Statistical Analysis of Resistivity Anomalies Caused by Underground Caves

Abstract

Geophysical prospecting of underground caves being performed on a construction site is often still a challenging procedure. Estimation of a likelihood level of an anomaly found is frequently a mandatory requirement of a project principal due to necessity of risk/safety assessment. However, the methodology of such estimation is not hitherto developed. Aiming to put forward such a methodology the present study (being performed as a part of an underground caves mapping prior to the land development on the site area) consisted of application of electrical resistivity tomography (ERT) together with statistical analysis utilized for the likelihood assessment of underground anomalies located. The methodology was first verified via a synthetic modeling technique and applied to the in situ collected ERT data and then crossed referenced with intrusive investigations (excavation and drilling) for the data verification. The drilling/excavation results showed that the proper discovering of underground caves can be done if anomaly probability level is not lower than 90 %. Such a probability value was shown to be consistent with the modeling results. More than 30 underground cavities were discovered on the site utilizing the methodology.

Integrated MASW and ERT Imaging for Geological Definition of an Unconfined Alluvial Aquifer Sustaining a Coastal Groundwater-Dependent Ecosystem in Southwest Portugal

“…This performance analysis provides two important remarks: (1) theoretical fitting functions do not introduce noticeable mismatching between M and P data, i.e., do not generate spurious values, because the number and magnitude of original outliers is low to negligible; and (2) computation and fitting processes reproduce well the homogeneity of this alluvial medium, in which a general predictable behavior of variables VS and ER in non-surveyed sites can be anticipated from the results obtained in the surveyed ones, as show in next Section 5.2. Performance of the VS and ER models was better to that reported in similar experiences using the same methodology for MASW [59,63,64] and ERT [71][72][73]. As deduced, the VS and ER models are reliable enough to produce a confident geological model conceptualization for groundwater modeling purposes.…”

Double-shield TBM Mounted Seismic Ahead-prospecting System and its Application

“…However, when confronted adverse geology, TBM has a low adaptability and is prone to disaster, so predicting the distribution of geological conditions and adverse geology (faults, fractured zones, karst caves, etc.) in front of the tunnel face is crucial for construction safety [3][4][5][6][7][8][9][10]. What's more, the dense equipment and limited space inside the TBM put forward higher requirements for ahead-prospecting inside the TBM.…”

Modelling of seismic assessment for large geological systems

“…Underground caves and faults are sources of stress concentration and hence possible fracture. Detection of anomalies and underground inhomogeneities (see [21,22]) is important to the assessment of the crack nucleation [23] and failure in the context of problems of geophysics.…”