How Soil Testing Can Reduce Potholes on Nigerian Roads

Mayowa Adeseko – Geotechnical Engineer, Fundamental Integrated Site Appraisal Services (FISAS) Limited, Abuja

Potholes are areas on road surface that have created defect or depression, cracked, worn away and eventually formed a hole. The hole varies in size and shape. Potholes are a major problem for the government and all road users across the world. Government and private owners of roads spend a lot of resources on the repair of potholes on an annual basis.

These depressions created on the road surface are as a result of the failure of asphalt pavement used in making the road. The asphalt pavement failure occurs due to the presence of water in the soil beneath the road and the continuous movement of cars and heavy-duty trucks passing over the affected area over a period of time. In other words, potholes occur when the road surface has started losing support in some locations because the supporting soil beneath it has been weakened.

Soil is the foundation for all roads in the world, therefore specific attention is required to study and determine how the characteristics of the soil will best support the roadway. Soil properties can be known through testing of the material/soil beneath the road.

Soil testing to reduce/eliminate potholes on the road is important because it helps engineers to know how the soil will behave through varying seasons (rainy and dry). It also shows if the strength of the soil under pressure can withstand movement of heavy-duty trucks for a period of time and will not cause it to sink. It enables engineers to understand if the soil can retain water so that erosion does not damage the roads after construction.

In-situ and/or laboratory testing of soil is used to gather information on the soil properties which will be needed/useful to construct the road. In-situ tests like Dynamic Cone Penetration Test (DCPT), Dynamic Probe Test (DPT) and California Bearing Ratio (CBR) among others. Also, common soil laboratory tests for road construction includes; soil classification, moisture content determination, particle size distribution, liquid and plastic limits tests, specific gravity and CBR which is used for the evaluation of subgrade strength of roads.

There is soil beneath all roads. A good knowledge of the engineering properties of soil through soil testing (in-situ and laboratory test) will reduce/eliminate potholes and lead to more stable, long-lasting and safe roads.

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