عنوان مقاله [English]
In this research the productivity and cost of Komatsu D60 bulldozer in earth working operations of secondary forest road was studied in Lolet forests, lied in one of the Tajan river watersheds. The daily work elements of the machine including productive time, unproductive time, technical, operational and personal delays for 12 days and in two slopes of 30 to 50 and 50 to 70 percents were investigated by time study method. To estimate the daily productivity, the cross sections of road were taken every 20 meters and then their section areas were calculated. The hourly cost of bulldozer and system was estimated by conventional method. Comparison of the results by Tokey test showed no significant difference between the length of constructed road in the slopes 30 to 50 and 50 to 70 percents. This was also true for earth working volume, but, hourly earth working volume and work volume in each meter of the road increased with increasing the hillside gradient and the length of constructed road was reduced. The mean production rates for bulldozer in the slopes 30-70 percents in productive time were 144.92 m3/h and 22.87 m/h. The hourly costs for the bulldozer and system were estimated 121890.7 and 286890.7 rials, respectively. Finally, the costs of each cubic meter of the earth work and each meter of the road excavation by bulldozer in the slopes 30 to 70 percents were 1979.65 and 12544.41 rials, respectively.