APPLICATION OF VERTICAL GRAVITY GRADIENT METHOD FOR SUBSURFACE UTILITY IDENTIFICATION IN ITB GANESHA CAMPUS AREA

• Main Author: Bintang Fadhiil, Muhammad
• Format: Final Project
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/86273
• Institution: Institut Teknologi Bandung

Underground utility networks provide essential things for daily life and have a limited useful life, so maintenance needs to be carried out to avoid potential disasters due to utility damage. However, there are limitations in terms of direct observation of the existence of subsurface utilities and inaccurate mapping of utilities. Based on this, in this study, the vertical gravity gradient method is used which is a development of the gravity method. The application of the vertical gravity gradient method is carried out by measuring gravity from a minimum of two different heights at each measurement point. Through this method, it is hoped that it can overcome limitations, including in terms of vertical accuracy, labor effectiveness, and cost. Based on the results of the calculation of vertical gravity gradient anomalies, the existence of subsurface utility limits can be identified. To get better results, forward modeling is carried out. Modeling was carried out by making two tracks, namely the A-A' track with the Southwest-Northeast direction and the B-B' track with the Southeast-Northwest direction. The results of forward modeling with an error of 0.004 mGal/m showed the existence of geomaterials in the form of topsoil with a density of 1.6 g/cm3, subsoil with a density of 2.2-2.4 g/cm3, loose soil with a density of 1.2 g/cm3, concrete with a density of 2.2 g/cm3, and cast iron pipes with a density of 7.8 g/cm3. In addition, utility was detected in the form of two manholes with a height of 2.6 m, a diameter of 1.05 m, and a cover thickness of 0.05 m, as well as three branched pipes detected with a diameter of 0.18 m which were reduced to two branches with a diameter of 0.24 m at a depth of 1 m from the ground level. The modeling results are validated by visual tracing and have shown the suitability of the results. Thus, it can be stated that the vertical gravity gradient method can be used as one of the alternative methods to identify the existence of subsurface utility.