Caverns in hard limestone form natural karstic features. Surveying, detecting, and managing caverns are valuable as they provide an accurate and reliable understanding of the geohazards that caverns represent. With the construction of the highway network in Duqm (Duqm Port, Sultanate of Oman), near-surface stability problem (caverns) appeared. Three geophysical tools – ground penetrating radar, electrical resistivity tomography, and multichannel analysis of surface waves – were utilized to delineate the subsurface cavities beneath an area of 10,000 m2 (200 m × 50 m). Based on interpretation of the results of two-dimensional and three-dimensional ground penetrating radar, electrical resistivity tomography and multichannel analysis of surface waves, the caverns are found to extend in the N–S direction. The results show two cavern systems of varying thicknesses. The caverns are separated at the top, but at some locations they become an one-unit cavern system, especially in the northerly direction. The cavern system is not completely hollow; at some locations, they are filled with materials of different physical properties than the host rock. The depth of the cavern system varies between 0 and 5.2 m. The caverns are found only within the limestone rock unit. There is no evidence of caverns within the shale rock unit. The results from the three methods show good agreement in terms of depth and dimensions of the detected caverns.
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