Bench Height in Opencast Mining: Width, Berms and Haul Roads

Bench height in opencast mining is decided by one machine: the excavator or shovel that digs the face. DGMS permission conditions put it plainly, saying the height of a bench shall not be more than the reach of the machine used for digging, and the bench must be at least as wide as the larger of three yardsticks tied to the machines and the dumpers that use it.

That one rule explains why a village stone quarry works 5 or 6 m faces while a large coal mine can run benches two or three times higher. Same principle, bigger machine.

This guide covers what a bench is, how its height and width are worked out, what a berm is, and the width and gradient a haul road needs. It uses the published working ranges of mining-class excavators so you can see how the numbers line up. It carries no rupee figures: what changes from mine to mine is the ground and the permission, and the geometry does not.

What is a bench in opencast mining?

A bench is a flat step cut into the side of an opencast pit. An opencast mine is not dug as one deep hole with straight walls. It is worked downwards in layers, and each layer leaves a step behind, so the finished pit looks like a giant staircase. The types of mines guide explains where opencast working fits beside underground mining and quarrying.

Each step has its own parts, and mine plans and permission letters use these words all the time:

Benches exist for safety and for access. A stepped wall stops a falling stone from rolling all the way down the pit, and every step gives the machines a level place to work and a road to reach it.

What is the height of a bench in opencast mining?

The height of a bench in opencast mining should not exceed the reach of the machine that digs it. That condition appears in the DGMS permission conditions for the Sattupalli opencast coal project, reproduced in a National Green Tribunal record, which read: “The height of the benches shall not be more than the reach of the machine used for digging, excavation or removal.”

The reason is simple. If the face is taller than the bucket can reach, the top of it is left hanging. Nobody can dress it, loose rock builds up near the crest, and sooner or later it comes down on the machine or on people at the toe.

The same set of conditions adds two tighter limits that a first-time quarry owner should know:

• Soft overburden. Black cotton soil, alluvial soil and clay are to be removed only by a backhoe excavator cutting below the level it stands on, with benches no higher than 5.0 m and no narrower than 10 m.
• Weak ground. Where workings come within 15 m of a fault or other geological disturbance, benches are kept to 5 m high and at least twice the normal width.

Large mines run much taller benches because their machines reach further. Wikipedia’s article on open-pit mining gives 12 to 15 m as a general height for large mine benches. A small stone quarry working with a 20-tonne excavator sits at the other end, and its face height follows that machine’s reach.

How is bench height matched to the excavator?

Read “reach” as the figure for the way the machine actually works the face. A backhoe excavator can work a bench in two ways, and each uses a different number from its specification sheet:

• Standing on the floor and digging upwards into the face. The limit is the maximum digging height.
• Standing on top of the bench and cutting down below its own tracks. The limit is the maximum digging depth. This is the method the soft-overburden condition above calls for.

The two figures are far apart, and the gap grows with machine size. Table 2 sets them side by side for mining-class excavators.

Figures as published on each machine’s specification sheet, read in October 2026; both of the sheet’s specification sections agree for every machine listed. Working ranges change with boom, arm and bucket, so check the sheet for the exact build you are buying.

Three things stand out. First, digging height climbs from about 9.4 m on a 20-tonne machine to about 14 m on the 190 to 260-tonne class, and past 16 m on the largest. Second, digging depth hardly moves: it stays between about 6 and 9.4 m across a nearly forty-fold range of weight. So a machine that cuts down from the bench top is limited to a low bench whatever its size, and the tall benches of big mines are worked from the floor upwards.

Third, the 20-tonne class that most small quarries run has a digging height a little over 9 m. Leave a margin below that figure: a face built right up to it leaves no room for a high spot or a loose block near the crest. The guides to excavator digging depth and excavator digging reach explain how these working-range figures are measured.

Thinking of the machine for a bench of a given height? Compare live mining excavators side by side, with their working ranges, and ask a dealer for the sheet of the exact boom and arm on offer.

How wide should a bench be?

A bench must be at least as wide as the largest of three figures. Under the same DGMS conditions, the width of any bench shall not be less than:

1. the width of the widest machine working on the bench, plus 2 m;
2. where dumpers run on the bench, three times the width of the dumper;
3. the height of the bench.

Whichever of the three is biggest decides it. Here is how that works on a small quarry bench. Say the face is 6 m high, the loading machine is a Tata Hitachi EX 210 Infra 2.99 m wide, and the tippers are 2.5 m wide across the body.

Once tippers come onto the bench, their width almost always decides it. That is the point many first-time operators miss: the bench is sized for the truck as much as for the excavator. Measure your own tipper or dumper body, because widths vary by make and body type.

The excavator also has to load that tipper from where it stands. Its dumping height must clear the tipper’s side with room to spare, and the guide to excavator dumping height shows how to check it.

In big mines the treads are far wider than these minimums because the dumpers are bigger and need room to turn and pass. Wikipedia’s open-pit mining article puts large-mine benches at 20 to 40 m wide.

What is a berm in mining?

A berm in mining means one of two things, and it helps to know which one someone means.

The first is the flat step itself. Engineers often call the tread of a bench a berm, especially a step left in a finished pit wall to catch falling rock. In this sense the berm and the bench floor are the same thing.

The second is a safety bank along an edge. This is a raised bank of earth or a wall built along the outer edge of a road or bench so a vehicle cannot roll over the side. The DGMS conditions require that wherever a road sits above the surrounding ground, it has strong parapet walls or embankments not less than 1 m high. DGMS asked mines for strong, well-compacted embankments or berms for the same reason in its December 2025 safety alert, after a loaded tipper lost its brakes, rolled back and toppled on the haul road of a 3-acre stone mine in Jharkhand.

Dumps of overburden are benched as well. The same conditions say a spoil bank over 30 m high must be benched so that no single bench is over 30 m, with an overall slope no steeper than 1 m vertical to 1.5 m horizontal. The guide to overburden removal in opencast mining covers where that material comes from and how it is moved.

What gradient and width should a haul road have?

A haul road in an opencast mine should be no steeper than 1 in 16, which is a rise of 1 m for every 16 m of road, or 6.25%. The DGMS conditions allow up to 1 in 10 (10%) only on ramps over short stretches, and only with permission. DGMS repeated the 1 in 16 limit as a best practice in its August 2025 safety alert on a granite quarry in Andhra Pradesh, where a dumper ran out of control down a steep haul road and fell from the third bench to the fourth, killing two workers.

Width follows the largest vehicle using the road. Two DGMS documents put it differently, and it is worth knowing both:

The newer safety alert asks for roughly twice the older figure. Build to the wider one unless your own permission says otherwise. The older conditions also want a clear view of at least 30 m around every bend, and a separate up road and down road with a median wherever that view cannot be had.

A haul road only stays safe if it is kept smooth, drained and damp. Motor graders keep the camber and fill potholes, and water tankers keep the dust down. The guide to motor grader blade depth and reach shows how a grader cuts the drains and roadside berms.

Who decides the bench and road figures for a mine?

The figures for any one mine are set in its own approvals, so start there. The mining plan fixes how deep the pit goes and the bench heights it will use, a step covered in the quarry lease guide. DGMS then sets working conditions when it allows heavy machines and deep-hole blasting, and the mine manager is responsible for keeping to them.

The law behind these conditions is changing. The Mines Act, 1952 has been replaced by the Occupational Safety, Health and Working Conditions Code, 2020, and the regulations under the new Code decide the exact wording from here on. The physics does not change with the law: a face taller than the bucket can reach, a bench too narrow for the truck or a ramp too steep for a loaded dumper is dangerous under any rule. Check the current requirement with DGMS or your mine manager before you cut the first bench.

For the machines that work these benches, see the guide to mining equipment in India, compare mining excavators and mining dozers, and find more under mining.

Prices, specifications and features are indicative, vary by variant, location and date, and should always be confirmed with the official OEM or authorised dealer before any purchase decision. DesiMachines is not liable for decisions taken on the basis of information that may have changed after publication.

References: DGMS (Hyderabad Region) permission and conditions for working Sattupalli Opencast Project-I with heavy earth moving machinery, 2005, Part I clauses 1.1, 1.2, 1.6, 1.7, 3.1 and 4.1 to 4.5, as reproduced in a National Green Tribunal record. DGMS Safety Alert 20 (22 August 2025) and Safety Alert 36 (4 December 2025). Wikipedia, Open-pit mining. Machine figures are taken from the specification sheets published against each machine.