Real Time 3D Geospatial Data for Tunnel Clearances

Transcription

1 Real Time 3D Geospatial Data for Tunnel Clearances Contributor: Ryan Leonard, Rail & Tunnel Specialist, Maser Consulting, P.A. Presented by

2 TABLE OF CONTENTS Introduction... 1 Larger loads means lower tracks... 1 Tunnels leave little room for error... 2 The Tunnel Hill project... 3 Old solutions vs. new solutions... 4 Key points to using geospatial data... 5 A solution, and a continuous process... 6 Deliverables... 8 Conclusion... 9 Biography... 10

3 INTRODUCTION Railroads have been doing tunnel clearances in much the same way for 150 years. But recently, this old industry has looked to new geospatial technology to improve operations and reduce costs. Capturing the continuous dimensions of rail tracks may look like an easy 3D scanning project, but working in the confined space of dark tunnels demands extra flexibility under additional safety, time and cost constraints. Ryan Leonard of Maser Consulting explains how 3D scanning can deliver precise measurements in a short turnaround with the case study of a tunnel expansion of Tunnel Hill, a mountain tunnel and railroad built in This particular tunnel has seen wear and tear: 25 freight trains travel through this tunnel on a daily basis. The railroad needed to improve clearance in the tunnel to accommodate ever-larger train loads. However, the high cost of delaying freight trains on the track meant train crews had a limited time each day to work, reopen the tunnel, and insure its safety. Every hour a train was delayed cost the railroad company $10,000. Leonard compares various approaches to this daily construction problem and shows how geospatial imaging improved accuracy and safety with daily deliverables. LARGER LOADS MEANS LOWER TRACKS Railways are facing an increasing demand for larger freight loads with larger dimensions. Since the U.S. has been trying to fit bigger and more frequent loads through the existing infrastructure, time and traffic had taken a toll on Tunnel Hill, as well as many others. The CSX railroad corporation is a competitive business, and knew that to ship bigger loads, they would need to increase clearance capacity in the tunnel. One way to gain more clearance in a tunnel is to lower the track running through it. So understanding the tunnel and where the rails lie within that tunnel was critical to the renewal project. 1

4 Figure 1 This particular tunnel is under the Atlanta Division and the CSX railroad. It was built back in 1928, is 1,400 feet of single track and is not all that different from any other tunnels in the Appalachians, in the Cascades or anywhere else in the United States. However, nearly a century of maintenance in this tunnel has led to a slow re-adjusting track positions over time. Rails are living and breathing things. As the trains travel over the tracks, tracks lift, rise, settle, and they move. Rails need maintenance just like a door in a home would need it over time. While a century of maintenance on these tracks led to the tracks moving from their original position, the tunnel walls, of course, remained stationary. This meant moving the tracks again to allow for more clearance would be a tricky, labor-intensive thing to do. TUNNELS LEAVE LITTLE ROOM FOR ERROR There are always some general engineering problems and considerations when replacing single tracks in tunnels. Lifting a track is easy, but dropping a track is very difficult. It takes a lot of track time. It takes a lot of hardware, tools, and labor to do so. The primary goal is to move things quickly and safely. Measuring margins in this situation are extremely tight even six or seven inches off is not acceptable. It's also dusty work, and done in the dark. 2

5 Figure 2 To keep costs down, the rail crews work in 12-hour shifts each day, after which freight trains waiting to go through the tunnel need an all clear for safety. Here is where 3D scans are needed: to measure the tunnel and offer dispatch a thumbs-up or thumbs-down on whether it was ready to pass. THE TUNNEL HILL PROJECT Rail renewals are typically done with something called a tamper, which is an impressive piece of machinery. First, the tines (the arms) go down into the rock ballast and basically pick up the rail, shimmy it, put a vibration on it, and then set the track back down. Then there are chains hundreds and hundreds of feet of these machines moving down the track all simultaneously to keep it smooth. The rail crew had five days to remove the track, drop it down, and put it back in. There were 37 sections of 39-foot tracks to move in all. These tracks are pre-built in a yard, brought in by truck, by train, by crane, and then set them off to the side. The crew moved 10 panels per shift, covering about 400 feet of track a day. 3

6 Figure 3 After the work is done, the verification process is key. All track that was removed must be replaced before the end of the shift to allow the freights to run at night. Most of the labor force that works on these tracks today can look over 1,400 feet, and can see variations that may cause a problem for a train coming. However, it's very challenging to look into a dark tunnel 22 feet long and find a variation as small as a bolt that s half an inch wide in diameter sticking out. This is where the surveyor and geospatial data come in to measure the clearances at the end of each shift. OLD SOLUTIONS VS. NEW SOLUTIONS The need to verify track continuity and clearances in tunnels is not a new problem. Occasionally when faced with a clearance issue, railroad workers will run a high-rail type vehicle to map it out and process the data before giving the all-clear. However, this was not as feasible in the Tunnel Hill case due to time constraints. Another method is to use an old caboose with hammered-in tie or lumber and move it through the tunnel and look for places where a larger load would touch the tunnel, if a larger road were on those tracks. In some cases construction team even put brooms onto a little car body, and then moved the car body through the tunnel. Whenever the broom touched, crews would slide the 4

7 broom in and measure the distance to verified the clearance. Clearly, geospatial data was a much more sophisticated method. Figure 4 KEY POINTS TO USING GEOSPATIAL DATA Once the crew decided on using geospatial data to ensure the tunnel safety during the track renewal project, there were some key points the team needed be able to address with the 3D scanner. The rail company needed the distance from the top of the rail to the top of the tunnel, which of course could be done with imaging technology such a Reflectorless Total Station. In this case, the tunnel surface was irregular, which makes it a perfect application for scanning. Scanning gives an objective point of view and it allows someone to see things the naked eye cannot. The team also needed a baseline of the tunnel each day to start work on the next 400-foot section. This would have been possible with a traditional survey, but would require a lot of timeout and track outages to complete. In this case, the team needed a quick rendering of the scanned images to comply with the 12-hour time frame. And, of course, time was of the essence at the end of each day, as the 5

8 crew needed to confirm measurements nearly on the spot so as to not keep the trains waiting for the all clear. A SOLUTION, AND A CONTINUOUS PROCESS In this case, a trolley from Amberg Technologies GRP 5000 was outfitted with a Zoller & Fröhlich phase based scanner and mounted on a battery column. This set-up had the advantage of a gauge piston positioned on the underside of the inside rail, which gave the surveyors a reference point of the centerline. This system also synchronized with the odometer to allow all measurements to be tied back to the distance from the station. Figure 5 Several key features allowed the scanning unit to run continuously for maximum time savings. The unit came with a heads-up display so that the user could walk and take notes of any visual discrepancies down to an inch-by-inch accuracy along the rail. This also gave the rail workers a chance to address issues on the track in real time, while the scanning unit continued to process and store information. The trolley also used polyurethane wheels to avoid contact with the electrified tracks. This allowed the scanning unit to travel along the tracks without disturbing train dispatchers with a 6

9 false positive that there was a car on the railway. The electrical tracks can also be dangerous, so the polyurethane wheels were an added safety feature for the crew. Figure 6 Each day a worker walked the trolley-scanner unit the whole length of the tunnel to establish a baseline in a relative environment, meaning relative to the centerline, relative to the track and relative to the nearest station. On average, it took 20 minutes to run and store the entire tunnel. It would then take another 45 minutes to process the data on the walk back through the tunnel. With this set-up, the team could have deliverables every 5 feet in cross sections for the project manager, which could be compared to the baseline from the day before. 7

10 Figure 7 DELIVERABLES The geospatial scans created several deliverables for the rail company. There were color-coded scans where red was coded as any potential dangerous interference to a train's clearance. Such scans could pick up an interference such as a boulder, or something in the ballast that got kicked to the side during the day. Scans could also present a topographical view of the tunnel, where the elevations change by color according to how many inches an object lies away relative to a train car's body. 8

11 Figure 8 The client could also review the data in archived form, meaning in excel spreadsheets of heights and staggers, and a value from the existing car body. These deliverables had to be very precise, at exactly every 5 feet in cross sections. There were rock bolts throughout the tunnel, and if a half-inch of rebar that was bolted up to the ceiling was somehow left sticking down, with just half a foot error in a cross section scan, the crew could miss that object and the next train coming through could strike it. Pictures tell a thousand words and a very faint little red line is quite catastrophic to the top of a train running at 69 mph. CONCLUSION Delays are always expensive, but the cost and safety concerns of the Tunnel Hill rail renewal project were particularly high. CSX corporation needed to increase the clearance in a 1,400-foot, single track tunnel while leaving the tunnel open and safe for freight traffic each day. About 25 freight trains needed to pass through the tunnel each day, and every hour a train was delayed cost the railroad company $10,000. Construction crews had five days to complete the renewal work, which meant crews had to install new track in 400-foot sections, scan the tunnel and catch any obstructions all within a 12-hour shift. 9

12 Geospatial technology was used to accurately and quickly ensure the safety of the tunnel. In this case, a specially designed rail cart (the Amberg GRP 5000) was outfitted with a 3D scanner (a Z&F scanner). The cart was walked through the tunnel each day to establish a baseline condition that provided CSX with information about existing car-body clearances compared to the scan data of the tunnel. Clearances were computed as soon as the data was collected during the walk-through, allowing CSX railroad to receive and confirm a thumbs-up (or thumbs-down) safety clearance for trains to pass through the tunnel at the end of the day. Deliverables from the geospatial data included tables of preconstruction clearances and daily results. A final, as-built survey was performed after all work on the tunnel was completed and indicated an additional clearance of 3-6 inches was gained. This scenario shows how leveraging geospatial technology for accurate, fast verifications can have significant impact on revenue and operations. BIOGRAPHY Ryan Leonard is a rail and tunnel specialist at Maser Consulting, P.A. He has 10 years of experience in technical training and support for the measuring sciences including HDS Scanning, Global Positioning Systems (RTK and Static), Total Stations, Geodetic Reference Networks, Structural Monitoring, and Geographic Information Systems. His experience with cutting edge, measuring technology helped to establish new surveying services in the rail and tunnel industries in North America with the use of Amberg Technologies GRP Trolley. Leonard earned his B.S. in geography/gis at Northern Illinois University. He served 5 years in the US Coast Guard as a shipboard navigator, where he was responsible for charting global and intra-coastal transits. Note: This whitepaper is the product of the transcript of a presentation given at SPAR International 2015, and available online at While the speakers are cited here as contributors, this whitepaper was not written by the contributors or speakers who appeared in the presentation, nor is it endorsed by the contributors or speakers, or any company, organization or entity they represent. For more information on how this whitepaper was produced, send inquiries via to info@sparpointgroup.com. 10