Question 1

Which of the following is a type of a retaining wall system?&#10;A)Cantilever&#10;B)Tied-back&#10;C)Soil nailing&#10;D)All of the above

Accepted Answer

Cantilever, tied-back and soil nailing are all types of retaining wall systems. Retaining walls systems are used to hold back the earth and maintain a difference of ground surface elevations. Generally, the cost to construct a retaining wall system is usually higher than the cost to form a new slope. As such, a retaining wall system should be used only when it is cost-effective, and the retained soil height should be kept as low as feasibly possible.

Question 2

A retaining wall system can be classified according to three factors. Which of the following is not generally considered as a classification factor?&#10;A)System rigidity&#10;B)Construction method&#10;C)Situational use&#10;D)Load support mechanism

Accepted Answer

Situational use is not generally considered as a classification factor for a retaining wall system. The common classification factors are as follows:
• System rigidity - rigid or flexible walls
• Construction method - fill or cut walls
• Load support mechanism - external or internal stabilized walls

Question 3

Which of the following earth retaining wall systems is generally considered to be rigid?&#10;A)Gravity walls&#10;B)Braced&#10;C)Cantilever&#10;D)All of the above

Accepted Answer

Gravity walls are generally considered to be rigid. Rigid walls move as a unit in rigid body rotation and do not experience bending deformation. Flexible walls are designed so that lateral pressures are redistributed from flexible portions of the wall to stiffer portions of the system when they experience bending deformations.

Question 4

Which of the following statements applies to support of excavation (SOE) temporary earth support systems (ERS)?&#10;A)Life cycle is based on actual project conditions&#10;B)Commonly designed to less restrictive criteria than permanent systems&#10;C)Design is typically based more on system stability than minimizing ground movements&#10;D)All of the above

Accepted Answer

All of the statements listed apply to support of excavation (SOE) temporary earth support systems (ERS). The life cycle of an SOE temporary ERS is commonly stated to be 18-to 36-months; however, the life cycle is dependent on the actual timeline to construct the ERS permanent system. The design of SOE systems is usually assigned to contractor that is installing the permanent system.

Question 5

Which of the following is not considered to be a lateral earth pressure that an earth retaining system (ERS) is typically designed to resist?&#10;A)At-rest&#10;B)Active&#10;C)Passive&#10;D)Aggressive

Accepted Answer

Retaining wall systems are not typically designed to resist "aggressive" lateral earth pressure. At-rest earth pressure exerts no lateral deformation on an ERS. Active earth pressure develops as an ERS moves away from the backfill or retained soil. Passive earth pressure develops as an ERS moves towards the backfill or soil it is retaining.

Question 6

In the cases of active and passive lateral earth pressure acting on a retaining wall, the failure zone is typically bounded by the failure surface of the retained soil mass and which of the following points?

A)Back face of the wall
B)Failure wedge
C)Top of the wall
D)Not enough information provided

Accepted Answer

The failure zone is created by active and passive lateral earth pressure acting on a retaining wall is typically bounded by the failure surface of the retained soil mass and the back face of the wall. The failure surface of the retained soil mass is along the plane at which the soil has attained limiting equilibrium. The distribution of active and passive lateral pressures is assumed to be triangular, and the impact of the pressures can be calculated using Coulomb's method.

Question 7

Which of the following measures is taken to minimize frost-related stresses that may develop behind earth retaining systems that hold back fine-grained soils?&#10;A)Install permeable drainage system or impervious barrier to isolate backfill from groundwater&#10;B)Use pervious backfill and install weep holes in retaining structure&#10;C)Provide an impervious soil layer near the ground surface and direct surface water away from structure&#10;D)All of the above

Accepted Answer

All of the measures listed above can be taken to minimize frost-related stresses that develop behind earth retaining systems that hold back fine-grained soils. Lateral pressures caused by the volume expansion of ice in fine sand, silt, and clay are difficult to predict. Because the volume expansion of the retained soil can result in significantly high pressures, structures in frost-potential areas should be designed to minimize the impact of icing damage.

Question 8

Which of the following measures are commonly used to reduce the impact of swelling pressure from expansive clay soil that may be present behind a retaining wall?&#10;A)Treat soil with lime&#10;B)Use granular filter material between clay backfill and back of wall&#10;C)Excavate and replace soils with acceptable borrow material&#10;D)All of the above

Accepted Answer

The impact of expansive clay swelling pressure that may be present behind a retaining wall may be reduced by treating the expansive clay soil with lime, using granular filter material between the clay backfill and the back of the wall, or excavating and replacing soils with acceptable borrow material.
The use of a granular filter material will allow groundwater to be drained from the soil and act as a buffer between the soil and the wall. Lime can be used to reduce the swelling potential of expansive soils only if the soil does not contain gypsum. If the soil contains gypsum, the addition of lime may lead to the formation of ettringite - a material with a much greater welling potential than untreated expansive soils.

Question 9

Which of the following is not considered to be a vertical surface load that may be applied over a limited area of an earth retaining system?&#10;A)Shape&#10;B)Strip&#10;C)Line&#10;D)Point

Accepted Answer

A "shape" load is not considered to be a vertical surface load that may be applied over an earth retaining system. Examples of vertical surface loads are as follows:
- Strip: roadway
- Line: railway track
- Point: traffic signal support structure

Deck 1: Earth Retention