IDENTIFICATION OF THE EXISTENCE OF SUBSURFACE PIPES USING ELECTRICAL RESISTIVITY METHOD

• Main Author: Nasro, Mohamad
• Format: Theses
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/74566
• Institution: Institut Teknologi Bandung

Identification of the subsurface is important to determine subsurface conditions. Many cases are found where there is an object beneath the surface, such as pipes, cables, and utilities. In identifying the existence of an object can use geophysical methods. The geophysical method used in this study is the resistivity geoelectric method. The working principle of this method is to measure the potential difference from the injection of an electric current into the subsurface. The resistivity geoelectric method has various types of configurations in field measurement surveys. Each configuration type has different data coverage, signal strength, sensitivity, and data resolution. This study aims to determine the best configuration of the three types of configurations that will be used through two stages, namely synthetic modeling and field data measurement. The configurations used are the Dipole – Dipole, Wenner Alpha, and Wenner – Schlumberger configurations as a comparison, where no research has discussed the comparison between these configurations in one study. In this study, synthetic modeling and field data measurements used a spacing between electrodes of 0.10 m and a total of 32 electrodes. Synthetic modeling using RES2DMOD software by varying the placement depth (0.12, 0.21, 0.30, 0.42, 0.52) m of iron pipe with a diameter of 0.10 m and 0.20 m below the homogeneous surface. Meanwhile, field data measurements involve 2 perpendicular paths that pass through iron pipes (CS1 and CS2), 2 perpendicular paths that do not pass through iron pipes (CS3 and CS4), and 1 line parallel to iron pipes (LS). After obtaining synthetic data and field data, then the data is processed using the Least-Square inversion technique from RES2DINV software. The results of synthetic modeling inversion on iron pipes with a diameter of about 0.10 m placed under a homogeneous surface show that the Dipole-Dipole configuration can identify the presence of iron pipes at depths of 0.12 m to 0.42 m and the Wenner-Schlumberger configuration can identify at depths of 0.12 m to 0.30 m. Meanwhile, the Wenner Alpha configuration is unable to identify the presence of iron pipes. Furthermore, for the results of synthetic modeling inversion on iron pipes with a diameter of about 0.20 meters placed under a homogeneous surface, it is found that the Dipole – Dipole configuration can identify the presence of hollow iron pipes at a depth of 0.12 m to 0.52 m and the Wenner – Schlumberger configuration can identify at a depth of 0.12 m up to 0.30m. Meanwhile, the Wenner Alpha configuration is only able to identify the presence of iron pipes at a depth of 0.12 m below a homogeneous surface. The results of field data inversion on a perpendicular path passing through iron pipes (CS1 and CS2) with a diameter of 0.10 m show that only the Dipole – Dipole configuration is capable of detecting the presence of iron pipe anomalies below the soil surface. Furthermore, the results of the inversion of field data on lines parallel to the direction of the iron pipe (LS) with a length of about 1.90 m iron pipe found that all the configurations used in this study (Dipole – Dipole, Wenner Alpha, and Wenner – Schlumberger) can detect the presence of pipeline anomalies iron below ground level. Based on this research, from the inversion results of synthetic modeling and field data measurements, it can be concluded that the Dipole – Dipole configuration gives better results in identifying the presence of pipes below the surface than the Wenner Alpha and Wenner – Schlumberger configurations.