Wave propagation through discontinuous media in rock engineering

The analysis of wave propagation in jointed rock masses is of interest for solving problems in geophysics, rock protective engineering, rock dynamics and earthquake engineering. At present, more than in the past, analyses of underground structures in seismic conditions need be considered. The aim of the present thesis is to contribute to the understanding of wave propagation in rock masses and of its influence on the stability of underground structures. The research is focused first on the analysis of the phenomenon through analytical, numerical and experimental methods. Then, static and dynamic stability analyses of a real case study such as the water storage cavern of the Tel Beer Sheva archaeological site in Israel (Iron age 1200-1700bc) are carried out. An analytical method such as the Scattering Matrix Method (SMM) is developed for the study of wave propagation through rock masses. This method (SMM) is based on the scattering matrix and is borrowed from electromagnetic wave propagation theory of transmission lines such as coaxial cables, optical fibres, strip-lines, etc. The scattering matrix is composed of reflection and transmission coefficients of a single joint or a set of parallel joints. Dry, fluid filled or frictional joints are considered. The computation can also be performed with material damping. Both P, SV or SH-waves can be applied to the model with any oblique angle of incidence. The analytical solution is obtained in the frequency domain and allows one to consider multiple wave reflections between joints. The analytical results obtained with the SMM are compared with other analytical methods and with the Distinct Element Method (DEM) by using the UDEC and 3DEC codes (from Itasca Consulting Group). The results obtained with the SMM applied to different joint models are compared with those obtained experimentally with the Hopkinson pressure bar (SHPB) tests. Resonant column laboratory tests are also performed to investigate the effects of fractures on wave propagation in a soft rock. A three-dimensional DEM model is implemented to simulate the resonant column test. Numerical and experimental results are compared. The stability of the water storage cavern of the Tel Beer Sheva archaeological site in Israel, excavated in a jointed chalk is assessed by means of static and dynamic DEM analyses in two and in three dimensional conditions. A back analysis of both the roof collapse during construction and of the cavern in its present configuration with a pillar installed in the centre is also carried out. Finally dynamic analyses are performed to evaluate the influence of wave propagation on the stability of the cavern with a deconvoluted motion produced by the Nuweiba earthquake (1995) being applied as input. Additional numerical analyses are performed to evaluate the dependence of the damage on the amplitude, duration, frequency and direction of the input wave

Wave propagation through discontinuous media in rock engineering

The analysis of wave propagation in jointed rock masses is of interest for solving problems in geophysics, rock protective engineering, rock dynamics and earthquake engineering. At present, more than in the past, analyses of underground structures in seismic conditions need be considered. The aim of the present thesis is to contribute to the understanding of wave propagation in rock masses and of its influence on the stability of underground structures. The research is focused first on the analysis of the phenomenon through analytical, numerical and experimental methods. Then, static and dynamic stability analyses of a real case study such as the water storage cavern of the Tel Beer Sheva archaeological site in Israel (Iron age 1200-1700bc) are carried out. An analytical method such as the Scattering Matrix Method (SMM) is developed for the study of wave propagation through rock masses. This method (SMM) is based on the scattering matrix and is borrowed from electromagnetic wave propagation theory of transmission lines such as coaxial cables, optical fibres, strip-lines, etc. The scattering matrix is composed of reflection and transmission coefficients of a single joint or a set of parallel joints. Dry, fluid filled or frictional joints are considered. The computation can also be performed with material damping. Both P, SV or SH-waves can be applied to the model with any oblique angle of incidence. The analytical solution is obtained in the frequency domain and allows one to consider multiple wave reflections between joints. The analytical results obtained with the SMM are compared with other analytical methods and with the Distinct Element Method (DEM) by using the UDEC and 3DEC codes (from Itasca Consulting Group). The results obtained with the SMM applied to different joint models are compared with those obtained experimentally with the Hopkinson pressure bar (SHPB) tests. Resonant column laboratory tests are also performed to investigate the effects of fractures on wave propagation in a soft rock. A three-dimensional DEM model is implemented to simulate the resonant column test. Numerical and experimental results are compared. The stability of the water storage cavern of the Tel Beer Sheva archaeological site in Israel, excavated in a jointed chalk is assessed by means of static and dynamic DEM analyses in two and in three dimensional conditions. A back analysis of both the roof collapse during construction and of the cavern in its present configuration with a pillar installed in the centre is also carried out. Finally dynamic analyses are performed to evaluate the influence of wave propagation on the stability of the cavern with a deconvoluted motion produced by the Nuweiba earthquake (1995) being applied as input. Additional numerical analyses are performed to evaluate the dependence of the damage on the amplitude, duration, frequency and direction of the input wav

Wave propagation in discontinuous media

Wave propagation in discontinuous media, which is of interest for design analysis of underground structures and geotechnical works in general, is studied in this paper with the scattering matrix method. This method determines the response of a system, i.e. the discontinuous medium, excited by an elastic wave. Both P, SV or SH waves can be applied to the model with any oblique angle of incidence. The scattering matrix is composed of reflection and transmission coefficients of a single joint or a set of parallel joints. The analytical solution is obtained in the frequency domain and allows one to consider multiple wave reflections between joints. Reflected and transmitted waves are calculated for one and more joints in dry or fluid filled conditions. The solutions obtained are compared with analytical and numerical solutions available in the literature or obtained independently by using the Distinct Element Metho

LE GALLERIE METROPOLITANE COME SCAMBIATORI DI CALORE: UNA IDEA DI APPLICAZIONE A TORINO

L’attivazione termica dei rivestimenti delle gallerie urbane può consentire di sfruttare l’inerzia termica del sottosuolo al fine di riscaldare o raffrescare gli edifici in superficie. Nell’ambito di una ricerca in corso al Politecnico di Torino, la nota descrive una possibile applicazione alla metropolitana di Torino descrivendo alcuni risultati di analisi numeriche finalizzate a studiare gli effetti dell’attivazione termica del rivestimento della galleria sulla falda preesistente

Interfacial Morphology Addresses Performance of Perovskite Solar Cells Based on Composite Hole Transporting Materials of Functionalized Reduced Graphene Oxide and P3HT

The development of novel hole transporting materials (HTMs) for perovskite solar cells (PSCs) that can enhance device's reproducibility is a largely pursued goal, even to the detriment of a very high efficiency, since it paves the way to an effective industrialization of this technology. In this work, we study the covalent functionalization of reduced graphene oxide (RGO) flakes with different organic functional groups with the aim of increasing the stability and homogeneity of their dispersion within a poly(3-hexylthiophene) (P3HT) HTM. The selected functional groups are indeed those recalling the two characteristic moieties present in P3HT, i.e., the thienyl and alkyl residues. After preparation and characterization of a number of functionalized RGO@P3HT blends, we test the two containing the highest percentage of dispersed RGO as HTMs in PSCs and compare their performance with that of pristine P3HT and of the standard Spiro-OMeTAD HTM. Results reveal the big influence of the morphology adopted by the single RGO flakes contained in the composite HTM in driving the final device performance and allow to distinguish one of these blends as a promising material for the fabrication of highly reproducible PSCs

A Retrospective Analysis of User Exposure to (Illicit) Cryptocurrency Mining on the Web

In late 2017, a sudden proliferation of malicious JavaScript was reported on the Web: browser-based mining exploited the CPU time of website visitors to mine the cryptocurrency Monero. Several studies measured the deployment of such code and developed defenses. However, previous work did not establish how many users were really exposed to the identified mining sites and whether there was a real risk given common user browsing behavior. In this paper, we present a retroactive analysis to close this research gap. We pool large-scale, longitudinal data from several vantage points, gathered during the prime time of illicit cryptomining, to measure the impact on web users. We leverage data from passive traffic monitoring of university networks and a large European ISP, with suspected mining sites identified in previous active scans. We corroborate our results with data from a browser extension with a large user base that tracks site visits. We also monitor open HTTP proxies and the Tor network for malicious injection of code. We find that the risk for most Web users was always very low, much lower than what deployment scans suggested. Any exposure period was also very brief. However, we also identify a previously unknown and exploited attack vector on mobile devices

Long-term monitoring of mammal communities in the Peneda-Gerês National Park using camera-trap data

In the past decades, agricultural land abandonment and declining land-use intensity became common, especially in the Mediterranean countries of southern Europe. In some areas, this development opened up possibilities for rewilding and the recolonisation or expansion of large mammal populations. Yet, in some instances, co-occurrence of wild mammals and free-ranging domestic herbivores might lead to potential conflicts. It is, therefore, necessary to study the ecological interactions between wild and domestic mammal species to understand the effects of land abandonment and rewilding on biodiversity and ecosystem services. Camera traps are an effective tool for studying species interactions and occupancy dynamics as they allow for long-term monitoring with minimal interference. We conducted a long-term monitoring programme with camera traps in the Peneda-Gerês National Park in northern Portugal. The area has undergone substantial land-use changes following the abandonment of agricultural areas in the past 60 years. While agro-pastoral activities, especially the breeding of free-ranging horses and cattle, are still common in the area, the intensity of these activities has decreased significantly, promoting natural succession and an increase or return of several large mammal species in recent years. Overall, our project aims at: (1) assessing the population trends of the medium and large sized mammals in the area over time; (2) analysing the effects of passive rewilding on occurrence, abundance and behaviour; and (3) understanding potential interactions or conflicts between wild and domestic herbivores. In this publication, we present results of a primary occupancy analysis between 2015 and 2020, as well as a comparison between occupancy and density estimates for 2019.Our publication provides a dataset from long-term camera-trap monitoring in the Peneda-Gerês National Park between 2015 and 2021. We established a 16 km² grid of 64 cameras deployed yearly during the summer months. Together with this publication, we publish the data and images collected between 2015 and 2021, using both the Camtrap DP standard and the GBIF Darwin Event Core. We obtained a total of 934,810 pictures on 41,234 trap nights. The pictures were automatically grouped into sequences with each sequence representing a distinct occurrence event, resulting in 80,191 occurrences. Out of those, 14,442 contained observations of a species, while the remaining were either blank or the species was not identifiable. We only obtained the information whether a species was present or absent on a picture, disregarding the number of individuals. Most observations were of domestic cattle (Bos taurus) and horses (Equus caballus), followed by European roe deer (Capreolus capreolus) and wild boar (Sus scrofa). Further observations include red fox (Vulpes vulpes), gray wolf (Canis lupus), Eurasian badger (Meles meles), stone marten (Martes foina), common genet (Genetta genetta), Iberian ibex (Capra pyrenaica) and red deer (Cervus elaphus). We estimated occupancy and densities for the most common species. The project is on-going and additional data will be included in the future. The dataset is freely available for ecological analysis, but also for training machine-learning systems in automated image classification as all pictures have been manually classified