Ponències/Comunicacions de congressos
http://hdl.handle.net/2117/3579
20160210T00:50:37Z

Reaction of a pile group against deep swelling
http://hdl.handle.net/2117/81904
Reaction of a pile group against deep swelling
Alonso Pérez de Agreda, Eduardo; Ramon Tarragona, Anna; Sauter, Simon
A singular case of development of deep soil expansions in the vicinity of pile groups supporting bridge pillars motivated the analysis. A semianalytic procedure, which uses some available fundamental solutions for cavity expansion and the presence of concentrated loads in an elastic halfspace, has been developed. The analysis requires an estimation of the soil displacements under the combined action of the stresses induced by the pile, the external loads and the volumetric deformations imposed by the soil expansion. “In situ” measurements provided an estimation of the deep volumetric deformations. The pile cap was also monitored and the evolution of its rotations and displacements was available. The analysis shows that all the piles of a group develop considerable bending stresses, which explain the cracking observed in the contact between the pile and the pile cap. The procedure developed predicts reasonably well the displacements and rotations experienced by the pile cap of the pile group.
20160122T16:36:39Z
Alonso Pérez de Agreda, Eduardo
Ramon Tarragona, Anna
Sauter, Simon
A singular case of development of deep soil expansions in the vicinity of pile groups supporting bridge pillars motivated the analysis. A semianalytic procedure, which uses some available fundamental solutions for cavity expansion and the presence of concentrated loads in an elastic halfspace, has been developed. The analysis requires an estimation of the soil displacements under the combined action of the stresses induced by the pile, the external loads and the volumetric deformations imposed by the soil expansion. “In situ” measurements provided an estimation of the deep volumetric deformations. The pile cap was also monitored and the evolution of its rotations and displacements was available. The analysis shows that all the piles of a group develop considerable bending stresses, which explain the cracking observed in the contact between the pile and the pile cap. The procedure developed predicts reasonably well the displacements and rotations experienced by the pile cap of the pile group.

Incorporating a microstructural state variable in constitutive modelling
http://hdl.handle.net/2117/81821
Incorporating a microstructural state variable in constitutive modelling
Pinyol Puigmartí, Núria Mercè; Alonso Pérez de Agreda, Eduardo; Gens Solé, Antonio
The selection of constitutive variables has been extensively discussed when modeling unsaturated soils. In general, suction and degree of saturation have been involved in the definition of constitutive variables. Recently, microstructural features have also been included due to their relevant effects on the mechanical and hydraulic soil response. This is the case of a model recently published by the same authors which includes a state variable in the definition of the constitutive variables to take into account microstructural effects. Details of the performance of this model, which has a relatively simple elastoplastic formulation, are presented. The simulation of isotropic stress paths illustrates the capabilities of the model and the effect of the microstructural state variable.
20160121T16:32:22Z
Pinyol Puigmartí, Núria Mercè
Alonso Pérez de Agreda, Eduardo
Gens Solé, Antonio
The selection of constitutive variables has been extensively discussed when modeling unsaturated soils. In general, suction and degree of saturation have been involved in the definition of constitutive variables. Recently, microstructural features have also been included due to their relevant effects on the mechanical and hydraulic soil response. This is the case of a model recently published by the same authors which includes a state variable in the definition of the constitutive variables to take into account microstructural effects. Details of the performance of this model, which has a relatively simple elastoplastic formulation, are presented. The simulation of isotropic stress paths illustrates the capabilities of the model and the effect of the microstructural state variable.

An undrained upper bound solution for the face stability of tunnels reinforced by micropiles
http://hdl.handle.net/2117/81818
An undrained upper bound solution for the face stability of tunnels reinforced by micropiles
Pinyol Puigmartí, Núria Mercè; Alonso Pérez de Agreda, Eduardo
Tunnel in difficult soils may require procedures to prevent tunnel face failures. Face stabilization can be achieved by the installation of some structural elements. This paper presents an analysis of face stability of shallow tunnels in undrained soils reinforced by an umbrella of subhorizontal micropiles. Upper bound solutions for two dimensional plane strain conditions are given including the effect of micropiles. The micropile umbrella is embedded in the soil and supported on the tunnel lining. The kinematically admissible collapse mechanism defined to calculate the upper bound solution includes the action provided by a subhorizontal micropile at limiting conditions. The solutions are given in practical dimensionless charts which are useful to quantify easily the effect of the umbrella of micropiles. The plots provide a simple procedure to design the umbrella. The most relevant properties defining the umbrella are grouped into a single dimensionless coefficient which includes the yielding conditions and the geometry of the micropiles as well as the distance between them.; Tunnel in difficult soils may require procedures to prevent tunnel face failures. Face stabilization can be achieved by the installation of some structural elements. This paper presents an analysis of face stability of shallow tunnels in undrained soils reinforced by an umbrella of subhorizontal micropiles. Upper bound solutions for two dimensional plane strain conditions are given including the effect of micropiles. The micropile umbrella is embedded in the soil and supported on the tunnel lining. The kinematically admissible collapse mechanism defined to calculate the upper bound solution includes the action provided by a subhorizontal micropile at limiting conditions. The solutions are given in practical dimensionless charts which are useful to quantify easily the effect of the umbrella of micropiles. The plots provide a simple procedure to design the umbrella. The most relevant properties defining the umbrella are grouped into a single dimensionless coefficient which includes the yielding conditions and the geometry of the micropiles as well as the distance between them.
20160121T15:14:14Z
Pinyol Puigmartí, Núria Mercè
Alonso Pérez de Agreda, Eduardo
Tunnel in difficult soils may require procedures to prevent tunnel face failures. Face stabilization can be achieved by the installation of some structural elements. This paper presents an analysis of face stability of shallow tunnels in undrained soils reinforced by an umbrella of subhorizontal micropiles. Upper bound solutions for two dimensional plane strain conditions are given including the effect of micropiles. The micropile umbrella is embedded in the soil and supported on the tunnel lining. The kinematically admissible collapse mechanism defined to calculate the upper bound solution includes the action provided by a subhorizontal micropile at limiting conditions. The solutions are given in practical dimensionless charts which are useful to quantify easily the effect of the umbrella of micropiles. The plots provide a simple procedure to design the umbrella. The most relevant properties defining the umbrella are grouped into a single dimensionless coefficient which includes the yielding conditions and the geometry of the micropiles as well as the distance between them.
Tunnel in difficult soils may require procedures to prevent tunnel face failures. Face stabilization can be achieved by the installation of some structural elements. This paper presents an analysis of face stability of shallow tunnels in undrained soils reinforced by an umbrella of subhorizontal micropiles. Upper bound solutions for two dimensional plane strain conditions are given including the effect of micropiles. The micropile umbrella is embedded in the soil and supported on the tunnel lining. The kinematically admissible collapse mechanism defined to calculate the upper bound solution includes the action provided by a subhorizontal micropile at limiting conditions. The solutions are given in practical dimensionless charts which are useful to quantify easily the effect of the umbrella of micropiles. The plots provide a simple procedure to design the umbrella. The most relevant properties defining the umbrella are grouped into a single dimensionless coefficient which includes the yielding conditions and the geometry of the micropiles as well as the distance between them.

Sustainability assessment of earth retaining wall structures: preliminary model and simplified application
http://hdl.handle.net/2117/81547
Sustainability assessment of earth retaining wall structures: preliminary model and simplified application
García Adroguer, Eduard; Puig Damians, Ivan; Josa GarciaTornel, Alejandro; Lloret Morancho, Antonio; Bathurst, Richard
Earth retaining wall (RW) structures have been used for centuries but new technologies and innovations in materials continue to emerge. While different wall types can perform the same function, a rigorous sustainability assessment protocol should be part of the selection procedure. This paper describes benchmarks for the development of sustainability assessment methods for RW structures, with criteria based on technical, environmental, economic and social factors. A wide range of materials and constructive solutions are available for RW structures. This study focuses on the most common wall types: gravity, cantilever and mechanically stabilized earth (MSE) walls (both geosynthetic and metallic reinforcement). The sustainability assessment methodology is explained and a simplified sustainability model applied to four 5 mhigh RW structures falling in the three categories mentioned. The results of analyses demonstrate that MSE wall alternatives are the best solution from the sustainability point of view.
20160115T16:26:26Z
García Adroguer, Eduard
Puig Damians, Ivan
Josa GarciaTornel, Alejandro
Lloret Morancho, Antonio
Bathurst, Richard
Earth retaining wall (RW) structures have been used for centuries but new technologies and innovations in materials continue to emerge. While different wall types can perform the same function, a rigorous sustainability assessment protocol should be part of the selection procedure. This paper describes benchmarks for the development of sustainability assessment methods for RW structures, with criteria based on technical, environmental, economic and social factors. A wide range of materials and constructive solutions are available for RW structures. This study focuses on the most common wall types: gravity, cantilever and mechanically stabilized earth (MSE) walls (both geosynthetic and metallic reinforcement). The sustainability assessment methodology is explained and a simplified sustainability model applied to four 5 mhigh RW structures falling in the three categories mentioned. The results of analyses demonstrate that MSE wall alternatives are the best solution from the sustainability point of view.

Highly expansive granular mixtures
http://hdl.handle.net/2117/81160
Highly expansive granular mixtures
Alonso Pérez de Agreda, Eduardo; Pinyol Puigmartí, Núria Mercè; Hoffmann Jauge, Christian
The paper describes the behavior of mixtures of highly compacted bentonite pellets. They are considered as a suitable impervious and tight barrier for nuclear waste disposal. Laboratory experiments aimed at identifying the hydraulic and mechanical properties of these mixtures are described. They are characterized by a very marked twosize pore space. The large pores and its evolution during wetting explain the rapid drop in permeability. The paper describes also the wetting rate effects, which are pronounced in these materials. These effects may be described if the usual assumption of local suction equilibrium is removed. Parameters of a double structure expansive model are determined by backanalysis of a set of suction controlled tests. Then, the measured performance of a large scale wetting test is compared with model predictions. © 2014 Taylor & Francis Group, London.
20160108T14:18:22Z
Alonso Pérez de Agreda, Eduardo
Pinyol Puigmartí, Núria Mercè
Hoffmann Jauge, Christian
The paper describes the behavior of mixtures of highly compacted bentonite pellets. They are considered as a suitable impervious and tight barrier for nuclear waste disposal. Laboratory experiments aimed at identifying the hydraulic and mechanical properties of these mixtures are described. They are characterized by a very marked twosize pore space. The large pores and its evolution during wetting explain the rapid drop in permeability. The paper describes also the wetting rate effects, which are pronounced in these materials. These effects may be described if the usual assumption of local suction equilibrium is removed. Parameters of a double structure expansive model are determined by backanalysis of a set of suction controlled tests. Then, the measured performance of a large scale wetting test is compared with model predictions. © 2014 Taylor & Francis Group, London.

Equivalent interface properties to model soilfacing interactions with zerothickness and continuum element methodologies
http://hdl.handle.net/2117/80340
Equivalent interface properties to model soilfacing interactions with zerothickness and continuum element methodologies
Puig Damians, Ivan; Yu, Yan; Lloret Morancho, Antonio; Bathurst, Richard; Josa GarciaTornel, Alejandro
Soilfacing mechanical interactions play an important role in the behavior of earth retaining walls. Generally, numerical analysis of earth retaining structures requires the use of interface elements between dissimilar component materials to model soilstructure interactions and to capture the transfer of normal and shear stresses through these discontinuities. In the finite element method PLAXIS software program, soilstructure interactions can be modelled using “zerothickness” interface elements between the soil and structural components. These elements use a strength/stiffness reduction factor that is applied to the soil adjacent to the interface. However, in some numerical codes where the zerothickness elements (or other similar special interface elements) are not provided, the use of continuum elements to model soilstructure interactions is the only option. The continuum element approach allows more control of the interface features (i.e., material strength and stiffness properties) as well as the element sizes and shapes at the interfaces. This paper proposes parameter values for zerothickness elements that will give the same numerical outcomes as those using continuum elements in PLAXIS. The numerical results show good agreement for the computed loads transferred from soil to structure using both methods (i.e., zerothickness elements and continuum elements at interfaces).
20151209T16:37:39Z
Puig Damians, Ivan
Yu, Yan
Lloret Morancho, Antonio
Bathurst, Richard
Josa GarciaTornel, Alejandro
Soilfacing mechanical interactions play an important role in the behavior of earth retaining walls. Generally, numerical analysis of earth retaining structures requires the use of interface elements between dissimilar component materials to model soilstructure interactions and to capture the transfer of normal and shear stresses through these discontinuities. In the finite element method PLAXIS software program, soilstructure interactions can be modelled using “zerothickness” interface elements between the soil and structural components. These elements use a strength/stiffness reduction factor that is applied to the soil adjacent to the interface. However, in some numerical codes where the zerothickness elements (or other similar special interface elements) are not provided, the use of continuum elements to model soilstructure interactions is the only option. The continuum element approach allows more control of the interface features (i.e., material strength and stiffness properties) as well as the element sizes and shapes at the interfaces. This paper proposes parameter values for zerothickness elements that will give the same numerical outcomes as those using continuum elements in PLAXIS. The numerical results show good agreement for the computed loads transferred from soil to structure using both methods (i.e., zerothickness elements and continuum elements at interfaces).

Crystal growth and soil expansion: the role of interfacial pressure and pore structure
http://hdl.handle.net/2117/79438
Crystal growth and soil expansion: the role of interfacial pressure and pore structure
Ramon Tarragona, Anna; Alonso Pérez de Agreda, Eduardo
The paper summarizes first a set of field observations in connection with the severe heave experienced by Lilla tunnel excavated in a Tertiary anhydritic claystone. Heave and swelling pressures against the tunnel rigid lining were a consequence of gypsum crystal growth on discontinuities. This process requires water because gypsum crystals precipitate from supersaturated solutions of calcium sulfate. The paper concentrates on the precipitation of crystal in pores of varying geometry with the purpose of deriving theoretical expressions for the crystal pressure against the (assumed rigid) pore walls. The problem is solved by two complementary approaches: the thermodynamic requirements for the equilibrium of the chemical reaction of precipitation and the consideration of the surface energy at the crystalsolution interface. The phenomenon has strong similarities with other interfaces of interest in unsaturated soil mechanics which are highlighted. The expressions found for the crystal pressure are considered an upper bound for pressures likely to develop
20151118T16:40:13Z
Ramon Tarragona, Anna
Alonso Pérez de Agreda, Eduardo
The paper summarizes first a set of field observations in connection with the severe heave experienced by Lilla tunnel excavated in a Tertiary anhydritic claystone. Heave and swelling pressures against the tunnel rigid lining were a consequence of gypsum crystal growth on discontinuities. This process requires water because gypsum crystals precipitate from supersaturated solutions of calcium sulfate. The paper concentrates on the precipitation of crystal in pores of varying geometry with the purpose of deriving theoretical expressions for the crystal pressure against the (assumed rigid) pore walls. The problem is solved by two complementary approaches: the thermodynamic requirements for the equilibrium of the chemical reaction of precipitation and the consideration of the surface energy at the crystalsolution interface. The phenomenon has strong similarities with other interfaces of interest in unsaturated soil mechanics which are highlighted. The expressions found for the crystal pressure are considered an upper bound for pressures likely to develop

EPB tunnelling in mixed geological formations: a case study
http://hdl.handle.net/2117/27860
EPB tunnelling in mixed geological formations: a case study
Di Mariano, Alessandra; Gens Solé, Antonio
Tunnels for the new Barcelona Metro Line 9 are being constructed in a densely built urban area, close to sensitive structures. The paper presents a case history involving tunnelling in difficult mixed geological conditions belowan existing Metro Line (Line 4).Tunnelling was performed with a dual EPB boring machine and the closed mode of operation was prescribed beneath all sensitive structures. Despite this original prescription, an open mode excavation (with a partially filled pressure chamber) had to be adopted to avoid the interruption of the boring process in the area below the existing Metro Line 4. The paper describes the geological conditions of the site, presents some of the ground movement observations prior to the change of excavation mode and discusses the rationale that allowed the change in the prescribed tunnelling mode as well as the results obtained. Observations of displacements during the excavation in open mode confirmed that no soil inrush into the head chamber occurred and that in addition, with the new excavation procedure, ground movements were reduced significantly.
20150508T18:16:09Z
Di Mariano, Alessandra
Gens Solé, Antonio
Tunnels for the new Barcelona Metro Line 9 are being constructed in a densely built urban area, close to sensitive structures. The paper presents a case history involving tunnelling in difficult mixed geological conditions belowan existing Metro Line (Line 4).Tunnelling was performed with a dual EPB boring machine and the closed mode of operation was prescribed beneath all sensitive structures. Despite this original prescription, an open mode excavation (with a partially filled pressure chamber) had to be adopted to avoid the interruption of the boring process in the area below the existing Metro Line 4. The paper describes the geological conditions of the site, presents some of the ground movement observations prior to the change of excavation mode and discusses the rationale that allowed the change in the prescribed tunnelling mode as well as the results obtained. Observations of displacements during the excavation in open mode confirmed that no soil inrush into the head chamber occurred and that in addition, with the new excavation procedure, ground movements were reduced significantly.

THM analysis of pelletbased materials for engineered barriers for nuclear waste
http://hdl.handle.net/2117/27443
THM analysis of pelletbased materials for engineered barriers for nuclear waste
Gens Solé, Antonio; Barboza De Vasconcelos, Ramon; Villar Galicia, María Victoria
A promising alternative to form engineered barriers for high level nuclear waste repositories is the use of pelletsbased material because high dry densities can be achieved with no or minimal compaction effort. It is also planned to subject these materials to temperatures significantly higher than 100ºC. The paper reports the results of coupled THM analyses of a heatinghydration test performed on a granular assembly of MX80 bentonite pellets. The goal is to characterize the material under conditions akin to those of an engineered barrier. It is shown that the numerical analyses are able to reproduce satisfactorily the observations of the test. This enhances the confidence placed on the computational tool for predicting the behaviour of actual engineered barriers constructed with pelletsbased
materials.
20150417T17:42:00Z
Gens Solé, Antonio
Barboza De Vasconcelos, Ramon
Villar Galicia, María Victoria
A promising alternative to form engineered barriers for high level nuclear waste repositories is the use of pelletsbased material because high dry densities can be achieved with no or minimal compaction effort. It is also planned to subject these materials to temperatures significantly higher than 100ºC. The paper reports the results of coupled THM analyses of a heatinghydration test performed on a granular assembly of MX80 bentonite pellets. The goal is to characterize the material under conditions akin to those of an engineered barrier. It is shown that the numerical analyses are able to reproduce satisfactorily the observations of the test. This enhances the confidence placed on the computational tool for predicting the behaviour of actual engineered barriers constructed with pelletsbased
materials.

Importance of sample volume changes and material degradation on gas transport properties in Boom Clay
http://hdl.handle.net/2117/27439
Importance of sample volume changes and material degradation on gas transport properties in Boom Clay
González Blanco, Laura; Romero Morales, Enrique Edgar; Li, Xiang Ling; Sillen, X.
An experimental study on Boom Clay –one of thepotential deep clay formationsin Belgium for the geological disposal of longliving and heatemitting radioactive waste–has been performed using controlled volumerate gas injection tests on highpressure oedometer cells. These experiments intend to analyse the influence of the gas injection rate, the stress state and deformation history, the anisotropic flow conditions (flows parallel and orthogonal to bedding) on the gas migration process. Results of selected tests on two sample orientations are presented, paying particular attention to sample volume changes on gas injection and dissipation stages. The gas pressurisation process at constant vertical stress acts as an unloading stage, which may induce expansion and degradation on the clay that have important consequences on gas migration properties.
20150417T17:28:09Z
González Blanco, Laura
Romero Morales, Enrique Edgar
Li, Xiang Ling
Sillen, X.
An experimental study on Boom Clay –one of thepotential deep clay formationsin Belgium for the geological disposal of longliving and heatemitting radioactive waste–has been performed using controlled volumerate gas injection tests on highpressure oedometer cells. These experiments intend to analyse the influence of the gas injection rate, the stress state and deformation history, the anisotropic flow conditions (flows parallel and orthogonal to bedding) on the gas migration process. Results of selected tests on two sample orientations are presented, paying particular attention to sample volume changes on gas injection and dissipation stages. The gas pressurisation process at constant vertical stress acts as an unloading stage, which may induce expansion and degradation on the clay that have important consequences on gas migration properties.