Innovazioni nella Gestione Forestale Sostenibile - Repository of ...

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Grafico (Log) 8: the principal working phase
From an analysis of average duration of each applied work phase, the travel time of the unloaded
vehicle is often high and in the case of the Cat D7G tractor is longer than the loaded travel, due
to the necessity to mark out the trail for the first time in this phase.
For the productivity calculation the daily volume extracted by vehicles has been taken into
account bringing to a total value of 1,136.54 m 3 . In this case, even if used for bigger extraction
distance, the specialized skidder CAT 535 C is capable of ensuring a significant productivity , in
average higher than that of the crawler, due to a major velocity, but also major maneuverability
and agility of the vehicle.
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CAT 535 C CAT D7G
Gross productivity PSH15 [m 3 h -1 team -1 ] 28.921 22.670
Net productivity PSH0 [m 3 h -1 team -1 ] 30.562 24.709
Gross productivity PSH15 [m 3 h -1 worker -1 ] 9.640 7.557
Net productivity PSH0 [m 3 h -1 worker -1 ] 10.187 8.236
Tabella (Log) 3: winching and skidding productivity
Putting in relation the working time for each of extracted volume, a correlation between the two
data has been investigated by using two different methods:
• the first mathematical, R2, obtained directly from Excel according to the extracted curve
equation, which shows a correlation between the variables with a R2 value equal to 0,27;
• the second, purely statistical, is based on the Spearman correlation coefficient for ranks
which provides a R of 0,51 (p-level 0.00004).