Pothole Formation on Unpaved Roads

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Water is the biggest contributor to the deterioration of unpaved roads. Regardless whether it seeps in from above or below, water simply destroys roads. Besides rutting and eroding away an unsealed road surface, water causes the development of potholes.

Problems with an unpaved road can quickly develop if there is no properly shaped crown and drainage ditches to shed rainwater. High shoulders, if present will further add to the problem. Without proper drainage, water can collect on the road surface during rain events and soften the crust. Under traffic this can lead to rutting which then can be exacerbated when the moisture seeps into and softens the subgrade. And since water is a good lubricant of soil and aggregates, traffic can pound out saturated depressions on the road surface leading to the two factors required for the development of potholes: water and traffic. Besides, the absence of a properly shaped road crown, problems associated with poor drainage can be associated with:

• Standing water in drainage ditches that can cause lateral seepage into the sides of the road;
• Capillary water rising from the underlying water table;
• Seasonally high water tables; and
• Cracks and porosity of the unpaved road surface

The road aggregates can also affect infiltration where the size and extent of the pores between the aggregate particles can facilitate water absorption. It is important that the surface of the unpaved road be compacted and constructed of a proper type of material that will shed water and minimize the infiltration of moisture.

Water often enters the road aggregate from below through capillary action. Here, even if the water table is sufficiently low, moisture can travel upwards into the road material. Capillary rise can be substantial, up to 20’ or more on smaller grain sized soils. Capillary rise can be a problem in areas of high groundwater tables.

During the freeze-thaw cycle, water that has infiltrated into the road material will freeze and expand during sub-freezing temperatures. Then, when temperatures warm back up, the frozen material will thaw and contract. This will leave voids in the road material that will collect more water and experience more sub-surface deterioration after additional freeze-thaw cycles. It is these voids in the road material that can be broken through and pounded out by traffic… causing potholes to form.

Although potholes will be a perpetual challenge on many roads, their formation can be minimized by stabilizing the road base material with a water resistant stabilizer such as Earthbind® Stabilizer.

Earthbind® Stabilizer works by binding loose soil or aggregate particles together, strengthening and adding water resistance to the soil/aggregate matrix. This water resistance will make the treated road soil/aggregate more hydrophobic and inhibit capillary rise from groundwater and minimize lateral migration form water standing in roadside ditches. In addition, Earthbind® Stabilizer will not re-solubilize in rainwater after curing.

Earthbind Stabilizer can be used when road construction includes undesirable soil or aggregates. In addition to increasing the strength and durability of a road base, Earthbind Stabilizer will also control erosion and fugitive dust on unpaved surfaces.
As a soil stabilizer, Earthbind® Stabilizer provides:

• Increased density
• Increased stability
• Waterproofing
• Decreased aggregate replacement costs
• Decreased grading costs
• Simple application using a water truck or pressurized distributor truck
• Easy clean up – it washes off of equipment and vehicles before curing

For more information on how Earthbind® Stabilizer can work for your project, please contact an EnviRoad sales engineer at 503-279-2600.

References:
Clifton Associates Limited. “Pothole identification: Assessment and Repair Guidelines”. https://suma.org/img/uploads/documents/communities_of_tomorrow/Pothole%20Guidelines.pdf
Johnston, Rod. “Road Repair: The Complete Guide to Fixing Roads and Driveways”. Trans Mountain Publishing.
Ken Skorseth Ali and A. Selim, Ph.D., P.E. “Gravel Roads Maintenance and Design Manual”
https://www.epa.gov/sites/production/files/2015-10/documents/2003_07_24_nps_gravelroads_gravelroads.pdf
Pavement Interactive: Subsurface drainage. https://pavementinteractive.org/reference-desk/design/design-parameters/subsurface-drainage/
Robert A. Eaton, Robert H. Joubert, and Edmund A. Wright. “Pothole Premier”: Special Report 81-21. Army Corps of Engineers. https://apps.dtic.mil/dtic/tr/fulltext/u2/a107294.pdf
Zhang, Chaohan. “The Effect of High Groundwater Levels on Pavement Subgrade Performance”. Florida State University, 2004. https://fsu.digital.flvc.org/islandora/object/fsu:168695/datastream/PDF/view