disengaged. Additionally, set the brake, and lower theblade.. When towing a heavy load downgrade, keep thedozer in low gear. Coasting is dangerous. A coastingdozer with a towed load is likely to jackknife.. Before dismounting a dozer and at the end of aworkday, secure the dozer blade by lowering it to theground. Lowering the blade prevents the dozer fromrolling; more importantly, it eliminates the possibility ofthe blade falling on someone. Whenever it is necessaryto work on the dozer with the blade up, especially whenchanging cutting edges, the blade must be securelyblocked to prevent it from falling accidentally.l Wear required personal protective equipment,such as steel toe safety shoes and hard hats.ROLLERSAny time soil is disturbed, it becomes expanded andvery loosely packed. During the construction of a fill orsubgrade, this loose soil must be compacted into a solidmass. The process of compressing The loose soil into asolid mass is called compaction. If the soil is notproperly compacted during construction, it will settlecausing roads, building foundations, or runways tocollapse.Soil may be compacted naturally (settled) byweather and time. If the soil is porous, settlement maybe speeded by soaking it and allowing it to dry. Thisprocess is slow and cannot be depended upon to producethe high densities required by project specification.Another method of compaction is through chemicalstabilization that involves the application of one ormore chemicals to a soil to achieve a desired change inits characteristics. Mechanical compaction is normallyrequired to supplement chemical stabilization. Toaccomplish mechanical compaction, you can usevarious compaction techniques and types of compactionequipment, such as vibratory rollers, pneumatic-tiredrollers, and steel-wheeled rollers.VIBRATORY ROLLERSVibratory rollers provide compactive force by acombination of weight and vibration of their steelcompaction rolls, commonly referred to as drums.Those used for compaction are self-propelled and varyin weight from 7 to 17 tons.Propulsion for single-drum models is provided bypneumatic-tired wheels, as shown in figure 11-39. TheFigure 11-39.—Vibratory roller.11-19
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