Rockfall Analysis for Preliminary Hazard Assessment of the Cliff of Taormina Saracen Castle (Sicily)

Abstract

Abstract:A rockfall analysis at one of the most relevant cultural heritage sites of northeastern Sicily (Italy) is presented herein with the aim of assessing the hazard arising from the unstable conditions of the rock cliff of Taormina city, upon which the Saracen Castle is perched on its top. Several rockfalls affected this area in the latest years, representing a serious threat for the safety of inhabitants and tourists. Therefore, the qualitative Evolving Rockfall Hazard Assessment (ERHA) was applied for the hazard zonation, supported by rock mass surveys and Terrestrial Laser Scanner prospecting. Kinematic analysis revealed that the unstable rock failure patterns are represented by planar/wedge sliding and toppling, while simulation of potential rockfalls allowed studying the impact of future events in terms of trajectory and energy. This is higher at the foot of scarps and in steeper sectors, where the application of ERHA identified a critical zone close to the inhabited center, which is one of the main elements at risk, along with a pedestrian tourist path. Achieved results represent a starting point for the definition of risk management strategies and provide a scientific contribution to the study of hazard and risk arising from rockfall occurrence.

Sustainable Fruition of Cultural Heritage in Areas Affected by Rockfalls

“…In fact, this territory has been suffering a relevant rockfall problem for decades. The geological and tectonic setting are mainly responsible to a poor-fair geomechanical quality of the rock masses (e.g., [32][33][34][35]), which often gives rise to rock volume detachments, especially after heavy rainfalls. The most critical detachment points are located along carbonate rock masses belonging to the Liassic greyish-white limestones and dolostones formation described by [36].…”

“…Sector 1a: Enclosing the highest portion of PPW, in the proximity of the entrance of the castle, where remedial measures have never been performed and where loose rocks were surveyed (Figure 4a Starting from these field observations, with the aim of applying the RRRS to this slope, the collection of data on the historical rockfalls was carried out by local interviews and scientific literature. Mineo et al [35] presented a preliminary hazard analysis of the cliff, highlighting that PPW mainly falls within a high-to-moderate hazard sector according to the application of a hazard matrix. Nevertheless, the final PPW segment, close to the entrance of the castle, was not taken into account by the above mentioned study, although local people told us about frequent rockfalls involving smaller boulders (about 0.05 m 3 ), which represent a threat for the passing visitors (Figure 3d).…”

“…Sector 1a: Enclosing the highest portion of PPW, in the proximity of the entrance of the castle, where remedial measures have never been performed and where loose rocks were surveyed (Figure 4a) Sector 1b: Enclosing the downstream portion of PPW, which is still affected by boulders detaching from the northwestern cliff ( Figure 4a) The geostructural setting of the rock mass was studied by Mineo et al [35], who performed rock mass surveys highlighting that the most frequent unstable kinematic pattern is the planar sliding, followed by toppling and some wedge configurations (Figure 4b). The geomechanical quality of the rock, assessed by the Rock Mass Rating system (RMR, [47]) was assessed as "fair rock" (RMR between 41 and 60), and some simulated trajectory of blocks underline that PPW is affected by block bounces at several spots (Figure 4c).…”

Analysis of rockfall hazards along NH-15: a case study of Al-Hada road

“…Other factors include seismic shock, rainfall timing, duration, and intensity, freeze-thaw, and anthropogenic activities [5,[11][12][13][14]. Rockfall incidents have been associated with large monetary losses and loss of life [15,16]. Since the heights, inclination, topography, and slope characteristics vary considerably, rockfall behavior becomes quite erratic and difficult to predict.…”

“…The specific program is commonly in use to investigate the rockfall such as the rocscience product RocFall and Colorado Rocfall Simulation Program (CRSP). Currently, RocFall (rocscience inc.) is the most widely used [15,16,21] to identify the assessment of slopes at risk for rockfalls. Therefore, RocFall program was used in this study because of more advantages compared to CRSP [22].…”