The intersection of 590th street and county Road M21 in Cherokee County had an extremely short sight distance. The county secondary road department plans to put a new pavement on M21 in spring of 2014 and needed to increase sight distance at the intersection prior to paving in 2014. The intersection construction consisted of 6 foot of fill in some area and 6 foot of excavation in others to accomplish adequate sight distance. The county had some concerns with the subgrade and chose to use a Tensar TriAx Geogrid Product. One concern was differing soil types and the distinct possibility of differential settlement once the road was paved and trafficked , another concern was a few areas had poor soil strengths. The county contacted Coleman Moore Company and Tensar Corp for assistance on which TriAx Geogrid would work best for the situation. After a review of the soils and pavement section, Tensar’s TX5 geogrid chosen as the most economical engineered product for project.
The cross section of the temporary road surface is the TX5 product placed on the subgrade and 12″ to 14″ of asphalt millings placed on top of the geogrid. The millings were rolled with a compactor and then a Chip Seal was place on top of the millings. This process needed to be completed not only take care of any differential settlement that may take place, but get the road opened back up for local traffic and the 2013 fall’s harvest traffic.
The 2014 paving project will consist Milling off the top 2″, then will recycle the next 4″ with Cold In Place (CIP). An additional 4″ of HMA with then be placed of the CIP.
Chip Seal Road has been open to the heavy traffic of harvest and farm equipment as well as the typical 20 – 25% truck traffic for two months.
So what does the county think:
“We have not seen any rutting or soft spots in the grade for the two months it has been open. The grid has solidified the base and distributed the loading out so well that the Chip Seal is behaving as if it were placed on a paved surface.”