Road Construction Techniques/Unstable Terrain RRET 3275

Upon successful completion, the student will be able to:

Module 1 - Introduction

• Describe the current needs for improvement of road engineering and construction in potentially unstable terrain.
• Define the terms instability, erosion, and landslide and their associated synonyms.
• Explain the landslide-erosion continuum.
• Discuss the various types and characteristics of erosion including sheet erosion, rill erosion, gully erosion, and channel erosion.
• Describe the effect of slope gradient and flow depth on water velocity and transport capability.

Module 2 - Typical Problems and Impacts

• List the three primary factors that contribute to increased driving forces on a slope and describe their effect.
• List the factors that contribute to decreased resisting forces on a slope and describe their effect.
• Discuss the primary errors in road construction practice that lead to landslides and erosion.
• Discuss the primary errors in water management that lead to landslides and erosion.
• Discuss the factors that cause a delay or time-lag in the formation of unstable slope conditions.

Module 3 - Field Indicators of Slope Instability

• Identify the most common slope features and shapes that could be associated with actual or potential instability.
• Explain how these potentially unstable slope features likely developed.
• Identify the most common characteristics of vegetation that could be associated with actual or potential instability.
• Explain how these potentially unstable characteristics likely developed.
• Discuss what field evidence of groundwater can be obtained, even in cases where the water is only present periodically.

Module 4 - Route Selection Methodology

• List the primary steps employed in the route selection methodology.
• Explain the uses and limitations of terrain stability mapping.
• Explain how stability issues are integrated into other aspects of Total Chance planning in developing tentative routes.
• Describe how corridor-specific stability assessments are conducted by geotechnical professionals.
• Define the word hazard and explain how it relates to risk.
• Define the word risk and how it relates to hazard and consequence.
• Explain how risk assessment results should be integrated into the planning process.

Module 5 - Construction Techniques without Reinforcement

• Explain the key geometric factors that determine the feasibility of constructing a stable road prism.
• Describe at least three of the most common construction techniques that can be used on uniform slopes.
• Explain how compaction increases the stable slope angle of soil.

Module 6 - Construction Techniques with Reinforcement

• Describe the utility and potential failings of the use of wood in fill for temporary roads.
• List the various types of geosynthetics and describe their primary uses in slopes and retaining walls.
• Describe the uses and limitations of using trees and shrubs in stabilizing slopes.
• Identify the principal types of retaining walls and the general practicability of using each.

Module 7 - Construction Techniques in Rock

• List proper blasting techniques used in the construction of forest roads.
• Explain some of the negative impacts that come from overblasting.
• Describe the most common techniques used in stabilizing rock slopes.
• Describe effective ways of protecting a road from the impacts of rockfall.

Module 8 - Gully Construction Techniques

• Explain the difference between a debris torrent and a water flood and identify channel features that would suggest the dominance of either.
• Discuss the various ways to construct and protect fills within gullies.
• Discuss the pros and cons of using bridges, culverts or fords in specific gully situations.
• Discuss the primary considerations when specifying the use of a ford.
• Discuss the primary considerations in placing bridges in gullies.
• Identify and discuss the primary considerations when placing a culvert in a gully fill.

Module 9 - Drainage Control to Prevent Landslides

• Explain how controlled water can initiate landslides.
• Describe the primary alternatives for controlling water to prevent landslides.
• Discuss the key and sometimes conflicting considerations in locating culverts to minimize both erosion landsliding.
• List the primary reasons why culverts fail.
• Discuss practical ways to prevent the blockage of culverts.
• Discuss practical ways of preventing decoupling.
• Discuss the various considerations in determining where to place a culvert to minimize downslope impacts.
• Explain how water spilling onto an armoured fill slope can, in some cases, result in a fill slope failure.
• Discuss the ways to convey water past a sloughing slope.
• Discuss road grading requirements at gully crossings that prevent water avulsion.

Module 10 - Landslide Stabilization

• Define the neutral axis of a landslide and explain its significance in landslide rehabilitation.
• Explain the primary alternatives for supporting the toe of a landslide.
• Explain the primary alternatives for unloading the head of a landslide.
• Explain the primary alternatives for draining water away from a landslide.

Effective as of Fall 2003