Claudia Madiai | Università degli Studi di Firenze (University of Florence) (original) (raw)
Papers by Claudia Madiai
ISPRS International Journal of Geo-Information, 2019
In this paper, a MATLAB tool for the automatic detection of the best locations to install a wirel... more In this paper, a MATLAB tool for the automatic detection of the best locations to install a wireless sensor network (WSN) is presented. The implemented code works directly on high-resolution 3D point clouds and aims to help in positioning sensors that are part of a network requiring inter-visibility, namely, a clear line of sight (LOS). Indeed, with the development of LiDAR and Structure from Motion technologies, there is an opportunity to directly use 3D point cloud data to perform visibility analyses. By doing so, many disadvantages of traditional modelling and analysis methods can be bypassed. The algorithm points out the optimal deployment of devices following mainly two criteria: inter-visibility (using a modified version of the Hidden Point Removal operator) and inter-distance. Furthermore, an option to prioritize significant areas is provided. The proposed method was first validated on an artificial 3D model, and then on a landslide 3D point cloud acquired from terrestrial la...
Acta Geotechnica, Nov 27, 2022
Colloidal silica (CS) grouting is a soil improvement technique introduced as an innovative remedi... more Colloidal silica (CS) grouting is a soil improvement technique introduced as an innovative remedial measure against seismic liquefaction. It consists of injecting soils with a time-hardening, nanosilica-based solution forming a silica gel among soil particles. This paper presents the results of an experimental study on the effects of an initial static shear stress on the behaviour of a cyclically loaded clean sand stabilised with 5% CS. Undrained cyclic triaxial tests were performed to analyse the cyclic response of loose untreated and stabilised sand specimens, isotropically or anisotropically consolidated at the same initial mean effective stress. The consolidation stage was used to provide insight on the compressibility of stabilised soil. Stress-strain behaviour, pore water pressure response and cyclic shear resistance were investigated. The results showed that: (i) stabilised sand exhibits higher compressibility than the untreated one during isotropic consolidation; (ii) cyclic strength is higher for stabilised sand than for the untreated one, increasing as the degree of anisotropic initial stress increases; and (iii) extra pore water pressure development does not depend on the degree of initial anisotropy for stabilised sand, while the same does not hold for untreated sand. Simplified relationships are proposed to describe the consolidation process and the residual extra pore water pressure build-up process.
World Congress on Civil, Structural, and Environmental Engineering
A significant number of tailings dam failures have occurred around the world in the last few deca... more A significant number of tailings dam failures have occurred around the world in the last few decades resulting in fatalities, damage to infrastructure and environmental harm. Among these, many have been caused by the liquefaction phenomenon that can suddenly transform an earthen dam into a liquid river of mud. To date, many general aspects related to tailings dam failures and tailing management have been dealt with in the literature. However, the materials used to build the dams, mainly consisting of underconsolidated silts, are still poorly studied and adequate modeling of their behavior is still an open challenge. This paper presents the state of existing knowledge on this latter topic. The problem related to the storage of mining residues in tailings dams is first described. For this purpose, fifteen scientific articles, in which numerical modeling is carried out on this type of structures, are analyzed. Aspects relating to the type of structure investigated and connected to numerical modeling such as software and constitutive models used are reported and commented. A summary of the main geotechnical parameters used in the modeling is presented and analyzed. Finally, the most salient aspects of the results obtained from the various analysis are exposed.
The provisions of European (EC7 and EC8) and Italian (NTC-08) building codes for stability analys... more The provisions of European (EC7 and EC8) and Italian (NTC-08) building codes for stability analyses of man-made slopes (i.e. embankments and cut slopes) are discussed in the paper and the major criticalities and uncertainties are identified. These relate to: 1. The values of the reduction coefficient of the expected horizontal peak ground acceleration for the pseudo-static analyses; 2. The use of the partial coefficients for the ultimate limit state (ULS) and the serviceability limit state (SLS) analyses; 3. The selection of recorded and/or artificial acceleration time histories in the Newmark sliding block procedures; 4. Reference requirements for a judgment on the stability of slopes given that the permanent displacement increases exponentially as the critical seismic coefficient decreases. For each of the four points listed above is proposed an interpretation of the examined Codes, where the rules are unclear, or an integration, where the rules are absent. The safety verifications of an actual artificial slope, the embankments of a reservoir basin for flood reduction of the Parma stream, a tributary on the right side of the Po River (Italy), are considered to exemplify concretely the proposed suggestions. The aforementioned basin has recently been the object of a detailed study performed in order to evaluate its safety conditions following the new national seismic classification. An in-depth survey was carried out within the study and the necessary information needed to define a reliable geotechnical modelling of the embankment and soil foundation was obtained. Seismic stability analyses of the embankment of the reservoir basin were performed on a number of representative sections using both pseudo-static and Newmark displacement methods. The peak ground acceleration values and the acceleration time histories at the base of the embankment were assessed by means of onedimensional ground response analyses. Reference input motions for ground response analyses were obtained from the recent Italian seismic hazard estimates in accordance with NTC-08 requirements. Return periods of the seismic event of 50, 475, and 975 years were considered. Stability analyses discussed in the present paper were performed referring to the 475-year return period of the earthquake and relate to the internal side of the embankment of the most critical section in the reservoir conditions of rapid water drawdown. RÉSUMÉ Cette communication examine les dispositions des normes européennes (EC7 et EC8) et des normes italiennes (NTC-08) pour l'analyse de la stabilité des pentes artificielles et identifie les critiques et les incertitudes les plus importantes. Celles-ci concernent: 1. Les valeurs du coefficient de réduction de la valeur maximale de l'accélération attendue au site pour les analyses pseudo-statiques; 2. L'utilisation des coefficients partiels pour l'analyse de l'état limite ultime (ULS) et de service (SLS); 3. Le choix des accélérogrammes naturels et/ou artificiels pour l'application des méthodes basées sur l'analyse de Newmark; 4. Les indications de référence pour une évaluation de la stabilité des pentes, compte tenu que le déplacement permanent augmente de façon exponentielle par rapport à la diminution du coefficient sismique critique. Pour chacun des quatre points mentionnés ci-dessus, nous proposons une interprétation des codes examinés, au cas où les règles ne seraient pas claires, ou une intégration, au cas où les règles seraient absentes. Pour illustrer les suggestions proposées, nous avons considéré les contrôles de sécurité d'une pente artificielle (les levées d'un bassin pour la réduction des crues de la rivière Parma-Italie) qui ont été récemment l'objet d'une 1 Corresponding Author. brought to you by CORE View metadata, citation and similar papers at core.ac.uk provided by Florence Research étude détaillée, dans le but d'évaluer la situation de sécurité selon la nouvelle classification sismique nationale. Des analyses de la stabilité des remblais dans des conditions sismiques ont été effectuées sur un certain nombre de sections représentatives, en utilisant la méthode pseudo-statique et la méthode basée sur l'analyse de Newmark. Les valeurs de l'accélération maximale et les accélérogrammes à la base du remblai ont été évalués par des analyses numériques 1-D de la réponse sismique. Les données sismiques pour l'analyse de la réponse locale, ont été obtenues à partir des estimations récentes de l'aléa sismique conformément aux normes NTC-08, en faisant référence à des analyses des périodes de retour des séismes de 50, 475 et 975 ans. Les analyses de stabilité discutées dans cette étude ont été effectuées pour une période de récurrence de séisme de 475 ans et se concentrent sur le côté interne de la section la plus critique du remblai en cas de vidange rapide du bassin.
Experience has shown that soil-structure interaction can play an important role on structural beh... more Experience has shown that soil-structure interaction can play an important role on structural behaviour during earthquakes. A complete soil-structure interaction analysis consists of two parts: a site response analysis for free field motions and an interaction analysis for structural response. In the present study the effects of soil-structure interaction are evaluated on a two-storey concrete building about 10 m high with a rectangular horizontal section of about 11m x 28 m. The building, of public interest, is equipped with several accelerometers. The structure and the foundation system were idealised by a 3-D finite elements model, while the underlying soil is represented by a semi-infinite visco-elastic 1-D model. The soil-structure interaction analysis was performed by using the substructuring method implemented by the SASSI2000 numerical code. The accelerograms recorded during a low magnitude earthquake (ML = 4) by a free field seismic station, about 5m away from the building,...
Seismic protection of historical urban nuclei in Garfagnana: an example Garfagnana region was rep... more Seismic protection of historical urban nuclei in Garfagnana: an example Garfagnana region was repeatedly struck by destructive earthquakes up until quite recently. The region is mainly mountainous and very rocky, and is crossed by different systems of active faults. Many urban nuclei are situated on steep hillside and along deep valleys. The morphological and geotechnical conditions are favourable for producing topographic and stratigraphic amplification effects. The physical phenomena associated to these effects, generally disregarded in risk analyses on large scale and from the Italian seismic building code, have been object, in the last twenty years, of extensive research of the scientific community. The present research describes a few preliminary analyses for the site effects evaluation in the historical centre of Castelnuovo Garfagnana.
Dynamic geotechnical testing and seismic response analyses in two sites of the Commune of Nocera ... more Dynamic geotechnical testing and seismic response analyses in two sites of the Commune of Nocera Umbra, Italy Teresa Crespellani*, Claudia Madiai*, Giacomo Simoni ... 44 Crespei.LANi - Madiat - Simoni - Vannucchi frequencies of about 10 and 23 Hz for all four input motions. ...
... Claudia Madiai Johann Facciorusso Giacomo Simoni Page 2. ... 1-D Frontiera e base elastica SH... more ... Claudia Madiai Johann Facciorusso Giacomo Simoni Page 2. ... 1-D Frontiera e base elastica SHAKE91 (PROSHAKE) FONTE METODO DI ANALISI LEGAME COSTITUTIVO GEOMETRIA, CONDIZIONI AL CONTORNO CODICE DI CALCOLO Berkeley Schnabel et al. ...
Geotechnical Research, 2020
The effectiveness of colloidal silica (CS) treatment in increasing the liquefaction resistance of... more The effectiveness of colloidal silica (CS) treatment in increasing the liquefaction resistance of sandy soils is by now amply demonstrated. However, the best value of the CS content to achieve high performance, minimising economic cost and impact on buildings and the environment, has not yet been quantified. This paper presents the results of a laboratory study aimed to evaluate the influence of different CS contents on the behaviour of a liquefiable sand. The investigation included direct shear, cyclic triaxial, hydraulic conductivity and oedometer tests. CS contents 0, 2 and 5% (by weight) were used for all tests, except for direct shear tests (CS contents 0 and 2%) and oedometer tests (CS contents 0, 2, 3, 5, 10 and 13%). The test results showed that 2% CS content was enough to increase the soil strength under cyclic and monotonic loading conditions. The hydraulic conductivity of treated soil decreased significantly as CS content increased. Oedometer tests pointed out that the ma...
Bulletin of Earthquake Engineering, 2020
Bulletin of the Seismological Society of America, 2017
Bulletin of Earthquake Engineering, 2019
The investigation of soil response to dynamic loads is necessary to predict site-specific seismic... more The investigation of soil response to dynamic loads is necessary to predict site-specific seismic hazard. This paper presents the results of cyclic and dynamic laboratory tests carried out after the 2016-2017 Central Italy Earthquake sequence, within the framework of the seismic microzonation studies of the most damaged municipalities in the area. The database consists of 79 samples investigated by means of dynamic resonant column tests, cyclic torsional shear tests or cyclic direct simple shear tests. Results are firstly analysed in terms of field and laboratory values of small-strain shear wave velocity, highlighting the influence of the sample disturbance and of the mean effective consolidation pressure. The cyclic threshold shear strains as a function of plasticity index are then compared with findings from the published literature and the outliers are analysed. Subsequently, the dynamic soil behaviour is investigated with reference to the small-strain damping ratio. Differences between results from different tests are analysed in the light of the loading frequencies. Finally, the database is used to develop a predictive model for soil nonlinear curves according to plasticity index, mean effective confining stress, and loading frequency. The model represents a useful tool to predict the nonlinear stress-strain behaviour of Central Italy soils, necessary to perform site-specific ground response analyses. Keywords Soil dynamics • Laboratory tests • Shear modulus and damping ratio • Smallstrain material damping • Shear wave velocity Communicated by S.I.: Seismic Microzonation of Central Italy.
Journal of Performance of Constructed Facilities, 2017
AbstractThis paper summarizes the main aspects of geotechnical modeling and soil–structure intera... more AbstractThis paper summarizes the main aspects of geotechnical modeling and soil–structure interaction analyses performed for the seismic risk assessment of the San Gimignano towers. Morphological,...
ISPRS International Journal of Geo-Information, 2019
In this paper, a MATLAB tool for the automatic detection of the best locations to install a wirel... more In this paper, a MATLAB tool for the automatic detection of the best locations to install a wireless sensor network (WSN) is presented. The implemented code works directly on high-resolution 3D point clouds and aims to help in positioning sensors that are part of a network requiring inter-visibility, namely, a clear line of sight (LOS). Indeed, with the development of LiDAR and Structure from Motion technologies, there is an opportunity to directly use 3D point cloud data to perform visibility analyses. By doing so, many disadvantages of traditional modelling and analysis methods can be bypassed. The algorithm points out the optimal deployment of devices following mainly two criteria: inter-visibility (using a modified version of the Hidden Point Removal operator) and inter-distance. Furthermore, an option to prioritize significant areas is provided. The proposed method was first validated on an artificial 3D model, and then on a landslide 3D point cloud acquired from terrestrial la...
Acta Geotechnica, Nov 27, 2022
Colloidal silica (CS) grouting is a soil improvement technique introduced as an innovative remedi... more Colloidal silica (CS) grouting is a soil improvement technique introduced as an innovative remedial measure against seismic liquefaction. It consists of injecting soils with a time-hardening, nanosilica-based solution forming a silica gel among soil particles. This paper presents the results of an experimental study on the effects of an initial static shear stress on the behaviour of a cyclically loaded clean sand stabilised with 5% CS. Undrained cyclic triaxial tests were performed to analyse the cyclic response of loose untreated and stabilised sand specimens, isotropically or anisotropically consolidated at the same initial mean effective stress. The consolidation stage was used to provide insight on the compressibility of stabilised soil. Stress-strain behaviour, pore water pressure response and cyclic shear resistance were investigated. The results showed that: (i) stabilised sand exhibits higher compressibility than the untreated one during isotropic consolidation; (ii) cyclic strength is higher for stabilised sand than for the untreated one, increasing as the degree of anisotropic initial stress increases; and (iii) extra pore water pressure development does not depend on the degree of initial anisotropy for stabilised sand, while the same does not hold for untreated sand. Simplified relationships are proposed to describe the consolidation process and the residual extra pore water pressure build-up process.
World Congress on Civil, Structural, and Environmental Engineering
A significant number of tailings dam failures have occurred around the world in the last few deca... more A significant number of tailings dam failures have occurred around the world in the last few decades resulting in fatalities, damage to infrastructure and environmental harm. Among these, many have been caused by the liquefaction phenomenon that can suddenly transform an earthen dam into a liquid river of mud. To date, many general aspects related to tailings dam failures and tailing management have been dealt with in the literature. However, the materials used to build the dams, mainly consisting of underconsolidated silts, are still poorly studied and adequate modeling of their behavior is still an open challenge. This paper presents the state of existing knowledge on this latter topic. The problem related to the storage of mining residues in tailings dams is first described. For this purpose, fifteen scientific articles, in which numerical modeling is carried out on this type of structures, are analyzed. Aspects relating to the type of structure investigated and connected to numerical modeling such as software and constitutive models used are reported and commented. A summary of the main geotechnical parameters used in the modeling is presented and analyzed. Finally, the most salient aspects of the results obtained from the various analysis are exposed.
The provisions of European (EC7 and EC8) and Italian (NTC-08) building codes for stability analys... more The provisions of European (EC7 and EC8) and Italian (NTC-08) building codes for stability analyses of man-made slopes (i.e. embankments and cut slopes) are discussed in the paper and the major criticalities and uncertainties are identified. These relate to: 1. The values of the reduction coefficient of the expected horizontal peak ground acceleration for the pseudo-static analyses; 2. The use of the partial coefficients for the ultimate limit state (ULS) and the serviceability limit state (SLS) analyses; 3. The selection of recorded and/or artificial acceleration time histories in the Newmark sliding block procedures; 4. Reference requirements for a judgment on the stability of slopes given that the permanent displacement increases exponentially as the critical seismic coefficient decreases. For each of the four points listed above is proposed an interpretation of the examined Codes, where the rules are unclear, or an integration, where the rules are absent. The safety verifications of an actual artificial slope, the embankments of a reservoir basin for flood reduction of the Parma stream, a tributary on the right side of the Po River (Italy), are considered to exemplify concretely the proposed suggestions. The aforementioned basin has recently been the object of a detailed study performed in order to evaluate its safety conditions following the new national seismic classification. An in-depth survey was carried out within the study and the necessary information needed to define a reliable geotechnical modelling of the embankment and soil foundation was obtained. Seismic stability analyses of the embankment of the reservoir basin were performed on a number of representative sections using both pseudo-static and Newmark displacement methods. The peak ground acceleration values and the acceleration time histories at the base of the embankment were assessed by means of onedimensional ground response analyses. Reference input motions for ground response analyses were obtained from the recent Italian seismic hazard estimates in accordance with NTC-08 requirements. Return periods of the seismic event of 50, 475, and 975 years were considered. Stability analyses discussed in the present paper were performed referring to the 475-year return period of the earthquake and relate to the internal side of the embankment of the most critical section in the reservoir conditions of rapid water drawdown. RÉSUMÉ Cette communication examine les dispositions des normes européennes (EC7 et EC8) et des normes italiennes (NTC-08) pour l'analyse de la stabilité des pentes artificielles et identifie les critiques et les incertitudes les plus importantes. Celles-ci concernent: 1. Les valeurs du coefficient de réduction de la valeur maximale de l'accélération attendue au site pour les analyses pseudo-statiques; 2. L'utilisation des coefficients partiels pour l'analyse de l'état limite ultime (ULS) et de service (SLS); 3. Le choix des accélérogrammes naturels et/ou artificiels pour l'application des méthodes basées sur l'analyse de Newmark; 4. Les indications de référence pour une évaluation de la stabilité des pentes, compte tenu que le déplacement permanent augmente de façon exponentielle par rapport à la diminution du coefficient sismique critique. Pour chacun des quatre points mentionnés ci-dessus, nous proposons une interprétation des codes examinés, au cas où les règles ne seraient pas claires, ou une intégration, au cas où les règles seraient absentes. Pour illustrer les suggestions proposées, nous avons considéré les contrôles de sécurité d'une pente artificielle (les levées d'un bassin pour la réduction des crues de la rivière Parma-Italie) qui ont été récemment l'objet d'une 1 Corresponding Author. brought to you by CORE View metadata, citation and similar papers at core.ac.uk provided by Florence Research étude détaillée, dans le but d'évaluer la situation de sécurité selon la nouvelle classification sismique nationale. Des analyses de la stabilité des remblais dans des conditions sismiques ont été effectuées sur un certain nombre de sections représentatives, en utilisant la méthode pseudo-statique et la méthode basée sur l'analyse de Newmark. Les valeurs de l'accélération maximale et les accélérogrammes à la base du remblai ont été évalués par des analyses numériques 1-D de la réponse sismique. Les données sismiques pour l'analyse de la réponse locale, ont été obtenues à partir des estimations récentes de l'aléa sismique conformément aux normes NTC-08, en faisant référence à des analyses des périodes de retour des séismes de 50, 475 et 975 ans. Les analyses de stabilité discutées dans cette étude ont été effectuées pour une période de récurrence de séisme de 475 ans et se concentrent sur le côté interne de la section la plus critique du remblai en cas de vidange rapide du bassin.
Experience has shown that soil-structure interaction can play an important role on structural beh... more Experience has shown that soil-structure interaction can play an important role on structural behaviour during earthquakes. A complete soil-structure interaction analysis consists of two parts: a site response analysis for free field motions and an interaction analysis for structural response. In the present study the effects of soil-structure interaction are evaluated on a two-storey concrete building about 10 m high with a rectangular horizontal section of about 11m x 28 m. The building, of public interest, is equipped with several accelerometers. The structure and the foundation system were idealised by a 3-D finite elements model, while the underlying soil is represented by a semi-infinite visco-elastic 1-D model. The soil-structure interaction analysis was performed by using the substructuring method implemented by the SASSI2000 numerical code. The accelerograms recorded during a low magnitude earthquake (ML = 4) by a free field seismic station, about 5m away from the building,...
Seismic protection of historical urban nuclei in Garfagnana: an example Garfagnana region was rep... more Seismic protection of historical urban nuclei in Garfagnana: an example Garfagnana region was repeatedly struck by destructive earthquakes up until quite recently. The region is mainly mountainous and very rocky, and is crossed by different systems of active faults. Many urban nuclei are situated on steep hillside and along deep valleys. The morphological and geotechnical conditions are favourable for producing topographic and stratigraphic amplification effects. The physical phenomena associated to these effects, generally disregarded in risk analyses on large scale and from the Italian seismic building code, have been object, in the last twenty years, of extensive research of the scientific community. The present research describes a few preliminary analyses for the site effects evaluation in the historical centre of Castelnuovo Garfagnana.
Dynamic geotechnical testing and seismic response analyses in two sites of the Commune of Nocera ... more Dynamic geotechnical testing and seismic response analyses in two sites of the Commune of Nocera Umbra, Italy Teresa Crespellani*, Claudia Madiai*, Giacomo Simoni ... 44 Crespei.LANi - Madiat - Simoni - Vannucchi frequencies of about 10 and 23 Hz for all four input motions. ...
... Claudia Madiai Johann Facciorusso Giacomo Simoni Page 2. ... 1-D Frontiera e base elastica SH... more ... Claudia Madiai Johann Facciorusso Giacomo Simoni Page 2. ... 1-D Frontiera e base elastica SHAKE91 (PROSHAKE) FONTE METODO DI ANALISI LEGAME COSTITUTIVO GEOMETRIA, CONDIZIONI AL CONTORNO CODICE DI CALCOLO Berkeley Schnabel et al. ...
Geotechnical Research, 2020
The effectiveness of colloidal silica (CS) treatment in increasing the liquefaction resistance of... more The effectiveness of colloidal silica (CS) treatment in increasing the liquefaction resistance of sandy soils is by now amply demonstrated. However, the best value of the CS content to achieve high performance, minimising economic cost and impact on buildings and the environment, has not yet been quantified. This paper presents the results of a laboratory study aimed to evaluate the influence of different CS contents on the behaviour of a liquefiable sand. The investigation included direct shear, cyclic triaxial, hydraulic conductivity and oedometer tests. CS contents 0, 2 and 5% (by weight) were used for all tests, except for direct shear tests (CS contents 0 and 2%) and oedometer tests (CS contents 0, 2, 3, 5, 10 and 13%). The test results showed that 2% CS content was enough to increase the soil strength under cyclic and monotonic loading conditions. The hydraulic conductivity of treated soil decreased significantly as CS content increased. Oedometer tests pointed out that the ma...
Bulletin of Earthquake Engineering, 2020
Bulletin of the Seismological Society of America, 2017
Bulletin of Earthquake Engineering, 2019
The investigation of soil response to dynamic loads is necessary to predict site-specific seismic... more The investigation of soil response to dynamic loads is necessary to predict site-specific seismic hazard. This paper presents the results of cyclic and dynamic laboratory tests carried out after the 2016-2017 Central Italy Earthquake sequence, within the framework of the seismic microzonation studies of the most damaged municipalities in the area. The database consists of 79 samples investigated by means of dynamic resonant column tests, cyclic torsional shear tests or cyclic direct simple shear tests. Results are firstly analysed in terms of field and laboratory values of small-strain shear wave velocity, highlighting the influence of the sample disturbance and of the mean effective consolidation pressure. The cyclic threshold shear strains as a function of plasticity index are then compared with findings from the published literature and the outliers are analysed. Subsequently, the dynamic soil behaviour is investigated with reference to the small-strain damping ratio. Differences between results from different tests are analysed in the light of the loading frequencies. Finally, the database is used to develop a predictive model for soil nonlinear curves according to plasticity index, mean effective confining stress, and loading frequency. The model represents a useful tool to predict the nonlinear stress-strain behaviour of Central Italy soils, necessary to perform site-specific ground response analyses. Keywords Soil dynamics • Laboratory tests • Shear modulus and damping ratio • Smallstrain material damping • Shear wave velocity Communicated by S.I.: Seismic Microzonation of Central Italy.
Journal of Performance of Constructed Facilities, 2017
AbstractThis paper summarizes the main aspects of geotechnical modeling and soil–structure intera... more AbstractThis paper summarizes the main aspects of geotechnical modeling and soil–structure interaction analyses performed for the seismic risk assessment of the San Gimignano towers. Morphological,...