Search

The use of the Equotip hardness tester in engineering geology has increased significantly in recent years, especially in estimating the strength of weak and weathered rock materials. Weathering and fracturing, besides lithology, influence the overall behaviour of the rock mass and the response of the non-destructive tester. In this study, more than 9,000 Equotip rebound measurements were collected from twelve rock outcrops of several geological formations in central Italy, using a regular measurement grid approach. In addition, linear scan lines were combined with the analysis of photogrammetric sampling windows to determine geomechanical indexes such as Rock Quality Designation (RQD), Joint Volumetric Count (Jv) and Fracture intensity (P21) to be coupled with the Equotip measurements. A strong correlation was found between RQD, Jv, P21 and the Equotip rebound. The study presents an innovative approach by integrating extensive Equotip rebound measurements with geomechanical indices (RQD, Jv, P21) and advanced photogrammetric techniques. This combination provides new quantitative constraints on the relationship between fracture intensity, lithological variation, and mechanical properties of rock masses. Our findings highlight the potential of Equotip testing as a fast and reliable tool for in-situ rock mass quality assessment, also in heterogeneous geological settings, improving hazard management and engineering design. [ABSTRACT FROM AUTHOR]

This paper proposes a non-destructive approach based on the Equotip hardness tester to assess weathering deterioration in a protected sandstone monument located in the historic centre of Camerino (Italy). The approach is tested on one sandstone column, where various forms of weathering, such as discolouration, scaling and loss of stone volume, are observed. The mechanical characterisation with Equotip was performed on 24 measuring points, systematically distributed in the column. Innovatively, the two probes available from Proceq (Proceq© 2010) were used to assess differences among surface and in-depth hardness values of the column. In addition, an un-weathered rock core from the original extraction site was also analysed and compared with the rock matrix of the column. The obtained results show a 15% hardness reduction from depth to the surface of the column and a 25% overall hardness reduction with respect to the fresh sandstone core samples. Equotip results were coupled with grain size analyses, mercury intrusion porosimetry, scanning electron microscopy and X-ray diffractometry results, and a correlation between hardness and grain size was evaluated. By combining these approaches, it was possible to identify the processes that occurred during weathering: (a) freeze-thaw cycles that caused a decrease in micropore volume and an increase in macropores connected with low Equotip values; (b) iron oxide and sulphuric acid released from pyrite oxidation contribute to the dissolution and precipitation of calcium carbonate, which can be rearranged in the outer and surface macroporosity. The quantitative approach proposed in this study may be a valid low-cost and quick tool to assess weathering heterogeneities on building stone materials and to provide insights for effective preservation strategies of historical monuments. [ABSTRACT FROM AUTHOR]

Nowadays, groundwater is the most important resource on our planet. However, due to population growth, urbanisation, and climate change, this resource is often overexploited or contaminated. In this context, carbonate aquifers provide drinking water to approximately 25% of the global population. Due to aquifers heterogeneities and anisotropic fracture systems, they can be affected by potential contamination and their optimal exploitation represents a challenge aspect. In this particular scenario, carbonate mountain aquifers encompass valuable groundwater resources due to their high recharge rates and excellent water quality; therefore, the understanding of their hydrogeological characteristics are vital for aquifers protection and water management. A valid solution to explore water movement within such aquifers and to quantify the groundwater amount can be offered using artificial tracers. At the same time, the geomechanical surveys can deep the knowledge on fracture density and orientation, providing valuable insights about fracture connection and conductivity. This study combines the advantages of six artificial tracer tests performed in four deep wells (260-500 m b.g.l.) and a geomechanical survey used, among other, to estimate hydraulic conductivity of a mountainous carbonate aquifer located in Central Italy. The results obtained by different methods highlighted the presence of multiple layers with higher conductivity values, able to sustain the groundwater flow without significant piezometric level drawdown during water pumping operations. This approach provides an effective support to the water management company operating. [ABSTRACT FROM AUTHOR]

In the framework of landslides, the hydrogeological features play an essential role in slope stability, governing water movement and thus resulting in modification of the effective stress in the soil. In this framework, the hydrogeological conceptualization of landslide areas and the identification of groundwater origin are key points to developing risk mitigation measures. In fact, groundwater recharge cannot always be attributed to local precipitation alone. Mixing processes between water derived from local infiltration and deep water upflow along tectonic lineaments or anthropogenic water can affect the groundwater balance on a local scale. This study aims to define the potential groundwater origin of one of the highest risk urban landslides in central Italy and to define a hydrogeological conceptual model by exploiting its existing drainage system network. This research is based on a multiple-techniques approach based on hydrological water balance, artificial tracer tests during recharge period, seasonal monitoring of the water stable-isotope content, hydro-chemical survey during low-flow periods, and analysis of the piezometric level fluctuation. All these analyses are coupled with a detailed reconstruction of the geology of the area depicted from boreholes and drill holes. Two groundwater bodies have been evidenced from the study. The shallower one is located in the landslide unstable zone and is hydraulically connected to a deeper groundwater body hosted in the underlying bedrock. Results highlighted that the local rainfall regime could not fully explain the hydro-chemical facies. Local water contributions to the landslide area coming from leakage of the urban sewerage system have been evidenced, excluding deep groundwater upflow from the fault system. [ABSTRACT FROM AUTHOR]

The stability of a rock slope is strongly influenced by the pattern of groundwater flow through the fracture system, which may lead to an increase in the water pressure in partly open joints and the consequent decrease in the rock wall strength. The comprehension of the fracture pattern is a challenging but vital aspect in engineering geology since the fractures' spatial distribution, connectivity, and aperture guide both the water movement and flow quantity within the rock volume. In the literature, the most accepted methods to hydraulically characterise fractured rocks in situ are the single borehole packer test, the high-resolution flow meters for fractures, and the artificial tracer tests performed in boreholes. However, due to the high cost a borehole requires and the general absence of wells along coastal cliffs, these methods may not be appropriate in rockfall-prone areas. In this study, an unsaturated rocky cliff, strongly affected by rockfalls, was investigated by combining kinematic analysis, Discrete Fracture Network (DFN) modelling, and artificial tracer tests. The DFN model and potential rock block failure mechanisms were derived from high-resolution 3D virtual outcrop models via the Structure from Motion (SfM) photogrammetry technique. An artificial tracer was injected using a double ring infiltrometer atop the recharge zone of the slope to determine the infiltration rate and validate the DFN results. The DFN and tracer test methods are frequently used at different spatial scales and for different disciplines. However, the integration of digital photogrammetry, DFN, and tracer tests may represent a new step in rockfall and landslide studies. This approach made possible the identification of groundwater flow patterns within the fracture system and revealed about a 10-day tracer transit time from the injection area and the monitored slope, with similar conductivity values gathered from both the DFN and tracer test. Planar and wedge failures with volumes ranging from 0.1 and 1 m3 are the most probable failure mechanisms in the areas. The results were consistent with the delay between the intense rainfall and the slope failures previously documented in the study area and with their mechanisms. [ABSTRACT FROM AUTHOR]

Carbonate aquifers are characterised by strong heterogeneities and their modelling is often a challenging aspect in hydrological studies. Understanding carbonate aquifers can be more complicated in the case of strong seismic events which have been widely demonstrated to influence groundwater flow over wide areas or on a local scale. The 2016–2017 seismic sequence of Central Italy is a paradigmatic example of how earthquakes play an important role in groundwater and surface water modifications. The Campiano catchment, which experienced significant discharge modifications immediately after the mainshocks of the 2016–2017 seismic sequence (Mmax = 6.5) has been analysed in this study. The study area is within an Italian national park (Sibillini Mts.) and thus has importance from a naturalistic and socio-economic standpoint. The research strategy coupled long-period artificial tracer tests (conducted both before and after the main earthquakes), geochemical and discharge analyses and isotope hydrology with hydrogeological cross-sections. This study highlights how the seismic sequence temporarily changed the behaviour of the normal faults which act predominantly as barriers to flow in the inter-seismic period, with water flow being normally favoured along the fault strikes. On the contrary, during earthquakes, groundwater flow can be significantly diverted perpendicularly to fault-strikes due to co-seismic fracturing and a consequent permeability increase. The interaction between groundwater and surface water is not only important from the point of view of scientific research but also has significant implications at an economic and social level. [ABSTRACT FROM AUTHOR]

This study wants to give a contribution to the semi-automatic evaluation of rock mass discontinuities, orientation and spacing, as important parameters used in Engineering. In complex and inaccessible study areas, a traditional geological survey is hard to conduct, therefore, remote sensing techniques have proven to be a very useful tool for discontinuity analysis. However, critical expert judgment is necessary to make reliable analyses. For this reason, the open-source Python tool named DCS (Discontinuities Classification and Spacing) was developed to manage point cloud data. The tool is written in Python and is based on semi-supervised clustering. By this approach the users can: (a) estimate the number of discontinuity sets (here referred to as "clusters") using the Error Sum of Squares (SSE) method and the K-means algorithm; (b) evaluate step by step the quality of the classification visualizing the stereonet and the scatterplot of dip vs. dip direction from the clustering; (c) supervise the clustering procedure through a manual initialization of centroids; (d) calculate the normal spacing. In contrast to other algorithms available in the literature, the DCS method does not require complex parameters as inputs for the classification and permits the users to supervise the procedure at each step. The DCS approach was tested on the steep coastal cliff of Ancona town (Italy), called the Cardeto–Passetto cliff, which is characterized by a complex fracturing and is largely affected by rockfall phenomena. The results of discontinuity orientation were validated with the field survey and compared with the ones of the FACETS plug-in of CloudCompare. In addition, the algorithm was tested and validated on regular surfaces of an anthropic wall located at the bottom of the cliff. Eventually, a kinematic analysis of rock slope stability was performed, discussing the advantages and limitations of the methods considered and making fundamental considerations on their use. [ABSTRACT FROM AUTHOR]

Environmental isotopes are essential in hydrogeological studies, thanks to their contribution to the understanding of aquifers dynamics, vulnerability, water resources assessment, and management issues. The environmental isotopic approach plays a vital role in tracing the hydrological cycle and identifying various sources of contamination in the environment and gives independent information concerning what can be determined by a traditional hydrogeological study. Even in the framework of COP-26, isotopes have been indicated as fingerprints of climate change and therefore suitable for the evaluation of water balance and assessment of processes involved therein; in pollution studies they are used as fundamental support of traditional geochemical measures. Tritium, in particular, has been used since the 1960s to identify potential leaks in the containment walls of waste disposal sites, since its presence in the leachate (at very high levels in some cases) depends on the incorrect waste disposal of some peculiar items. Its use as a tracer of pollution by landfills is highlighted and emphasized by the very low concentrations of tritium in the natural environment. By comparing tritium content of leachate to that of water downflow from the waste disposal site, it is therefore possible to establish with a good success rate whether leachate have migrated or not out of the landfill, in the surrounding environment. An additional potential of tritium is to give a prompt indication of pollution risk in the environment indicating leaching even before the chemical indicator of pollution can be detected. This article wants to provide a contribution to the scientific community, collecting all the existing research in this field and providing data and benchmarks about this method, in particular stressing the role of tritium as an indicator of leachate transfer out of waste disposal sites. [ABSTRACT FROM AUTHOR]

The determination of mechanical parameters of historical mortars is a crucial aspect in the analysis of masonry in ancient buildings, especially for evaluating their quality and planning the appropriate restoration interventions. Due to conservation reasons, creating a comprehensive database is generally not possible because cutting out masonry specimens relates to damaging historical structures. This study starts with the need to characterize the mortar quality of different buildings in the town of Camerino (Central Italy) which has been strongly damaged by the 2016–2017 seismic sequence. A non-destructive collecting data strategy based on the use of the Equotip hardness tester (EQ) has been set up by evaluating the most appropriates impact strategy (single or repeated) and the range of measurements to calculate the basic statistics. The seismic damage suffered by the buildings allowed the rare opportunity to take samples from several walls and carry out laboratory tests to determine their Uniaxial Compressive Strength (UCS). The comparison between the results of the two types of tests made it possible to calibrate a relationship between the EQ values and the UCS. The Pearson's coefficient of determination derived from an exponential interpolation (R2 = 0.81) confirmed a strong relationship between the EQ values derived from the tests on the specimens and the UCS. Moreover, comparing the in situ EQ measurements with the ones performed on the specimens prepared for the compressive tests, a general underestimation of the in situ EQ values has been observed, possibly due to the presence of a superficial alteration layer of the exposed mortar. From these results, we propose a correction of the in situ measurements able to obtain a more appropriate strength estimate of the historical mortars. [ABSTRACT FROM AUTHOR]

In the Western Alps, a steeply dipping km-scale shear zone (the Ferriere-Mollières shear zone) cross-cuts Variscan migmatites in the Argentera-Mercantour External Crystalline Massif. Structural analysis joined with kinematic vorticity and finite strain analyses allowed to recognize a high-temperature deformation associated with dextral transpression characterized by a variation in the percentage of pure shear and simple shear along a deformation gradient. U-Th-Pb dating of syn-kinematic monazites was performed on mylonites. The oldest ~ 340 Ma ages were obtained in protomylonites, whereas ages of ~ 320 Ma were found in mylonites from the core of the shear zone. These ages indicate that the Ferriere-Mollières shear zone is a still preserved Variscan shear zone. Ages of ~ 320 Ma obtained in this work are in agreement with ages of the dextral transpressional shear zones occurring in the Maures-Tanneron Massif and Corsica-Sardinia. However, transpression in the Argentera-Mercantour Massif started earlier than in other sectors of the southern Variscan Belt. This is possibly caused by the curvature of the belt triggering the progressive migration of shear deformation. Our data allow a correlation between the Argentera-Mercantour Massif and other segments of the Southern European Variscan Belt, in particular with Maures-Tanneron Massif and Corsica-Sardinia, and contribute to fill a gap in the age of activity and in the kinematics of the flow of the system of dextral shear zones of the southern portion of the EVSZ. [ABSTRACT FROM AUTHOR]

The Ferriere-Mollieres Shear Zone (FMSZ) is a regional shear zone cross-cutting the Argentera External Crystalline Massif (Western Alps). It shows a NW-SE striking dextral shear zone separating two Variscan migmatitic complexes: the Tinèe to the SW and the Gesso-Stura-Vesubiè to the NE. Geological-structural mapping at 1:10,000 scale focused on the characterization of mylonitic deformation. A deformation gradient has been observed towards the core of the shear zone marked by the occurrence of ultramylonites and rare phyllonitic layers. Protomylonites passing to unsheared migmatites occur in the outer zones. Low-angle shear zones with a top-to-the S and SW sense of shear cross-cut the previous mylonitic foliation. The FMSZ is a Variscan transpressive shear zone activated during the Late Carboniferous under amphibolite-facies metamorphic condition. The shear zone has been partially reactivated under greenschist-facies metamorphic conditions during Alpine Orogenesis. [ABSTRACT FROM AUTHOR]