Prediction of Settlement of Road Embankment Using Electrical Resistivity Tomography (ERT)

Electrical resistivity tomography (ERT) is a non-invasive sub-surface technique which is widely used for investigation of various geological and engineering problems. The conventional test includes soil boring and collection of soil samples for finding out the subsurface soil profile and engineering behavior of soil. These conventional tests are borehole specific and cannot give an overall picture of the subsurface, particularly when the investigation area is large and heterogeneous. In such a condition, geophysical tests like ERT, seismic refraction, spectral analysis of surface waves, etc., are worthy, economic, and time efficient but the accuracy and reliability depend upon the accuracy in interpretation of the field data. The present study consists of performing ERT along a newly constructed bypass road which showed sinking in some locations during embankment construction. The survey gave a clear picture of the subsurface soil profile and the extent of penetration of top stiff soil into the soft organic stratum below. Some boreholes were also dug in the affected area to confirm the ERT results. It is observed that the ERT gives a better prediction of soil behavior in an erratic site.