Geophysical investigation of abandoned back-filled railway line: implication on adjacent buildings

Abstract

A geophysical investigation was carried out on a back-filled segment of an abandoned railway route at Okebadan Estate, Ibadan using electrical resistivity imaging. The study is aimed at depicting the cause(s) of settlement that led to building foundation failure. Five profile lines were established during the study and the apparent resistivity values obtained from the traverse were plotted against the mid-point of electrode separation using least-squares inversion algorithm. Pockets of low resistivity region were obtained from the inverted sections with resistivity values ranging from 77 Ω-m to ˂400 Ω-m. The suspected back-filled earth materials were suspected to be clay and clayey sand. Results indicated that materials used in back filling the abandoned rail route were not well compacted. Consequently, the structural failure of buildings along this abandoned route was attributed to differential settlements of clays and clayey sands on which they were erected.

Keywords: Backfill, Foundation, Resistivity, Settlement