Alejo Sfriso - Academia.edu (original) (raw)
Papers by Alejo Sfriso
Acta Geotechnica, Oct 7, 2010
A constitutive model for sands in monotonic shear is presented. The model is designed to simulate... more A constitutive model for sands in monotonic shear is presented. The model is designed to simulate the behavior of sands in the whole stress and strain range of engineering interest with enough accuracy for practical usage. Material parameters were chosen to be state independent and easy to calibrate using conventional testing procedures. The formulation is based on effective stresses, pressure-dependent hyperelasticity, non-associative elastoplasticity, an isotropic hardening law and Rowe's stress-dilatancy theory. The implementation of Rowe's stress-dilatancy theory within the framework of elastoplasticity theory is discussed. It is found that Rowe's theory produces a volumetric plastic strain rate function that has a discontinuity in its first derivative w.r.t. stress, and a smoothed form is proposed instead. Finally, some experimental tests are simulated and the results are briefly discussed.
Symposium on Energy Geotechnics 2023, Sep 28, 2023
Computers and Geotechnics
Computers and Geotechnics
Congresso Brasileiro de Mecânica dos Solos e Engenharia Geotécnica
The interest of the mining industry on the assessment of tailings static liquefaction has exacerb... more The interest of the mining industry on the assessment of tailings static liquefaction has exacerbated after recent failures of upstream-raised tailings storage facilities (TSF). Standard practices to evaluate global stability of TSFs entail the use of limit equilibrium analyses considering peak and residual undrained shear strengths; thus, neglecting the work input required to drive the softening process that leads to progressive failure of susceptible tailings. This paper presents a simplified procedure to evaluate the static liquefaction triggering of upstream-raised TSFs by means of finite element models employing the well-known Hardening Soil model with small-strain stiffness (HSS). A calibration methodology is proposed to overcome the model limitation of not being implemented in a critical state framework, focusing on the stiffness parameters that control the rate of shear-induced plastic volumetric strains. A real TSF is modelled in Plaxis 2D to evaluate its vulnerability to liquefy due to an undrained lateral spreading at the foundation. Results show that minor movements near the toe induce the material into a strain-softening regime that leads to a progressive failure towards the structure crest.
Tunnels and Underground Cities: Engineering and Innovation meet Archaeology, Architecture and Art, 2019
The operation yard of Terminal Logística Bopicua is a 24.000 m2 unprotected, post-tensioned concr... more The operation yard of Terminal Logística Bopicua is a 24.000 m2 unprotected, post-tensioned concrete pavement, heavily loaded by stackers and cranes, with spans up to 70 meters between joints. In this kind of structures, the post-tensioning stresses have losses governed by friction between the structural plate and the pavement base, developed during and after stressing. To put these losses to a minimum, the engineers chose a friction reduced interface made by 3 - 5 mm of Río Uruguay sand and two sheets of polyethylene film. Friction coefficients recommended for this interfaces range 0.60 - 0.80, if no special testing is performed. These coefficients, along with post tensioning stresses of 2.5 MPa and spans of 70 m, produce friction losses around 20% of the initial tension load, with economic impact. This decided the project engineers to perform a friction test specifically devised to verify the behavior of the interface chosen in the structural design. A testing device was de...
srk.ru.com
FIGURA 1. Diagrama de polos del macizo en la embocadura del aliviadero. AGRADECIMIENTOS Los autor... more FIGURA 1. Diagrama de polos del macizo en la embocadura del aliviadero. AGRADECIMIENTOS Los autores agradecen a Energía Provincial Sociedad del Estado (EPSE), SanJuan, el apoyo recibido para la realización del presente artículo.
Computers and Geotechnics, 2022
Soil Dynamics and Earthquake Engineering, 2021
Time-history deformation analyses of upstream-raised tailings dams use seismic records as input d... more Time-history deformation analyses of upstream-raised tailings dams use seismic records as input data. Such records must be representative of the in-situ seismicity in terms of a wide range of intensity measures including PGA, Arias intensity, cumulative absolute velocity, source-to-site distance, duration, and others. No single IM is a sufficient descriptor of seismic demand because different records, all of them compliant with any IM, can produce a very wide range of results from negligible damage to global failure. The use of brute-force, where hundreds of seismic records compliant with a set of IMs is employed, has proven to be a reasonable workaround of this limitation, at least able to produce a probabilistic density function of demand indicators like crest settlement of the dam or slope deformation. This procedure, however, requires a large number of numerical models to be run, and is therefore time-consuming. Brute-force analyses can be optimized if an a-priori simple tool is...
In this paper, Rowe’s stress-dilatancy theory is reviewed from the viewpoint of its implementatio... more In this paper, Rowe’s stress-dilatancy theory is reviewed from the viewpoint of its implementation as a flow rule for conventional plasticity. Operational expressions are derived, the theoretical and numerical consequences of their mathematical form are discussed and some elements towards its experimental validation are outlined.
Buenos Aires, Argentina, is expanding it’s metro network. Some 22 km of new tunnels and a number ... more Buenos Aires, Argentina, is expanding it’s metro network. Some 22 km of new tunnels and a number of metro stations have been constructed between 1998 and 2011, and three new lines including 20 km of tunnels are scheduled for construction in the near future. During these years, construction procedures for underground stations have achieved significant improvements that had a heavy impact on design, costs and speed of construction. Some of these improvements are described in this paper, along with a brief update of the characterization of Buenos Aires soils for NATM tunneling.
arXiv: Geophysics, 2020
Recent failures of upstream-raised tailings storage facilities (TSF) raised con-cerns on the futu... more Recent failures of upstream-raised tailings storage facilities (TSF) raised con-cerns on the future use of these dams. While being cost-effective, they entail higher risks than conventional dams, as stability largely relies on the strength of tailings, which are loose and normally-consolidated materials that may exhibit strain-softening during un-drained loading. Current design practice involves limit equilibrium analyses adopting a fully-softened shear strength; while being conservative, this practice neglects the work input required to start the softening process that leads to progressive failure. This paper describes the calibration and application of the NGI-ADPSoft constitutive model to evaluate the potential of static liquefaction of an upstream-raised TSF and provides an indirect measure of resilience. The constitutive model incorporates undrained shear strength anisotropy and a mesh-independent anisotropic post-peak strain softening. The calibration is performed using labora...
The numerical analysis of a 171m high asphalt-faced rockfill dam for tailings storage and power g... more The numerical analysis of a 171m high asphalt-faced rockfill dam for tailings storage and power generation is presented for both static and seismic conditions. For static loading, the effect of compaction was investigated and FoS were computed in both 2D and 3D geometries. For seismic loading, 30 ground-motion records were selected from a large database using a proxy model and fed into 2D simulations, and four were run in 3D simulations. It is concluded that the design settlement of the dam is 1.20.2 m after construction and additional 5.4m for the design earthquake. RÉSUMÉ: L'analyse numérique en conditions statiques et sismiques d'un barrage en enrochement á masque en béton armé de 171m de hauteur pour le stockage des résidus et la production d'énergie est présentée. Pour le chargement statique, l'effet de compactage a été étudié et le facteurs de sécurité ont été calculés dans les géométries 2D et 3D. Pour le chargement sismique, plus de 30 enregistrements de mou...
This paper describes two numerical models that were performed to study the dynamic interaction be... more This paper describes two numerical models that were performed to study the dynamic interaction between a crusher, a mechanically stabilized earth wall and a stockpile for the primary crusher at important mining project in Peru. The models were implemented in the finite element program Plaxis 2D AE and were aimed to evaluate the interaction between crusher and earth fill, the effect of the of the position of stockpile on the behavior of the structure, and the safety factor for different positions of the stockpile with respect to the crusher station. This article presents the details and results of these models.
The friction angle of sands is computed by Bolton as the sum of the critical state friction angle... more The friction angle of sands is computed by Bolton as the sum of the critical state friction angle and a dilatancy term which is a function of mean effective pressure and void ratio. Critical state is reached when dilatancy vanishes, either due to volume change – in drained shear – or effective pressure change – in undrained shear. Therefore, equating Bolton’s dilatancy term to zero yields, at least theoretically, an implicit relationship between mean pressure and the critical state void ratio of sands. It is found that this relationship yields unrealistic results, mainly because Bolton’s expression if of phenomenological nature and was not intended to be used for this purpose. In this paper, a minor modification to Bolton’s dilatancy term is proposed. It is proved that the modified expression has the capacity to predict both the peak friction angle and the critical state void ratio for any void ratio and effective pressure within the range of engineering interest. RÉSUMÉ L ́angle de...
Proceedings of the WTC 2019 ITA-AITES World Tunnel Congress (WTC 2019), 2019
Acta Geotechnica, Oct 7, 2010
A constitutive model for sands in monotonic shear is presented. The model is designed to simulate... more A constitutive model for sands in monotonic shear is presented. The model is designed to simulate the behavior of sands in the whole stress and strain range of engineering interest with enough accuracy for practical usage. Material parameters were chosen to be state independent and easy to calibrate using conventional testing procedures. The formulation is based on effective stresses, pressure-dependent hyperelasticity, non-associative elastoplasticity, an isotropic hardening law and Rowe's stress-dilatancy theory. The implementation of Rowe's stress-dilatancy theory within the framework of elastoplasticity theory is discussed. It is found that Rowe's theory produces a volumetric plastic strain rate function that has a discontinuity in its first derivative w.r.t. stress, and a smoothed form is proposed instead. Finally, some experimental tests are simulated and the results are briefly discussed.
Symposium on Energy Geotechnics 2023, Sep 28, 2023
Computers and Geotechnics
Computers and Geotechnics
Congresso Brasileiro de Mecânica dos Solos e Engenharia Geotécnica
The interest of the mining industry on the assessment of tailings static liquefaction has exacerb... more The interest of the mining industry on the assessment of tailings static liquefaction has exacerbated after recent failures of upstream-raised tailings storage facilities (TSF). Standard practices to evaluate global stability of TSFs entail the use of limit equilibrium analyses considering peak and residual undrained shear strengths; thus, neglecting the work input required to drive the softening process that leads to progressive failure of susceptible tailings. This paper presents a simplified procedure to evaluate the static liquefaction triggering of upstream-raised TSFs by means of finite element models employing the well-known Hardening Soil model with small-strain stiffness (HSS). A calibration methodology is proposed to overcome the model limitation of not being implemented in a critical state framework, focusing on the stiffness parameters that control the rate of shear-induced plastic volumetric strains. A real TSF is modelled in Plaxis 2D to evaluate its vulnerability to liquefy due to an undrained lateral spreading at the foundation. Results show that minor movements near the toe induce the material into a strain-softening regime that leads to a progressive failure towards the structure crest.
Tunnels and Underground Cities: Engineering and Innovation meet Archaeology, Architecture and Art, 2019
The operation yard of Terminal Logística Bopicua is a 24.000 m2 unprotected, post-tensioned concr... more The operation yard of Terminal Logística Bopicua is a 24.000 m2 unprotected, post-tensioned concrete pavement, heavily loaded by stackers and cranes, with spans up to 70 meters between joints. In this kind of structures, the post-tensioning stresses have losses governed by friction between the structural plate and the pavement base, developed during and after stressing. To put these losses to a minimum, the engineers chose a friction reduced interface made by 3 - 5 mm of Río Uruguay sand and two sheets of polyethylene film. Friction coefficients recommended for this interfaces range 0.60 - 0.80, if no special testing is performed. These coefficients, along with post tensioning stresses of 2.5 MPa and spans of 70 m, produce friction losses around 20% of the initial tension load, with economic impact. This decided the project engineers to perform a friction test specifically devised to verify the behavior of the interface chosen in the structural design. A testing device was de...
srk.ru.com
FIGURA 1. Diagrama de polos del macizo en la embocadura del aliviadero. AGRADECIMIENTOS Los autor... more FIGURA 1. Diagrama de polos del macizo en la embocadura del aliviadero. AGRADECIMIENTOS Los autores agradecen a Energía Provincial Sociedad del Estado (EPSE), SanJuan, el apoyo recibido para la realización del presente artículo.
Computers and Geotechnics, 2022
Soil Dynamics and Earthquake Engineering, 2021
Time-history deformation analyses of upstream-raised tailings dams use seismic records as input d... more Time-history deformation analyses of upstream-raised tailings dams use seismic records as input data. Such records must be representative of the in-situ seismicity in terms of a wide range of intensity measures including PGA, Arias intensity, cumulative absolute velocity, source-to-site distance, duration, and others. No single IM is a sufficient descriptor of seismic demand because different records, all of them compliant with any IM, can produce a very wide range of results from negligible damage to global failure. The use of brute-force, where hundreds of seismic records compliant with a set of IMs is employed, has proven to be a reasonable workaround of this limitation, at least able to produce a probabilistic density function of demand indicators like crest settlement of the dam or slope deformation. This procedure, however, requires a large number of numerical models to be run, and is therefore time-consuming. Brute-force analyses can be optimized if an a-priori simple tool is...
In this paper, Rowe’s stress-dilatancy theory is reviewed from the viewpoint of its implementatio... more In this paper, Rowe’s stress-dilatancy theory is reviewed from the viewpoint of its implementation as a flow rule for conventional plasticity. Operational expressions are derived, the theoretical and numerical consequences of their mathematical form are discussed and some elements towards its experimental validation are outlined.
Buenos Aires, Argentina, is expanding it’s metro network. Some 22 km of new tunnels and a number ... more Buenos Aires, Argentina, is expanding it’s metro network. Some 22 km of new tunnels and a number of metro stations have been constructed between 1998 and 2011, and three new lines including 20 km of tunnels are scheduled for construction in the near future. During these years, construction procedures for underground stations have achieved significant improvements that had a heavy impact on design, costs and speed of construction. Some of these improvements are described in this paper, along with a brief update of the characterization of Buenos Aires soils for NATM tunneling.
arXiv: Geophysics, 2020
Recent failures of upstream-raised tailings storage facilities (TSF) raised con-cerns on the futu... more Recent failures of upstream-raised tailings storage facilities (TSF) raised con-cerns on the future use of these dams. While being cost-effective, they entail higher risks than conventional dams, as stability largely relies on the strength of tailings, which are loose and normally-consolidated materials that may exhibit strain-softening during un-drained loading. Current design practice involves limit equilibrium analyses adopting a fully-softened shear strength; while being conservative, this practice neglects the work input required to start the softening process that leads to progressive failure. This paper describes the calibration and application of the NGI-ADPSoft constitutive model to evaluate the potential of static liquefaction of an upstream-raised TSF and provides an indirect measure of resilience. The constitutive model incorporates undrained shear strength anisotropy and a mesh-independent anisotropic post-peak strain softening. The calibration is performed using labora...
The numerical analysis of a 171m high asphalt-faced rockfill dam for tailings storage and power g... more The numerical analysis of a 171m high asphalt-faced rockfill dam for tailings storage and power generation is presented for both static and seismic conditions. For static loading, the effect of compaction was investigated and FoS were computed in both 2D and 3D geometries. For seismic loading, 30 ground-motion records were selected from a large database using a proxy model and fed into 2D simulations, and four were run in 3D simulations. It is concluded that the design settlement of the dam is 1.20.2 m after construction and additional 5.4m for the design earthquake. RÉSUMÉ: L'analyse numérique en conditions statiques et sismiques d'un barrage en enrochement á masque en béton armé de 171m de hauteur pour le stockage des résidus et la production d'énergie est présentée. Pour le chargement statique, l'effet de compactage a été étudié et le facteurs de sécurité ont été calculés dans les géométries 2D et 3D. Pour le chargement sismique, plus de 30 enregistrements de mou...
This paper describes two numerical models that were performed to study the dynamic interaction be... more This paper describes two numerical models that were performed to study the dynamic interaction between a crusher, a mechanically stabilized earth wall and a stockpile for the primary crusher at important mining project in Peru. The models were implemented in the finite element program Plaxis 2D AE and were aimed to evaluate the interaction between crusher and earth fill, the effect of the of the position of stockpile on the behavior of the structure, and the safety factor for different positions of the stockpile with respect to the crusher station. This article presents the details and results of these models.
The friction angle of sands is computed by Bolton as the sum of the critical state friction angle... more The friction angle of sands is computed by Bolton as the sum of the critical state friction angle and a dilatancy term which is a function of mean effective pressure and void ratio. Critical state is reached when dilatancy vanishes, either due to volume change – in drained shear – or effective pressure change – in undrained shear. Therefore, equating Bolton’s dilatancy term to zero yields, at least theoretically, an implicit relationship between mean pressure and the critical state void ratio of sands. It is found that this relationship yields unrealistic results, mainly because Bolton’s expression if of phenomenological nature and was not intended to be used for this purpose. In this paper, a minor modification to Bolton’s dilatancy term is proposed. It is proved that the modified expression has the capacity to predict both the peak friction angle and the critical state void ratio for any void ratio and effective pressure within the range of engineering interest. RÉSUMÉ L ́angle de...
Proceedings of the WTC 2019 ITA-AITES World Tunnel Congress (WTC 2019), 2019