Construction Layout & Staking Flashcards

A vertical curve is needed to connect a +3.50% grade to a −2.00% grade. If the curve length is 600 ft, what is the algebraic difference in grades (A)?

Answer: 5.50%

A = g2 − g1 = −2.00% − (+3.50%) = −5.50%, and the absolute value |A| = 5.50% is used in design calculations.

During culvert layout, the surveyor must set the flow-line elevation at the inlet. The design calls for the culvert to have a 0.5% grade over a 120-ft run. What is the elevation difference between inlet and outlet?

Answer: 0.60 ft

Elevation difference = grade × length = 0.005 × 120 = 0.60 ft, so the outlet is 0.60 ft lower than the inlet.

A contractor requests the surveyor to set grade stakes for a parking lot at a 50-ft grid. What is the most efficient instrument to use for this task?

Answer: Automatic level with a rod and grade sheet

An automatic level is the most efficient instrument for setting a large number of grade stakes on a flat parking lot grid where only elevations are needed.

In tunnel surveying, gyroscope attachments or gyrotheodolites are used primarily to:

Answer: Maintain directional control independent of magnetic interference and surface control

Gyrotheodolites determine true north by sensing Earth's rotation, providing azimuth independent of magnetic fields and without needing line of sight to surface control.

A horizontal curve has a radius of 1,200 ft and a delta angle of 24°30'. What is the tangent length (T)?

Answer: 261.5 ft

T = R × tan(Δ/2) = 1200 × tan(12°15') = 1200 × 0.21736 ≈ 260.8 ft, approximately 261.5 ft.

What staking method is used when a design point falls in an inaccessible location such as a pond or existing structure?

Answer: Set witness stakes at measured offsets from the design point in two or more directions

Witness stakes are placed at known offsets from an inaccessible design point so the point can be reconstructed by measuring back from the witnesses.

When staking a sewer line by the invert method, the cut noted on the stake refers to:

Answer: The depth from the top of the stake to the pipe invert elevation

In sewer staking, 'cut' is the vertical distance from the top of the offset stake to the design pipe invert, telling the excavator exactly how deep to dig.