Corrugated Polyethylene Pipe Testing under 315,000-Pound Cars at FAST

Letter Report No. P-09-052 Prepared for Plastic Pipe Institute by Joseph A. LoPresti Transportation Technology Center, Inc.

…a subs id ia ry o f the Assoc iat ion of Amer ican Ra i l roads P. O. Box 11130, Pueblo, Colorado 81001 USA, December 28, 2009

Revised January 14, 2010

Disclaimer: This report was prepared for Plastic Pipe Institute (PPI) by Transportation Technology Center, Inc. (TTCI), a subsidiary of the Association of American Railroads, Pueblo, Colorado. It is based on investigations and tests conducted by TTCI with the direct participation of PPI to criteria approved by them. The contents of this report imply no endorsements whatsoever by TTCI of products, services or procedures, nor are they intended to suggest the applicability of the test results under circumstances other than those described in this report. The results and findings contained in this report are the sole property of PPI. They may not be released by anyone to any party other than PPI without the written permission of PPI. TTCI is not a source of information with respect to these tests, nor is it a source of copies of this report. TTCI makes no representations or warranties, either expressed or implied, with respect to this report or its contents. TTCI assumes no liability to anyone for special, collateral, exemplary, indirect, incidental, consequential, or any other kind of damages resulting from the use or application of this report or its contents.

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Table of Contents 1.0 Introduction ................................................................................................. 1 2.0 Test Preparation.......................................................................................... 1

2.1 Pipe Instrumentation ........................................................................ 1 2.2 Pipe Installation ................................................................................ 4

3.0 Testing ........................................................................................................ 8 3.1 Measuring Strains and Deflections ................................................... 8

3.1.1 Strains and Deflections From Construction Loads ................... 8 3.1.2 Strains and Deflections from Dynamic Loads after

1 MGT of HAL Traffic ............................................................. 10 3.1.3 Strains and Deflections from Dynamic Loads

after 96 MGT .......................................................................... 15 3.1.4 Results of Leaving Loaded Cars Parked Over the

Pipes for 6 Weeks .................................................................. 19 4.0 Summary ................................................................................................... 19 Appendix A. Instrumentation Photographs ......................................................... 21 Appendix B. Installation Photographs ................................................................ 23 Appendix C. Appendix B Time Histories, 1 MGT Dynamic

Measurements, Lap 7 .................................................................... 29 Appendix D. Time Histories, 96 MGT Dynamic Measurements, Lap 7 .............. 37

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List of Figures Figure 1. String Pot Locations ............................................................................. 2 Figure 2. Strain Gage Locations ......................................................................... 3 Figure 3. HTL at FAST ........................................................................................ 5 Figure 4. Cross Section Depicting As-Constructed Conditions at

Pipe Test Sites ..................................................................................... 5 Figure 5. Installation Plan View ........................................................................... 6 Figure 6. Installation Profile View ........................................................................ 7 Figure 7. Pipe Wall Strains from Backfill and Construction Loads ...................... 9 Figure 8. Pipe Deflections from Backfill and Construction Loads ........................ 9 Figure 9. Gage Orientation Relative to Train Direction ..................................... 10 Figure 10. Maximum Pipe Wall Strains Measured during 40 mph

Train Operations ................................................................................ 11 Figure 11. Peak-to-peak Changes in Strains due to Dynamic Loads ................. 11 Figure 12. Maximum Pipe Deflections Measured during 40 mph

Train Operations ................................................................................ 12 Figure 13. Peak-to-peak Changes in Deflections due to Dynamic Loads .......... 12 Figure 14. Sample Dynamic Strain and Deflection Data during 40 mph

Train Operations ................................................................................ 13 Figure 15. Dynamic Vertical Loads Measured under the Train at FAST ............ 13 Figure 16. Maximum Pipe Wall Strains Measured during 40 mph

Train Operations ................................................................................ 15 Figure 17. Peak-to-peak Changes in Strains due to Dynamic Loads ................. 16 Figure 18. Maximum Pipe Deflections Measured during 40 mph

Train Operations ................................................................................ 16 Figure 19. Peak-to-peak Changes in Deflections due to Dynamic Loads .......... 17 Figure 20. Cars Parked over Pipes to Evaluate Long-term Pipe Response ....... 19

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List of Tables Table 1. Measurement Description Summary .................................................... 3 Table 2. Statistics from Lap 7 Measurements during 40 mph

Train Operations after 1 MGT ............................................................ 14 Table 3. Statistics from Measurements during 40 mph

Train Operations after 96 MGT .......................................................... 18

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1.0 INTRODUCTION Transportation Technology Center, Inc. (TTCI) conducted a test of corrugated high-density polyethylene pipes for the Plastic Pipe Institute (PPI) at the Facility for Accelerated Service Testing (FAST). The pipes were manufactured by Advanced Drainage Systems, Inc. (ADS). FAST operates as a test bed for railroad track and components, and for rail vehicles and components. The Federal Railroad Administration, the Association of American Railroads, and individual railroads and railroad suppliers (through in-kind contributions) have cooperatively funded the operations at FAST and its test programs. The program has focused on increased axle loads and their implications for track components, maintenance practices, and interaction of vehicles and track since 1988 when the nominal axle load of the train at FAST was increased from 33 tons to 39 tons. Typically, the train consist at FAST is four GP-40 locomotives and 80 315,000-pound gross rail load (GRL) cars. Approximately 120 million gross tons (MGT) of heavy axle load (HAL) traffic accumulate each year at FAST. Testing at FAST allows for safe, controlled testing of components without incurring the risk of in-service evaluations.

The pipes were instrumented to allow data collection during train operations. Transducers were installed at various locations on the pipes to measure pipe wall strains and lateral, vertical, diagonal, and circumferential deflections. Strains and deflections were measured when the pipes were in place before the trenches were backfilled, after backfill, during normal operations at FAST after accumulating 1 MGT of HAL traffic, and after accumulating 96 MGT of HAL traffic. Also, the pipes were monitored visually and with a video camera.

2.0 TEST PREPARATION 2.1 Pipe Instrumentation Short (58-inch) sections of the pipes were instrumented inside, in a controlled temperature environment prior to in-track installation. The 58-inch length was selected so the joints would be nearly directly under the rails when the pipe was installed. Representatives from the plastic pipe industry were at the Transportation Technology Center (TTC) to observe and assist in the installation of the instrumentation. The instrumentation is described below.

• String potentiometers (string pots) were installed to measure horizontal, vertical, and diagonal deflections approximately 6 inches from the spigot end of the watertight inline bell spigot joint, and approximately 6 inches from the cut end of the split coupler connection joint. Deflections were measured at the quarter points of the pipe; i.e., clock positions: 12:00 to 6:00, 1:30 to 7:30, 3:00 to 9:00, and 4:30 to 10:30. The string pots were Celesco PT8101-0005-111-4120.

• Also, string pots were installed to measure circumferential shortening. The string pots were installed as close to the strain gages as practicable. Sixteen

2

eyelets were attached to the interior pipe wall at approximately a 9.5-inch spacing. The “string” was threaded through the eyelets around the circumference of the pipe. Figure 1 shows the string pot locations.

• Strain gages were installed to measure pipe wall strains at five circumferential locations. Strains were measured at the crowns and valleys of the corrugations at three locations and only at the valleys in two locations. Gages placed on the inside crown of the pipes were placed through elliptical access ports cut through the pipe’s smooth interior liner. Measurements were taken at clock positions: 12:00 (crown and valley), 1:30 (valley), 3:00 (crown and valley), 6:00 (valley), and 9:00 (crown and valley). Strain gage locations are illustrated in Figure 2. The strain gages were placed as close to the deflection gages as practicable. The strain gages were Vishay Measurements Group EP-08-250BF-350 designed for high elongation measurements (crown) and Vishay Measurements Group EP-08-500BL-350 (valley).

• Internal wall temperatures were measured in each pipe, and ambient air temperature was measured.

• Instrumentation summary: two instrumentation locations at each of the two test sites = a total of four instrumentation sites ─ Each instrumentation location:

Four deflection gages (4 x 4 = 16 deflection gages) Eight strain gages (total 8 x 4 = 32 strain gages) One circumferential shortening gage (total 1 x 4 = 4 circumferential

shortening gages)

Figure 1. String Pot Locations

String Pot Locations

3

Figure 2. Strain Gage Locations

Table 1 summarizes the measurement names and locations. Appendix A shows photographs of the instrumentation.

Table 1. Measurement Description Summary

S or D 1 or 2 B or N 0, 45… 0, 45… V or C

Name Type Pipe Site

Joint Type

Pipe Location (degrees)

Pipe Location (clock

position) Crown or

Valley

S1B0C Strain 1 WT 0 12:00 C S1B0V Strain 1 WT 0 12:00 V S1B45V Strain 1 WT 45 1:30 V S1B90C Strain 1 WT 90 3:00 C S1B90V Strain 1 WT 90 3:00 V S1B180V Strain 1 WT 180 6:00 V S1B270C Strain 1 WT 270 9:00 C S1B270V Strain 1 WT 270 9:00 V S1N0C Strain 1 Split 0 12:00 C S1N0V Strain 1 Split 0 12:00 V S1N45V Strain 1 Split 45 1:30 V S1N90C Strain 1 Split 90 3:00 C S1N90V Strain 1 Split 90 3:00 V S1N180V Strain 1 Split 180 6:00 V S1N270C Strain 1 Split 270 9:00 C S1N270V Strain 1 Split 270 9:00 V S2B0C Strain 2 WT 0 12:00 C S2B0V Strain 2 WT 0 12:00 V S2B45V Strain 2 WT 45 1:30 V

4

Table 1. (Continued) Measurement Description Summary

S or D 1 or 2 B or N 0, 45… 0, 45… V or C

Name Type Pipe Site

Joint Type

Pipe Location (degrees)

Pipe Location (clock

position) Crown or

Valley

S2B90C Strain 2 WT 90 3:00 C S2B90V Strain 2 WT 90 3:00 V S2B180V Strain 2 WT 180 6:00 V S2B270C Strain 2 WT 270 9:00 C S2B270V Strain 2 WT 270 9:00 V S2N0C Strain 2 Split 0 12:00 C S2N0V Strain 2 Split 0 12:00 V S2N45V Strain 2 Split 45 1:30 V S2N90C Strain 2 Split 90 3:00 C S2N90V Strain 2 Split 90 3:00 V S2N180V Strain 2 Split 180 6:00 V S2N270C Strain 2 Split 270 9:00 C S2N270V Strain 2 Split 270 9:00 V D1B0 Displacement 1 WT 0 12:00-6:00 N/A D1B45 Displacement 1 WT 45 1:30-7:30 N/A D1B270 Displacement 1 WT 270 3:00-9:00 N/A D1B315 Displacement 1 WT 315 4:30-10:30 N/A D1BC Displacement 1 WT Circ. N/A N/A D1N0 Displacement 1 Split 0 12:00-6:00 N/A D1N45 Displacement 1 Split 45 1:30-7:30 N/A D1N270 Displacement 1 Split 270 3:00-9:00 N/A D1N315 Displacement 1 Split 315 4:30-10:30 N/A D1NC Displacement 1 Split Circ. N/A N/A D2B0 Displacement 2 WT 0 12:00-6:00 N/A D2B45 Displacement 2 WT 45 1:30-7:30 N/A D2B270 Displacement 2 WT 270 3:00-9:00 N/A D2B315 Displacement 2 WT 315 4:30-10:30 N/A D2BC Displacement 2 WT Circ. N/A N/A D2N0 Displacement 2 Split 0 12:00-6:00 N/A D2N45 Displacement 2 Split 45 1:30-7:30 N/A D2N270 Displacement 2 Split 270 3:00-9:00 N/A D2315 Displacement 2 Split 315 4:30-10:30 N/A D2NC Displacement 2 Split Circ. N/A N/A T1A Temperature 1 N/A N/A N/A N/A T2A Temperature 2 N/A N/A N/A N/A TEA Temperature Air N/A N/A N/A N/A

2.2 Pipe Installation The pipes were installed in two adjacent locations in a fill on the High Tonnage Loop (HTL) at FAST. The HTL is the 2.7-mile test loop where HAL tests are conducted at FAST. It is comprised of various curved, spiral, and tangent test sections. The pipes were installed in a tangent section (section 5). Figure 3 shows the HTL and the location of the pipe installation. The height of the fill facilitated excavation and allowed access to both ends of the pipes after installation. There is no water flow at the fill location, and the

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pipes remained dry for the duration of the test. The pipes were installed 50 feet apart, center-to-center. The variable between the two sites was the composition and preparation of the backfill material, as Figure 4 shows.

Figure 3. HTL at FAST

Figure 4. Cross Section Depicting As Constructed Conditions at Pipe Test Sites

5

HTL

PPI Pipe Test

6

Differences in composition and preparation of the backfill material between the two pipe test sites are described as follows:

• Site 1 — Approximately 80 feet of 48-inch pipe was installed perpendicular to the track beneath a 4-foot cover (Figure 5). The backfill was fractured rock (No. 57 stone) wrapped with Geotex 1201 fabric manufactured by Propex. The stone was vibrated in place. The soil above the pipes was compacted to 98 percent standard proctor density (SPD).

• Site 2 — Approximately 80 feet of 48-inch pipe was installed perpendicular to the track beneath 4-foot cover (Figure 5). The backfill is native soil that conforms to AASHTO M145 A-2-4 (ASTM D2321 class III) specifications. The soil around the pipes was compacted to 94 percent SPD. The soil above the pipes was compacted to 98 percent SPD.

Figure 5. Installation Plan View

• The excavations were sloped to comply with OSHA regulations. • Cover depth was measured from the bottom of the tie to the outside top of the

pipe, and it included the thickness of the ballast layer. Native soil was used as cover material between the specified backfill and the ballast. The native soil was placed in two lifts and compacted to 98 percent SPD. Lightweight compaction equipment was used to compact the first 2 feet of cover over the pipes.

• Compaction testing was contracted by TTCI and performed by a third party geotechnical firm.

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• The subballast depth of 6 inches and ballast depth of 12 inches below the bottom of the tie are typical of the granular layer depth at FAST. The track cross section, a 15- to 18-inch shoulder and 2:1 side slope, is representative of the typical cross section at FAST.

• ADS constructed its standard watertight (WT) inline bell spigot joint, and its standard fabric wrapped split coupler connection for each pipe. The connections in each pipe were placed just outside the centerline of the rails (Figure 6). Pipe installation followed standards outlined in ASTM D2321 and in this document. Appendix B shows photographs of the installation.

Figure 6. Installation Profile View

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3.0 TESTING 3.1 Measuring Strains and Deflections The instrumented sections of the pipes were moved to the HTL after the instrumentation was completed and the functionality of the transducers had been verified. The pipes were placed in their respective trenches, and the sections of pipe were coupled together. The transducers were zeroed, and the readings at this point were designated as the starting (zero) condition. Strains and deflections were measured:

• Statically, when backfill and track construction was complete • Statically, after accumulating 1 MGT of HAL traffic • Dynamically, during 10 laps of train operations after accumulating 1 MGT of

HAL traffic • Statically, prior to train operations after accumulating 96 MGT of HAL traffic • Dynamically, during 10 laps of train operations after accumulating 96 MGT of

HAL traffic

3.1.1 Strains and Deflections From Construction Loads The transducers had been set to zero after the pipes were set in place, but before backfilling began. Values from all transducers were recorded again after the trenches had been filled, the native soil placed and compacted, and the ballast and track installed. This subsection describes those results. Figure 7 shows measured strains that were induced by the backfill. Maximum strain was about 7,300 microstrain (compressive) at the site 1 pipe, 0 degree (top of pipe), split joint, in the valley of a corrugation. Most of the other strains were also compressive; however, tensile strains were measured at four locations in the site 2 pipe. The strains at the split joint were generally higher than the corresponding strains at the WT bell joint.

9

‐10000

‐8000

‐6000

‐4000

‐2000

0

2000

0º Crown

0º Valley

45º Valley

90º Crow

n90º Valley

180º Valley

270º Crown

270º Valley

Wall Strain (m

icrostrain)

Site 1 WT Joint

Site 1 Split Joint

Site 2 WT Joint

Site 2 Split Joint

Figure 7. Pipe Wall Strains from Backfill and Construction Loads

Figure 8 shows the deflections. Lateral compression of the pipes produced the highest deflections. The distances between the 3:00 and 9:00 clock positions (270 degrees) decreased by 0.4 inch to 0.7 inch. The heights of the pipes tended to increase as the sides of the pipes were squeezed in.

‐1

‐0.8

‐0.6

‐0.4

‐0.2

0

0.2

0.4

0.6

0.8

1

 0 Degree

45 Degree

270 Degree

315 Degree

Circum

frential

Displacem

ents  (in)

Site 1 WT Joint

Site 1 Split Joint

Site 2 WT Joint

Site 2 Split Joint

Figure 8. Pipe Deflections from Backfill and Construction Loads

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3.1.2 Strains and Deflections from Dynamic Loads after 1 MGT of HAL Traffic

One MGT of HAL traffic (approximately one night of train operations at FAST) was accumulated to consolidate and settle the fills and track. Strains and deflections were then measured during 10 laps of train operations. Speed during the first lap was approximately 5 mph. Train speed had increased to 40 mph, typical operating speed at FAST, by the fourth lap. Train speed for laps for 4 to 10 was 40 mph. There was little difference in strains or deflections within the range of test speeds, though the higher speeds produced slightly higher values. Train direction during testing was counterclockwise. Travel was from the 90-degree side (3:00 clock position) toward the 270-degree side (9:00 clock position), as Figure 9 shows.

Figure 9. Gage Orientation Relative to Train Direction

Figure 10 shows maximum strains (compared to pre-backfill conditions) measured during lap 7 (lap 7 was chosen arbitrarily and is representative of the other 40 mph laps). Maximum strains tended to increase compared to those resulting from construction loads. Maximum strain was about 8,200 microstrain (compressive) at the site 2 pipe, 45-degree, split joint, in the valley of a corrugation. Figure 11 shows peak-to-peak changes in strains due to dynamic loads. The site 2 pipe tended to show greater response to dynamic loading. However at all measured locations, the train-induced strains were much lower than the strains caused by the construction loads.

Train Direction

2

2 2

1

1

11

‐10000

‐8000

‐6000

‐4000

‐2000

0

2000

0º Crown

0º Valley

45º Valley

90º Crow

n90º Valley

180º Valley

270º Crown

270º Valley

Strain (m

icrostrain)

Site 1 WT Joint

Site 1 Split Joint

Site 2 WT Joint

Site 2 Split Joint

Figure 10. Maximum Pipe Wall Strains Measured during 40 mph Train Operations

‐1500

‐1300

‐1100

‐900

‐700

‐500

‐300

‐100

100

300

500

0º Crown

0º Valley

45º Valley

90º Crow

n

90º Valley

180º Valley

270º Crown

270º Valley

Strain (m

icrostrain)

Site 1 WT Joint

Site 1 Split Joint

Site 2 WT Joint

Site 2 Split Joint

Figure 11. Peak-to-peak Changes in Strains due to Dynamic Loads

Figure 12 shows maximum deflections (compared to pre-backfill conditions) for lap 7. Figure 13 shows peak-to-peak changes in deflections due to dynamic loads. Deflection trends were similar to strains. The site 2 pipe tended to show greater response to dynamic loading, and the train-induced deflections were much lower than the deflections caused by the construction loads. Maximum dynamic deflection was approximately 0.06 inch. As expected, loads from the train compressed the pipe vertically and expanded it horizontally. Construction loads had produced the opposite deflections, so in many cases the trainloads decreased the total deflections compared to pre-backfill conditions. Figure 14 shows a sample of the dynamic data used to produce the plots. The

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lower strains and deflections at the beginning of the train are from the locomotives that have lighter axle loads than the test cars. The lower strains and deflections at the end of the train are from the cars loaded to 286,000 pounds (compared to the 315,000-pound cars in the rest of the train). Most channels show similar differences. Table 2 shows statistics for each channel. Appendix C shows time histories for all channels from lap 7.

‐1

‐0.8

‐0.6

‐0.4

‐0.2

0

0.2

0.4

0.6

0.8

1

 0 Degree

45 Degree

270 Degree

315 Degree

Circum

frential

Displacem

ent (in

)

Site 1 WT Joint

Site 1 Split Joint

Site 2 WT Joint

Site 2 Split Joint

Figure 12. Maximum Pipe Deflections Measured during 40 mph Train Operations

‐0.1

‐0.08

‐0.06

‐0.04

‐0.02

0

0.02

 0 Degree

45 Degree

270 Degree

315 Degree

Circum

frential

Displacem

ent (in

)

Site 1 WT Joint

Site 1 Split Joint

Site 2 WT Joint

Site 2 Split Joint

Figure 13. Peak-to-peak Changes in Deflections due to Dynamic Loads

13

Figure 14. Sample Dynamic Strain and Deflection Data during 40 mph Train Operations

Figure 15 shows the distribution of dynamic vertical loads for the train at FAST. These loads were measured with rail mounted strain gages in a section of tangent track with track geometry similar to the geometry at the pipe test. Average vertical load was 38,000 pounds, 99th percentile load was 52,000 pounds, and maximum load was 83,000 pounds.

0

1000

2000

3000

4000

5000

6000

7000

0 20 40 60 80

Wheel Load (1,000 pounds)

Num

ber o

f Occ

uran

ces

Figure 15. Dynamic Vertical Loads Measured Under the Train at FAST

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Table 2. Statistics from Lap 7 Measurements during 40 mph Train Operations after 1 MGT

Channel Name Average Maximum MinimumS1B0C -794.1 -581.7 -1066.5S1B0V -2438.2 -2326.8 -2710.8S1B45V -4597.5 -4337.3 -5052.7S1B90C -4238.5 -3982.7 -4609.2S1B90V -2358.5 -2048.2 -2816.3S1B180V -4813.1 -4698.8 -4939.8S1B270C -2704.7 -2461.2 -3072.8S1B270V -1999.5 -1709.3 -2492.5S1N0C -2465.7 -2200.2 -2864.0S1N0V -7562.4 -7379.5 -7808.7S1N45V -5761.4 -5406.6 -6370.5S1N90C -4721.0 -4474.9 -5086.5S1N90V -2442.1 -2146.1 -2921.7S1N180V -6038.6 -5911.1 -6174.7S1N270C -2576.4 -2327.0 -2923.6S1N270V -1641.2 -1347.9 -2146.1S2B0C -3479.4 -3289.1 -3773.9S2B0V -2742.5 -2560.2 -3019.6S2B45V -7213.6 -6852.4 -7906.6S2B90C -4988.0 -4706.1 -5444.5S2B90V -209.0 128.0 -760.5S2B180V -457.4 -361.4 -564.8S2B270C -4010.3 -3729.1 -4482.4S2B270V -414.3 -82.8 -948.8S2N0C -5360.8 -5079.1 -5839.8S2N0V -3853.6 -3667.2 -4164.2S2N45V -7381.4 -6988.0 -8162.7S2N90C -5916.1 -5638.4 -6376.8S2N90V -816.0 -459.3 -1453.3S2N180V 287.8 376.5 158.1S2N270C -4186.2 -3893.2 -4653.9S2N270V -650.1 -316.3 -1212.3D1B0 0.5 0.5 0.5D1B45 -0.2 -0.1 -0.2D1B270 -0.6 -0.5 -0.6D1B315 -0.1 -0.1 -0.2D1BC -0.2 -0.2 -0.2D1N0 0.5 0.6 0.5D1N45 -0.2 -0.2 -0.2D1N270 -0.7 -0.7 -0.7D1N315 -0.2 -0.2 -0.3D1NC -0.5 -0.5 -0.5D2B0 0.1 0.1 0.1D2B45 0.3 0.3 0.2D2B270 -0.6 -0.6 -0.6D2B315 -0.1 -0.1 -0.1D2BC -0.2 -0.2 -0.2D2N0 -0.2 -0.2 -0.3D2N45 0.2 0.2 0.2D2N270 -0.4 -0.4 -0.4D2315 -0.2 -0.2 -0.2D2NC -0.5 -0.5 -0.5T1A 52.7 53.0 52.4T2A 53.3 53.6 53.0TEA 58.5 59.5 57.8

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3.1.3 Strains and Deflections from Dynamic Loads after 96 MGT The measurements taken after accumulating 1 MGT of HAL traffic were repeated after accumulating 96 MGT of HAL traffic (8 months). Data was collected during 10 laps of train operations. Train speed increased from approximately 5 mph to 40 mph. Again, there was little difference in strains or deflections within the range of test speeds, though the higher speeds produced slightly higher values.

Figure 16 shows maximum strains measured during lap 7 (lap 7 was chosen to match the 1 MGT data; it is representative of the other 40 mph laps). Figure 17 shows peak-to-peak changes in strains due to dynamic loads. Figure 18 shows maximum deflections (compared to pre-backfill conditions) for lap 7. Figure 19 shows peak-to-peak changes in deflections due to dynamic loads. The general trends measured after 1 MGT of HAL traffic accumulation continued after accumulating 96 MGT of HAL traffic; however, there were moderate increases in maximum strains and deflections. Maximum strain increased from approximately 8,200 microstrain to approximately 8,800 microstrain. The pipes tended to flatten vertically during the period. The shortening between the 12:00 and 6:00 clock positions increased from about 0.3 inch to about 0.5 inch during the period. Maximum circumferential shortening increased from about 0.5 inch to nearly 0.8 inch. Dynamic strains and deflections were similar to those measured after accumulating 1 MGT of HAL traffic. Table 3 shows statistics for each channel. Appendix D shows time histories for all channels from lap 7.

‐10000

‐8000

‐6000

‐4000

‐2000

0

2000

0º Crown

0º Valley

45º Valley

90º Crow

n

90º Valley

180º Valley

270º Crown

270º Valley

Strain (m

icrostrain)

Site 1 WT Joint

Site 1 Split Joint

Site 2 WT Joint

Site 2 Split Joint

Figure 16. Maximum Pipe Wall Strains Measured during 40 mph Train Operations

16

‐1500

‐1300

‐1100

‐900

‐700

‐500

‐300

‐100

100

300

500

0º Crown

0º Valley

45º Valley

90º Crow

n

90º Valley

180º Valley

270º Crown

270º Valley

Strain (m

icrostrain)

Site 1 WT Joint

Site 1 Split Joint

Site 2 WT Joint

Site 2 Split Joint

Figure 17. Peak-to-peak Changes in Strains due to Dynamic Loads

‐1

‐0.8

‐0.6

‐0.4

‐0.2

0

0.2

0.4

0.6

0.8

1

 0 Degree

45 Degree

270 Degree

315 Degree

Circum

frential

Displacem

ent (in

)

Site 1 WT Joint

Site 1 Split Joint

Site 2 WT Joint

Site 2 Split Joint

Figure 18. Maximum Pipe Deflections Measured during 40 mph Train Operations

17

‐0.1

‐0.08

‐0.06

‐0.04

‐0.02

0

0.02

 0 Degree

45 Degree

270 Degree

315 Degree

Circum

frential

Displacem

ent (in

)

Site 1 WT Joint

Site 1 Split Joint

Site 2 WT Joint

Site 2 Split Joint

Figure 19. Peak-to-peak Changes in Deflections due to Dynamic Loads

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Table 3. Statistics from Measurements during 40 mph Train Operations after 96 MGT

Channel Name Average Maximum MinimumS1B0C -2811.5 -2602.9 -3072.8S1B0V -1687.2 -1513.6 -1867.5S1B45V -7456.3 -7191.3 -7936.7S1B90C -6155.3 -5906.9 -6533.4S1B90V -5461.1 -5173.2 -5926.2S1B180V -6551.0 -6423.2 -6679.2S1B270C -4786.8 -4534.6 -5153.6S1B270V -6528.0 -6219.9 -7033.1S1N0C -5661.5 -5422.1 -6018.8S1N0V -8385.7 -8177.7 -8659.6S1N45V -5677.8 -5436.7 -6031.6S1N90C -7553.2 -7279.2 -8025.1S1N90V -6111.9 -5813.3 -6603.9S1N180V -6449.3 -6325.3 -6603.9S1N270C -4130.9 -3908.1 -4445.1S1N270V -3693.3 -3433.7 -4119.0S2B0C -3060.6 -2916.2 -3274.2S2B0V -2943.0 -2793.7 -3140.1S2B45V -8386.1 -8170.2 -8795.2S2B90C -4230.2 -4049.8 -4489.9S2B90V -1213.9 -1001.5 -1536.1S2B180V -32.2 45.2 -113.0S2B270C -4581.1 -4400.4 -4855.3S2B270V -1173.5 -956.3 -1506.0S2N0C -6772.2 -6563.2 -7085.3S2N0V -4067.5 -3900.6 -4307.2S2N45V -8276.0 -8004.5 -8704.8S2N90C -6547.7 -6339.5 -6831.7S2N90V -2030.6 -1784.6 -2409.6S2N180V 1389.0 1468.4 1310.2S2N270C -5200.7 -5019.4 -5466.9S2N270V -1335.2 -1122.0 -1664.2D1B0 0.1 0.2 0.1D1B45 -0.2 -0.2 -0.3D1B270 -0.4 -0.3 -0.4D1B315 -0.2 -0.2 -0.3D1BC -0.5 -0.5 -0.5D1N0 0.2 0.2 0.1D1N45 -0.2 -0.2 -0.2D1N270 -0.6 -0.6 -0.6D1N315 -0.4 -0.4 -0.4D1NC -0.8 -0.8 -0.8D2B0 0.0 0.0 -0.1D2B45 0.3 0.3 0.2D2B270 -0.6 -0.6 -0.6D2B315 -0.1 -0.1 -0.1D2BC -0.3 -0.3 -0.3D2N0 -0.5 -0.5 -0.5

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3.1.4 Results of Leaving Loaded Cars Parked over the Pipes for 6 Weeks One of the unknowns at the start of the test was the response of the pipes to long-term static loads. Two loaded cars at FAST were parked over the pipes for 6 weeks. One set of wheels from each car was directly over one of the pipes (Figure 20). There were slight depressions in the rails under the wheels at the end of the 6-week period. The rails rebounded when the cars were moved, and no track geometry maintenance was needed.

Figure 20. Cars Parked over Pipes to Evaluate Long-Term Pipe Response

4.0 SUMMARY Transportation Technology Center, Inc. conducted a test of corrugated high-density polyethylene pipe for PPI in the HTL at FAST. The pipes were supplied by ADS. Two pipes were installed 50 feet apart under tangent track in a fill on the HTL. There was a 4-foot cover, including the typical granular layer at FAST, between the pipes and the bottoms of the ties. The backfill for one pipe was fractured rock; it was native soil for the other pipe. The pipes were instrumented to allow data collection before and during train operations. Gages were installed at various locations on the pipes to measure lateral, vertical, diagonal, and circumferential deflections; and pipe wall strains. Measurements were taken at the following times:

• Statically, when backfill and track construction was complete • Statically, after accumulating 1 MGT of HAL traffic • Dynamically, during 10 laps of train operations after accumulating 1 MGT of

HAL traffic • Statically, prior to train operations after accumulating 96 MGT of HAL traffic • Dynamically, during 10 laps of train operations after accumulating 96 MGT of

HAL traffic

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The train that was operated over the pipes typically consists of three to four locomotives and approximately 80 315,000-pound GRL cars.

Results of testing are summarized below:

• The pipes performed acceptably through 96 MGT. • No track geometry maintenance was required at the test site due to pipe deflection

or fill settlement. • Locomotive engineers who operated the FAST train during the test period

reported that ride quality over the pipes was satisfactory. • A locomotive-mounted, accelerometer-based, ride quality measurement system

recorded no exceptions over the pipes during the test period. • One loaded car was parked over each of the pipes continuously for six weeks

during a scheduled pause in train operations. The minor track settlement that occurred did not require track geometry maintenance.

• The maximum strain (compressive) from construction loads was 7,300 microstrain.

• The maximum horizontal deflection from construction loads was 0.7-inch horizontal shortening.

• The maximum vertical shortening from construction loads was less than 0.1 inch. • The maximum circumferential shortening from construction loads was 0.4 inch. • The maximum strain (compressive) from the combination of construction loads

and dynamic train loading after 96 MGT was 8,800 microstrain. • The maximum horizontal deflection from the combination of construction loads

and dynamic train loading after 96 MGT was 0.6-inch horizontal shortening • The maximum vertical deflection from the combination of construction loads and

dynamic train loading after 96 MGT was 0.5-inch vertical shortening. • The maximum circumferential shortening from the combination of construction

loads and dynamic train loading after 96 MGT was 0.8 inch. The portion of the shortening caused by the dynamic loads was inconsequential.

• The maximum measured deflection in any direction caused by dynamic loads was less than 0.065 inch.

Acknowledgment ADS Regional Engineer Shawn Coombs was the project engineer representing PPI; Joseph LoPresti was the project engineer for TTCI; David Williams led the instrumentation and data collection effort for TTCI. They were supported by many others from TTCI, ADS, and various subcontractors.

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Appendix A: Instrumentation Photographs

Figure A1. Installation of Valley and Crown Mounted Strain Gages –

Held in Place with Vacuum Cups

Figure A2. Strain Gage Close-up

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Figure A3. Pipe Section being Instrumented

Figure A4. Instrumentation Check

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Appendix B: Installation Photographs

Figure B1. Track Fill Excavated for Pipe Installation

Figure B2. Instrumented Section Being Placed in Trench

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Figure B3. Pipes Being Aligned so Joints are under Rails

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Figure B4. Site 1, Crushed River Rock Backfill — Vibrated with Jumping Jack

Figure B5. Site 2, Native Soil Backfill — Vibrated with Jumping Jack

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Figure B6. Initial Compaction of Native Soil Cover Material

Figure B7. Final Compaction of Native Soil Cover Material

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Figure B8. Track Surfacing at Test Site

Figure B9. Instrumented Pipe in Place

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Figure B10. Preparation for Data Collection

Figure B11. Train Approaching for Dynamic Test

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Appendix C: Time Histories, 1 MGT Dynamic Measurements, Lap 7

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Appendix D: Time Histories, 96 MGT Dynamic Measurements, Lap 7

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