Page 262 - Civil Engineering Formulas
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196                    CHAPTER EIGHT

                        TABLE 8.3 Average Speeds of Rollers
                           Type         mi/h      (km/h)
                        Grid rollers     12        (19.3)
                        Sheepsfoot rollers  3      (4.8)
                        Tamping rollers  10        (16.1)
                        Pneumatic rollers  8       (12.8)



             Compaction production can be computed from
                                          16WSLFE
                                    3
                                3
                              yd /h (m /h)                      (8.41)
                                             P
           where W   width of roller, ft (m)
                S   roller speed, mi/h (km/h)
                L   lift thickness, in (mm)
                                           3
                                              3
                                 3
                              3
                F   ratio of pay yd (m ) to loose yd (m )
                E   efficiency factor (allows for time losses, such as those due to turns):
                   0.90, excellent; 0.80, average; 0.75, poor
                P   number of passes
           FORMULAS FOR EARTHMOVING

           External forces offer rolling resistance to the motion of wheeled vehicles, such
           as tractors and scrapers. The engine has to supply power to overcome this resis-
           tance; the greater the resistance is, the more power needed to move a load.
           Rolling resistance depends on the weight on the wheels and the tire penetration
           into the ground:
                                 R   R f W   R p pW             (8.42)

           where R   rolling resistance, lb (N)
                R   rolling-resistance factor, lb/ton (N/tonne)
                 f
                W   weight on wheels, ton (tonne)
                R   tire-penetration factor, lb/ton in (N/tonne mm) penetration
                 p
                 p   tire penetration, in (mm)
           R usually is taken as 40 lb/ton (or 2 percent lb/lb) (173 N/t) and R as 30 lb/
            f
                                                             p
           ton  in (1.5% lb/lb  in) (3288 N/t  mm). Hence, Eq. (8.42) can be written as
                            R   (2%   1.5%p) W   R W            (8.43)

           where W     weight on wheels, lb (N); and R    2%   1.5%p.
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