alessandro flora - Academia.edu (original) (raw)
Uploads
Papers by alessandro flora
E3S Web of Conferences
Copan is an important heritage site known by its preserved Maya ruins and recognized by UNESCO as... more Copan is an important heritage site known by its preserved Maya ruins and recognized by UNESCO as a World Heritage Property since 1980. To investigate and understand the site development, extensive archaeological tunnels were excavated in the earthen fills of the temples in the twentieth century.Archaeologists found a series of superimposed temples, built one upon another, in a very complex chronological sequence and spatial disposition. Even though the tunnels were initially excavated in the earthen fill without putting in place any supporting structure, masonry lining was applied in parts of the unnels years after they were excavated, in areas that suffered local collapses. Thick walls were built, forming tunnels about 1.0 m wide and 2.0 to 3.0 m high. The excavated soil is unsaturated, and thus has a strength depending on its water content and suction. Since most of the observed collapses take place during raining events, the effect of the change of the saturation degree on tunne...
Indian Geotechnical Journal
Geotechnical Earthquake Engineering and Soil Dynamics V
Geotechnical Earthquake Engineering and Soil Dynamics V
Lecture Notes in Civil Engineering
Electrokinetic (EK) treatment is studied for fine grained dredged soils as an innovative and cost... more Electrokinetic (EK) treatment is studied for fine grained dredged soils as an innovative and cost-effective method to accelerate the dewatering and improve their mechanical behaviour. Owing to their high-water content, the dredged sediments take a very long time for the consolidation process, much more than those considered in the typical problems of geotechnical engineering.
Proceedings of the Institution of Civil Engineers - Ground Improvement
Electrokinetic (EK) treatment is becoming increasingly important in the geotechnical field, espec... more Electrokinetic (EK) treatment is becoming increasingly important in the geotechnical field, especially for treating fine-grained soils. Above all, dredged sediments (slurries) need to be treated in order to be reutilised. Applying an electric potential difference within the soil, three phenomena take place: electrophoresis, electro-osmosis and electromigration. Negative particles move towards the positive electrode while water and cations move towards the negative electrode. Although the literature is full of cases describing the parameters that affect the EK process, there is a need to understand its limits and fields of application. This paper summarises the results collected from several case studies to understand the influence of some parameters on the efficiency of EK treatment, specifically in terms of dewatering rate. Soil conditions (soil type, pH, pore fluid salinity and water content) and set-up design parameters (electrode materials, configurations and operational mode) a...
In the framework of the LIQUEFACT project a series of centrifuge tests were conducted at ISMGEO (... more In the framework of the LIQUEFACT project a series of centrifuge tests were conducted at ISMGEO (Italy) to verify the effectiveness of three mitigation techniques against soil liquefaction. This paper is focused on the study of horizontal drains as mitigation measure against liquefaction. The centrifuge layout with horizontal drains was numerically modelled and the change of boundary conditions reproduced by the FE code Plaxis 2D. Additionally, slightly different layouts from those tested in the centrifuge were also modelled to expand the scope of the experimental work. Horizontal drains were installed in the model, to analyse their effectiveness in reducing the pore pressure build up as a function of their spacing. The soil was characterized by an advanced coupled soils constitutive model implemented in the Plaxis code: PM4sand. The input parameters for the model are evaluated on the basis of both laboratory element tests and centrifuge tests. <br>
On May 20, 2012, a seismic event of moment magnitude MW = 6.1 hit and caused severe damage on a l... more On May 20, 2012, a seismic event of moment magnitude MW = 6.1 hit and caused severe damage on a large area in the river Po Valley, located in the northern Italy. This earthquake was characterized by extensive occurrence of soil liquefaction and basin effects lying over deep deposits. Within the scope of the European research project titled LIQUEFACT, a reference site located in the countryside near the hamlet of Pieve di Cento (at the boundary of the province of Bologna towards Ferrara) was selected as a trial field in order to assess the effectiveness of several mitigation measures against liquefaction. As a first step of the task, this paper presents the geotechnical model of the site based on in-situ investigations and pre-existing geological studies, which allowed to locate the bedrock depth. As a second step, representative input motions for the LIQUEFACT project were selected aiming at simulating the 20.V.2012 seismic event as well as three possible future scenarios with an in...
Proceedings of the 8th International Conference on Computational Methods in Structural Dynamics and Earthquake Engineering (COMPDYN 2015), 2021
IABSE Symposium, Guimarães 2019: Towards a Resilient Built Environment Risk and Asset Management, 2019
Earthquakes induced liquefaction is one of the most significant causes of damage to structures du... more Earthquakes induced liquefaction is one of the most significant causes of damage to structures during an earthquake. Ground improvement is currently considered to be the most appropriate mitigation tecnique to prevent soil liquefaction. This work is aimed to compare different liquefaction mitigation techniques for protection of small-to-medium sized ‘critical’ infrastructures and low-rise buildings. The effectiveness of some techniques (densification, addition of fine contents, induced partial saturation and drainage systems) was verified via experimental evidences coming from laboratory testing, physical modelling and liquefaction field prototype tests. Starting from the calibration of advanced soil constitutive models, numerical modelling activities were extended to the back-analysis of centrifuge tests and field prototype tests, up to a parametric study with different geometrical layouts.
Journal of Earthquake Engineering, 2016
An approach to mitigate the seismic risk of existing structures by means of the creation of a con... more An approach to mitigate the seismic risk of existing structures by means of the creation of a continuous thin layer of grouted soil at a convenient depth is presented. A parametric numerical analysis is reported using different constitutive models with reference to two geometrical schemes. It is shown that if the grouted layer has a stiffness significantly lower than that of the surrounding soil, it may be effective in reducing the seismic demand. In the parametric analyses, the positive role of yielding is also observed, which indicates that the barrier is more effective with larger input amplitudes.
Journal of Cleaner Production, 2019
Geotechnical and Geological Engineering, 2013
Geotechnical and Geological Engineering, 2011
Géotechnique, 2019
Cyclic undrained triaxial tests were carried out on saturated and unsaturated loose specimens of ... more Cyclic undrained triaxial tests were carried out on saturated and unsaturated loose specimens of three fine-grained materials. The results confirm that, as the saturation degree decreases, liquefaction resistance sharply increases. In the interpretation of results, the first step was the assessment of the reliability of the use of the 5% strain amplitude criterion to define the attainment of liquefaction. With this aim, the tests were analysed assuming that the soil behaves as an equivalent viscous material. It is shown that the characteristic values of viscosity defining the start and completion of liquefaction depend on soil grading, increasing as the coefficient of uniformity increases. The equivalent viscosity corresponding to a condition of double strain axial amplitude of 5% is fairly constant for all soils. Then, starting from the observation of the relationship between the final volumetric strain and the initial degree of saturation, a theoretical interpretation of the tests...
Encyclopedia of Earth Sciences Series
E3S Web of Conferences
Copan is an important heritage site known by its preserved Maya ruins and recognized by UNESCO as... more Copan is an important heritage site known by its preserved Maya ruins and recognized by UNESCO as a World Heritage Property since 1980. To investigate and understand the site development, extensive archaeological tunnels were excavated in the earthen fills of the temples in the twentieth century.Archaeologists found a series of superimposed temples, built one upon another, in a very complex chronological sequence and spatial disposition. Even though the tunnels were initially excavated in the earthen fill without putting in place any supporting structure, masonry lining was applied in parts of the unnels years after they were excavated, in areas that suffered local collapses. Thick walls were built, forming tunnels about 1.0 m wide and 2.0 to 3.0 m high. The excavated soil is unsaturated, and thus has a strength depending on its water content and suction. Since most of the observed collapses take place during raining events, the effect of the change of the saturation degree on tunne...
Indian Geotechnical Journal
Geotechnical Earthquake Engineering and Soil Dynamics V
Geotechnical Earthquake Engineering and Soil Dynamics V
Lecture Notes in Civil Engineering
Electrokinetic (EK) treatment is studied for fine grained dredged soils as an innovative and cost... more Electrokinetic (EK) treatment is studied for fine grained dredged soils as an innovative and cost-effective method to accelerate the dewatering and improve their mechanical behaviour. Owing to their high-water content, the dredged sediments take a very long time for the consolidation process, much more than those considered in the typical problems of geotechnical engineering.
Proceedings of the Institution of Civil Engineers - Ground Improvement
Electrokinetic (EK) treatment is becoming increasingly important in the geotechnical field, espec... more Electrokinetic (EK) treatment is becoming increasingly important in the geotechnical field, especially for treating fine-grained soils. Above all, dredged sediments (slurries) need to be treated in order to be reutilised. Applying an electric potential difference within the soil, three phenomena take place: electrophoresis, electro-osmosis and electromigration. Negative particles move towards the positive electrode while water and cations move towards the negative electrode. Although the literature is full of cases describing the parameters that affect the EK process, there is a need to understand its limits and fields of application. This paper summarises the results collected from several case studies to understand the influence of some parameters on the efficiency of EK treatment, specifically in terms of dewatering rate. Soil conditions (soil type, pH, pore fluid salinity and water content) and set-up design parameters (electrode materials, configurations and operational mode) a...
In the framework of the LIQUEFACT project a series of centrifuge tests were conducted at ISMGEO (... more In the framework of the LIQUEFACT project a series of centrifuge tests were conducted at ISMGEO (Italy) to verify the effectiveness of three mitigation techniques against soil liquefaction. This paper is focused on the study of horizontal drains as mitigation measure against liquefaction. The centrifuge layout with horizontal drains was numerically modelled and the change of boundary conditions reproduced by the FE code Plaxis 2D. Additionally, slightly different layouts from those tested in the centrifuge were also modelled to expand the scope of the experimental work. Horizontal drains were installed in the model, to analyse their effectiveness in reducing the pore pressure build up as a function of their spacing. The soil was characterized by an advanced coupled soils constitutive model implemented in the Plaxis code: PM4sand. The input parameters for the model are evaluated on the basis of both laboratory element tests and centrifuge tests. <br>
On May 20, 2012, a seismic event of moment magnitude MW = 6.1 hit and caused severe damage on a l... more On May 20, 2012, a seismic event of moment magnitude MW = 6.1 hit and caused severe damage on a large area in the river Po Valley, located in the northern Italy. This earthquake was characterized by extensive occurrence of soil liquefaction and basin effects lying over deep deposits. Within the scope of the European research project titled LIQUEFACT, a reference site located in the countryside near the hamlet of Pieve di Cento (at the boundary of the province of Bologna towards Ferrara) was selected as a trial field in order to assess the effectiveness of several mitigation measures against liquefaction. As a first step of the task, this paper presents the geotechnical model of the site based on in-situ investigations and pre-existing geological studies, which allowed to locate the bedrock depth. As a second step, representative input motions for the LIQUEFACT project were selected aiming at simulating the 20.V.2012 seismic event as well as three possible future scenarios with an in...
Proceedings of the 8th International Conference on Computational Methods in Structural Dynamics and Earthquake Engineering (COMPDYN 2015), 2021
IABSE Symposium, Guimarães 2019: Towards a Resilient Built Environment Risk and Asset Management, 2019
Earthquakes induced liquefaction is one of the most significant causes of damage to structures du... more Earthquakes induced liquefaction is one of the most significant causes of damage to structures during an earthquake. Ground improvement is currently considered to be the most appropriate mitigation tecnique to prevent soil liquefaction. This work is aimed to compare different liquefaction mitigation techniques for protection of small-to-medium sized ‘critical’ infrastructures and low-rise buildings. The effectiveness of some techniques (densification, addition of fine contents, induced partial saturation and drainage systems) was verified via experimental evidences coming from laboratory testing, physical modelling and liquefaction field prototype tests. Starting from the calibration of advanced soil constitutive models, numerical modelling activities were extended to the back-analysis of centrifuge tests and field prototype tests, up to a parametric study with different geometrical layouts.
Journal of Earthquake Engineering, 2016
An approach to mitigate the seismic risk of existing structures by means of the creation of a con... more An approach to mitigate the seismic risk of existing structures by means of the creation of a continuous thin layer of grouted soil at a convenient depth is presented. A parametric numerical analysis is reported using different constitutive models with reference to two geometrical schemes. It is shown that if the grouted layer has a stiffness significantly lower than that of the surrounding soil, it may be effective in reducing the seismic demand. In the parametric analyses, the positive role of yielding is also observed, which indicates that the barrier is more effective with larger input amplitudes.
Journal of Cleaner Production, 2019
Geotechnical and Geological Engineering, 2013
Geotechnical and Geological Engineering, 2011
Géotechnique, 2019
Cyclic undrained triaxial tests were carried out on saturated and unsaturated loose specimens of ... more Cyclic undrained triaxial tests were carried out on saturated and unsaturated loose specimens of three fine-grained materials. The results confirm that, as the saturation degree decreases, liquefaction resistance sharply increases. In the interpretation of results, the first step was the assessment of the reliability of the use of the 5% strain amplitude criterion to define the attainment of liquefaction. With this aim, the tests were analysed assuming that the soil behaves as an equivalent viscous material. It is shown that the characteristic values of viscosity defining the start and completion of liquefaction depend on soil grading, increasing as the coefficient of uniformity increases. The equivalent viscosity corresponding to a condition of double strain axial amplitude of 5% is fairly constant for all soils. Then, starting from the observation of the relationship between the final volumetric strain and the initial degree of saturation, a theoretical interpretation of the tests...
Encyclopedia of Earth Sciences Series