What is Topsoil #
Topsoil is the outermost layer of soil which capable of growing and supporting vegetation. It is valuable resource due to its fertility (contains roots, organic matter, and nutrients). The topsoil layer should be counted separately and will affect the cut and fill calculations.
For reference, find the sample project file below:
Where to Input Topsoil Depth #
Topsoil depth in MiTS indicates the depth of the stripped topsoil. To include the topsoil depth, go to:
- Open project > Earthwork > Input > Boundary (Create boundary)
- Boundary > Spread Input > Topsoil Depth (key in topsoil depth that needs to be stripped for that particular boundary) > Click Analyse to go into cut and fill computation methods
Comparison of the Cut Section #
From the cut section, we can see that there is a top soil layer with the calculated area indicated in cyan blue color other than the cut and fill area. From Image 3.1, the line is visibly thicker as compared to Image 3.2 due to the topsoil depth of 300 mm that we assign to the boundary.
How Topsoil Depth Effect the Cut and Fill Computation #
The earthwork cut and fill computation will be affected when topsoil depth is defined. MiTS will consider the topsoil depth in all of the three methods available to compute the cut and fill. Below are the results comparison when topsoil depth is included and not included based on each method. Note that both project file samples have the exact same platform configuration and ground level profile.
From the summary table, the three methods agree with each other that the percentage difference is only around 1-3% (read more: Discrepancy in Earthwork Volume Calculation). All three methods considered the topsoil depth and from the project sample, the cut volume reduces and the fill volume increases when topsoil depth is included. This is due to the topsoil depth being considered and the level comparison will be the ground level minus the stripping depth with the platform level.
The cut and fill contour comparison can be observed in the Image 4.4 from the sample project file. We can see that there are differences in the cut and fill area where the fill area is larger when topsoil is included and vice versa. This shows that the topsoil depth is considered when comparing levels to generate the cut and fill contour.
Conclusion #
In conclusion, topsoil depth greatly affects the earthwork cut and fill calculation. When topsoil depth is assigned to the project area, it is important to understand how the software considers the value to avoid inaccurate cut and fill computation.
