Karst‐induced sinkhole detection using an integrated geophysical survey: a case study along the Riyadh Metro Line 3 (Saudi Arabia)

Abstract

Nowadays, most planned large infrastructure projects increasingly use multi‐technique geophysical methods integrated with geotechnical surveys to assess detection and exploration of karst‐related systems. This article focuses on the case of a large sinkhole found during the geophysical surveys that were carried out along Riyadh’s new Metro Line 3 (Saudi Arabia). This line is the longest (41 km) of the six that are currently under construction in the framework of the largest public rail infrastructure project, the Riyadh Metro Project (176 km). A multi‐technique geophysical survey combining seismic (1040 m of seismic refraction tomography and four downhole tests), electrical (1035 m of electrical resistivity tomography), and electromagnetic methods (1040 m of ground penetration radar) was conducted to shed light on the subsurface geology along the section of this case study. The combination of the geophysical methods led to early identification of a subsurface area of lower resistivity and seismic velocity than the background values of the carbonate bedrock. It also revealed smaller fractures that could lead to future sinkhole formation. A subsequent dense investigatory borehole grid (14 boreholes, five probeholes, 38 standard penetration tests, nine TV‐logging, and five pressuremeter tests) further confirmed the presence of a buried sinkhole. This paper shows the results of each individual geophysical method as well as the final geotechnical interpretation based on the combination of geophysical methods with borehole drilling. It concludes that the use of a single method for karst assessment, whether a geophysical method or borehole drilling, does not allow a sufficiently detailed geotechnical profile of the ground. This case study provides basic guidance on the most suitable and accurate techniques to detect similar karstic features across Riyadh.

Karst Detection, Prevention and Correction: A Case Study along the Riyadh Metro Line 3 (Saudi Arabia)

“…An integration of multi-technique geophysical survey was carried out to detect areas with poor engineering properties related to karst features down to 40-50 m depth [7]. This survey included 37.8 km of seismic refraction tomography, conducted with an equipment of 58 geophones of 10 Hz spaced 10 m apart; 39.7 km of electrical resistivity tomography with an instrument of 96 channels using Wenner-Schlumberger configuration; and 39.1 km of ground penetration radar using a system with 100 MHz antenna.…”

Detection of Cover Collapse Doline and Other Epikarst Features by Multiple Geophysical Techniques, Case Study of Tarimba Cave, Brazil

“…(2) microgravimetry is also proved as a successful technique for the detection of superficial empty and filled voids and to characterize karst heterogeneity [19]; (3) with Seismic Refraction Tomography (SRT), detailed and more in-depth information of karst features can be obtained [3,20,21]; (4) electrical resistivity tomography (ERT) is used to characterize karstic features. To date, most of the karstic structures identified are sinkholes [22,23] voids [24], soil and bedrock interfaces [25] and karstic aquifer geometries [17].…”

Detection of urban underground cavities using seismic scattered waves: a case study along the Xuzhou Metro Line 1 in China

“…However, weakly diffracted waves are difficult to extract using conventional seismic methods. Earlier efforts to detect shallow cavities using integrated near‐surface geophysical methods suggest that comparison and verification of multiple methods can indeed improve the detection accuracy (Cardarelli et al ., 2010; Cueto et al ., 2018; Mohamed et al ., 2019); however, the increased workload required for such integrated surveys is always not affordable for many engineering construction projects.…”