Drought crumbles pavement on Central Mississippi highways

 

JACKSON, Miss. (WJTV) —  The Mississippi Department of Transportation said the drought in Mississippi is  affecting the state’s highways.

“Our roads have suffered the effects of extreme loss of rainfall throughout Mississippi,” said Transportation Commissioner Dick Hall. “Our biggest problem is large cracks in the asphalt that are becoming a hazard for the traveling public.”

MDOT said the state has large deposits of at least three different types of expansive clay soils, including Yazoo clay, which are spread over the state.

These soils challenge MDOT during road construction and maintenance because of how they change with weather conditions.

When Yazoo clay becomes wet, it may expand and occupy up to 400 percent more space than when it is at normal moisture level.

When soil loses moisture, it shrinks. Shrinking creates a void between the soil and asphalt or layer of earth above it. As soil continues to shrink, the void becomes larger and the weight of the pavement and vehicles causes the roadway to sink and crack creating slides and drop offs.”

“As the trees reach further for water during extreme drought, the close proximity of trees to the roadway combined with expansive clay soils accelerate the shrinkage of the underlying roadbed materials,” said MDOT Executive Director Melinda McGrath.

When the drought ends, MDOT said crews will assess the extent of the damage before any roads are properly repaired.

“We already know it will take more than simply placing a lift of asphalt to repair most highways,” McGrath said. “Severe weather events such as droughts and ice storms prematurely age pavements forcing MDOT to alter the three-year paving schedule to repair damages.”

MDOT applies strategies in the design phase of a project to account for extreme weather conditions the project may encounter once construction is complete. Below is a list of current strategies:

  • specifying embankment materials that limit the amount of clay
  • undercutting and replacing problematic clay material just beneath the pavement structure
  • treating the soil at the bottom of the pavement structure with lime or cement
  • providing wide shoulders to support the edge of the pavement structure
  • providing gentle side slopes that are less prone to sliding

 

“Droughts are beyond MDOT’s control and unpreventable,” McGrath said. “Even though we can’t predict or stop a drought, we do take necessary, preventative measures to protect our highway system and keep the traveling public safe.”

“Unfortunately, we can’t control Mother Nature,” Hall said. “Our top priority is the safety of the traveling public in Mississippi. I’m proud of our maintenance crews and engineers for the commitment they have shown and continue to show to keeping our roads safe during this drought. Their efforts are protecting lives each and every day.”

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