Engineering exploration

The purpose of this survey was to use the ZZ Universal resistivity meter to explore possible geological reasons as part of a railway tunnel (from 370 to 430m) experienced settlement after completion. A total of 63 electrodes were laid on the surface above the tunnel and one was placed into the tunnel in the area of settlement. The following figure shows the inversion result from the survey: a few low resistivity anomalies are illustrated beneath the tunnel between 370 to 450m. After physically investigating the area, old coal mining tunnels filled with sand and mud beneath the railway tunnel were found.

This survey is aimed at finding voids for construction safety purposes, as the figure below shows, 32 and 20 electrodes were placed into two boreholes respectively. The inversion image found that the low resistivity areas beside the boreholes were likely to be karst caves. Later site investigation coincided with the inversion result.