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â 1.1 Impetus and Objectives NCHRP Project 21-09, âIntelligent Soil Compaction Sys- tems,â was initiated in 2006 to investigate intelligent compac- tion (IC) systems and to develop generic specifications for the application of IC in quality assurance (QA) of soil and aggregate base material compaction. The term âintelligent soil compaction systemsâ was defined in the NCHRP Project 21-09 Request for Proposals to include: â¢ Continuous assessment of mechanistic soil properties (e.g., stiffness, modulus) through roller vibration monitoring; â¢ On-the-fly modification of vibration amplitude and frequency; â¢ Integrated global positioning system to provide a complete geographic information systemâbased record of the earth- work site. Roller-integrated continuous compaction control (CCC)â defined, in essence, aboveâwas developed in Europe in the 1970s and has been used there for nearly 20 years. The first European specification for roller-integrated CCC was devel- oped in Austria in 1990. Today, four European countries have compaction QA specifications using roller-integrated CCC (Austria, Germany, Sweden, and Switzerland), and the Inter- national Society for Soil Mechanics and Geotechnical Engi- neering has endorsed the Austrian CCC specifications (Adam 2007). As described in this report, roller-integrated measurement of soil stiffness is strongly dependent on machine operating parameters (i.e., excitation force amplitude, frequency, and roller speed). Accordingly, current intelligent compaction technology employing on-the-fly or automatic modification of vibration amplitude and frequency should not be used during QA. IC can be used during compaction. The result- ing QA specifications therefore pertain to the use of roller- integrated CCC for QA of earthwork compaction. c h a p t e r 1 introduction 1.2 Work Plan Overview A 24-month, two-phase work plan was carried out to ad- dress NCHRP Project 21-09 objectives. Field testing was performed on earthwork construction projects in five states: Minnesota, Colorado, Maryland, Florida, and North Caro- lina (see Table 1.1 and Figure 1.1). Testing was conducted on granular soils, fine-grained soils, and aggregate base materials commonly used in subgrade, subbase, and base course con- struction. Roller compactors from Ammann, Ammann/Case, Bomag, Caterpillar, Dynapac, and Sakai were used through- out the study (see Table 1.2). The Ammann, Ammann/Case, Bomag, and Dynapac rollers included measurement systems, a global positioning system (GPS), and automatic feedback control of vibration amplitude and therefore are referred to as IC rollers. The Caterpillar and Sakai rollers included mea- surement systems and GPS only and therefore are referred to as CCC rollers. The study used both smooth drum and pad foot rollers. Field investigations were conducted on more than 200 test beds (TBs) across the five sites (see Figures 1.2 through 1.6). TBs ranged in size from single roller lane widths [i.e., 2.1 m (6.9 ft) by 20 m (65.6 ft) long] to multiple roller lane widths [i.e., 20 m (65.6 ft) by hundreds of meters long], more con- sistent with typical production earthwork compaction sec- tions. TBs involved single lifts of subgrade, subbase, and base course materials ranging in thickness from 150 to 300 mm (6 to 12 in) and, in some cases, multiple lifts and layered sys- tems to depths greater than 1.5 m (4.9 ft). Detailed informa- tion about the five sites, the soils tested, and individual TBs is provided in Appendix A. Single lane TBs were constructed to conduct detailed in- vestigations of the relationship between roller measurement values (MVs) and measurements from commonly used spot tests (see Figure 1.7). In these cases, soil mixers or reclaimers were often used to prepare the TB as homogeneously as pos- sible (e.g., see Figures 1.2 and 1.5). Descriptions of the spot-
table 1.1. Summary of field research sites. State Project Dates Rollersa Soilsb MN Mn/ROAD research site July 2006 Ammann SD Bomag SD, PD Caterpillar SD, PD Subgrade: A-6(5), A-4(3), A-2-6 Base: A-1-b, A-1-a CO I-25 reconstruction Aug.âOct. 2007 Bomag SD Caterpillar SD Dynapac SD Subgrade: A-6(7), A-4, A-4(3) Subbase: A-1-a Base: A-1-a MD I-70 interchange Nov. 2007 Bomag SD Dynapac SD, PD Sakai SD Subgrade: A-2-4, A-4 Base: A-1-a, A-1-b FL Branan Field Chaffe/ I-10 interchange April 2008 Case/Ammann SD Dynapac SD Sakai SD Subgrade: A-3, A-2-4 Base: A-1-b NC NC311/I-85 divided highway MayâJune 2008 Bomag SD Case/Ammann SD Sakai SD Subgrade: A-2-4, A-4, A-1-b Base: A-1-a aSD = smooth drum, PD = pad foot drum. bAmerican Association of State Highway and Transportation Officials classification provided; see Appendix A for more detail. Figure 1.1. Overview of the five NCHRP 21-09 field test sites.
â table 1.2. Summary of rollers used during the study. Roller MV Drum Length, m (ft) Drum Radius, m (ft) Static Mass, kg (lb) Static Linear Load, kN/m (kip/ft) Excitation Frequency, Hz Excitation Force, kN (kip) Ammann/Case AC110/SV212 k s 2.20 (7.22) 0.75 (2.46) 11,500 (25,350) 31.5 (2.2) 20â34 0â277 (0â62) Bomag BW113-BVC E vib 2.13 (7.00) 0.75 (2.46) 14,900 (32,850) 42.4 (2.9) 28 0â365 (0â82) Caterpillar CS563 CMV C MDP 2.13 (7.00) 0.76 (2.49) 11,100 (24,500) 26.9 (1.8) 32 133, 266 (30, 60) Dynapac CA362 CMV D 2.13 (7.00) 0.77 (2.53) 13,200 (29,100) 37.3 (2.6) 32 0â260 (0â58) Sakai SV510 CCV 2.13 (7.00) 0.75 (2.46) 12,500 (27,600) 32.2 (2.2) 37, 28 186, 245 (42, 55) Figure 1.2. IC/CCC rollers and TBs at the Minnesota work site.
0 Figure 1.3. IC/CCC rollers and TBs at the Colorado work site. Figure 1.4. IC/CCC rollers and TBs at the Maryland work site.
â Figure 1.6. IC/CCC rollers and TBs at the North Carolina work site. Figure 1.5. IC/CCC rollers and TBs at the Florida work site.
Figure 1.7. Spot-testing devices used in the study. Figure 1.8. Multilayered TBs.
â Figure 1.9. Installing in situ stress and strain sensors. test devices employed are provided in Appendix A. Full-width TBs were constructed to calibrate roller MVs to spot test mea- surements for evaluation of QA specification options (e.g., see Figures 1.3 and 1.5). These TBs were usually prepared ac- cording to typical construction practice. Multiple lift and lay- ered TBs were constructed with embedded instrumentation to investigate the in situ stress-strain field and measurement depth of roller MVs (see Figures 1.8 and 1.9). 1.3 Summary of Report Following this Introduction, the report contains eight ad- ditional chapters, summarized as follows: â¢ Chapter 2 summarizes the state of practice regarding prior CCC and IC research findings and provides a history of CCC and IC. The chapter also summarizes current CCC/ IC equipment and provides a detailed presentation of Eu- ropean CCC specifications. â¢ Chapter 3 investigates fundamental aspects of roller mea- surement systems, including MV and GPS position re- porting, comparison of roller MVs, MV dependence on machine parameters (i.e., vibration amplitude, frequency, roller speed, direction of travel), and the influence of local heterogeneity on roller MVs. â¢ Chapter 4 characterizes roller-soil interaction, in-ground soil behavior (stress, strain, modulus) during rolling, and the relationship between roller MVs and in-ground soil behavior. The chapter focuses on the measurement depth of roller MVs, how MVs may relate to in situ soil response, and why MVs vary with excitation parameters (e.g., force amplitude). â¢ Chapter 5 explores the operation and benefits of automatic feedback control IC. â¢ Chapter 6 evaluates the relationship between roller MVs and spot-test results (i.e., nuclear density and moisture gauge, lightweight deflectometer, dynamic cone pene- trometer, plate load test, and falling weight deflectometer). Through single and multiple variable regression analysis, this chapter addresses the influence of moisture, ampli- tude, and underlying layer stiffness. â¢ Chapter 7 presents recommended specifications for the use of roller-integrated CCC for QA of earthwork compaction. Six specification options are recommended. â¢ Chapter 8 presents six case studies carried out to evaluate the recommended specification options. The case studies are based on field tests in Colorado, Florida, North Caro- lina, and Minnesota. â¢ Chapter 9 presents the findings and conclusions from Proj- ect 21-09. â¢ The main body of the report was written with practical implementation in mind. Additional data and detailed information are presented in the appendixes. Appen- dixes A through D are available on the TRB website (www. trb.com) at http://www.trb.org/Main/Blurbs/164279. aspx.