Site Hazards, Ground Conditions and Stability on Slopes
What this domain tests
Reading ground conditions and gradients, and understanding why an articulated dumper is stable in some directions and not others.
Ground conditions
Soft ground, deep ruts, backfilled trenches, voids, buried services and standing water all threaten stability. Walk the route or use site knowledge before committing a loaded machine. Look for cracking, settlement, previous ruts filling with water and marker tape for services. Where the route crosses made ground or a service corridor, ask for the competent person's assessment rather than testing it yourself.
Stability and slopes
The centre of gravity rises with load and with the body, and it shifts towards the downhill side on a cross-slope. Climb and descend directly up and down the slope, never across it unless the handbook permits a stated maximum side slope - which is usually far lower than the fore-and-aft limit. Travel loaded uphill and unloaded downhill where the route allows, keep the body down, and select a low range before the gradient. Do not turn on a slope. Use differential locks in soft or slippery going, engaging before wheel spin.
Edges and tips
Stockpile edges, lagoons, embankments and excavations need physical edge protection, a windrow or a berm, positioned so the machine stops before the ground could fail. The adequacy of a tipping edge is a competent person's decision, not the driver's.
Worked example
A haul road descends at about 20 per cent to a fill area. You approach loaded, so you select a low range at the top, keep the body down, stay in a straight line and use the retarder, and you do not attempt to turn off partway down. On the return, unloaded, the same rules apply - an empty machine is not automatically safe on a slope.
Traps
- Assuming a 4x4 or 6x6 will get through anything.
- Turning on a slope to line up with a tip.
- Trusting a stockpile edge because it 'looked solid yesterday'.