Cut and fill volumes kept apart, with the bulking that decides how many trips leave site.
Foundation, roof and structure. 5 questions answered below, each with the arithmetic behind it and the limits of what the tool decides. Open the Earthworks Cut and Fill tool.
Cut and fill is the discipline of moving soil from where there is too much to where there is too little. The two volumes are calculated separately, because they behave separately: soil dug out of the ground gains volume, and soil placed and compacted loses it, so a site that balances on paper rarely balances in a lorry. The calculator computes cut from the areas and depths you enter and fill from the areas and depths you need, then applies bulking to the cut and compaction to the fill so the two can be compared honestly. Where they do not balance, the difference is a quantity of soil that has to be imported or removed, and that is the number the earthworks budget actually turns on.
A site with a hundred and twenty cubic metres of cut and ninety of fill does not have thirty cubic metres spare. At a bulking factor of one point two five the cut is a hundred and fifty loose, and at a compaction factor of zero point nine the fill needs a hundred in its placed state, so the surplus is fifty cubic metres to remove rather than thirty. At eight cubic metres a lorry that is seven loads, not four. The two factors are what turn a balanced site into a haulage order.
Area multiplied by depth for each excavation and each area to be raised, then adjusted for how soil behaves when it is moved. The calculator takes each area and depth you enter, sums the cut and the fill separately, and applies bulking to the former and compaction to the latter. What it will not do is assume a factor: both are inputs, because they vary with the soil and the method.
Because excavated soil occupies more space than it did in the ground, and compacted fill occupies less. Adding the two raw volumes and subtracting one from the other produces a balance that no lorry can achieve. Keeping them separate lets each be adjusted by its own factor, and the difference between them becomes a real quantity of soil to import or remove, which is the number the haulage is priced on.
Bulking accounts for the increase in volume when soil is disturbed, which is why a cubic metre of cut becomes more than a cubic metre in a lorry. Compaction accounts for the reduction when fill is placed in layers and rolled, which is why a cubic metre of fill needs more than a cubic metre of loose material to achieve it. Both are properties of the soil and the method, so both are yours to enter rather than defaults the tool invents.
Haulage is calculated from the volume to be moved and the capacity of the vehicle you enter, in loads. What is not included is the distance, the rate per load or the time, because those are commercial terms rather than quantities. You get the number of loads, which is the figure a haulier quotes against, and the surplus or deficit that decides whether they are taking soil away or bringing it in.
No. It is a volume calculation for a site whose levels have been designed. Soil classification, bearing capacity, slope stability, groundwater and contamination are geotechnical questions, and the factors you enter are assumptions that a geotechnical assessment would confirm or correct. Use the takeoff to price the movement you have designed, and use a geotechnical engineer to decide what can be moved and where it can go.