1,720,991 research outputs found
A project addressed toward mitigation of the sinkhole risk
No full textNatural or anthropogenic sinkholes have become a serious hazard in Italy (Parise & Vennari, 2013), often causing damage to society. With the goal to provide a contribution toward mitigation of the related risk, we present the outcomes of a dedicated Project. It consisted in developing a variety of activities to identify and model failure mechanisms, to implement stability analysis and to define possible mitigation interventions. Articulated in two levels (from urban area to single cavity), the approach first aimed at defining the different aspects of the problem and selecting the case studies. Then, innovative survey technologies were applied, integrated by geomechanical studies and geotechnical modeling; further, a detailed economical analysis was performed, taking into account the historical-cultural values, as a necessary step before choosing appropriate stabilization works.
The selected case studies are Canosa di Puglia and Massafra (Apulia), and the San Lazzaro di Savena area (Emilia Romagna). Canosa di Puglia is characterized by many underground calcarenite quarries (type E1 in the Artificial Cavities Classification; Parise et al., 2013), excavated to extract building materials. With expansion of the urban area, a number of sinkholes occurred, also causing casualties. Massafra is characterized by deep valleys incised in the carbonate rocks. In this territory, due to spreading of the rupestrian civilization (Fonseca, 1980), many cavities were dug, especially as worship sites. Eventually, the San Lazzaro di Savena area (Gessi Bolognesi e Calanchi dell’Abbadessa Park) was studied due to co-existence of natural and artificial caves, these latter being extensive gypsum mines, nowadays abandoned.
The proposed multi-disciplinary approach can be applied from metropolitan areas to small cities, and is strongly based upon the main characters of the cave and its interaction with the built-up environment. The final goal is to identify the critical situations, to define the most proper analysis for stability evaluation, and to choose the actions aimed at mantaining the cavity in safety conditions, eventually allowing its public fruition, at least for those of historical and cultural value
A methodological approach to assess the hazard of underground cavities subjected to environmental weathering
No full textSoft highly porous carbonate rocks, such as calcarenites, and soluble sulphate rocks, such as gypsum, are very common in the Mediterranean region and, due to their microstructure and chemical composition, are prone to water induced weathering mechanisms. Cliffs, underground cavities and other morphological features in such formations are hence affected by intense erosion phenomena and weathering processes responsible for unexpected collapses and sinkholes. Just considering the Apulian region (Italy), 150 sinkholes have been recorded since 1925, with increasing frequency since 2000 (Fiore et al., 2018). The geosystem's failure is often the short- or long-term result of a very complex hydro-chemo-mechanical process taking place at the micro-scale which can be detected and analysed by means of field and laboratory experimental test campaigns. Therefore, stability problems are often related to changes of the mechanical properties of the rock forming the cave caused by environmental weathering processes, despite the external boundary conditions are not changing with time. The paper deals with the assessment of hazard associated with the stability of abandoned underground caves, which is nowadays frequently required for land and urban planning activities. A methodological approach for hazard assessment based on a step-by-step procedure is proposed. This includes in-situ surveys, laboratory experimental studies, theoretical analyses and finally numerical investigations. The approach derives from the experience developed from several case studies analysed by the authors. In this work, two of these are presented. The first one concerns the stability of an anthropic cavity in a calcarenite formation which is affected by a water induced short-term and long-term debonding processes. The second one regards the stability of a three-level abandoned gypsum mine, the lowest level being partially flooded by water. The methodological procedure aims to evaluate the factors controlling the change of the mechanical properties of the rock so that efficient remediation measures can be designed in order to avoid any further decay of the rock mass stability with time. The proposed methodological approach, validated on real case studies, shows the convenience of performing advanced experimental, theoretical and numerical studies to properly assess the hazard in space and time and to better design the mitigation measures if they are required. The adoption of the proposed approach reduced the remediation costs of the second case study of one order of magnitude
Mechanical effects of chemical degradation of bonded geomaterials in boundary value problems
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Landslides and geophysical investigations: advantages and limitations
Full text linkThis special issue is dedicated to the geophysical methods applied to investigate, characterize, and monitor landslides. Over the years, both the advantages and limitations of these techniques have been highlighted, and some drawbacks are still open. Some papers were submitted to this special issue, and, after a thorough peer review process, only five articles were selected to be included in this special issue. This relatively small number is probably caused by the difficulty in applying geophysical techniques on slope movements given hard-operating conditions (e.g., high slopes, distance from access roads, and lack of security for the technical operator) and not because the methods limitations are greater than the advantages
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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