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The compilation and maintenance of experimental databases are of crucial importance in all research fields, allowing for researchers to develop and test new methodologies. In this work, we present a flat-file database of experimental dispersion curves and shear wave velocity profiles, mainly from active surface wave testing, but including also data from passive surface wave testing and invasive methods. The Polito Surface Wave flat-file Database (PSWD) is a gathering of experimental measurements collected within the past 25 years at different Italian sites. Discussion on the database content is reported in this paper to evaluate some statistical properties of surface wave test results. Comparisons with other methods for shear wave velocity measurements are also considered. The main novelty of this work is the homogeneity of the PSWD in terms of processing and interpretation methods. A common processing strategy and a new inversion approach were applied to all the data in the PSWD to guarantee consistency. The PSWD can be useful for further correlation studies and is made available as a reference benchmark for the validation and verification of novel interpretation procedures by other researchers.

Geophysical surveys are frequently applied in mining prospection to detect the presence and volume of ore bodies of different nature. Particularly, in gypsum ore bodies exploitation, electrical resistivity measurements are usually the most used methodology. However, it has been observed that different electrical resistivity values can be obtained depending on geometrical features and composition of gypsum. Indeed, electrical resistivity of gypsum rocks depends on several parameters, such as gypsum purity, nature of secondary minerals, porosity, saturation and interstitial fluid properties. Saturation and hydrogeological setting, in particular, were recognized as the most influencing parameters. Hydrogeological conditions of gypsum rock masses are also very relevant for exploitability, safety conditions and economic feasibility and should be accurately known during the prospection and planning phases of the quarries. In this work, a relationship between electrical resistivity and saturation degree of gypsum is proposed. The possibility to estimate gypsum porosity with the use of this relationship is also investigated. The reliability of laboratory measurements is finally verified in comparison with field and modelled resistivity data. The reported results underline the potentiality of the proposed approach to obtain a reliable characterization of the studied ore body. Keywords: Gypsum rock, Electrical resistivity, Saturation, Porosity, Archie, ERT, Quarry

The existence of hidden chambers and corridors adjacent to Tutankhamun's tomb (code name KV62) has been long debated. In 2015 it was suggested that these chambers may host the as yet undiscovered burial of Nefertiti. In order to test this hypothesis, two Ground Penetrating Radar (GPR) surveys, conducted in 2015 and 2016 from inside KV62, were carried out, but gave contradictory results. To solve these uncertainties and obtain a more confident and conclusive response, a third GPR survey was conducted by our team in February 2018. The results of this third radar scan are reported in this article. Three GPR systems with multiple frequency bands (from 150 MHz to 3000 MHz) and very dense spatial sampling were adopted. After careful data processing, no evidence of marked discontinuities due to the passage from natural rock to artificial blocking walls were found in the radargrams. It is therefore concluded that there are no hidden chambers immediately adjacent to the Tomb of Tutankhamun.

Carbonate rocks have a widespread diffusion in the Earth crust and are extensively used in cultural heritage and buildings. These rocks can be naturally or anthropically exposed to high temperatures. Consequently, relating physical properties to temperature-induced damage is extremely important. Six sets of compositionally and texturally different carbonate rocks, spanning from limestones and marbles to dolomitic marbles, were analysed in this study. Different physical properties, such as porosity, seismic wave velocities and electrical resistivity, were measured before and after thermal treatments with heating/cooling ranges between 105 and 600°C. Microstructural observations and optical analyses were used to investigate how temperature-induced damage affects the physical measured properties of the different microstructures. This integrated approach allowed to define a generalised relationship between physical properties and thermal-induced damage, by way of an induced damage index valid for a broad suite of carbonate rocks.

A blast-induced liquefaction test was conducted in the surroundings of Mirabello (NE Italy), where extensive liquefaction phenomena were observed after the 2012 Emilia earthquake. This experiment is the first blast-induced liquefaction test carried out in Italy. Several geophysical investigations were performed at the site to define initial soil condition and to evaluate the variations of the geophysical parameters over time. Specifically compressional ( VP) and shear ( VS) wave velocities were measured using both invasive (down-hole) and non-invasive (surface wave) tests. Electric Resistivity Tomography (ERT) tests were also carried out. Tests results before and after the blast-induced liquefaction are here presented and discussed with respect to the observed liquefaction effects. The evolution of measured geophysical parameters suggests that the soil modifications due to blasting ( i.e., changes in porosity and soil structure) can be imaged with the adopted approaches.

A case study on the use of direct and indirect investigations for the effectiveness evaluation of jet-grouting interventions for bridge scour protection is presented. The major concern of this scour countermeasure is that a reliable verification and imaging of the exact dimensions and shape of the grouted elements and their related strength and integrity are difficult to obtain. An integrated cost-effective and slightly invasive approach, by means of indirect surveys, is proposed in this work to limit re-drilling and core sampling of jet columns. Tests are performed on a bridge located in the Province of Cuneo (NW Italy). On site, active fluvial activity was scouring four of the 19 bridge piers and jet-grouting interventions were designed to prevent bridge collapse. A dual approach was consequently applied to evaluate the goodness of jet-grouting treatments: results of direct tests (visual and mechanical characterization of core drillings, with Point Load and Uniaxial Compressive Strength tests) have been compared to indirect investigations (seismic down-hole tests and 2-D cross-hole tomography, laboratory Ultrasonic Pulse Velocity measurements). All the techniques showed potentiality in identifying variations of the jet-grouting properties within the columns. Generally, worsening in jet-grouting properties was coherently identified by a decrease in the seismic velocities and in the mechanical parameters and confirmed by visual inspection of core drillings. Local anomalies and discrepancies between the adopted method were however highlighted and critically discussed as a function of the limitations, disturbances and investigated volumes of each method.

Surface waves (SWs) in seismic records can be used to extract local dispersion curves (DCs) along a seismic line. These curves can be used to estimate near-surface S-wave velocity models. If the velocity models are used to compute S-wave static corrections, the required information consists of S-wave time-average velocities that define the one-way time for a given datum plan depth. However, given the wider use of P-wave reflection seismic with respect to S-wave surveys, the estimate of P-wave time-average velocity would be more useful. We therefore focus on the possibility of also extracting time-average P-wave velocity models from SW dispersion data. We start from a known 1D S-wave velocity model along the line, with its relevant DC, and we estimate a wavelength/depth relationship for SWs. We found that this relationship is sensitive to Poisson’s ratio, and we develop a simple method for estimating an “apparent” Poisson’s ratio profile, defined as the Poisson’s ratio value that relates the time-average S-wave velocity to the time-average P-wave velocity. Hence, we transform the time-average S-wave velocity models estimated from the DCs into the time-average P-wave velocity models along the seismic line. We tested the method on synthetic and field data and found that it is possible to retrieve time-average P-wave velocity models with uncertainties mostly less than 10% in laterally varying sites and one-way traveltime for P-waves with less than 5 ms uncertainty with respect to P-wave tomography data. To our knowledge, this is the first method for reliable estimation of P-wave velocity from SW data without any a priori information or additional data.

River embankments are linear earth structures, worldwide diffused, commonly used for flood protection. Their integrity and stability are fundamental prerequisites for the protection efficiency they can offer to the increasing frequency and magnitude of extreme flood events associated to changes in climate. Proper characterization and monitoring are essential to verify the construction requirements of newly built structures and to evaluate the durability of aged ones. Considering the linear extent of river embankments, their characterization requires not only local geotechnical investigations but also the application of efficient and economically affordable methods. This is even more essential when the investigations are performed after, or in foresee of, significant flood events, when these structures get stressed and timing of the surveys is crucial. In these conditions, new survey methodologies, with the use of mobile systems, are a main research topic. In this paper the application of a new electric streamer, specifically designed for these aims, is presented. The technical solutions adopted for its construction are described and its application to the characterization of three different river embankments is presented. These case studies were chosen in accordance with the Po River Interregional Agency (AIPO), which is the authority deputed to the safety of flood protection structures in North-West Italy, along the hydrographic network of the Po River. The selected embankments are all earth structures, constructed above the natural alluvial soils, but are characterized by different conditions and challenges. The results obtained with the new system were comparable to standard Electric Resistivity Tomography (ERT) methods. The new system has significant advantages in terms of reducing the survey time, improving the efficiency of the surveys and increasing the data coverage. This resulted in a better definition of potentially dangerous anomalies.

Alpine glaciers are key components of local and regional hydrogeological cycles and real-time indicators of climate change. Volume variations are primary targets of investigation for the understanding of ongoing modifications and the forecast of possible future scenarios. These fluctuations can be traced from time-lapse monitoring of the glacier topography. A detailed reconstruction of the ice bottom morphology is however needed to provide total volume and reliable mass balance estimations. Non-destructive geophysical techniques can support these investigations. With the aim of characterizing ice bottom depth, ground-penetrating radar (GPR) profiles and single-station passive seismic measurements were acquired on the terminal lobes of Belvedere Glacier (NW Italian Alps). The glacier is covered by blocks and debris and its rough topography is rapidly evolving in last years, with opening and relocation of crevasses and diffuse instabilities in the frontal sectors. Despite the challenging working environment, ground-based GPR surveys were performed in the period 2016–2018, using 70-MHz and 40-MHz antennas. The 3D ice bottom morphology was reconstructed for both frontal lobes and a detailed ice thickness map was obtained. GPR results also suggested some information on ice bottom properties. The glacier was found to probably lay on a thick sequence (more than 40 m) of subglacial deposits, rather than on stiff bedrock. Week deeper reflectors were identified only in the frontal portion of the northern lobe. These interfaces may indicate the bedrock presence at a depth of around 80 m from the topographic surface, rapidly deepening upstream. Single-station passive seismic measurements, processed with the horizontal-to-vertical spectral ratio (HVSR) method, pointed out the absence of sharp vertical contrast in acoustic impedance between ice and bottom materials, globally confirming the hypotheses made on GPR results. The obtained results have been compared with previous independent geophysical investigations, performed in 1961 and 1985, with the same aim of ice thickness estimation. The comparison allowed us to validate the results obtained in the different surveys, supply a reference base map for the glacier bottom morphology and potentially study ice thickness variations over time.

Underground Thermal Energy Storage systems have showed to be a useful and increasing technical solution for covering heating and cooling and domestic hot water buildings' demand. Thermal influence of these plants is however not still debated as it deserves and correct monitoring strategies appear to be of major importance both to better understand processes and to highlight their environmental effects into high populated areas. Litho-, hydro- and bio-sphere can indeed be adversely affected by temperature variations induced in the underground by heat storage applications. For this purpose, a geophysical monitoring approach using time-lapse electrical resistivity measurements contemporary to analogical simulations is here tested at laboratory scale. Results of the experiments are reported comparing measured apparent resistivity with direct temperature measurements and numerical simulations of heat propagation. Data presented confirmed that electrical resistivity has powerful relation with temperature variation in monitored media. In addition, they showed that also without performing data inversion valid temperature estimation can be carried out. Post-processing calibration of apparent resistivity data showed to be in acceptable agreement with both temperature measurements and numerical simulations. Simple apparent electrical resistivity variations appear therefore to be a promising, economic, quick and non-invasive tool for mapping thermal modifications induced in the underground by shallow geothermal applications.

Electrical resistivity tomography (ERT) of the area surrounding Tutankhamun's tomb (KV62) in the Valley of the Kings (Luxor, Egypt) reveals the presence of two anomalies located a few meters from Tutankhamun's funerary chamber. The strategy for ERT data acquisition and the adopted methods for data analysis are discussed in detail in this article, together with the possible archaeological significance of the detected anomalies.

The high sedimentological variability of gypsum rocks has the effect that a univocal characterization of this material is not easy to establish. This is particularly true from the geomechanical point of view: when the mechanical properties of gypsum rocks are requested, it is therefore necessary to undertake detailed characterization analyses. Common facies of gypsum was observed in the Upper Miocene evaporitic succession (Messinian Salinity Crisis) within the whole Mediterranean Basin. In this work, mechanical tests were conducted on a site-specific facies, represented by the microcrystalline branching selenite. The tested samples came from the Monferrato area (northwestern Italy). Uniaxial compressive strength (UCS) tests were performed in order to obtain reference mechanical parameters. More rapid and economic point load test (PLT) and ultrasonic pulse velocity (UPV) measurements were additionally performed to verify their applicability as complementary/alternative methods for site characterization. Rock-type specific PLT-UCS and UPV-UCS relationships were established. A wide dispersion of the mechanical parameters was observed due to the heterogeneities of the studied material. Consequently, compositional, textural and microstructural observations on selected samples were performed. Two main material classes were recognized based on average grain size and total gypsum content, underlining the significant influence of the grain sorting on the measured mechanical properties. Keywords: Gypsum, Uniaxial compressive strength (UCS), Point load test (PLT), Mechanical properties, Geological heterogeneity

The effect of high temperatures as a degrading factor of rock materials is investigated in this study. Valdieri Marble samples, collected in a quarry in North-western Italian Alps, were subjected to thermal cycles (ranging from 105° to 600 °C) and to subsequent non-destructive and destructive laboratory tests with the aim of evaluating the variation of physical and mechanical properties as a function of temperature variations. Physical and mechanical measurements were complemented with microscopic observations on thin sections. The increase of crack density with temperature and the consequent porosity increases were found to be the main causes of degradation of physical and mechanical properties. In general, density, ultrasonic pulse velocity, wet electrical resistivity, uniaxial compressive strength and Young's moduli decrease as temperature increases. By contrast, peak strain and porosity increase. Correlations between temperature and physical-mechanical properties were proposed and compared to other relationships already established in scientific literature. A damage parameter to quantify the degradation of mechanical properties with temperature is also proposed.

The seasonal storage of thermal energy in the ground is a useful application able to provide H&C and DHW demand of commercial or residential buildings. Several examples in Canada and Northern Europe demonstrated the reliability and convenience of these systems in terms of both energy and economic savings, but more demonstration sites are however necessary. The surrounding litho-, hydro- and bio-sphere are influenced by the plant's activity and a trustworthy supervision of the temperature field would bring advantages to both the environment and the system's efficiency. Usually numerical modeling is used to forecast the system behavior but results of simulations can be strongly dependent from assumed material characteristics and should be strictly calibrated on real data. To better understand thermal processes in the ground related to thermal injection and thermal storage, a field scale BTES living lab was build up nearby Torino (Northern Italy) within unsaturated alluvial deposits. Results show that approximately 9.1 GJ were transferred to the ground during the first year, raising the undisturbed temperature by 2 °C, and that a correct comparison of monitoring data and numerical simulations can be obtained following a specific site characterization.

This paper is devoted to the study of a conglomerate rock formation (Molare Formation) outcropping in southern Piedmont that forms a natural arch of environmental interest. Awareness with respect to the stability of this structure emerged after some intense rains which caused small collapses at the arch foot. The need for a proper characterization of the material in its natural state and its deterioration following increased water saturation is needed. A multidisciplinary approach based on the integration of both in situ and laboratory geophysical tests for the assessment of the rock structure at different scales was performed. Geological surveys together with seismic tomography and GPR have been executed on site. Petrographical and compositional studies of the matrix, ultrasonic pulse velocity measurements, electrical resistivity determinations and standard UCS test on large specimens are under development in laboratory.

The investigation and prediction of geological anomalies in underground quarries is fundamental to ensure safety, efficiency and economic convenience of the exploitation. For these aims, non-destructive geophysical surveys may be an effective alternative approach to classical destructive prospecting techniques (i.e. horizontal drilling), with great advantages particularly in complex geological frameworks and in areas subjected to specific geo-hazards. Ground Penetrating Radar (GPR), for its high resolution, is a suitable technique for underground excavations, particularly for the identification of water bodies, fissures and fractured rocks. The present study is focused on the application of GPR for the prediction of karst structures in underground gypsum quarries. Karst phenomenon is a main risk factor for gypsum orebodies, where large cavities may be intersected by the excavation. The possible filling with clay or pressurized water of these cavities exponentially increases the dangerousness of the phenomenon, due to swelling problems and violent water inrushes. The aim of the present study is to propose, through modelling and field surveys, a description of GPR outputs for principal elements of karst hazard in gypsum bodies, with particular attention to the discrimination of fillings (air, water or clay).

A borehole thermal energy storage living lab was built nearby Torino (Northern Italy). The aim of this living lab is to test the ability of the alluvial deposits of the north-western Po Plain to store the thermal energy collected by solar panels. Monitoring the temperature distribution induced in the underground and the effectiveness of the heat storage in this climatic context is not an easy task. For this purpose, different temperature evolution strategies are compared in this paper: Local temperature measurements, numerical simulations and geophysical surveys. These different approaches were compared during a single day of operation of the living lab. The results of this comparison allowed to underline the effectiveness of time-lapse 3D electric resistivity tomography as a non-invasive and cost-effective qualitative heat monitoring tool. This was obtained even in a test site with unfavorable thermo-hydrogeological conditions and high-level anthropic noise. Moreover, the present study demonstrated that, if properly calibrated with local temperature values, time-lapse 3D electric resistivity tomography also provides a quantitative estimation of the underground temperature.

A new seismic dilatometer (SPDMT) has been developed to combine the measurements of the flat dilatometer (DMT) geotechnical parameters with both P- and S- waves velocities. This new SPDMT is composed of the traditional mechanical DMT and four sensors for measuring the body waves velocities placed above the DMT blade. This SPDMT device is presented here, and the test procedure and the interpretation of P- and S-wave measurements are discussed. Results of the application of this new instrument are reported in a test site located in Bondeno (Emilia Romagna, Italy). Here, challenging water table conditions offer the opportunity to evaluate the advantage of a combined measure of the two propagation velocities, together with DMT geotechnical parameters, with the same apparatus for the porosity evaluation and a more calibrated liquefaction assessment.

In some areas, the estimation of static corrections for land seismic data is a critical step of the processing workflow. It often requires the execution of additional surveys and data analyses. Surface waves (SWs) in seismic records can be processed to extract local dispersion curves (DCs) that can be used to estimate near-surface S-wave velocity models. Here we focus on the direct estimation of time-average S-wave velocity models from SW DCs without the need to invert the data. Time-average velocity directly provides the value of one-way time, given a datum plan depth. The method requires the knowledge of one 1D S-wave velocity model along the seismic line, together with the relevant DC, to estimate a relationship between SW wavelength and investigation depth on the time-average velocity model. This wavelength/depth relationship is then used to estimate all the other time-average S-wave velocity models along the line directly from the DCs by means of a data transformation. This approach removes the need for extensive data inversion and provides a simple method suitable for industrial workflows. We tested the method on synthetic and field data and found that it is possible to retrieve the time-average velocity models with uncertainties less than 10% in sites with laterally varying velocities. The error on one-way times at various depths of the datum plan retrieved by the time-average velocity models is mostly less than 5 ms for synthetic and field data.