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Old 05-21-2009, 07:58 AM
kingofbotswana
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Question Road Construction - Calculating Tonnes material required

Hi Guys, busy calculating how many loads of 19mm and 9.5mm road stone I need to transport to a job site 340km away from my home. Will be able to transport 30 tonnes at a time with my truck.

OK, the road is 45KM long, 9 metres wide. In the Bill of Quantities, the 19mm stones goes on as one layer and the 9.5mm stone as another layer on top over the entire 45 KM road.

The specific gravity for the 19mm stone and 9.5mm stone ranges between 1.55 and 1.65, so lets use 1.6 as a standard to keep it simple. I need to calculate the exact amount of loads required for each type of stone to cover the entire road. These stones are spread with a chip spreader so they are basically evenly spread.

My thinking is like this, feel free to give me some insight:

1. OK, 45000 metres long road x 9 metre width x 0.019M (stone) = 7695 Cubic metres

2. 7695 Cubic metres x 1.6 SG of material = 12312 Tonnes

3. 12312 Tonnes divide by 30 tonnes per load = 410 Loads

That is my thought on the 19mm stone , now for the 9.5 mm stone:

1. 45000 metres x 9 metres x 0.0095 = 3847.5 Cubic metres


2. 3847.5 Cubic metres x 1.6 SG of material = 6156 Tonnes

3. 6156 Tonnes divide by 30 tonnes per load = 205.2 Loads

Please give me some input guys, much appreciated.

Regards

Cedric
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Old 05-21-2009, 08:40 AM
JohnS JohnS is offline
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Default Re: Road Construction - Calculating Tonnes material required

I agree with your calculation EXCEPT for step 1 in each case. I very much doubt that a single layer of each stone is an adequate base for the road.

I suggest reviewing the specifications, but I would guess the base layers need to be 0.1 - 0.2 m (each) even for a light duty road, and more if it needs a load limit suitable for heavy trucks.

Once you replace the thickness with a more suitable value, your methodology looks correct.
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Old 05-21-2009, 03:18 PM
Dirtman Dirtman is offline
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Default Re: Road Construction - Calculating Tonnes material required

Cedric:

It would be great to haul 30 T of material per truck. Here in the USA, a 23 T payload is about the max!

Although itís not part of the question, Iím assuming the material youíre moving is crushed and uniformly graded, from the max size to somewhere around 75 Ķm as the minimum.

On step 1: Adding to what John stated, are you sure this is the thicknesses of the sections? You may have superimposed the size of the rock instead of the thickness of the lift.

On step 2: One concern I have is that youíre not addressing the compaction of the material. Looks as if the specific gravities you quoted are for loose material. I donít know what material youíre using but if this is compacted density, itís really light weight stuff!

In my experience, the average densities of compacted road base is in the range of 2.16 T/m2 to 2.4 T/m2.

More information on exactly what you're doing would really be useful.

Is there a soil tech or engineer onsite you can talk to? This would be the place to start BUT . . . if you're simply trucking this for another contractor, why not let them tell you the amount to haul?
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Old 05-21-2009, 03:31 PM
Dirtman Dirtman is offline
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Default Re: Road Construction - Calculating Tonnes material required

Cedric:

Is this a chip seal operation? This would partially explain the question of lift thicknesses.

You may not call it chip seal where you are. It's applying a layer of hot liquid asphalt to existing pavement, covered by a thin layer of washed, screened aggregate, followed by another layer of hot asphalt, then a finish course of smaller, screened aggregate on top. After it cures for a few days, the remaining loose aggregate is broomed off to the side.

It's not done alot anymore as this method eats windshields.
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