MSR  Mecànica del Sòls i de les Roques
http://hdl.handle.net/2117/3576
Tue, 09 Feb 2016 13:51:36 GMT
20160209T13:51:36Z

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.
Fri, 22 Jan 2016 16:36:39 GMT
http://hdl.handle.net/2117/81904
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.

Mecanismos de expansión en rocas sulfatadas
http://hdl.handle.net/2117/81897
Mecanismos de expansión en rocas sulfatadas
Ramon Tarragona, Anna
Los mecanismos que conducen al hinchamiento en túneles en rocas sulfatadas se han descrito en la literatura; sin embargo, se propone una interpretación alternativa. La precipitación de cristales de yeso en discontinuidades de la roca. La presión máxima ejercida por crecimiento de cristales se ha estimado desde un punto de vista termodinámico. Se ha desarrollado un modelo acoplado HidroMecánico y Químico formulado en medio poroso para simular expansiones volumétricas explicadas por la precipitación de yeso. El modelo se ha validado con el levantamiento experimentado por el viaducto.
Fri, 22 Jan 2016 14:29:55 GMT
http://hdl.handle.net/2117/81897
20160122T14:29:55Z
Ramon Tarragona, Anna
Los mecanismos que conducen al hinchamiento en túneles en rocas sulfatadas se han descrito en la literatura; sin embargo, se propone una interpretación alternativa. La precipitación de cristales de yeso en discontinuidades de la roca. La presión máxima ejercida por crecimiento de cristales se ha estimado desde un punto de vista termodinámico. Se ha desarrollado un modelo acoplado HidroMecánico y Químico formulado en medio poroso para simular expansiones volumétricas explicadas por la precipitación de yeso. El modelo se ha validado con el levantamiento experimentado por el viaducto.

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.
Thu, 21 Jan 2016 16:32:22 GMT
http://hdl.handle.net/2117/81821
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.
Thu, 21 Jan 2016 15:14:14 GMT
http://hdl.handle.net/2117/81818
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.

Caisson failure induced by wave action
http://hdl.handle.net/2117/81817
Caisson failure induced by wave action
Alonso Pérez de Agreda, Eduardo; Pinyol Puigmartí, Núria Mercè; Fernández, P.
In 2001 a storm induced the failure of four caissons recently built for the construction of a dyke in a new entrance to the Barcelona Harbor. Understanding the failure required the analysis of the construction history and the wave action. The caissons were founded on a thick layer of soft silty clays potentially liquefactable. The main properties of foundation soils are discussed based on laboratory and field data. A backanalysis of the failure is developed using an analytical and a numerical procedure. The analytical procedure is based on wellknown solutions and concepts in Soil Mechanics. It involves the calculation of pore water pressure distributions on the foundation, its dissipation, the induced increase of the undrained strength, and the caisson stability during construction stages. An analysis of liquefaction, which explains the collapse observed, is also described. The problem is also solved numerically using a commercial finite difference code. This second analysis allowed a crosschecking of the analytical solution and the quantification of some simplifications introduced that can be properly accounted for in the numerical analysis. In the final part of the paper an alternative stable design of the caisson dyke is presented.
Thu, 21 Jan 2016 14:55:56 GMT
http://hdl.handle.net/2117/81817
20160121T14:55:56Z
Alonso Pérez de Agreda, Eduardo
Pinyol Puigmartí, Núria Mercè
Fernández, P.
In 2001 a storm induced the failure of four caissons recently built for the construction of a dyke in a new entrance to the Barcelona Harbor. Understanding the failure required the analysis of the construction history and the wave action. The caissons were founded on a thick layer of soft silty clays potentially liquefactable. The main properties of foundation soils are discussed based on laboratory and field data. A backanalysis of the failure is developed using an analytical and a numerical procedure. The analytical procedure is based on wellknown solutions and concepts in Soil Mechanics. It involves the calculation of pore water pressure distributions on the foundation, its dissipation, the induced increase of the undrained strength, and the caisson stability during construction stages. An analysis of liquefaction, which explains the collapse observed, is also described. The problem is also solved numerically using a commercial finite difference code. This second analysis allowed a crosschecking of the analytical solution and the quantification of some simplifications introduced that can be properly accounted for in the numerical analysis. In the final part of the paper an alternative stable design of the caisson dyke is presented.

Recent developments of the Material Point Method for the simulation of landslides
http://hdl.handle.net/2117/81776
Recent developments of the Material Point Method for the simulation of landslides
Alonso Pérez de Agreda, Eduardo; Yerro Colom, Alba; Pinyol Puigmartí, Núria Mercè
The paper describes first the theoretical framework of a "single layer" three phase material. The formulation is general and particular cases are dry and fully saturated soils. The formulation and discretization of the motion and balance equations is presented. Two constitutive equations are used in the applications described: A brittle model for saturated soils and a MohrCoulomb elastoplastic soil formulated in terms of net stress and suction. Three aspects of the behaviour of landslides are discussed: first time failures in overconsolidated clays; internal shearing in deep seated landslides and rain induced failures in unsaturated slopes. The discussion is supported by three real cases which are described and analyzed in detail.
Wed, 20 Jan 2016 19:40:58 GMT
http://hdl.handle.net/2117/81776
20160120T19:40:58Z
Alonso Pérez de Agreda, Eduardo
Yerro Colom, Alba
Pinyol Puigmartí, Núria Mercè
The paper describes first the theoretical framework of a "single layer" three phase material. The formulation is general and particular cases are dry and fully saturated soils. The formulation and discretization of the motion and balance equations is presented. Two constitutive equations are used in the applications described: A brittle model for saturated soils and a MohrCoulomb elastoplastic soil formulated in terms of net stress and suction. Three aspects of the behaviour of landslides are discussed: first time failures in overconsolidated clays; internal shearing in deep seated landslides and rain induced failures in unsaturated slopes. The discussion is supported by three real cases which are described and analyzed in detail.

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.
Fri, 15 Jan 2016 16:26:26 GMT
http://hdl.handle.net/2117/81547
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.
Fri, 08 Jan 2016 14:18:22 GMT
http://hdl.handle.net/2117/81160
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.

A permafrost test on intact gneiss rock
http://hdl.handle.net/2117/81089
A permafrost test on intact gneiss rock
Duca, S; Alonso Pérez de Agreda, Eduardo; Scavia, Claudio
Changes in permafrost conditions in high mountain rocks have increased the risk of dangerous instabilities. Ice segregation within the rock mass has been interpreted as one of the mechanisms involved in high mountain bedrock degradation. A long term laboratory test on a cube of intact gneiss has been designed to reproduce field temperature gradients and water supply conditions. Test results demonstrate that ice crystallization in a permafrost fringe (T=0 degrees C to 3 degrees C) leads to the formation of continuous icefilled cracks which explain the loss of rock continuity and the observed rock failures. A coupled thermohydromechanical model which incorporates the thermodynamics of icewater mixtures has been used to reproduce test results. The model, which follows existing formulations for unsaturated porous media, was capable of capturing the main observations derived from the experiment. Calculated tensile stresses are close to the gneiss tensile strength. The analysis performed is a step forward in understanding field observations and in the application of computational tools to real cases. (C) 2015 Elsevier Ltd. All rights reserved.
Wed, 23 Dec 2015 19:13:23 GMT
http://hdl.handle.net/2117/81089
20151223T19:13:23Z
Duca, S
Alonso Pérez de Agreda, Eduardo
Scavia, Claudio
Changes in permafrost conditions in high mountain rocks have increased the risk of dangerous instabilities. Ice segregation within the rock mass has been interpreted as one of the mechanisms involved in high mountain bedrock degradation. A long term laboratory test on a cube of intact gneiss has been designed to reproduce field temperature gradients and water supply conditions. Test results demonstrate that ice crystallization in a permafrost fringe (T=0 degrees C to 3 degrees C) leads to the formation of continuous icefilled cracks which explain the loss of rock continuity and the observed rock failures. A coupled thermohydromechanical model which incorporates the thermodynamics of icewater mixtures has been used to reproduce test results. The model, which follows existing formulations for unsaturated porous media, was capable of capturing the main observations derived from the experiment. Calculated tensile stresses are close to the gneiss tensile strength. The analysis performed is a step forward in understanding field observations and in the application of computational tools to real cases. (C) 2015 Elsevier Ltd. All rights reserved.

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).
Wed, 09 Dec 2015 16:37:39 GMT
http://hdl.handle.net/2117/80340
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).