KNOXVILLE (WATE) – As work continues to repair the massive sinkhole on Alcoa Highway near UT Medical Center, a University of Tennessee professor helped explain how a sinkhole forms.

Prof. Eric Drumm with the UT Institute of Agriculture Construction Science Program says it helps to understand there is a layer of strong, stiff clay overlying limestone rock that, over a long period of time, has been carved out by underground water. Drumm says this is why there are so many caves and underground caverns in East and Middle Tennessee.Previous story:Excavation begins on Alcoa Highway sinkhole, lanes closed near Cherokee Trail

“This overlying soil can be quite strong, but it sometimes has to bridge the opening in the rock. And therefore, sometimes during construction activities, if we decrease the thickness of that soil layer, or if we do something that can introduce more water to the soil, it can cause that soil to erode into the underground rock and at some point the soil isn’t strong enough to support a big hole or void in the soil above,” said Drumm.

Drumm says water is usually the cause of sinkholes, but construction activities can cause them as well.

“Usually the hydraulic conditions, the water conditions cause them to form. But we have TDOT on the job. They are experts in repair of these structures. They are typically repaired by installing what’s called an inverted drain, where you start with large rock and you make them smaller and smaller in the layer and cover them with soil to bridge that cavity. When TDOT is finished, I’m convinced we’ve have a safe remediation,” said Drumm.

Drumm says if you think you have a sinkhole on your property, make sure there isn’t any water directed toward that area. You should also probably contact a geotechnical engineer or geologist.