Tips For Calculating Appropriate Measurements For Earthworks
For earthwork companies, an accurate estimate of the volume of earth moving is a key to survival. Without an exact cost estimate, the contractor has little or no chance of submitting an exact offer, let alone a successful offer. Removing an accurate estimate of the earthworks volume, the contractor will not be able to correctly assign construction facilities or create a project schedule.
Estimating the construction of earthworks requires many assumptions and unknowns. For this reason, this part of the construction project represents the greatest financial risk for the contractor. The construction work involves lives of many innocent people. Hence the work must be done with utter care with the calculations and estimations.
Minimizing the source of Error
An earthwork estimate is only as good as the location information used as the basis for the estimate.
- No appraiser should ever calculate an earthwork volume without physically exploring as much of the construction site as possible with a copy of the movement plans in hand.
- Even in the age of Computer Aided Design and Drawing (CADD) and Global Positioning Systems (GPS) there is no substitute for old-fashioned construction site detection:
- Contractors keep finding that construction site plans and surveys are sometimes wrong was carried out during the survey or the location has been physically changed since the last survey.
- To correct these errors, the estimator must refer to the surveyor's source, the reference points, and ensure that they are still valid. It is necessary to closely inspect a site.
However, it may be acceptable to use location-specific local "landmarks". A document search related to the excavation site is also essential and should be done during the first phase of the survey.
Using proper equations for calculations
It is very important to properly calculate the earthwork before starting any procedures. Before volumes can be calculated, excavation areas must be determined, either horizontally or vertically. The horizontal surfaces are linked with cross-sections through the volume of the earth structure and the vertical surfaces with the volumes of the digital terrain model (DTM). Either the extent of the excavation area and the horizontal areas should be enclosed by contour lines.
The areas are calculated by connecting these points in a series of continuous triangles that extend through the area. To the north and east of each of the three corner points of each triangle and the length of each of the three sides of the triangles, the area of each triangle can be calculated as follows:
A = sort[s * (s - a) * (s - b) * (s - c)]
Where, A = the area of the triangular area (square feet) a, b, c, = the lengths of the three sides of the triangle (feet) s = (a + b + c) / 2.
Use of Anecdotes
Insight family of software users include Landmark Enterprises of Auburn, NY. Recordings from CADD files make it easy to stakeout critical stakeout points. Associated Field General software guides the observer precisely to each referenced viewpoint. Around a location, a continuous display of surface data (present, suggested, depth of cut, subsurface height, depth of cut or fill, strata layers, etc.) is shown on the screen. As of the prism pole, it leads to very quick measurements and staking out locations.
Now, a contractor does not have to account for every shovel of earthworks. For most jobs, small errors in cutting and stuffing will, on average, make next to nothing. And given the inherent inaccuracies in terrain and air surveys, a small difference in altitude can be a useful survey is a survey that enables a DTM to be performed in accordance with current precision standards.
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