Effects of Subsurface Drainage on Pavement Performance: Analysis of the SPS-1 and SPS-2 Field Sections (2007) / Chapter Skim
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Pages 63-84
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From page 63... ...
63 Performance Data Analysis Approach The effects of several factors, including the experimental design factors, on the development of roughness and distress in SPS-1 flexible and SPS-2 rigid pavements are examined in this chapter. The SPS-1 experimental design factors include • AC thickness, • Base thickness, • Base type, • Subdrainage, • Climate, • Subgrade, and • Traffic.
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From page 64... ...
64 into account in the appropriate manner. This does mean, however, that an analysis of this nature only has something to say about the statistical significance of the one factor analyzed.
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From page 65... ...
base types is present. The values assigned to each of the base variables, as well as to the DRN variable, for each of the five base types are shown in Table 22.
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66 base at all, and some sections with a cement-aggregate mixture base. The presence of one of these three base types is indicated by a value of 1 for the base variable B3, B4, or B5.
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Fluctuations in IRI not Due to Pavement Deterioration The expectation is that IRI will tend to increase over time, as the pavement deteriorates. IRI does not, however, always increase steadily over time.
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From page 68... ...
68 from SPS-2 sections than from SPS-1 sections. Figures 91 and 92 together indicate that, in general, better initial smoothness levels were obtained in the construction of the SPS-1 test sections than in the SPS-2 test sections.
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From page 69... ...
trend line for last IRI versus initial IRI for each base type. It is not surprising that the pavement sections that are rougher soon after construction would also be rougher at a later point in time.
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70 to differences in base stiffness and not differences in drainage. The relative contributions of the SPS-1 factors to the r2 of the regression model for change in IRI (latest minus initial)
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71 y = -0.1544x + 0.3484 R2 = 0.0054 -1.0 -0.5 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 0.0 0.5 1.0 1.5 2.0 2.5 3.0 First IRI (m/km)
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From page 72... ...
72 higher cumulative percentage levels indicates that the largest changes in IRI tended to occur in this group, and this is confirmed by Figure 95 as well. The small differences in median change in IRI raise the question of whether different rates of change in IRI over time in service are entirely responsible for the differences seen in last IRI for the different groups.
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From page 73... ...
The backcalculated equivalent thickness of the pavement structure was the second most influential factor in the regression for rutting, raising the r2 by another 10%. Rutting values are plotted against the backcalculated equivalent thicknesses of the SPS-1 pavement sections in Figure 99.
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From page 74... ...
74 Average annual temperature, backcalculated subgrade modulus, Thornthwaite moisture index, and average annual precipitation were the next most influential factors in the regression for rutting. The base type/drainage factors, together with the remaining factors considered (accumulated ESALs, base thickness, and AC surface thickness, all of which are correlated to other factors already in the model)
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From page 75... ...
have not yet developed much cracking, which is probably because of the relatively low truck traffic levels at most of the SPS-1 sites. The cumulative frequency distributions of cracking for the five different base type/drainage combinations in the SPS-1 experiment are shown in Figure 102.
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From page 76... ...
76 asphalt-treated base) , accumulated ESALs, Thornthwaite moisture index, temperature, and the BAR variable (indicating the presence or absence of dowel bars)
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From page 77... ...
undrained aggregate base, but not better than pavements with undrained asphalt-treated base, it is reasonable to conclude that the differences in performance are attributable primarily to the stiffness of the base, and not to the presence or absence of subdrainage. In the case of rigid pavements, however, the base stiffness that optimizes performance by achieving the best balance between load-related stresses and curling-related stresses is one that is neither too weak nor too stiff.
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From page 78... ...
78 average annual precipitation made very slight contributions (3% and 1%, respectively) to the regression.
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among the initial IRI distributions for the different types of SPS-2 pavements is even greater than for the different types of SPS-1 pavements (see Figure 97)
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80 pavements. Furthermore, the differences in IRI by base type are not entirely attributable to different rates of change in IRI over the time that the SPS-2 pavements have been in service, because there is evidence of some significant differences in initial IRI values by base type.
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From page 81... ...
81 PCC/AGG PCC/LCB PCC/PATB PCC/HMAC PCC/CAM 0 10 20 30 40 50 60 70 80 90 100 0.00-0.50 -0.25 0.25 0.50 0.75 1.00 1.25 1.50 1.75 2.00 2.25 2.50 2.75 3.00 3.25 3.50 3.75 4.00 4.25 4.50 Change in IRI (m/km) Pe rc en t o f s ec tio ns Figure 106.
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From page 82... ...
82 wheelpath faulting: in a 2000 evaluation of LTPP faulting data, in more than 90% of the pairs of edge and wheelpath faulting measurements examined, the difference between the two measurements was found to be between −1 mm and 1 mm (37)
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From page 83... ...
possible r2 of 42%. Accumulated ESALs, average annual temperature, and average annual precipitation were the next most influential variables.
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From page 84... ...
84 Ohio, and Washington. The sections that exhibited the most cracking were the sections with lean concrete base and thin (8-in.)
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