inspection himself due to potential safety hazards. To solve this problem, a robot is deployed to travel through the entire length of the DTSS and collect visual and other data on the interior conditions of the tunnel. Kelvin will use this data to determine the extent of deterioration in the tunnel's conditions or structures and recommend the appropriate maintenance plan for the entire length of the DTSS.
B. Ad-hoc Inspection of the Deep Tunnel Sewerage System Tunnel
Zack received information about construction work near the DTSS that involves piling and heavy machinery. He is worried about the potential impact of the construction on the DTSS. Zack deploys a robot from the nearest shaft to the construction site and controls it to perform a close-up inspection of the tunnel condition. During the inspection, the robot discovers a new crack in the tunnel. Zack takes immediate action and issues a notice to halt the construction work to prevent further damage to the DTSS.
By the end of the pilot, the project should aim to develop a site-tested prototype that can complete the inspection for a section of DTSS (up to 6km) tunnel successfully, without requiring human entry into DTSS. Additionally, a method to safely launch and retrieve for the solution should be established. Once the inspection has been completed, a report documenting the interior conditions of the inspected section shall be generated.
The pilot project is to be completed within a period of 18 months. Below are the suggested project scope and timeline:
1. Identify site and safety requirements – 1 month
2. Build and customise initial prototype – 1- 4 months
3. Testing, review and refinement of prototype – 3 – 12 months
a. Participants are advised to perform offsite testing to lower the rate of failure before onsite deployment.
b. Participants need to be prepared to build and deploy multiple prototypes in case of failure to retrieve prototype during actual testing within DTSS.
4. Detailed feasibility studies, techno-economic analysis and reporting – 1 month.
If the pilot is successful, PUB would be interested to deploy the solution through a service model where the equipment is owned, operated, and maintained by the company.
Challenge Owners
Background
PUB is responsible for managing Singapore's water cycle, which includes the crucial process of reclaiming used water into NEWater, a major source of water supply. To achieve water sustainability, it is integral to collect and convey used water to our Water Reclamation Plants (WRPs). Deep Tunnel Sewerage System (DTSS) is a mega underground used water superhighway which centralises the collection of used water to the water reclamation plants entirely via gravity. The DTSS has been designed and constructed to last 100 years, with a length of 48km for DTSS Phase 1, diameters of 3.3 - 6m and depths of 18 - 50m.
To enter the DTSS, there are a total of 38 shafts, with 22 of them being direct shafts situated directly above the tunnel. These direct shafts are interspersed with 16 other offset shafts which are typically 30 - 50m away from the tunnel. The diameters of shafts range between 1.8m to 7m (typically about 3m).
As a preventive measure, PUB is keen to regularly inspect the physical condition of the DTSS’ corrosion protection lining (CPL) and the structural integrity of the tunnel. Currently, PUB faces challenges in carrying out routine inspection of the DTSS due to the lack of cost-effective technologies locally that can be used to inspect the entire length of DTSS tunnel safely (i.e. without man entering the DTSS tunnel).
Current Practice
Ad-hoc inspections on some of the tunnel stretches have been carried out by civil contractors working near the DTSS, using large-size floating CCTV pontoons. These inspections are costly and are done to fulfil PUB's sewer protection requirement for pre- and post-construction CCTV surveys. On average, one to two ad-hoc inspections are carried out annually. However, it is not practical to expand the use of existing floating CCTV pontoons to cover the entire tunnel due to the high cost and difficulty of launching them into the tunnel. This operation requires the use of a heavy lifting crane to remove the concrete cover of the tunnel shaft. Additionally, the floating CCTV pontoons are unable to traverse long distances because the pontoons are limited by the length of the tether cable.
We are seeking remotely operated or autonomous unmanned vehicles that can navigate and inspect the Deep Tunnel Sewerage System (DTSS) tunnel to provide imagery or recordings of the tunnel interior without requiring human entry.
To eliminate the need for human entry, the solution must either be adaptable to the different configurations of the tunnel shaft (i.e., able to be deployed from both direct and offset shafts) or travel longer distances. Additionally, it must be easy to launch (without the need for deployment of heavy machinery) and able to withstand the diverse and harsh conditions in the tunnels, such as different types of water flow conditions, high air flow speeds, and corrosive environments, and be intrinsically safe.
If successful, this solution will enable PUB to develop a method for routine inspection of the DTSS tunnel. This is crucial for ensuring its structural soundness and maintaining water sustainability in Singapore.
In addition to routine inspections, if the solution can stream real-time video from within DTSS, PUB will be able to conduct thorough real-time inspections of tunnel conditions in the event of urgent damage scenarios, such as damage from nearby construction activities or explosions. Furthermore, the solution could be developed to be multi-functional such as performing measurements within the tunnel.
A. Operation Requirements
1. The distance to be covered during inspection will depend on whether the solution can be deployed and retrieved via direct shaft, indirect shaft, or both. Please refer to the information below to determine the distance required to be covered during the unmanned operation.
a. The maximum distance between direct shafts is approximately 6km.
b. The maximum distance between adjacent shafts is approximately 2.85km.
c. The shafts have a vertical distance of 18 - 50m.
d. The adit tunnels have a horizontal distance of 30 - 50m.
e. The adit tunnels are typically dry and connects to the top of the main tunnel, which are located 0.5 - 1m from the bottom of the main tunnel. Some adit tunnels have steps cascading into the main tunnel.
2. The solution can comprise of multiple components and tools to launch and retrieve the main inspection module, as long as it does not require any handling by human personnel within the shafts and tunnel.
3. There are two types of removable openings for accessing the DTSS shafts: the cast iron sewerage manhole frameset and the removable concrete slab structure. The cast iron sewerage manhole has a diameter of 900mm and is preferred option for the deployment and retrieval of the solution. The concrete slab structure requires the use of heavy lifting equipment to be removed.
4. The operation or failure of the solution should not inflict any damage to the CPL or structure of the tunnel at any time.
B. Tunnel Conditions
The accumulation of used water flowing downstream of the tunnel creates diverse conditions within the DTSS tunnel. Ideally, the solution should be adaptable to all types of conditions within the tunnels. However, we are open to having multiple solutions tailored to perform in selected conditions, especially if the solution is more cost-effective. The known conditions include:
1. Varied water levels in the tunnel, ranging from 0.5m (in upstream sections) to 5m (in the downstream sections).
2. The design water flow inside DTSS tunnel has a velocity ranging from greater than 0.9m/s to less than 3m/s. Mean velocity in dry weather is 2.1m/s.
3. Lateral inflows from the soffit of the tunnel can cause waterfall-like features obstruct the navigation path.
4. The water flows at the downstream section of the tunnel are known to be turbulent. Lateral inflows might occur suddenly and cause localised turbulence.
5. The wind speed in DTSS tunnel should be similar to the water flow speed when the manhole is closed. When the manhole is open, the wind speed near the manhole opening can reach speeds of up to 14m/s.
6. Silt deposits accumulate under the flowing water.
7. Water droplets are present in the air within the tunnel.
8. The environment is unilluminated and GPS-denied.
C. System Requirements
The solution shall be equipped with the following:
1. 360° view and high-resolution (HD) cameras that can capture clear imagery and video footage while withstanding turbulent conditions and water splashes.
2. Data communication systems, either wired or wireless, that can function across the distance to be covered during the inspection and in a GPS-denied environment.
3. Suitable illumination devices to ensure clear video footages are recorded during the deployment.
4. Odometer or other positioning tools that can provide the accurate location and distance travelled.
5. Components that comply with intrinsic safety requirements.
6. Tether cable that is neutral buoyant and of sufficient length, for solutions that require a tether cable.
D. ‘Good-to-have’ features
The following ‘good-to-have’ features are not mandatory but can be useful for our operations:
1. Real-time inspection video footage.
2. Water flow and level measurement.
3. Gas pressure, flow and level measurement.
4. Circumferential laser profiling capable of detecting minor cracks (given Code of Practice stipulate allowable crack width not more than 0.1mm).
5. Underwater sonar imaging to detect sedimentation.
A. Limitations of trialled technologies
1. Floating CCTV pontoon
a. The pontoon cannot float in the tunnel sections with low flows.
b. The pontoon can only be launched into DTSS tunnel via direct shafts and requires the lifting of the concrete slab to access the shaft due to its large size.
c. The maximum tethered distance that the pontoon can cover is 3 km, and only in the downstream direction.
2. Drones
a. A drone prototype developed for an R&D project was able to fly in both upstream and downstream directions. However, the following challenges were encountered:
B. Other possible technologies that were considered
1. Smart floating balls or buoys
a. There are commercially available smart floating balls or buoys with video capabilities that can inspect small diameter sewers. However, this solution is currently not feasible for DTSS because there are no methods to retrieve the balls or buoys without avoiding human entry into DTSS tunnel.
2. Autonomous drones
a. Autonomous drones have the advantage of being able to operate in complete darkness, without GPS and radio communication. However, these drone solutions are not proven to have the ability to be launched and retrieved autonomously via the shafts and adit tunnels.
A. Routine Inspection of the Deep Tunnel Sewerage System Tunnel
Kelvin needs to inspect the Deep Tunnel Sewerage System (DTSS) to assess its physical condition and structural integrity, specifically the corrosion protection lining (CPL). However, it's not safe for him to do the inspection himself due to potential safety hazards. To solve this problem, a robot is deployed to travel through the entire length of the DTSS and collect visual and other data on the interior conditions of the tunnel. Kelvin will use this data to determine the extent of deterioration in the tunnel's conditions or structures and recommend the appropriate maintenance plan for the entire length of the DTSS.
B. Ad-hoc Inspection of the Deep Tunnel Sewerage System Tunnel
Zack received information about construction work near the DTSS that involves piling and heavy machinery. He is worried about the potential impact of the construction on the DTSS. Zack deploys a robot from the nearest shaft to the construction site and controls it to perform a close-up inspection of the tunnel condition. During the inspection, the robot discovers a new crack in the tunnel. Zack takes immediate action and issues a notice to halt the construction work to prevent further damage to the DTSS.
By the end of the pilot, the project should aim to develop a site-tested prototype that can complete the inspection for a section of DTSS (up to 6km) tunnel successfully, without requiring human entry into DTSS. Additionally, a method to safely launch and retrieve for the solution should be established. Once the inspection has been completed, a report documenting the interior conditions of the inspected section shall be generated.
The pilot project is to be completed within a period of 18 months. Below are the suggested project scope and timeline:
1. Identify site and safety requirements – 1 month
2. Build and customise initial prototype – 1- 4 months
3. Testing, review and refinement of prototype – 3 – 12 months
a. Participants are advised to perform offsite testing to lower the rate of failure before onsite deployment.
b. Participants need to be prepared to build and deploy multiple prototypes in case of failure to retrieve prototype during actual testing within DTSS.
4. Detailed feasibility studies, techno-economic analysis and reporting – 1 month.
If the pilot is successful, PUB would be interested to deploy the solution through a service model where the equipment is owned, operated, and maintained by the company.
