Pavement humps are classified as small, localized humps visible in the pavement surface. Sags are classified as small, abrupt depressions visible in the pavement surface. Both issues are commonly related to buckling or bulging of underlying PCC slabs or frost heave. In order for roads to avoid the need for repairs, both the pavement and the subgrade must be in prime condition. That being said, subgrade quality is a big contributor to sags and humps.
Sags and humps are typically related to damages seen in the wheel path, although they can impact other parts of the roadway as well. Sags and humps are often found in desolate stretches of roadway surfaces.
Sags and humps indicate the possibility of:
- Pavement shoving
- Displacement caused by subgrade swelling
- Displacement related to growing tree roots.
Identifying the cause of sagging or bulging is fundamental to finding the best course of repair.
How Severe Are Sags & Humps In Roadways?
At some point in time we have all driven over a bumpy road pitted in humps or sags. This leads to a less than smooth car ride, and if the damage is bad enough it can increase the risk for roadway accidents. Sags and humps vary from minor to severe, although minor sags and humps can turn severe if the underlying issue is not resolved in a timely manner.
Actual severity of humps and sags are ranked in accordance to the maximum vertical deviation. This is measured using a 10-foot straightedge placed on the pavement parallel to the centerline of the road. The maximum deviation from this 10-foot straightedge marks the severity of sags or humps.
Low Severity: Anything that measures 1/8 of an inch to 2 inches per 10 feet. Low severity will create minor issues or discomforts associated with ride quality.
Medium Severity: Anything that measures 2 inches to 4 inches per 10 feet. Medium severity distress will cause moderate issues and discomfort with ride quality.
High Severity: Over 4 inches per 10 feet. High severity causes major issues with ride quality.
How To Determine Measurements For Sags & Humps In Pavement
There are 2 options to determine measurements for sags and humps.
The actual extent is calculated as a percent of the surface area impacted. Damaged areas are classified into different segments based upon percentages:
1-9% of the area of the segment
10-24% of the area of the segment
25% or greater of the area of the segment
Severity is determined by measuring the max difference in elevation within the 10-foot straightedge length when it is centered over the area of displacement. The highest observed level marks the overall rate of distress.
Segment: 1/10 mile = 528 feet
Sag is measured at 2 ½ inches deep and 25 feet long within the segment.
That means it is rated as 5% medium sag OR, 1-9%, which is also classified as medium, if you use ranges of extent.
Using this option, the overall extent of humps and sags is written in square feet regarding the total survey area.
Just like before, you will determine overall severity by measuring the max variance in elevation as measured within a 10-foot straightedge length centered over the roadway. The overall distress is rated according to the highest observed level.
How To Fix Humps & Sags
There are generally two main ways to fix pavement distress. The first is to remove and replace the damaged roadway as well as the surfacing or base material. Another option is to cover the affected area with an overlay material that is suitable to renew the surface, seal off the defected area and stabilize the pavement. These repairs are often referred to as ‘overlays’ or ‘dig-outs,’ depending upon the method used. It’s important to note that humps and sags generally require more invasive repair techniques than simply applying a seal coat on top.
Kleenco Construction successfully solves pavement challenges for some of the largest companies in America. We understand that the root of the problem is not always visible to the naked eye. It takes some undercover work and precise calculations to identify the cause as well as the most cost-effective solution. If you are dealing with humps or sags in roadways, there’s no one more qualified than us to tackle the issue and help prevent it from happening again.