Written from the quarry floor

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GSB Grading I to VI as per MoRTH Clause 401

Six gradings, one table, and a sentence in the clause that decides which of them your drawing is allowed to use. This is the table, and what it means at the plant.

11 min read

10mm, 20mm and 40mm Aggregate: Where Each Size Goes

The size on a delivery challan is a name, not a measurement. What the sieves allow inside a load of 20mm, and which layer or mix each size is made for.

10 min read

Aggregate Weight: Converting Cubic Metre, CFT and Brass to Tonnes

The unit conversions are exact. The density is not, and that is where a brass of 20mm turns into anything from four tonnes to four and a half.

9 min read

Choosing an Aggregate Supplier for a Highway Package: A Vendor Checklist

The rate is the easiest thing to compare between suppliers and the least likely to be what goes wrong. These are the checks that decide whether the stone arrives, passes and can be paid for.

11 min read

Crusher Dust vs M-Sand vs River Sand

All three pass a 4.75 mm sieve. Only one of them is made on purpose. What separates the by-product from the product, and where the by-product is the better buy.

10 min read

GSB vs WMM: The Difference, Layer by Layer

Both are grey, both arrive in tippers and both are rolled to 98 per cent. Almost everything else about them is different, starting with what each one is there to do.

10 min read

How Much Aggregate Does One Kilometre of Four-Lane Highway Need?

About 28,000 tonnes of crushed stone goes into the pavement of one kilometre, on the section assumed here. The method is worth more than the answer, because your drawing will not match this one.

12 min read

Lead Distance: Why a Delivered Aggregate Rate Moves with Every Kilometre

Two suppliers make the same stone for much the same money and deliver it at very different rates. The difference is lead, and most of it can be worked out before anyone picks up a phone.

11 min read

The Layers of a Highway Pavement, from Sub-grade to Wearing Course

Every layer has a clause, a job and a stockpile at the crusher that feeds it. Read from the bottom up, the way a road is built.

10 min read

WMM as per MoRTH Clause 406: Grading, Mixing and Laying

One grading envelope, nine sieves, and a mixing plant the clause describes part by part. What Clause 406 asks of wet mix macadam, and where the layer usually goes wrong.

11 min read

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Own a Crusher or Contract the Crushing? The Per-Tonne Arithmetic

What a crusher costs per tonne is decided less by the price of the plant than by how many tonnes it makes while it is yours. This is the arithmetic without the rupees, so you can put your own in.

12 min read

Licences and Clearances a Stone Crusher Needs in India

There is no single stone crusher licence in India. There is a file of permissions from several different offices, and a plant can be stopped for want of any one of them.

12 min read

Mobile vs Stationary Crusher Plants for Road Projects

A track-mounted crusher is working within hours of coming off the trailer. A fixed three-stage plant takes a fortnight. Which one a road needs depends on how many tonnes a month it wants, and how exactly they have to be graded.

10 min read

Setting Up a Stone Crusher Plant on a Highway Site, Week by Week

About a month separates an order from steady production if the site cooperates. This is what fills that month, in the order it has to happen, and the things that stretch it.

11 min read

What TPH Crusher Plant Does a Highway Package Need?

Multiply TPH by hours and days and you get a number no plant has delivered for a season. This is what the rating means, where the hours go, and how to size a plant from the programme instead of the brochure.

10 min read

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Jaw, Cone and VSI: What Each Stage of a Crusher Plant Does

A 700 mm boulder and a 10mm chip are seventy times apart. No single crusher covers that gap, and each machine in the line is there because of something the one before it does badly.

12 min read

Aggregate Tests for Highway Work and Their MoRTH Limits

A quarry becomes a source when a file of test certificates says so. These are the limits for each pavement layer, the IS code behind each test, and what each number is really predicting about the road.

11 min read

Basalt, Granite, Limestone, Sandstone: Which Rock Makes Good Road Aggregate

The specification never names a rock. It names tests, and each of the four common quarry rocks in India passes some of them easily and fights with others.

11 min read

Flakiness and Elongation Index: Limits, Test and How a Plant Fixes It

Two gauges, one added-up number, and a limit of 35 per cent that most highway layers share. What the test measures, how MoRTH combines the two indices, and what a plant changes when the result comes back high.

11 min read

Jaw Plates and Cone Liners: What Decides Wear Life

Manganese steel gets harder the more it is hit, which is why the same jaw plate lasts twice as long on one site as on another. What wears, what speeds it up, and when a set should come out.

11 min read

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Opening a Stone Quarry: From Lease to First Tonne

The ground work takes weeks. The paper that lets it begin takes months, and the order the two are done in decides whether a plant ever stands idle beside a face nobody may work.

12 min read

Bench Height, Width and Slope in a Stone Quarry

The regulation gives a hand-worked quarry a number and a mechanised quarry a permission. Everything else about a bench follows from the drill, the excavator and the rock.

11 min read

Overburden Removal and the Stripping Ratio

A quarry sells rock and digs soil. How much soil lies over each tonne is the one figure in the rate that cannot be seen from the road, and it is settled before the first blast.

11 min read

Quarry Lease, Royalty, DMF and Transit Pass: Minor Mineral Paperwork Explained

A load of stone is only as legal as the pass travelling with it. This is the paper behind a tonne of aggregate, who issues each piece, and what it proves when a bill is being checked.

11 min read

Running a Quarry and Crusher Through the Monsoon

Rain does not stop a quarry in one place. It takes a little from every link between the face and the road, and the plan that limits the loss is made in the dry months.

12 min read

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Blast Hole Drilling: DTH, Top Hammer and Wagon Drills Compared

Five ways of putting a hole in rock, and only three or four of them belong on a stone quarry. What separates them is where the hammer sits and how much of its blow reaches the bit.

11 min read

Blast Hole Deviation: What a Crooked Hole Costs

A blast design assumes every hole is where the drawing put it. The bench is under no obligation to agree, and the difference is paid for in boulders, toe and flyrock.

11 min read

Burden, Spacing and Sub-drilling: How a Drilling Pattern Is Set Out

Six numbers describe a bench blast before a kilogram of explosive is ordered. All six hang off the hole diameter, and all six are starting points that the first shot corrects.

11 min read

Compressor Air and Bit Selection for Blast Hole Drilling

A drill rig turns diesel into compressed air and compressed air into a hole. The bit is the only part that touches rock. Most slow drilling traces back to one or the other.

11 min read

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Controlled Blasting Techniques: Pre-splitting, Smooth, Cushion and Muffled

Controlled blasting is not one method. It is a family of them, each controlling a different thing, and a contract that says only "controlled blasting" has not yet said which.

12 min read

Blast Vibration Limits in India: The DGMS PPV Table Explained

One table of fifteen numbers, issued by DGMS in 1997, decides how much explosive may go off in one instant near a house. The row is chosen by the building. The column is chosen by the ground.

12 min read

Explosives Licences, Magazines and Shotfirers: Who Needs What

Two regulators, two sets of rules, and one question a principal contractor has to be able to answer: who on this site is allowed to hold explosives, move them and fire them.

11 min read

Flyrock: Causes, the Danger Zone and How a Blast Is Kept Inside It

Vibration cracks plaster. Flyrock kills people. The regulations draw a circle around every shot for that reason, and the blast design exists so that nothing reaches its edge.

12 min read

Fragmentation: Why Crusher Output Is Decided at the Face

A crusher plant's hourly output is usually blamed on the plant. More often it was fixed a day earlier, by a drilling pattern and a delay sequence at the far end of the haul road.

10 min read

Powder Factor: Explosive per Tonne, and What It Tells You

One number is supposed to say whether a blast was cheap or dear. It can, if you know which way round it was quoted and what the rock did when it reached the crusher.

10 min read

Rock Breaker or Blasting? Choosing for Rock Excavation on a Highway

The choice is rarely free. Distance to the nearest house, the classification in the contract and the months left in the programme usually make it before the contractor does.

11 min read

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Embankment Construction as per MoRTH Clause 305

Two tables and a short list of banned soils decide whether an embankment layer is accepted. This is what Clause 305 asks of the borrow area, the grader and the roller, in the order the work happens.

12 min read

Cut and Fill: Balancing Earthwork with a Mass Haul Diagram

Earthwork is measured once on the cross-sections and paid for again in tipper hours. The mass haul diagram is the page that shows where each cut should go, and rock from a cutting is the part of it worth most.

11 min read

OMC, MDD and the Field Density Test

Two laboratory numbers and one hole in the ground decide whether a layer of earthwork is accepted. This is how each is found, and how the hole goes wrong.

12 min read

Sub-grade: CBR, Compaction and Why Pavements Fail from Below

The sub-grade is 500 mm of soil that nobody sees again once the GSB goes down. Its CBR sets the thickness of every layer above it, and its density decides whether those layers stay where they were laid.

11 min read

Which Roller for Which Layer: Smooth, Vibratory, Padfoot and Pneumatic

A roller is chosen by what the layer is made of and how thick it is. Most density failures begin with the wrong drum on the right soil. One table first, then the MoRTH numbers that sit behind it.

11 min read

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Tipper Capacity in Tonnes and Cubic Metres: 6, 10, 12 and 16 Wheelers

A tipper has two capacities: the tonnes its registration certificate allows and the cubic metres its body will hold. With crushed stone the first runs out long before the second.

11 min read

How Many Tippers? Cycle Time and Fleet Sizing for a Haul

The number of tippers a haul needs falls out of one figure, the cycle time, and most of the cycle is decided by the lead and the road before a single driver is hired.

11 min read

Moving a Crusher Plant Between States: Low-beds, ODC Permits and Sequence

A three-stage plant comes apart into trailer loads of steel, and a few of them are wider, taller or heavier than a public road allows without permission. The move is planned backwards from the order the plant goes up in.

11 min read

Quarry Haul Road Design: Gradient, Width and Why It Pays Back

The haul road is the one part of a quarry that every tonne crosses twice. Its gradient and width are safety matters with DGMS numbers attached. Its surface is a cost matter that turns up in tyres, diesel and cycle time.

12 min read

HAM, EPC and BOT: What Each Highway Contract Model Means for Material Supply

The contract model decides who is paying for the road, when the money arrives, and how long somebody answers for the result. All three reach the quarry.

10 min read