Gravel Roads - Gravel Roads - Design and Design and Maintenance Maintenance Original Presentation for National ASCE Original Presentation for National ASCE Webinar Webinar Presented by Presented by : : Ken Skorseth, Program Manager Ken Skorseth, Program Manager SD Local Transportations Assistance SD Local Transportations Assistance Program (SDLTAP) Program (SDLTAP) South Dakota State University South Dakota State University
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Gravel Roads - Design and Maintenance Original Presentation for National ASCE Webinar Presented by : Ken Skorseth, Program Manager SD Local Transportations.
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Gravel Roads - Gravel Roads - Design and Design and
MaintenanceMaintenanceOriginal Presentation for National ASCE Original Presentation for National ASCE
WebinarWebinarPresented byPresented by::
Ken Skorseth, Program ManagerKen Skorseth, Program Manager
SD Local Transportations Assistance Program SD Local Transportations Assistance Program (SDLTAP)(SDLTAP)
South Dakota State UniversitySouth Dakota State University
Note: Total roadway width includes the width of both traveled way and shoulders.
Guidelines for Total Roadway Width for New Construction of Very Low-Volume Local Roads in Rural Areas
From: AASHTO – Guidelines for Geometric Design of Very Low-Volume Local Roads (ADT <400)
Major Access road classification requires only 18 ft. (5.5 m) roadway width at 40 mph (64 km) design speed
Design Issue – Crown:
An important design issue is crown on gravel road surfaces. Generally recommended crown for gravel surfaces is 4% which is double the crown used in pavements.
Clear illustration of 2% crown on road to the left and 4% on the road to the right. Water will not drain off an aggregate surface with only 2% crown. This must be addressed in design and during construction.
Design Issue – Crown: (con’t)There are conflicting views on crown:
•2 to 6% for “low-type pavements” recommended by AASHTO Green Book pg 387 – 2001 edition.
•The FHWA Gravel Roads Manual recommends crown at or near 4%.Note: in arid and semi-arid regions, gravel roads may perform with less crown, but don’t use less than 3 %.
Gravel Rds Maint & DesignGravel Rds Maint & DesignValue of Quality Surface Value of Quality Surface GravelGravel Less corrugation (washboard)Less corrugation (washboard)
Less loose aggregate Less loose aggregate accumulating between wheel accumulating between wheel paths and on shoulderpaths and on shoulder
Less blade maintenance needed to Less blade maintenance needed to keep road in good conditionkeep road in good condition
Less dustLess dust
Less public complaintLess public complaint
Gravel Rds Maint & DesignGravel Rds Maint & DesignA Current SDDOT Research A Current SDDOT Research Project Comparing Surface Project Comparing Surface Gravel QualityGravel Quality Three test sections have been Three test sections have been
constructed.constructed. Each test section has three surface Each test section has three surface
materialsmaterials1.1. Substandard, but commonly usedSubstandard, but commonly used
2.2. Meets SD Standard Specification for Meets SD Standard Specification for Gravel Surfacing – low percentage passing Gravel Surfacing – low percentage passing #200 (#200 (75 µm) sieve and low plasticitysieve and low plasticity
3.3. Modified Specification having minimum Modified Specification having minimum 10% passing the #200 (10% passing the #200 (75 µm) sieve and sieve and minimum plasticity index of 7minimum plasticity index of 7
When gravel road geometry When gravel road geometry and material quality are and material quality are understood and well managed, understood and well managed, stabilization may be the next stabilization may be the next step when paving is not step when paving is not feasible.feasible.
A gravel road stabilized with liquid MgCl2 in Meade County, SD. No blade maintenance was been done between construction in summer of 2011 and retreatment in July 2012!
How do How do you move you move it legally it legally on a state on a state or federal or federal
hwy?hwy?
General principles for managing gravel roads can be found in the FHWA Gravel Roads Manual. It can be found online by searching for “Gravel Roads Manual”