Loaded Descent on Wet Clay
You are driving a fully loaded 30-tonne articulated dumper down a 120 m haul road with a gradient of about 1 in 6. The surface is wet clay with shallow ruts, and there is a 90-degree left bend at the bottom next to a drainage ditch. You are in fourth gear at the top, doing about 12 km/h. The retarder is available and the service brakes are hot from the previous descent. A banksman at the bottom waves you on. The load is close to the rated capacity, and the centre of gravity is high. Another loaded dumper has just descended and left fresh tyre marks toward the ditch. The site speed limit is 15 km/h, but the haul road has no gradient sign or speed board.
1. How should you set up and carry out the descent?
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Stop at the top and set up before the gradient. Select a low gear, probably first or second, while stationary; do not change down halfway down. Test the service brake, confirm the retarder is working and keep it engaged. Descend at walking pace, well below the 15 km/h limit, with the transmission in gear and the engine in the retarder’s effective range. Avoid riding the service brake continuously; use engine braking and the retarder. Keep smooth, small steering inputs because the machine is articulated and the load is high. Stay away from the ditch edge. If speed builds or the surface is greasier than expected, stop safely at a wide point and reassess.
2. What would you do if the machine begins to slide or the brakes fade mid-slope?
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If the machine slides, do not stamp on the brakes or spin the steering. Ease off the power, keep the steering steady and let the retarder and engine braking reduce speed. If the brakes fade, select a lower gear if the transmission allows it without shock, keep using the retarder, sound the horn and look for a safe run-off away from the ditch. Do not aim for the bend at speed. Once stopped, apply the parking brake, lower the body, report the fade and do not continue until the brakes are checked. Warn the banksman immediately.
3. What site factors make this descent high risk, and what would you report?
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The main risks are the 1 in 6 gradient, wet clay, ruts, the 90-degree bend, the ditch, hot brakes from the previous descent and a near-capacity load with a high centre of gravity. The lack of gradient or speed signage and the banksman’s position at the bottom also matter. Report the need for a lower speed limit, gradient signs, drainage or surface improvement, a stop block or barrier at the ditch, and a rule on brake checks before descent. Ask whether loaded and empty routes can be separated.