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From page 401... ... 390 CHAPTER 8 - CONCLUSIONS AND RECOMMENDATIONS 8.1 INTRODUCTION This chapter presents a summary of findings from a comprehensive evaluation of SPS-1, SPS-2 and SPS-8 experiments, based on mid-term performance trends [Release 17 (Level-E) Read the entire page →
From page 402... ... 391 subgrade soil type. A total of 32 flexible pavement sections in 15 sites and 14 rigid pavement sections in 5 sites were constructed for the experiment. Read the entire page →
From page 403... ... 392 8.2 EFFECTS OF STRUCTURAL FACTORS FOR FLEXIBLE PAVEMENTS -- SPS-1 EXPERIMENT The SPS-1 experiment, entitled Strategic Study of Structural Factors for Flexible Pavements, is one of the nine special pavement studies in the LTPP program. The effects of the experimental factors on fatigue cracking, structural rutting, roughness, transverse cracking, and longitudinal cracking (WP and NWP) Read the entire page →
From page 404... ... 393 • Among un-drained pavements, on average, an increase in HMA surface thickness from 102 mm (4-inch) to 178 mm (7-inch) Read the entire page →
From page 405... ... 394 Structural Rutting The extent of structural rutting among the test sections in the SPS-1 experiment is 6.5 mm, on average, with a standard deviation of 2.4 mm. Their average age is about 7 years with a range between 4.5 and 10 years. Read the entire page →
From page 406... ... 395 • Among un-drained sections located in WNF zone, those with 305 mm (12-inch) base have less rutting than those with 203 mm (8-inch) Read the entire page →
From page 407... ... 396 • For un-drained pavements built on coarse-grained soils, an increase in base thickness from 203 mm (8-inch) to 305 mm (12-inch) Read the entire page →
From page 408... ... 397 • On average pavements in WF zone have shown higher levels of longitudinal cracking-WP than those in WNF, especially among pavements built on fine-grained subgrade. This effect was found to be only marginally significant. Read the entire page →
From page 409... ... 398 longitudinal cracking. Base thickness has secondary effects on performance, especially in the case of roughness and rutting. Read the entire page →
From page 410... ... 399 8.2.2 Effect of Design and Site Factors on Pavement Response Three pavement response parameters were chosen for ANOVA−peak deflection under FWD load (d0) , far-sensor deflection (d6) Read the entire page →
From page 411... ... 400 8.2.3 Apparent Relationship between Response and Performance Two types of relations between flexible pavement response (FWD) and performance were explored for the SPS-1 pavements -- explanatory and predictive. Read the entire page →
From page 412... ... 401 • No apparent relation was observed between AREA and longitudinal cracking-NWP or transverse cracking, implying that these distresses could be independent of the pavement structural capacity. Dynamic Load Response for OH (39) Read the entire page →
From page 413... ... 402 • The occurrence of transverse cracking among pavements constructed with LCB is higher than that among those with PATB/DGAB or with DGAB. Pavements with PATB/DGAB have shown the "best" performance (least occurrence of cracking) Read the entire page →
From page 414... ... 403 In general, pavements with standard lane [3.7 m (12 ft) wide lane] Read the entire page →
From page 415... ... 404 Effective Stiffness (ES) of the PCC slab. Read the entire page →
From page 416... ... 405 without drainage. Also, pavements with 6.2 MPa (900 psi) Read the entire page →
From page 417... ... 406 8.5 LIMITATIONS OF THE EXPERIMENTS AND ANALYSES All the above findings/observations on the effects of design and construction features on pavement performance and response should be considered in light of the limitations discussed herein. These limitations can be broadly classified under two categories -- experiment-related and data-related. Read the entire page →
From page 418... ... 407 inch) base thickness. Read the entire page →
From page 419... ... 408 material-related information were available for all the sections, the issues caused by performance variability could be better addressed. • Backcalculated layer moduli are unavailable for most of the sections in the SPS-1 and SPS-2 experiments. Read the entire page →
From page 420... ... 409 7) Some of the sites in both SPS-1 and SPS-2 experiments are very close to the thresholds (regarding average annual precipitation and freeze index) Read the entire page →
From page 421... ... 410 When the long-term performance data is available for most of the sections of the SPS-1 and SPS-2 experiments, the methods employed in this research would be more "powerful" to study the effect of design and construction features. Methods that analyze the time-series data (such as survival analysis and ANOVA with repeated measures) Read the entire page →

From page 401...

... 390 CHAPTER 8 - CONCLUSIONS AND RECOMMENDATIONS 8.1 INTRODUCTION This chapter presents a summary of findings from a comprehensive evaluation of SPS-1, SPS-2 and SPS-8 experiments, based on mid-term performance trends [Release 17 (Level-E)