Monitoring the perturbation zone near a foundation excavation with electrical resistivity tomography: Comparison between time-lapse 3D and 2D inversions in single-profile study

• Published in: Journal of applied geophysics Vol. 205; p. 104772
• Main Authors: Kim, Bitnarae, Joung, Inseok, Cho, Ahyun, Shin, Dong Keun, Han, Yushik, Nam, Myung Jin
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.10.2022
• Subjects: 4D resistivity inversion; Electrical resistivity tomography; Foundation pit; Time-lapse survey; Foundation pit; Electrical resistivity tomography; Time-lapse survey; 4D resistivity inversion
• ISSN: 0926-9851; 1879-1859
• DOI: 10.1016/j.jappgeo.2022.104772

On construction sites, ground loosening can trigger land collapses or sinkholes that compromise safety. Electrical resistivity tomography (ERT) is a very useful non-destructive method to monitor subsurface ground stability during the construction of foundation pits. We used inclined drilling to construct an artificial loosening zone near a test-bed excavation pit and performed time-lapse (TL) ERT surveys along lines lying over the loosening zone. The surveys were performed before and after excavation of the pit, and after construction of the loosening zone. As performing three-dimensional (3D) inversion for the ERT data, independent 3D inversion sequences monitor subsurface changes only when an appropriate initial model is available, which can be obtained via 2D inversion of ERT data. To overcome the limitations of 3D inversion, we subjected all TL ERT data to four-dimensional inversion, with consideration of the pit, to ensure that changes were accurately detected regardless of the initial model chosen. Our inversion strategy aids interpretation of TL ERT data obtained to monitor ground loosening on construction sites. •A relaxation zone was artificially made near an excavation pit in a test-bed.•Time-lapse ERT surveys were performed along a profile at different time points.•ERT 3D inversion failed to locate the relaxation zones due to pit effects.•A new inversion strategy considering the pit effects well detects relaxation zones.