Background

Among the most recent sinkhole events, registered in Apulia region, that occurred in Via Firenze at Gallipoli on March 29, 2007, greatly raised the attention by public opinion, having affected (likely, without causing any fatalities) the built-up areas of one of the largest towns in Salento. The event pointed out to the need to carry out detailed studies on the sinkholes related to artificial cavities.

Purpose

Main goal of the activity was to collect and analyse data regarding the geological-structural properties of the discontinuity systems of the calcarenite rock mass where the underground quarries of Via Firenze were excavated, as a first step to increase the knowledge on the area, and to move toward design of the most appropriate stabilization works.

Methods

The methods consisted of a detailed geological and structural survey of the discontinuity systems in the calcarenite rock mass, followed by the related elaboration through dedicated charts and diagrams. This, combined with the direct survey of all the undergound spaces, allowed to identify the different types of instability, their distribution, and the sectors with higher susceptibility to future failures.

Results

The integrated analysis of the geological-structural data, the spatial distribution of the occurred instabilities, the characters of the underground spaces, and the data processing, allowed to carry out an assessment of the susceptibility to future failures, highlighting those sectors of the underground quarries where the possibility of further instability is higher.

Products

Electronic database of the discontinuity data, and reated structural diagrams. Map of the instability phenomena in the underground quarry of Via Firenze. Map of susceptibility to failures of the underground quarry of Via Firenze.

Conclusions

The studies in the underground quarry at Via Firenze highlighted the severity of the situation, as regards the safeguard of the public and private safety. The presence, below built-up areas affected by heavy traffic, of a complex underground system showing widespread evidence of instability should be worth of specific and compelling analyses, aimed at mitigating the existing risk.