LARE Grading and Earthwork Flashcards

A designer specifies a 4:1 (H:V) slope for a graded embankment in a residential project. What percentage grade does this represent?

Answer: 25%

Grade % = (vertical rise ÷ horizontal run) × 100 = (1 ÷ 4) × 100 = 25%.

Which of the following correctly describes the prismatoid formula for earthwork volume calculation, and when is it preferred over the average end area method?

Answer: It uses the middle cross-section area and is more accurate when end areas differ significantly

The prismatoid formula incorporates the middle cross-section area (V = L/6 × (A1 + 4Am + A2)) and is more accurate than average end area when end areas differ significantly.

A landscape architect needs to establish finish floor elevation (FFE) for a building pad. The 100-year flood elevation is 215.5 feet. Per best practice, the FFE should be set at a minimum of:

Answer: 216.5 ft (1 foot above base flood elevation)

FEMA and most local floodplain regulations require the FFE to be set at a minimum of 1 foot above the base flood elevation (BFE) for freeboard.

During construction observation, you notice that fill is being placed in lifts that are 18 inches thick before compaction. The specification requires 8-inch maximum compacted lifts for structural fill. The correct course of action is:

Answer: Stop work and require the contractor to comply with the lift thickness specification

Lift thickness directly affects the ability of compaction equipment to achieve uniform density throughout the layer; exceeding the specified lift thickness requires stopping and correcting the work.

Two contour lines on a grading plan are spaced very close together. This indicates:

Answer: A steep slope or abrupt grade change

Closely spaced contour lines indicate a steep slope because the same vertical interval is covered over a short horizontal distance.

A grade break occurs where a 4% slope meets a 1% slope on a paved driveway. To provide a smooth transition for vehicles, a designer should:

Answer: Use a vertical curve to blend the grade change over a minimum distance

Vertical curves smooth the transition between different slopes, preventing abrupt grade breaks that can scrape low-clearance vehicles.

What is the primary purpose of a subdrain (French drain) installed in a graded fill slope?

Answer: To intercept and remove subsurface water from the fill mass, preventing hydrostatic pressure buildup

Subdrains intercept groundwater moving through the fill, relieving hydrostatic pressure that could cause slope failure or wall movement.