Underground loaders and trucks are the machines that move broken rock and ore in underground mines and tunnels. The loader, usually called an LHD (load, haul, dump) machine, is a low, long, articulated wheel loader designed to fit in narrow drifts. It loads material at the face or drawpoint, carries it in its bucket and dumps it into an ore pass, a crusher or a truck. The underground truck, also known as a mine truck or low-profile dump truck, carries larger loads over longer distances, for example up a decline ramp to the surface or to an underground crusher.
Together these machines form the core of trackless mining, the method that replaced rail haulage in most underground hard rock mines from the second half of the twentieth century. They are also used on tunnel projects excavated by drill and blast, where they clear the muck pile after each blast. Their design is shaped by tight headroom, poor visibility, rough floors, heat, dust and the need to keep exhaust emissions low in confined spaces.
Brief History of Underground Loaders & Trucks
Before trackless machines, broken rock underground was moved mostly by hand, by scrapers pulled with winches and by rail-mounted mucking machines loading into wagons. In the 1960s, Wagner Mining Equipment in the United States developed the articulated, low-profile loader that came to be known as the Scooptram, and Eddie Wagner has been described in the industry as the father of the LHD. The concept spread quickly because it allowed mines to use ramps and larger openings instead of rail, making mining faster and more flexible.
Underground trucks developed alongside the LHD as mines grew deeper and haul distances increased. Articulated steering, oscillating frames, enclosed cabs and diesel engines with exhaust treatment became standard over the following decades. From the 1990s remote control and later automation spread, first for loading in unsafe areas and then for autonomous tramming. Since the late 2010s battery-electric loaders and trucks have moved from prototypes to commercial ranges, driven by ventilation costs and emission limits.
How Underground Loaders & Trucks Work
- Articulated frame. Both loaders and trucks have a front and rear frame joined by a central hinge. Steering by articulation gives a tight turning circle in narrow drifts.
- Low profile. The operator’s cab is usually mounted sideways and low, between or beside the frames, so the machine fits under a low roof. The operator often faces across the machine to see in both directions.
- Bucket and boom (LHD). A short, heavy boom lifts a wide bucket. The machine digs into the muck pile, lifts the bucket and trams to the dumping point, where the bucket is tipped or, on some models, material is pushed out by an ejector plate.
- Dump body (truck). Trucks carry a heavy dump body, tipped by hydraulic cylinders. Some use an ejector system to empty the body where there is not enough height to tip it.
- Drivetrain. Most machines use a diesel engine with a torque converter transmission and four-wheel drive with heavy planetary axles. Electric versions run from a trailing cable or from batteries.
- Tyres. Large, deep-tread tyres are used to resist cuts from sharp rock. Tyres are a major operating cost underground.
- Protective structures. Cabs are built to rollover and falling object protection standards, and many machines are available with open canopies for low headroom.
Types of Underground Loaders & Trucks
Diesel LHDs
The most common type, used in mining and tunnelling where flexibility is needed. They require good ventilation and exhaust treatment to control diesel particulate and gases.
Cable Electric LHDs
Loaders powered through a trailing cable reeled on the machine. They produce no exhaust and less heat, but their range is limited by the cable length, so they suit fixed loading and dumping routes.
Battery-Electric Loaders and Trucks
Machines powered by onboard batteries that are charged on the machine or swapped. They reduce ventilation needs and heat, and are increasingly used in new mines designed around them.
Underground Mine Trucks
Articulated dump trucks for haulage up ramps and along main drifts. Most have diesel drives, although battery and trolley-assisted versions exist.
Low-Profile Machines
Very low loaders and trucks for narrow vein mining and low seams, some of them well under 2 metres high.
Tunnelling Loaders
Loaders adapted for civil tunnels, sometimes with side-dump buckets that allow loading into trucks in a narrow tunnel without turning.
Size Classes
| Class | Typical capacity | Typical use |
|---|---|---|
| Small LHD | about 1 to 4 t payload | Narrow vein mining, small tunnels |
| Medium LHD | about 5 to 12 t payload | General hard rock mining, tunnelling |
| Large LHD | about 13 to 25 t payload | Large mines, block and sublevel caving |
| Underground truck | about 20 to 65 t payload | Ramp haulage, main haulage drifts |
Figures are indicative and vary by manufacturer and model.
Main Manufacturers
- Sandvik, with a wide range of diesel and battery-electric loaders and trucks.
- Epiroc, formerly part of Atlas Copco, which took over the Wagner Scooptram name and builds loaders and Minetruck trucks.
- Caterpillar, with underground loaders and articulated trucks for hard rock mining.
- Komatsu, active in underground hard rock loading and haulage.
- GHH and Paus, German manufacturers of loaders and trucks for mining and tunnelling.
Main Uses of Underground Loaders & Trucks
- Loading and hauling ore and waste rock in underground metal mines.
- Mucking out after each blast in drill and blast tunnels.
- Feeding ore passes, crushers and conveyor systems underground.
- Haulage up decline ramps to the surface in mines without shafts.
- Development work, cleaning drifts and handling backfill material.
Choosing Underground Loaders & Trucks
- Match to the openings. Drift width, height and turning radii set the maximum machine size. It is usually cheaper to size the equipment and the mine design together than to fit machines into existing openings.
- Balance the fleet. The loader bucket size should suit the truck body, typically filling it in three to five passes.
- Consider the power source. Battery machines reduce ventilation and heat, but need charging or swapping infrastructure and planning around shift patterns.
- Plan for tyres and maintenance. Road conditions underground strongly affect tyre life, fuel use and component wear. Good floor maintenance pays back quickly.
- Think about automation. Remote control and automated tramming need communications infrastructure and changes to the way the mine works, but can keep production going in areas people cannot safely enter.
Safety
Underground mobile equipment operates in confined, dark and dusty spaces where collisions with people and other vehicles are a major risk. Proximity detection, collision avoidance systems, cameras, good lighting and strict traffic rules are widely used. Loading at open stopes and drawpoints exposes the operator to falling rock and mud rush, which is why remote-controlled loading is common in these areas. Fire is another serious hazard, so machines carry fire suppression systems and mines provide refuge chambers. Diesel emissions and heat must be controlled through ventilation and exhaust treatment. Operators also need protection from whole-body vibration on rough floors.
Trends and Technology
Battery-electric loaders and trucks are the most visible trend, with several manufacturers offering machines designed from the ground up for batteries rather than converted diesel models. Automation has matured from single remotely controlled loaders to fleets of autonomous machines supervised from a control room, sometimes on the surface. Telematics, tyre monitoring and payload weighing help mines manage productivity and maintenance. Collision avoidance technology is being extended and, in some jurisdictions, required.
Key Terms
- LHD: load, haul, dump, the standard underground loader concept.
- Drawpoint: an opening where ore is loaded from a stope or cave above.
- Ore pass: a vertical or steep opening down which ore is dumped to a lower level.
- Decline: an inclined ramp giving vehicle access to underground levels.
- Tramming: moving a loaded or empty machine between loading and dumping points.
- Ejector bucket: a bucket that pushes material out, used where there is little height to tip.
Frequently Asked Questions
What is the difference between an LHD and a surface wheel loader? An LHD is lower, longer and narrower, with a sideways cab and a heavy structure, so it can load and carry material in narrow tunnels. A surface loader is taller, has a better view and usually loads trucks rather than carrying material itself.
Why are battery machines popular underground? They produce no exhaust and much less heat, which reduces the amount of ventilation needed. Ventilation is a major energy cost in deep mines.
Can underground loaders be operated remotely? Yes. Line-of-sight remote control, teleoperation from a control room and automated tramming are all used, especially where operators would otherwise be exposed to unsupported ground.
How far do underground trucks travel? It depends on the mine. Trucks commonly haul over hundreds of metres to several kilometres, often up steep ramps.
What limits the size of an underground loader? The size of the mine openings, turning radii at intersections and the capacity of the ore passes and trucks it serves. Larger machines need larger openings, which cost more to excavate and support.
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