Constructing a roadway embankment over uneven terrain requires precise leveling to ensure stability and proper drainage. Surveyors use a leveling instrument and staff to calculate ground elevations and determine the required fill material at each point along the embankment alignment.
The process begins by positioning a leveling instrument near a benchmark with a known elevation. A backsight reading establishes the instrument height, which serves as a reference for subsequent measurements. A foresight reading is then taken on the leveling staff at the first point along the alignment to measure the difference in elevation. Sequential backsight and foresight readings are repeated to create a profile of ground elevations.
The required fill material at each location is calculated by subtracting the measured ground elevation from the target embankment height, set at 3 meters. If the leveling instrument is moved, the last calculated point is used as a temporary benchmark to re-establish the instrument height at the new position.
This systematic process ensures the embankment follows the intended height and gradual slope, preventing drainage and stability issues. Adhering to these methods guarantees accurate elevation control, enabling the embankment to meet design and safety standards.
A roadway embankment is planned across uneven ground, requiring a height of 3 meters above the current surface with a gradual slope.
To begin, set up a leveling instrument near a benchmark with a known elevation and record the backsight reading to establish the instrument's height.
Then, move the leveling staff to the next point along the embankment and record the foresight reading to measure the change in elevation from the starting point.
Take foresight readings on a leveling staff at each point to determine existing ground elevations.
Calculate the required fill material at each point by subtracting the ground elevation from the target embankment height.
When moving the instrument to continue measurements, use the last calculated point as a temporary benchmark to re-establish the instrument’s height. Repeat the process along the embankment.
At the endpoint, confirm that the elevation aligns with the intended height specified by the design’s slope requirements.
This method ensures a uniform slope across the embankment, which helps improve stability and prevent water drainage issues.
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