Locality Devils Town in Serbia hosts a rock formation constituting of weathered andesitic tephra deposits shaped by erosion into many bizarre landforms.Tephra layer comprises of homogeneous but poorly graded andesitic fragments ranging from pebble to boulder size, which are submerged into weathered volcaniclastic matrix. Through the years, erosion carved into loose material leaving more resilient parts to stand out. They appear as numerous closely spaced pillars, up to 15 m in height and a few meters across, commonly capped with a large andesitic boulder. The site is labeled as natural heritage and has been recently subjected to holistic monitoring projects, including non-invasive techniques such as terrestrial LiDAR, Structure from Motion and Photogrammetry. These have provided several sequences of point clouds, allowing change analysis to take place. Herein, a preliminary sequence, dating from 2017-2018 is used to reconstruct instabilities that have been recorded on the walls of one of these distinct pillars. The analysis was first targeted at locating source areas of minor rockfall events. Three such features were identified on the pillar north face, by recognizing negative change in point cloud surface, i.e., deficient rock mass. Underneath them, in the base of the pillar, less distinctive mass accumulations are noticed in the post event point cloud, which likely represent the runout zones. All source features depict irregular andesitic fragments of about 1–2 dm³ in volume, positioned in the upper third of the pillar. Trajectories of these detachments were simulated using 2D and 3D geotechnical tools. Rock fragment and ground properties required for running the simulations were assumed from field observations and index properties determined using the portable tools (SH70 needle penetrometer, Schmidt’s hammer, etc.). Reconstructed trajectories show good correlation with the post-event (2018) point cloud, where accumulated material, i.e., suffice of rock mass coincides with runout locations. Due to relatively ductile ground, fragments did not bounce significantly, and their kinetic energy is quickly dissipated, making them to stop within a close range around the pillar perimeter. In perspective, further systematic monitoring could help determine the rockfall rate, and related loss of mass on an annual basis. Such findings could help understanding the erosion and weathering process better and undertake strategies towards the site’s sustainability and resilience to climate change and extreme weather conditions.

Rockfalls are threatening natural hazards because of their rapidity and the few precursory phenomena associated, that, in highly frequented areas, result in a high geological risk. Stability analyses for risk mitigation strategies depend on the knowledge of discontinuities constituting the rock mass. However, the manual characterisation of rock joints can be hindered in case of large and/or inaccessible areas. This is the case of the Vallepietra shrine (Central Italy), site of historical and religious importance (whose origin dates back to the 11th century), destination of thousands of pilgrims, and located beneath a 200-m-high and 700-m-wide sub-vertical calcareous rock wall. Within a preliminary site characterization, a comparison between manual and semi-automated procedures of rock mass discontinuities recognition was performed on a test area close to the shrine, where in addition to a geomechanical station, a laser scanner survey was performed to obtain a point cloud of the rock mass. The latter was analysed through Discontinuity Set Extractor (DSE) software to obtain the main discontinuity sets in terms of dip and dip direction and then compare them to the outcomes of the manual survey. The results obtained from the two techniques were in good accordance and led to the recognition of four main discontinuity sets. Rock blocks were also retrieved from the rock wall for laboratory tests. Cylindrical samples of rock material were trimmed out of the blocks to perform unconfined compression (UCS) and splitting tensile strength (STS) tests. The use of radial and axial strain gauges allowed to evaluate the elastic moduli of the rock material. The results in terms of strength and stiffness were in good agreement with literature on similar rocks in Central Italy. The joint friction angle was determined by performing tilt tests both on jointed blocks and on specimens with planar-sawed joints, obtaining values typical of moderately weathered rock. The orientation of slope and discontinuities, together with experimental laboratory and field data (UCS, STS and Schmidt Hammer) on rock material and joints were used to determine the rock and slope mass ratings (RMR and SMR) as well as to perform kinematic analyses to check planar/wedge sliding and toppling failure compatibility. As a future perspective, by extending laser scanner surveys to other sectors of the rock wall and by further refining the point cloud analysis, the geomechanical characterisation of the entire rock wall could be achieved overtaking the manifest limitations of manual surveying in such distinctive areas.

Natural stone has been used for façade applications for centuries. Initially, stone elements were rather thick, when used as construction elements, and the durability was appropriate. Scientific research on properties of marble began in the late 19th century. In the years following, the thickness of natural facade stones decreased from over 1000 mm (as in construction elements) to typically 20-50 mm (in cladding applications) because of new cutting technologies and equipment being developed by the industry. Even though most marble claddings perform satisfactory, durability problems have begun to appear at an increasing rate after some 50 years of using thin cladding Well-known buildings such as the Amoco Building in Chicago, SCOR tower in Paris, and the Finlandia Hall in Helsinki have had their marble cladding replaced after less than 30 years at the cost of many millions of Euros. The deterioration gives a very considerable change in the appearance of the panels. They bow, warp or break. Most cases of bowing involve Italian marble from the Carrara area, simply because it is the most widespread and used marble type. It is, however, vital to emphasize that many building facades with Carrara marble perform well, and furthermore other marbles and limestones from other areas also exhibits durability problems. This study is dedicated to the physical and mechanical characterization of two marbles and two limestones: Carrara (IT) and Ruivina (PT), Pedra de Ançã (PT) and Estremadura (PT). It combines the analysis of experimental results (physical, mechanical, and aging properties) to allow the study of potential mechanical strength decay over time. The selected natural stone materials are often used as cladding materials and are different in mineralogy, texture, preferential orientation of grain shape and grain size distribution. The reduction in mechanical resistance was evaluated by initial bending strength and after thermal shock and freeze-thaw aging tests under standard test conditions according to the current standard in force. Other properties such as compressive strength, anchorage breaking load, elastic modulus, ultrasound velocity, volume mass, water absorption at atmospheric pressure and by capillarity and other physical indices were accessed. Result show that marble and limestone decay is linked to temperature variations and moisture. These factors are seen key features in the degradation processes. An updated and comprehensive review of the selected stones structural decay was made to consolidate the understanding of façades structural degradation.

The freeze-thaw action is an important decay process that frequently affects building rocks in cold regions. This phenomenon can lead to a degradation of their physico-mechanical properties, affecting the service life and compromising the aesthetic and structural functionality of stone construction elements. The aim of this research is to establish the physical and mechanical damage induced by the recurrent frost action on a porous limestone from the province of Alicante (south-eastern Spain) marketed worldwide as building material. For this purpose, specimens of the limestone were firstly fully saturated in water, then subjected to 20 and 40 freeze-thaw cycles and finally oven-dried at 70 ⁰ C until constant mass was reached. Each cycle lasted 24 h, consisting of 8 h of freezing at -20 ⁰C and 16 h of thawing in water at 20 ⁰C. Once the abovementioned conditioning treatment was performed, physical and mechanical parameters of the limestone, such as absorption, effective porosity, P- and S-wave velocities and uniaxial compressive strength, were determined in laboratory and compared with the corresponding parameter values of the intact (untreated) rock. The results showed that the freeze-thaw action increases the absorption and effective porosity and reduces the density, P- and S-wave velocities and uniaxial compressive strength of the porous limestone. In addition, the most-used coefficients to describe its weathering against the cyclic freeze-thaw action were calculated, which served to clarify its potential utilisation in cold climatic zones.