Field Performance of Corrugated Pipe Manufactured with Recycled Polyethylene Content (2018) / Chapter Skim
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9 2.1 Research Objectives The primary objective of this research project was to evaluate the field performance of corrugated HDPE pipes manufactured with recycled materials. The project was based in part on the research conducted in NCHRP Project 4-32 and reported in NCHRP Report 696 (1)
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10 2. Obtain and characterize several large-diameter corrugated HDPE test pipes manufactured with various blends of recycled and virgin materials typically used in the industry in accordance with this new test method; 3.
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11 measured properties of all the test pipes is shown in Table 2-1 and sample test reports for the pipes are shown in Appendix B Testing was done in accordance with the requirements of AASHTO M 294 (2)
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12 NCHRP Report 631 (30)
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13 106.1 13.7 4.9 32.3 59.8 9.0 6.8 16.0 12.7 87.9 18.4 3.9 16.9 32.5 8.3 5.8 18.1 14.1 0.0 20.0 40.0 60.0 80.0 100.0 120.0 1 2 3 4 5 6 7 8 9 N CL S (h ) Test Pipe Pipe Plaque Pipe Liner AASHTO M 294 Pipe Plaque NCLS Requirement = 24 Hours AASHTO M 294 Pipe Liner NCLS Requirement = 18 Hours Figure 2-2.
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14 2.2.3 Development of a Service Life Prediction Model Based on the UCLS Test As discussed earlier, one of the advantages of the UCLS test is that the elevated temperature test data can be bi-directionally shifted to predict the service life relative to Stage II brittle failures at other temperatures. Two common ways of doing this for polyethylene materials are the Popelar shift method, or PSM (31)
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15 1See Appendix C for log-based average failure times. Pipe Condition Log Avg.
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16 2.6 2.7 2.8 2.9 3.0 3.1 3.2 3.5 4.0 4.5 5.0 5.5 6.0 6.5 7.0 Lo g St re ss (p si)
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17 2.6 2.7 2.8 2.9 3.0 3.1 3.2 3.5 4.0 4.5 5.0 5.5 6.0 6.5 7.0 Lo g St re ss (p si )
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18 data point using the Student's t-distribution. This is illustrated in Equations 2.7 and 2.8.
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19 Figure 2-11. UCLS failures for Pipe 4 (manufactured with 49% PCR materials)
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20 Substituting into Equation 2.12 allows the calculation of A as follows: A 1.956 6233 343 353 343 2067 650 343 0.02915 0.73499 A A Log A 25.2 ( )
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21 y = -0.1432x + 3.7114 y = -0.1709x + 3.7638 2.6 2.7 2.8 2.9 3.0 3.1 3.2 Lo g St re ss (p si )
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22 y = -0.1757x + 3.8064 y = -0.2052x + 3.911 2.6 2.7 2.8 2.9 3.0 3.1 3.2 Lo g St re ss (p si )
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23 y = -0.1955x + 3.8018 y = -0.1904x + 3.9867 2.6 2.7 2.8 2.9 3.0 3.1 3.2 Lo g St re ss (p si )
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24 Shallowest slope y = -0.1709x + 3.7638 Steepest slope y = -0.2175x + 4.1196 2.4 2.6 2.8 3.0 3.2 3.4 3.6 Lo g St re ss (p si)
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25 manufactured with around 50% PCR content. The difference is not as discernible when analyzing the data with the RPM (Figure 2-19)
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26 ~50% PCR Pipes 98% PCR Pipes Pipe PSM RPM 3 6 7 4 8 9 -0.24 -0.22 -0.2 -0.18 -0.16 -0.14 -0.12 -0.1 Sl op e of B ri tt le C ur ve Figure 2-21. Comparison of projected brittle failure slopes for various pipes at service conditions of 23çC and 500 psi stress for the Popelar shift method and rate process method.
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27 Figure 2-23. Strain gages placed on loading rods to measure load reduction due to stress relaxation.
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28 Figure 2-25. Numerical designation for 12 gages placed around pipes.
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29 -4.00E+04 -3.00E+04 -2.00E+04 -1.00E+04 0.00E+00 1.00E+04 2.00E+04 3.00E+04 4.00E+04 St ra in (m ic ro st ra in ) Deflection (in.)
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30 -4.00E+04 -3.00E+04 -2.00E+04 -1.00E+04 0.00E+00 1.00E+04 2.00E+04 3.00E+04 4.00E+04 St ra in (m ic ro st ra in ) Deflection (in.)
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31 To see if either Equation 2.18 or 2.19 is valid for assessing the time-dependent modulus of elasticity of the blends of PCR and virgin HDPE materials used in manufacturing the pipes in this research project, the loads to hold the pipes at a constant deflection were monitored over time via straingage-based sensors in the loading rods. Figure 2-31 shows the responses of loading Pipes 3, 4, and 5 until the inside diameter was reduced from 0% to 20%, and Figures 2-32 and 2-33 show the decay in the measured load over the first 100 days and the first 250 days of loading, respectively.
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32 Pipe 3 - 98% PCR Pipe 4 - 49% PCR Pipe 5 - 0% PCR 0 50 150100 200 250 300 350 Time (d)
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33 A B Figure 2-34. First cracks observed in the crown of Pipe 3 underneath the loading plates: (A)
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34 Figure 2-36. Crack propagation observed in the Pipe 3 after 286 days of loading.
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35 The curves shown in Figure 2-38 were integrated and divided by the loading duration to determine an equivalent average stress in the pipe wall at the given locations, as shown in Equations 2.20 and 2.21.
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36 and 7.22 MPa (1309 and 1047 psi) conditions, conditions of 10.30 MPa (1500 psi)
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37 Figure 2-39. Peak strains in 750 mm (30 in.)
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38 Pipe PCR Content Analysis Method Predicted Time to Crown Cracking Predicted Time to Springline Cracking Load Duration Results 3 98% FEA PSM1 33–99 days 119–301 days 365 days Cracking commenced at 101 days on the inner crown and 131 days on the outer springline RPM2 70–178 days 265–673 days SG PSM3 1.5–3.7 years 143–364 days RPM4 4.4–11.0 years 332–843 days 4 49% FEA PSM1 1.0–2.3 years 2.4–5.6 years 365 days No cracks after 1 year of testing RPM2 4.0–9.3 years 12–27 years SG PSM3 7.8–18.2 years 2.8–6.5 years RPM4 48–111 years 14–32 years 5 0% N/A N/A 365 days No cracks after 1 year of testing 1 Analysis via the Popelar shift method to predict cracking based on peak local strains obtained from finite element model 2 Analysis via the rate process method to predict cracking based on peak local strains obtained from finite element model 3 Analysis via the Popelar shift method to predict cracking based on physical strain gage measurements 4 Analysis via the rate process method to predict cracking based on physical strain gage measurements Table 2-9. Summary of parallel plate test results.
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39 suggested by Brachman et al.
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40 Figure 2-43. Precast reinforced concrete chamber assembly and preparation for pipe installation.
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41 Manufacturer A) was installed in Chamber 1.
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42 -15.0% -10.0% -5.0% 0.0% 5.0% 10.0% 15.0% D efl ec ti on Time (d) Average Vertical Deflection Average Horizontal Deflection Average Diagonal Deflection 0 100 200 300 400 500 Figure 2-46.
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43 -20.0% -15.0% -10.0% -5.0% 0.0% 5.0% 10.0% 15.0% D efl ec ti on Time (d) Average Vertical Deflection Average Horizontal Deflection Average Diagonal Deflection 0 100 200 300 400 500 Figure 2-48.
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44 -20.0% -15.0% -10.0% -5.0% 0.0% 5.0% 10.0% 20.0% 15.0% D efl ec ti on Time (d) Average Vertical Deflection Average Horizontal Deflection Average Diagonal Deflection Note: Pipe was loaded, then excavated and re-installed due to instrumentation errors, resulting in vertical and horizontal pre-deflections of 5%.
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45 vertical and horizontal deflections of −5% and 4%, respectively)
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46 Figure 2-53. Image of ductile failure on outer springline of Pipe 3, leading to brittle cracking and localized buckling of the liner.
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47 Figure 2-54. Pipes 4 and 5 showed no cracking after 422 days of loading.
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48 Figure 2-56. Cracking in Pipe 6 at springline (left)
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49 Pipe Manufacturer PCR Content Predicted Time to Cracking Observed Time to CrackingPSM RPM 3 A 98% 58–148 days 113–288 days 105 days 4 A 49% 1.4–3.2 years 5.9–13.7 years No cracks after 422 days 5 A 0% N/A N/A No cracks after 422 days 6 B 98% 71–220 days 70–219 days 185 days 7 B 98% 73–172 days 10–24 days 185 days 8 C 54% 203–578 days1 18–52 days1 No cracks after 306 days 9 C 59% 139–357 days1 351–897 days1 300 days 1 Calculations for Pipes 8 and 9 conservatively assume a wall stress 10% greater than the other pipes [11.6 MPa (1700 psi)
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50 Figure 2-59. Google Maps® image of test location (pipes shown are not to scale)
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51 Pipe Label Location Description Measurement Model Type / Number Pipe 1 – Virgin SG1-V 0° (Crown) , Outer wall Strain CEA-00-375-UW-350 SG2-V 0° (Crown)
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Figure 2-61. String potentiometers and strain gages installed on test pipes.
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53 Figure 2-64. Transportation and installation of pipes and alignment of instrumentation.
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54 Figure 2-66. Compaction of the backfill material in lifts.
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55 Vibrating ballast penetrators Figure 2-69. Ballast tamper passing over installed pipes.
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56 -3500 -3000 -2500 -2000 -1500 -1000 -500 0 St ra in (m ic ro st ra in )
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57 -0.200 -0.150 -0.100 -0.050 0.000 0.050 D efl ec ti on (i n.
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59 -0.250 -0.200 -0.150 -0.100 -0.050 0.050 0.000 VERTICAL HORIZONTAL DIAGONAL - 45-225 DIAGONAL - 135-315 D efl ec ti on (i n.
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61 applications. For example, in Plastics Pipe Institute (PPI)
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64 -0.042 -0.177 -0.035 -0.189 -0.028 -0.193 -0.110 -0.143 -0.250 -0.200 -0.150 -0.100 -0.050 0.000 VERTICAL HORIZONTAL DIAGONAL - 45-225 DIAGONAL - 135-315 D efl ec ti on (i n.
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65 VERTICAL HORIZONTAL DIAGONAL - 45-225 DIAGONAL - 135-315 D efl ec ti on (i n.
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66 -0.4 -0.3 -0.2 -0.1 0 0.1 0.2 7/1/13 7/1/14 7/1/15 D efl ec ti on (i n.
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67 Figure 2-92. Typical SEPTA passenger railcar.
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68 C B A A = 6.3 mm (0.25 in.)
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69 0.000 0.002 0.004 0.006 0.008 0.010 0.012 0.014 0.016 1000 1500 2000 2500 3000 3500 4000 4500 5000 G ri p D is pl ac em en t (in .)
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70 2.2.6 AASHTO Material Specification and Design Methodology Proposals Based on the results from the laboratory and field studies, proposals were developed for AASHTO design methodology and material specification requirements for pipes manufactured with recycled materials. They are summarized in Chapter 3.
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