HOW TO ESTIMATE AMOUNT OF FILL REQUIRED

WHAT IS FILL?

First of all we need to understand the term  fills as used in construction industry.

Fills these are earthen materials that are used to artificially raise the existing ground to a required level these can be dirty fill (soil fill), aggregates, rocks or crushed paved blocks.

Hardcore fill Used as road bed to reduce capillary rise of water.

USES

1. They are used to fill a dug hole or depression.

2. They are used to raise the existing ground level to a required one e.g fills in low laying grounds, fills as road layers.

Soil Fill used as a road subgrade layer

WHY WE NEED TO KNOW HOW TO CALCULATE ITS VOLUME PRIOR AND DURING CONSTUCTION

1. Help in preparation the unit cost of materials that used in determination of unit rate of work during bidding a tender.

2.Help to know number of trucks required to bring fill to site.

3. Help to amount of material required for a unit work during construction at site.

HOW TO CALCULATE REQUIRED MATERIALS

1. Knowing important data

In fill material estimation first we need to have the following data

      a). Type of fill material to be used.

Each type of fill material has its own behavior on loading/compaction that is, it has its own degree/ percentage of reduction.

Let's say we are going to use soil as the fills material, soil as fill material mostly has tendency to  produce loose soil of about 1.25m3, when excavated from 1.0m3 hole, but when filled back and compacted its volume can become 0.9 m3.

      b). Coverage area of land to be filled.

This is the area to which the hole or depression occupies, which can be of regular or irregular shape.

      c). Excavation depth.

This is depth of hole/depression to be filled or depth of overlaying layer on the existing ground.

2. Amount of fill estimation 

After having important parameters for fill estimation, now we can start estimating amount of fill required.

 Amount of fill = Coverage area x depth of hole.

For example.

You are required to estimate amount of backfill material required to fill the classroom space to a hardcore level, where by classroom of 8m long and 6m wide, measured depth to be filled is 500mm to a floor level, Specification: fill material is soil, the soil is compacted in 2 layers below hardcore level.

Solution.

Amount of fill material to be used can be calculated as follows.

Amount of fill = coverage area x depth to be filled

                          = (8m x 6m) x 0.5m

                          = 48m2 x 0.5m

                          = 24m3

This amount of fill material we got here is loosen volume of fill, we need to find compacted volume of fill.

Compacted Volume = Loosen volume x Compaction factor.

For soil as fill material we normally use compaction factor of about 1.25 to 1.30 that's means there can be reduction of about 25% to 30% due to compaction and wastage, so this 25% to 30% is there to take account of reduced amount.

Compacted volume of fill = 24m3 x 1.30

                                               = 31.2m3