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  • Geotechnical Research Medal 2014

     Pinyol Puigmarti, Nuria Merce; Alonso Pérez de Agreda, Eduardo; Gens Sole, Antonio
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  • Expansion mechanisms in sulphated rocks and soils  Open access

     Ramon Tarragona, Anna
    Department of Geotechnical Engineering and Geo-Sciences, Universitat Politècnica de Catalunya
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    Las formaciones geológicas que contienen sulfatos están asociadas tradicionalmente al desarrollo de expansiones severas cuando son atravesadas por túneles. La intensidad del comportamiento expansivo observado en estos materiales es mayor que en otras rocas y suelos expansivos libres de sulfatos. El hinchamiento asociado a formaciones sulfatadas también puede ocurrir en el macizo rocoso aunque no se excave un túnel, y también en rellenos construidos con material compactado procedente de excavaciones en rocas sulfatadas. En la mayoría de casos la funcionalidad y estabilidad de las obras de ingeniería se ven afectadas.La predicción de deformaciones y presiones de hinchamiento en formaciones sulfatadas es una tarea difícil. En este sentido, la Tesis analiza y describe los mecanismos y las condiciones que conducen a expansiones en rocas sulfatadas, a través de la investigación detallada de tres casos excepcionales de daño debido a expansiones que involucran formaciones sulfatadas en España. El túnel de Lilla, el primer caso analizado, se excavó en arcillita anhidrítica. El desarrollo de expansiones condujo a un levantamiento severo de la solera y a presiones contra el revestimiento muy altas. El segundo caso, un puente cimentado en pilotes en una arcillita anhidrítica, el viaducto de Pont de Candí, experimentó un levantamiento inesperado de los pilares centrales debido al desarrollo de hinchamientos por debajo de las cimentaciones profundas. En el tercer caso, los terraplenes de acceso a otro puente, los terraplenes de Pallaressos, experimentaron una expansión volumétrica muy significativa y el puente resultó comprimido axialmente y dañado.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 explica el desarrollo de fenómenos de expansión en los dos primeros casos. La presencia de anhidrita juega un papel central en el fenómeno expansivo porque su disolución conduce a condiciones de sobresaturación del agua del macizo en sulfato cálcico respecto el yeso, que resulta en la precipitación de yeso. Se cree que el proceso de precipitación de yeso en discontinuidades actúa como gatos locales generando deformaciones. La presión máxima ejercida por crecimiento de cristales se ha estimado desde un punto de vista termodinámico.Las expansiones en el tercer caso son el resultado del crecimiento masivo de los minerales de etringita y thaumasita en terraplenes estabilizados con cemento Portland debido al ataque sulfático a los materiales cementantes. Ensayos mineralógicos y la simulación de las reacciones químicas involucradas en el ataque sulfático han mostrado que las expansiones en este tipo de terraplenes continuarían durante un periodo de tiempo largo, debido a la disponibilidad de los componentes necesarios para la formación de etringita y thaumasita. Un modelo de elementos finitos del hinchamiento del terraplén ha mostrado que estas expansiones pueden generar presiones muy altas contra estructuras rígidas.Se ha desarrollado un modelo acoplado Hidro-Mecánico y Químico formulado en medio poroso para simular expansiones volumétricas explicadas por la precipitación de yeso. El modelo es consistente con observaciones de campo y laboratorio y describe la cinética de la precipitación y disolución, el transporte de soluto y el desarrollo de deformaciones inducidas por cristalización. El modelo se ha aplicado para interpretar y simular el levantamiento experimentado por el viaducto. La capacidad de modelación se ha verificado frente a las medidas de levantamiento del viaducto en el tiempo y también, frente a la respuesta de las cimentaciones a la construcción de un terraplén en superficie para contrarrestar el hinchamiento

    Geological formations containing sulphates are commonly associated with the development of severe expansions when they are involved in tunnel excavation. The intensity of the observed expansive behaviour in these materials is greater than in other expansive soils and rocks free of sulphates. Swelling in sulphated formations can also occur in the rock mass although no tunnel is excavated, and also within fills made of compacted material from excavations in sulphated rocks. The functionality and stability of engineering works are affected in the majority of the cases. The prediction of strains and swelling pressures in sulphated formations is a difficult task. On that direction, the Thesis analyses and describes the mechanisms and conditions leading to expansions in sulphated rocks through the detailed investigation of three exceptional cases of damage induced by expansions involving sulphated formations in Spain. Lilla tunnel, the first case-history analysed, was excavated in Tertiary anhydritic claystone. Expansions developed led to severe tunnel floor heaving and to very high pressures against tunnel lining. The second case, a bridge founded on piles within an anhydritic claystone, Pont de Candí bridge, experienced an unexpected and sustained heave of the central pillars as a consequence of the development of swelling strains below the deep pile foundations. The third case, the compacted access embankments to another bridge, Pallaressos embankments, experienced a very significant volumetric expansion. As a result, the bridge was axially compressed and damaged. Mechanisms leading to swelling in tunnels in sulphated rocks have been described in the literature; however, an alternative interpretation is proposed. In the first two cases the development of swelling phenomena is explained by the precipitation of gypsum crystals in rock discontinuities. The presence of anhydrite plays a central role in the phenomenon because its dissolution leads to supersaturation conditions of groundwater in calcium sulphate with respect to gypsum, which will result into gypsum precipitation. The process of precipitation of gypsum in discontinuities is thought to act as local jacks inducing swelling strains. The maximum pressure exerted by crystal growth has been estimated under a thermodynamical point of view. Expansions in the third case analysed are a result of massive growth of ettringite and thaumasite minerals in embankments reinforced by Portland cement due to sulphate attack to cementitious materials. Mineralogical analysis and the simulation of the chemical reactions involved in sulphate attack have shown that expansions in this type of embankments would proceed for a long time because of the availability of the necessary components for ettringite and thaumasite formation. A finite element model of embankment swelling developed has shown that great loads can be generated due to swelling against rigid structures restraining the expansion in some direction. A coupled Hydro Mechanical and Chemical model formulated in a porous media has been developed to simulate volumetric expansions explained by gypsum precipitation. The model is consistent with field and laboratory observations and describes the kinetics of precipitation and dissolution of gypsum and anhydrite, the solute transport and the development of strains induced by crystallization. The model has been applied to interpret and simulate the heave experienced by Pont de Candí viaduct. Modelling capabilities were checked against the long term history of viaduct heave and also, against the foundation response when the vertical load from a surface embankment was added to counteract swelling.

    Las formaciones geológicas que contienen sulfatos están asociadas tradicionalmente al desarrollo de expansiones severas cuando son atravesadas por túneles. La intensidad del comportamiento expansivo observado en estos materiales es mayor que en otras rocas y suelos expansivos libres de sulfatos. El hinchamiento asociado a formaciones sulfatadas también puede ocurrir en el macizo rocoso aunque no se excave un túnel, y también en rellenos construidos con material compactado procedente de excavaciones en rocas sulfatadas. En la mayoría de casos la funcionalidad y estabilidad de las obras de ingeniería se ven afectadas. La predicción de deformaciones y presiones de hinchamiento en formaciones sulfatadas es una tarea difícil. En este sentido, la Tesis analiza y describe los mecanismos y las condiciones que conducen a expansiones en rocas sulfatadas, a través de la investigación detallada de tres casos excepcionales de daño debido a expansiones que involucran formaciones sulfatadas en España. El túnel de Lilla, el primer caso analizado, se excavó en arcillita anhidrítica. El desarrollo de expansiones condujo a un levantamiento severo de la solera y a presiones contra el revestimiento muy altas. El segundo caso, un puente cimentado en pilotes en una arcillita anhidrítica, el viaducto de Pont de Candí, experimentó un levantamiento inesperado de los pilares centrales debido al desarrollo de hinchamientos por debajo de las cimentaciones profundas. En el tercer caso, los terraplenes de acceso a otro puente, los terraplenes de Pallaressos, experimentaron una expansión volumétrica muy significativa y el puente resultó comprimido axialmente y dañado. 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 explica el desarrollo de fenómenos de expansión en los dos primeros casos. La presencia de anhidrita juega un papel central en el fenómeno expansivo porque su disolución conduce a condiciones de sobresaturación del agua del macizo en sulfato cálcico respecto el yeso, que resulta en la precipitación de yeso. Se cree que el proceso de precipitación de yeso en discontinuidades actúa como gatos locales generando deformaciones. La presión máxima ejercida por crecimiento de cristales se ha estimado desde un punto de vista termodinámico. Las expansiones en el tercer caso son el resultado del crecimiento masivo de los minerales de etringita y thaumasita en terraplenes estabilizados con cemento Portland debido al ataque sulfático a los materiales cementantes. Ensayos mineralógicos y la simulación de las reacciones químicas involucradas en el ataque sulfático han mostrado que las expansiones en este tipo de terraplenes continuarían durante un periodo de tiempo largo, debido a la disponibilidad de los componentes necesarios para la formación de etringita y thaumasita. Un modelo de elementos finitos del hinchamiento del terraplén ha mostrado que estas expansiones pueden generar presiones muy altas contra estructuras rígidas. Se ha desarrollado un modelo acoplado Hidro-Mecánico y Químico formulado en medio poroso para simular expansiones volumétricas explicadas por la precipitación de yeso. El modelo es consistente con observaciones de campo y laboratorio y describe la cinética de la precipitación y disolución, el transporte de soluto y el desarrollo de deformaciones inducidas por cristalización. El modelo se ha aplicado para interpretar y simular el levantamiento experimentado por el viaducto. La capacidad de modelación se ha verificado frente a las medidas de levantamiento del viaducto en el tiempo y también, frente a la respuesta de las cimentaciones a la construcción de un terraplén en superficie para contrarrestar el hinchamiento

  • Modelling swelling phenomena in Lilla tunnel

     Ramon Tarragona, Anna; Alonso Pérez de Agreda, Eduardo
    International Workshop on CRYStallization in POrous Media
    p. 47
    Presentation's date: 2014-06-13
    Presentation of work at congresses

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  • Best Paper in the Landslides Journal

     Pinyol Puigmarti, Nuria Merce; Alonso Pérez de Agreda, Eduardo; Corominas Dulcet, Jordi; Moya Sanchez, Jose
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  • Grupo de Geotecnia y Mecánica de Materiales

     Carol Vilarasau, Ignacio; Gens Sole, Antonio; Josa Garcia-tornel, Alejandro; Ledesma Villalba, Alberto; Lloret Morancho, Antonio; Olivella Pastalle, Sebastian; Prat Catalan, Pere; Romero Morales, Enrique Edgar; Vaunat, Jean; Lopez Garello, Carlos Maria; Arroyo Alvarez de Toledo, Marcos; Pinyol Puigmarti, Nuria Merce; Rodriguez Dono, Alfonso; Alonso Pérez de Agreda, Eduardo
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    Thermo-hydro-mechanical analysis for the simulation of rapid sliding process in a new and fast ring shear prototype  Open access

     Serri, Victor; Romero Morales, Enrique Edgar; Lloret Morancho, Antonio; Suriol Castellvi, Jose; Alonso Pérez de Agreda, Eduardo
    International Conference on Vajont - 1963-2013
    p. 193-199
    DOI: 10.4408/IJEGE.2013-06.B-16
    Presentation's date: 2013-10-09
    Presentation of work at congresses

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    Vajont was a case of an extremely fast landslide and efforts to clarify the failure have been mainly concentrated in providing a consistent explanation taking into account this characteristic feature. Particularly in the case of Vajont landslide, attention has been essentially focused on the shearing properties of the sliding surface. An accepted explanation for the velocity reached is the thermo-hydraulic-mechanical coupling under saturated conditions, which induces thermal dilation and effective stress reduction due to pore pressure build-up. Nevertheless, lack of in situ and experimental information has become one of the main drawbacks when trying to explain these coupled processes. In situ information is difficult to obtain since temperature and pore pressure development during these fast processes are impossible of being measured. To overcome this limitation, a new fast sliding prototype -emulating a ring shear apparatus- has been recently developed at the Universitat Politècnica de Catalunya (Spain). This prototype can reach relatively high speeds along the sliding surface (up to 30 km/h) under relatively high total vertical stresses (up to 3 MPa). Temperature and pore pressure changes can be locally measured with miniature transducers located close to the shear band. The design of this complex prototype requires the use of simulation-aided techniques, to help with the interpretation of the coupled processes, as well as to estimate the maximum temperature and pore pressure changes. A thermo-hydro-mechanical formulation, applied to the ring shear test, is proposed in the paper to study pore water pressure build up and dissipation in a sliding surface being heated by the frictional work induced by the motion. Particularly, the proposed model is applied to simulate the evolution of the shear strength along the sliding surface during a fast sliding process.

  • A simplified procedure to assess the dynamic stability of a caisson breakwater

     Madrid, R.; Gens Sole, Antonio; Alonso Pérez de Agreda, Eduardo; Tarrago, Dani
    International Conference on Soil Mechanics and Geotechnical Engineering
    p. 2367-2370
    Presentation's date: 2013-09
    Presentation of work at congresses

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    The paper describes a simplified method of analysis used to evaluate the stability of a caisson breakwater to sea wave actions. An intensive laboratory program was performed in order to evaluate the static and dynamic characteristics of the foundation soil. Anisotropic and isotropic consolidated cyclic triaxial tests and cyclic simple shear tests were used to define the cyclic interaction diagram for the foundation soil. The possibility of foundation cyclic mobility due to wave loading and their effect on the breakwater stability was examined combining the cyclic interaction diagram with the results of finite element analysis. The potential reduction in soil strength is then incorporated into a conventional stability analysis. The procedure is illustrated by a specific application to a caisson breakwater that is part of the extension works of the Barcelona Harbour.

  • Analysis of ettringite attack to stabilized railway bases and embankments

     Ramon Tarragona, Anna; Alonso Pérez de Agreda, Eduardo
    International Conference on Soil Mechanics and Geotechnical Engineering
    p. 785-788
    Presentation's date: 2013-09
    Presentation of work at congresses

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    Two cases of massive sulphate attack to cement treated embankments and track bases in a high speed railway line are described. In the first case, two large access embankments to a railway viaduct were treated with jet¿grouting columns. In the second case a compacted cement treated soil was placed over a rigid concrete caisson. The treated layer, 1.5 m thick, expanded at a continuous rate of 0.9-1.3 mm/month. In the two cases the soil was excavated from nearby cuts in gypsiferous Tertiary (Oligocene) claystones. Ettringite and thaumasite crystals were found within the expanding levels. The chemical evolution of an interface between a cement treated body and a compacted soil is presented. Solutions adopted to remediate the created problem are briefly described.

    Two cases of massive sulphate attack to cement treated embankments and track bases in a high speed railway line are described. In the first case, two large access embankments to a railway viaduct were treated with jet–grouting columns. In the second case a compacted cement treated soil was placed over a rigid concrete caisson. The treated layer, 1.5 m thick, expanded at a continuous rate of 0.9-1.3 mm/month. In the two cases the soil was excavated from nearby cuts in gypsiferous Tertiary (Oligocene) claystones. Ettringite and thaumasite crystals were found within the expanding levels. The chemical evolution of an interface between a cement treated body and a compacted soil is presented. Solutions adopted to remediate the created problem are briefly described.

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    The Material Point Method: a promising computational tool in Geotechnics  Open access

     Yerro Colom, Alba; Alonso Pérez de Agreda, Eduardo; Pinyol Puigmarti, Nuria Merce
    International Conference on Soil Mechanics and Geotechnical Engineering
    p. 853-856
    Presentation's date: 2013-09-04
    Presentation of work at congresses

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    In recent years, the Material Point Method (MPM) has been applied to a number of geotechnical problems and has been extended to solve coupled flow-deformation problems. The dynamic formulation and the dual description of the media (lagrangian material points and an eulerian numerical mesh) provide the MPM the capabilities of handling problems involving large displacements and deformations. The paper presents four examples with the aim of highlighting the dynamic formulation and the capability of the method to analyze in a unified mathematical framework the static-dynamic transition of a slope failure.

  • Modelling swelling behavior of anhydritic clayey rocks

     Ramon Tarragona, Anna; Alonso Pérez de Agreda, Eduardo
    International Symposium on Computational Geomechanics
    p. 348-358
    Presentation's date: 2013-08-23
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    The swelling behavior observed in anhydritic rocks is explained by the precipitation of gypsum crystals in open discontinuities. Gypsum crystals growing in discontinuities contribute to open them and induce deformations or pressures (if the displacements are restrained). A model has been formulated to reproduce the expansive behavior in sulphated rocks. The formulation describes the kinetics of dissolution and precipitation of sulphated minerals and transforms the mass of precipitated gypsum to imposed swelling strains due to gypsum crystal growth. The model also keeps track of the solute transport and takes into account the effect of the existing load on crystal growth. A simulation of the heave observed in Pont de Candí Bridge is performed. The calculations reproduce the long term vertical displacements measured at the ground surface and the distribution of vertical strains measured in depth. A sensitivity analysis is also reported.

  • Microstructural evaluation of the water sensitivity of clayey rocks

     Pineda Jimenez, Jubert Andrés; Romero Morales, Enrique Edgar; Tarrago, Dani; Tauler Ferré, Esperança; Alonso Pérez de Agreda, Eduardo
    Biot Conference on Poromechanics
    p. 1454-1459
    DOI: 10.1061/9780784412992.173
    Presentation's date: 2013-07
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    The paper presents both macroscopic and microstructural evidence of the water sensitivity of a low porosity clayey rock from Northern Spain. Particular emphasis is focused on the effects of water sensitivity at micro level. Results obtained from Environmental Scanning Electron Microscopy (ESEM) using the common procedure of sample preparation show that this procedure of sample preparation is not enough to evaluate in a proper way the irreversible changes induced at micro level by hydraulic effects. An alternative procedure is described, which seems to improve the evaluation of rock degradation at micro scale.

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    VIII Simposio Nacional sobre Taludes y Laderas Inestables: volumen 1  Open access

    Date of publication: 2013-06-11
    Book

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    En Junio de 2013 tiene lugar en Palma de Mallorca el VIII Simposio Nacional sobre Taludes y Laderas Inestables. Este Simposio se ha consolidado como un foro independiente, abierto y pluridisciplinar, con el objeto de difundir los conocimientos entre los miembros de las comunidades técnica y académica, entre los investigadores, presentar los avances recientes y fomentar la discusión entre técnicos y científicos que trabajan en este apasionante campo. En los últimos años, especialmente desde finales de 2008, se han producido en la Isla de Mallorca diversos desprendimientos y deslizamientos que han llamado poderosamente la atención por su número y dimensiones. El debate sobre la causa de esta anómala concentración de eventos, incluyendo la influencia del cambio climático, sigue abierto a día de hoy. La edición 2013 es una excelente oportunidad para conocer de primera mano los detalles de estos eventos, los reconocimientos y soluciones adoptadas, así como las enseñanzas extraídas. Como en anteriores ocasiones, el Simposio tiene además por objetivo la presentación y discusión de los progresos realizados en los diversos ámbitos temáticos.

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    VIII Simposio Nacional sobre Taludes y Laderas Inestables: volumen 2  Open access

    Date of publication: 2013-06
    Book

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    En Junio de 2013 tiene lugar en Palma de Mallorca el VIII Simposio Nacional sobre Taludes y Laderas Inestables. Este Simposio se ha consolidado como un foro independiente, abierto y pluridisciplinar, con el objeto de difundir los conocimientos entre los miembros de las comunidades técnica y académica, entre los investigadores, presentar los avances recientes y fomentar la discusión entre técnicos y científicos que trabajan en este apasionante campo. En los últimos años, especialmente desde finales de 2008, se han producido en la Isla de Mallorca diversos desprendimientos y deslizamientos que han llamado poderosamente la atención por su número y dimensiones. El debate sobre la causa de esta anómala concentración de eventos, incluyendo la influencia del cambio climático, sigue abierto a día de hoy. La edición 2013 es una excelente oportunidad para conocer de primera mano los detalles de estos eventos, los reconocimientos y soluciones adoptadas, así como las enseñanzas extraídas. Como en anteriores ocasiones, el Simposio tiene además por objetivo la presentación y discusión de los progresos realizados en los diversos ámbitos temáticos.

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    VIII Simposio Nacional sobre Taludes y Laderas Inestables: volumen 3  Open access

    Date of publication: 2013-06
    Book

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    En Junio de 2013 tiene lugar en Palma de Mallorca el VIII Simposio Nacional sobre Taludes y Laderas Inestables. Este Simposio se ha consolidado como un foro independiente, abierto y pluridisciplinar, con el objeto de difundir los conocimientos entre los miembros de las comunidades técnica y académica, entre los investigadores, presentar los avances recientes y fomentar la discusión entre técnicos y científicos que trabajan en este apasionante campo. En los últimos años, especialmente desde finales de 2008, se han producido en la Isla de Mallorca diversos desprendimientos y deslizamientos que han llamado poderosamente la atención por su número y dimensiones. El debate sobre la causa de esta anómala concentración de eventos, incluyendo la influencia del cambio climático, sigue abierto a día de hoy. La edición 2013 es una excelente oportunidad para conocer de primera mano los detalles de estos eventos, los reconocimientos y soluciones adoptadas, así como las enseñanzas extraídas. Como en anteriores ocasiones, el Simposio tiene además por objetivo la presentación y discusión de los progresos realizados en los diversos ámbitos temáticos.

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    Rotura plana diferida de un desmonte en pizarras paleozoica  Open access

     Alonso Pérez de Agreda, Eduardo; Tarrago, Dani; Romero Morales, Enrique Edgar
    Simposio Nacional sobre Taludes y Laderas Inestables
    p. 302-313
    Presentation's date: 2013-06
    Presentation of work at congresses

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    Durante la ejecución de la excavación de los desmontes para la construcción de una nueva biblioteca pública de la zona norte de Barcelona, se produjo una rotura en el macizo rocoso excavado: una pizarra paleozoica fuertemente tectonizada. En el artículo se destaca la escasa seguridad de la excavación frente a roturas planas a favor de los planos de foliación de la pizarra. Se presentan resultados de ensayos de corte sobre estos planos y su relleno de arcillas plásticas. Se discuten también las causas que provocaron la rotura diferida del talud, a pesar de que su baja seguridad calculada haría suponer una rotura inmediata. Se han descrito dos mecanismos posibles: la contribución de la succión a incrementar los parámetros de resistencia al corte de juntas y la generación de presiones intersticiales negativas durante la excavación. En relación con el primer mecanismo se presentan resultados experimentales recientes.

    En Junio de 2013 tiene lugar en Palma de Mallorca el VIII Simposio Nacional sobre Taludes y Laderas Inestables. Este Simposio se ha consolidado como un foro independiente, abierto y pluridisciplinar, con el objeto de difundir los conocimientos entre los miembros de las comunidades técnica y académica, entre los investigadores, presentar los avances recientes y fomentar la discusión entre técnicos y científicos que trabajan en este apasionante campo. En los últimos años, especialmente desde finales de 2008, se han producido en la Isla de Mallorca diversos desprendimientos y deslizamientos que han llamado poderosamente la atención por su número y dimensiones. El debate sobre la causa de esta anómala concentración de eventos, incluyendo la influencia del cambio climático, sigue abierto a día de hoy. La edición 2013 es una excelente oportunidad para conocer de primera mano los detalles de estos eventos, los reconocimientos y soluciones adoptadas, así como las enseñanzas extraídas. Como en anteriores ocasiones, el Simposio tiene además por objetivo la presentación y discusión de los progresos realizados en los diversos ámbitos temáticos.

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    Análisis de procesos termo-hidro-mecánicos en deslizamientos rápidos en un nuevo equipo de corte anular rápido  Open access

     Serri, Victor; Romero Morales, Enrique Edgar; Lloret Morancho, Antonio; Suriol Castellvi, Jose; Alonso Pérez de Agreda, Eduardo
    Simposio Nacional sobre Taludes y Laderas Inestables
    p. 1157-1166
    Presentation's date: 2013-06
    Presentation of work at congresses

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    Se ha desarrollado un nuevo corte anular para estudiar deslizamientos rápidos donde se induzca calentamiento por fricción. La generación de presiones intersticiales en la banda de corte calentada por el trabajo friccional del movimiento se ha aceptado como una explicación para las velocidades alcanzadas en deslizamientos rápidos. La falta de datos experimentales ha sido un inconveniente para analizar estos procesos acoplados. El prototipo, que incorpora un control electrónico del par impuesto y de la velocidad, puede alcanzar velocidades de deslizamiento elevadas (hasta 30 km/h) bajo tensiones vertical es relativamente grandes (hasta 3MPa). El diseño del prototipo y la selección de los transductores requieren de modelaciones numéricas previas para predecir la magnitud de las variables a medir. Esta publicación presenta una formulación acoplada, su solución numérica con una geometría simplificada para el equipo y los resultados obtenidos para la modelación de la presión de poros, temperatura y fuerza de corte.

    En Junio de 2013 tiene lugar en Palma de Mallorca el VIII Simposio Nacional sobre Taludes y Laderas Inestables. Este Simposio se ha consolidado como un foro independiente, abierto y pluridisciplinar, con el objeto de difundir los conocimientos entre los miembros de las comunidades técnica y académica, entre los investigadores, presentar los avances recientes y fomentar la discusión entre técnicos y científicos que trabajan en este apasionante campo. En los últimos años, especialmente desde finales de 2008, se han producido en la Isla de Mallorca diversos desprendimientos y deslizamientos que han llamado poderosamente la atención por su número y dimensiones. El debate sobre la causa de esta anómala concentración de eventos, incluyendo la influencia del cambio climático, sigue abierto a día de hoy. La edición 2013 es una excelente oportunidad para conocer de primera mano los detalles de estos eventos, los reconocimientos y soluciones adoptadas, así como las enseñanzas extraídas. Como en anteriores ocasiones, el Simposio tiene además por objetivo la presentación y discusión de los progresos realizados en los diversos ámbitos temáticos.

  • Modelación de deslizamientos con el Método del Punto Material

     Yerro Colom, Alba; Alonso Pérez de Agreda, Eduardo; Pinyol Puigmarti, Nuria Merce
    Congreso de Métodos Numéricos en Ingeniería
    p. 1
    Presentation's date: 2013-06-26
    Presentation of work at congresses

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  • Coupled hydro-chemo-mechanical modelling of a foundation heave due to gypsum crystal growth

     Ramon Tarragona, Anna; Alonso Pérez de Agreda, Eduardo
    Computational Methods for Coupled Problems in Science and Engineering
    p. 1-2
    Presentation's date: 2013-06-18
    Presentation of work at congresses

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  • Modelling crystal growth

     Ramon Tarragona, Anna; Alonso Pérez de Agreda, Eduardo
    Workshop of CODE-BRIGHT Users
    p. 1-4
    Presentation's date: 2013-05-07
    Presentation of work at congresses

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    The sustained heave of Pont de Candí Bridge is a consequence of the development of swelling strains in the sulphated claystone located below the tips of the foundation piles of the central pillan; of the bridge. The development of swelling phenomena in sulphated claystone is explained by the precipitation of gypsum crystals in fractures. A model has been formulated to describe the kinetics of precipitation and dissolution of sulphated minerals, the development of strains induced by crystallization and the solute transport. The heave of Pont de Candí Bridge has been modelled and calculations have been compared with the field measurements.

  • Thermo-hydro-mechanical analysis of rapid sliding process in a new and fast ring shear prototype

     Serri, Victor; Romero Morales, Enrique Edgar; Lloret Morancho, Antonio; Suriol Castellvi, Jose; Alonso Pérez de Agreda, Eduardo
    International Conference on Landslides' Risk
    p. 165-173
    Presentation's date: 2013-03
    Presentation of work at congresses

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    A new experimental apparatus -emulating the annular shape of the ring shear- has been designed and developed at the Universitat Politecnica de Catalunya to study fast sliding processes promoted by heat induced friction. This mechanism, which involves pore water pressu regeneration and dissipation in the shear band being heated by the frictional work of the sliding motion, has been an accepted explanation for the high velocity reached in the case of Vajont landslide. Nevertheless, lack of in situ and experimental information has become one of the main drawbacks when trying to explain these coupled processes . The prototype, which incorporates electronic control of torque and speed to emulate force and displacement control conditions, can reach high velocity along the sliding surface (up to 30 km/h and of the order of magnitude of the Vajont case) under relatively high total vertical stresses (up to 3 MPa). The design of this complex prototype and the selection of transducers require the use of simulation-aided techniq ues to help with the interpretation of these coupled thermo-hydro-mechanical processes. The paper presents the coupled formulation, the numerical solution adopted and the simplified geometry used for the equipment, as well as selected results of the pore pressure, temperature and shear strength evolutions along the sliding surface of a synthetic fast sliding test. These results are used to better know the location, range, sensitivity and fast response required for the temperature and pore pressure transducers, which are located close to the sliding surface.

  • Rockfill mechanics

     Oldecop, Luciano; Alonso Pérez de Agreda, Eduardo
    Pan-American Conference on Unsaturated Soils
    p. 61-86
    Presentation's date: 2013-02
    Presentation of work at congresses

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    The paper examines several aspects of rockfill behaviour, which are relevant to interpret and analyze the field response of dams and embankments. Experimental observations on rockfill compressibility, time-dependent deformation and deviatoric stress-strain behaviour are presented. Special attention is given to the role of relative humidity. The physics of rockfill deformation, explained by particle breakage are described. Particle breakage is explained by crack propagation, a phenomenon discussed within the framework of fracture mechanics. A macroscopic elastoplastic constitutive model is outlined. Rockfill mechanics are also approached by a Distinct Element modelling of grain assemblages experiencing grain breakage. Finally, rockfill mechanics are discussed from the wider perspective offered by unsaturated soil mechanics.

  • DEM modeling of unsaturated rockfill: scale effects

     Tapias Camacho, Mauricio Alberto; Alonso Pérez de Agreda, Eduardo; Gili Ripoll, Jose Antonio
    Pan-American Conference on Unsaturated Soils
    p. 455-460
    Presentation's date: 2013-02
    Presentation of work at congresses

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    The large size of the particles in rockfill structures prevents the appropriate laboratory testing. Moreover, the humidity is a key point to explain changes in the long term deformability of rockfill. Therefore, prediction of field behavior requires the development of models that integrate size effects and humidity changes. The Distinct Element Method has been used to develop a numerical model that includes assemblies of several spherical particles in a pyramidal shape. These "macroparticles" break when a rupture criterion involving the subcritical propagation of cracks within grain is achieved. This propagation is a function of stress state, defect size and relative humidity. Size effects for particles ranging from 0.28 to 56 cm of average diameter have been investigated. The results were validated against some real oedometer tests. The present work demonstrates the capabilities of the method as an useful tool to extend the laboratory tests on gravels to the actual rockfill dimensions

  • Effect of loading and suction history on time dependent deformation of coarse crushed slate

     Romero Morales, Enrique Edgar; Alvarado de Menendez, Clara; Alonso Pérez de Agreda, Eduardo
    Pan-American Conference on Unsaturated Soils
    p. 451-454
    Presentation's date: 2013-02
    Presentation of work at congresses

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    The paper presents the results of an experimental investigation aimed at evaluating the time-dependent compressibility of coarse crushed quartzitic slate, focusing on the effects of the previous loading and hydraulic history. Long-term and large diameter compression tests under oedometer conditions were performed at different total suctions (relative humidity values) and vertical stresses but following different loading and hydraulic paths. A finding, which has practical implications in earthwork constructions, is that pre-compressing at increasing overconsolidation ratios or pre-soaking the crushed material at constant and elevated stresses leads to the progressive vanishing of long-term deformations. 2013 Taylor Francis Group, London.

    The paper presents the results of an experimental investigation aimed at evaluating the time-dependent compressibility of coarse crushed quartzitic slate, focusing on the effects of the previ- ous loading and hydraulic history. Long-term and large diameter compression tests under oedometer conditions were performed at different total suctions (relative humidity values) and vertical stresses but following different loading and hydraulic paths. A finding, which has practical implications in earthwork constructions, is that pre-compressing at increasing overconsolidation ratios or pre-soaking the crushed material at constant and elevated stresses leads to the progressive vanishing of long-term deformations.

  • Access to the full text
    Influencia del desembalse en la estabilidad de una ladera: caso real  Open access

     Pinyol Puigmarti, Nuria Merce; Alonso Pérez de Agreda, Eduardo; Corominas Dulcet, Jordi; Moya Sanchez, Jose
    Simposio Nacional sobre Taludes y Laderas Inestables
    p. 326-336
    Presentation's date: 2013
    Presentation of work at congresses

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    Un aspecto crítico a controlar en la gestión de embalses es la velocidad de descenso de nivel de agua debido al riesgo de inestabilidades en las laderas que lo forman. Este artículo presenta el estudio realizado para conocer las causas del desarrollo de un gran deslizamiento en la ladera de un embalse. Para ello se realizó en primer lugar un reconocimiento geológico y geotécnico con el fin de definir la tipología del movimiento, su geometría y materiales involucrados mediante la realización de sondeos profundos y la instalación de inclinómetros y piezómetros. Se determinó que se trataba de la reactivación de un antiguo deslizamiento traslacional de 40 Mm3. Mediante la observación detallada de los testigos y la información proporcionada por las medidas inclinómetricas, se determinó la posición de la superficie de deslizamiento. Ésta se localizó en un estrato arcilloso de edad Garumniense y de alta plasticidad. Se analizaron en el laboratorio muestras extraídas de esta arcilla y se evaluaron sus propiedades geotécnicas. La causa más probable del movimiento se asignó al descenso rápido del nivel del embalse que alcanzó velocidades de 1.2 m/s. El análisis se realizó para una sección representativa y mediante un programa de elementos finitos capaz de resolver de forma acoplada la respuesta mecánica e hidráulica. Se modeló la variación del nivel del embalse durante los 4 años previos a la rotura. La distribución de presión de agua calculada, determinante en el análisis de estabilidad, se validó mediante la comparación de los resultados con los valores medidos en los piezómetros instalados alrededor de la superficie de deslizamiento después de la rotura.

  • The Buen Pastor Cathedral in San Sebastián

     Gens Sole, Antonio; Alonso Pérez de Agreda, Eduardo; Jubany Casanovas, Jorge; Uzcanga, Luis
    Date of publication: 2013
    Book chapter

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    The construction of an underground car park required an excavation in sand under the water table adjacent to the cathedral of Buen Pastor in San Sebastián, Spain. Because of the close proximity of the cathedral and other buildings, control of ground movements was a paramount consideration in the design. Construction involved the use of diaphragm walls propped by the floor slabs using the top-down technique. A monitoring system was installed to control the performance of the excavation throughout. For water control during the excavation, the diaphragm walls reached an underlying low permeability silt layer. This decision required the adoption of special measures to connect hydraulically the foundation ground of the cathedral with the water levels prevailing in the outside area. Excavation was completed with very limited ground movements that caused no observable damage in the cathedral and other nearby structures. Piezometer records also proved that the installed hydraulic connection performed satisfactorily.

  • Preload improvement and monitoring in a newly reclaimed area

     Tarrago, Dani; Gens Sole, Antonio; Alonso Pérez de Agreda, Eduardo; Deu Lozano, Amadeu; Griell, R.
    International Conference on Ground Improvement and Ground Control
    p. 389-394
    Presentation's date: 2012-11
    Presentation of work at congresses

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    The paper describes the preload improvement of a newly reclaimed area that is part of the current development of the Barcelona Port. The area will provide the required surface of a new container terminal with a berth length of 1,600 m. The total surface area is 750,000 m2. The improvement affects both the hydraulic fill placed for the reclamation as well as the underlying soft natural ground. Improvement was required for both reducing subsequent settlements and providing an adequate level of stability during construction and quay commissioning. Special attention has been given to the reduction of the liquefaction potential of the hydraulic fill. The degree of improvement has been assessed comparing extensive site investigations performed before and after preloading. CPTu tests have proved especially useful in this regard. An extensive instrumentation scheme was deployed to observe the progress of preloading throughout the whole process. In some areas, preloading was supplemented by the installation of prefabricated vertical drains and by reinforcement using large-diameter gravel columns. The paper describes the ground improvement operations and the field monitoring observations performed during the works.

  • Access to the full text
    Crystal growth under bridge foundations  Open access  awarded activity

     Ramon Tarragona, Anna; Alonso Pérez de Agreda, Eduardo
    International Workshop of Young Doctor in Geomechanics
    p. 61-66
    Presentation's date: 2012-11-21
    Presentation of work at congresses

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    A high-speed railway viaduct experienced a sustained heave at high rates after its construction. The pillars of the bridge are founded on an Eocene hard anhydritic-gypsiferous claystone by means of massive foundations. Field investigations identified an active layer below the piles¿ tips where expansions occur as a result of gypsum crystal growth in discontinuities from supersaturated aqueous solutions. The construction of the bridge is supposed to have triggered the swelling mechanism. An embankment, partially filling the valley, was built to slow the heave rate. The presence of soluble gypsum and anhydrite and inert materials is considered in the model developed to reproduce the observed expansive mechanism. The formulation describes the kinetics of dissolution and precipitation of minerals and the induced swelling strains by crystal growth. The calculated heave is compared with the field long-term vertical displacements measured before and after the construction of the embankment. A sensitivity study is also reported.

    A high-speed railway viaduct experienced a sustained heave at high rates after its construction. The pillars of the bridge are founded on an Eocene hard anhydritic-gypsiferous claystone by means of massive foundations. Field investigations identified an active layer below the piles’ tips where expansions occur as a result of gypsum crystal growth in discontinuities from supersaturated aqueous solutions. The construction of the bridge is supposed to have triggered the swelling mechanism. An embankment, partially filling the valley, was built to slow the heave rate. The presence of soluble gypsum and anhydrite and inert materials is considered in the model developed to reproduce the observed expansive mechanism. The formulation describes the kinetics of dissolution and precipitation of minerals and the induced swelling strains by crystal growth. The calculated heave is compared with the field long-term vertical displacements measured before and after the construction of the embankment. A sensitivity study is also reported.

    W(H)YDOC PhD Prize 2012, durant el 4th International Workshop of Young Doctors in Geomechanics W(H)YDOC 2012.

  • Efecto de la expansión profunda sobre cimentaciones por pilotes

     Sauter, Simon; Alonso Pérez de Agreda, Eduardo; Ramon Tarragona, Anna
    Simposio Nacional de Ingeniería Geotécnica
    p. 385-398
    Presentation's date: 2012-10-17
    Presentation of work at congresses

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  • Effect of loading and suction history on time dependent deformation of crushed granular aggregates

     Romero Morales, Enrique Edgar; Alvarado de Menendez, Clara; Alonso Pérez de Agreda, Eduardo
    International Workshop Advances in Multiphysical Testing of Soils and Shales
    p. 99-104
    DOI: 10.1007/978-3-642-32492-5_9
    Presentation's date: 2012-09
    Presentation of work at congresses

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    The paper presents the results of an experimental investigation aimed at evaluating the time-dependent compressibility of a coarse crushed quartzitic slate, focusing on the effects of the previous loading and hydraulic history. Long-term and large diameter compression tests under oedometer conditions were performed at different relative humidity (total suctions) and vertical stresses but following different loading and hydraulic paths. A finding is that pre-compressing at increasing overconsolidation ratios or pre-soaking the crushed material at constant and elevated stresses leads to the progressive vanishing of long-term deformations.

  • Thaumasite and ettringite massive crystal growth in two railway embankments

     Ramon Tarragona, Anna; Alonso Pérez de Agreda, Eduardo
    Crystallization in Porous Materials
    p. 57-58
    Presentation's date: 2012-09-05
    Presentation of work at congresses

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  • Gypsum crystal growth under bridge foundations

     Alonso Pérez de Agreda, Eduardo; Ramon Tarragona, Anna
    Crystallization in Porous Materials
    p. 17-18
    Presentation's date: 2012-09-07
    Presentation of work at congresses

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  • Effect of loading history on time dependent deformation of rockfill

     Romero Morales, Enrique Edgar; Alonso Pérez de Agreda, Eduardo; Alvarado de Menendez, Clara; Wacker, F
    European Conference on Unsaturated Soils
    p. 419-424
    DOI: 10.1007/978-3-642-31116-1_57
    Presentation's date: 2012-06
    Presentation of work at congresses

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    The paper explores the time-dependent compressibility of coarse crushed quartzitic slate, focusing on the effects of the previous loading history. Large diameter oedometer tests were performed at different relative humidity (or total suctions) and different overconsolidation ratios (OCR). Preliminary results suggested that pre-compressing the rockfill material at increasing OCRs lead to the progressive vanishing of rockfill delayed deformations.

  • Rapid drawdown and landslides

     Pinyol Puigmarti, Nuria Merce; Alonso Pérez de Agreda, Eduardo; Olivella Pastalle, Sebastian
    International Symposium on Landslides
    p. 529-535
    Presentation's date: 2012-06
    Presentation of work at congresses

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    Predicting the pore pressure distribution in a slope after rapid drawdown conditions requires the solution of a coupled flow‐deformation analysis in a saturated‐unsaturated porous media. A fully coupled finite element code (Code_Bright), able to handle in a consistent manner the drawdown conditions, is used to simulate the pore water pressure measured in the upstream slope of an earth dam (Glen Shira Dam, Scotland) subjected to a controlled rapid drawdown event. A comparison of some calculation alternatives is then given and compared with field pressure records. The paper describes also the analysis performed to interpret a recent case of a major landslide triggered by a rapid drawdown in a reservoir. A key aspect of the case is the correct characterization of permeability of representative soil profiles. This is achieved by combining laboratory test results and a back analysis of pore water pressure time records during a period of reservoir level fluctuations.

  • Swelling and degradation of argillaceous rocks induced by relative humidity effects: an experimental study

     Pineda Jimenez, Jubert Andrés
    Department of Geotechnical Engineering and Geo-Sciences, Universitat Politècnica de Catalunya
    Theses

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  • Incorporating a microstructural state variable in constitutive modeling

     Pinyol Puigmarti, Nuria Merce; Alonso Pérez de Agreda, Eduardo; Gens Sole, Antonio
    Pan-American Conference on Unsaturated Soils
    p. 443-449
    Presentation's date: 2012-02
    Presentation of work at congresses

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    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

  • First Heim Lecture

     Alonso Pérez de Agreda, Eduardo
    Award or recognition

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  • Excavación de un pozo profundo para revisión de una tuneladora en el centro de Barcelona

     Ledesma Villalba, Alberto; Lloret Morancho, Antonio; de Santos, C.; Ramos, Gonzalo; Vázquez Suñé, Enric; Alonso Pérez de Agreda, Eduardo; Pujades Garnes, Estanislao; Carrera Ramírez, Jesús
    Simposio Nacional de Ingeniería Geotécnica
    p. 807-817
    Presentation's date: 2012
    Presentation of work at congresses

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  • Modelling compacted soil behaviour including microstructural features

     Pinyol Puigmarti, Nuria Merce; Alonso Pérez de Agreda, Eduardo; Gens Sole, Antonio
    European Conference on Unsaturated Soils
    p. vol 2: p. 119-127
    DOI: 10.1007/978-3-642-31343-1_15
    Presentation's date: 2012
    Presentation of work at congresses

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  • Deformation analysis of landslides: progressive failure, rate effects and thermal interactions

     Alonso Pérez de Agreda, Eduardo
    International Symposium on Landslides
    p. 175-214
    Presentation's date: 2012
    Presentation of work at congresses

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    Evaluating landslide risk and its consequences is hardly achieved by “safety factor” concepts, which essentially rely on static equilibrium concepts and forces. Rather, expected displacements, velocities and accelerations are key magnitudes which help to establish the risk of failure and assist in the management of its consequences. The paper focuses on three key aspects for landslide initiation and evolution which are difficult to quantify in practice and are also difficult to analyze by current models: the mechanisms of progressive failure in brittle materials, the thermo-mechanical interactions and the creep deformations. Landslides covered in the Lecture are described by kinematically acceptable mechanisms which are eventually explained by the development of shearing bands or sliding surfaces in clays or claystone materials. Progressive failure will be reviewed and particular attention will be given to a well documented case record (the failure of Aznalcóllar dam) which has received a sustained research effort to explain field behaviour. Thermo-mechanical interactions have been invoked as a plausible mechanism to explain the sudden acceleration of an otherwise “stable” slope if examined from the perspective of conventional static stability conditions. Vajont landslide is examined as an example of the analysis performed. Creep deformations are approached from the concept of rate dependence of shear strength available on shearing bands or discontinuities. Rate effects and thermo-mechanical interactions have been included in a calculation framework which is used to estimate the coupling between slow and fast motions. Attention will also be paid to the search for simple criteria which could be used in practice to estimate landslide risk.

    In addition to the awards, the conference also hosted the First Heim Lecture, delivered by Prof. E. Alonso

  • Rapid drawdown in embankment dams

     Pinyol Puigmarti, Nuria Merce; Alonso Pérez de Agreda, Eduardo; Olivella Pastalle, Sebastian
    DOI: 10.1201/b12130-1
    Date of publication: 2012
    Book chapter

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  • The Material Point Method and the analysis of dams and dam failures

     Zabala, Francisco; Alonso Pérez de Agreda, Eduardo
    DOI: 10.1201/b12130-1
    Date of publication: 2012
    Book chapter

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  • Environmental effects on earth embankments

     Olivella Pastalle, Sebastian; Alonso Pérez de Agreda, Eduardo
    DOI: 10.1201/b12130-1
    Date of publication: 2012
    Book chapter

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  • Placa conmemorativa i discurs a la X Croce Lecture

     Alonso Pérez de Agreda, Eduardo
    Award or recognition

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  • Hinchamiento en túneles por crecimiento de cristales y su modelación

     Ramon Tarragona, Anna; Alonso Pérez de Agreda, Eduardo
    Jornada de Recerca i Innovació a l'Escola de Camins
    p. 1-4
    Presentation's date: 2011-11-15
    Presentation of work at congresses

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  • Gypsum crystal growth in tunnels

     Ramon Tarragona, Anna; Alonso Pérez de Agreda, Eduardo
    ISRM European Rock Mechanics Symposium
    p. 1797-1802
    Presentation's date: 2011-10-20
    Presentation of work at congresses

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    Precipitation of gypsum crystals explains the severe swelling occurred in some tunnels crossing sulphate formations. The presence of groundwater and discontinuities, and the proportions of anhydrite and gypsum within the claystone rock mass play an important role for the development of swelling in tunnels. Evaporation of sulphated solutions and dissolution of anhydrite are two different mechanisms leading to supersaturation in gypsum, and therefore to gypsum crystal growth. The second mechanism has a major effect on the development of swelling in the rock. The two mechanisms should be taken into account for the modelling of expansions due to gypsum crystal growth in tunnels. The paper describes the case of Lila tunnel which required a substantial reconstruction after experiencing severe heave problems. Long term records of swelling pressures and stresses in the lining are also given.

  • Evaluation of alternative methodologies to minimize movements of a diaphragm wall close to buildings

     de Santos, C.; Ledesma Villalba, Alberto; Lloret Morancho, Antonio; Alonso Pérez de Agreda, Eduardo
    European Conference on Soil Mechanics and Geotechnical Engineering
    p. 1461-1466
    Presentation's date: 2011-09-13
    Presentation of work at congresses

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    In the framework of the construction of the high-speed railway passing through Barcelona, a large excavation (21m depth) has made to about 2 m of a building. The excavation was done in the quaternary material typical of the Barcelona plain which consists mainly of low plasticity and slightly cemented compact clays. This material due to its high stiffness can be considered as a "hard soil". In order to minimize movements, several methodologies were considered: change in the thickness of the diaphragm walls, increasing the length of the diaphragm walls and location of struts. The predictions of movements were performed using PLAXIS code, considering model parameters estimated from pressuremeter tests and resonant column. The smallest displacements were obtained if struts were placed in advance just below the maximum excavation level. Those struts had only 3 m thickness below the maximum excavation depth, and were built every 5.5 m in horizontal direction. The measured movements were somewhat lower than expected and the building suffered no damage. The paper demonstrates that struts below the maximum excavation level constitute a safe design when movements induced to buildings are a major concern.

  • Tracking degradation of argillaceous rocks using bender elements.

     Pineda, Jubert; Romero Morales, Enrique Edgar; Alonso Pérez de Agreda, Eduardo
    International Symposium on Deformation Characteristics of Geomaterials
    p. 240-245
    DOI: 10.3233/978-1-60750-822-9-240
    Presentation's date: 2011-09-01
    Presentation of work at congresses

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    The results of a comprehensive experimental program focused on the study of progressive degradation processes on a low permeability argillaceous rock induced by hydraulic cycles is presented in the paper. Relative humidity cycles were applied with vapour transfer technique, and bender elements were used to evaluate the evolution of shear stiffness during the application of hydraulic paths. The characterisation of the material included the determination of the water retention properties (water retention curve), as well as the pore size distribution using mercury intrusion porosimetry, complemented with SEM micrographs and elemental analysis using X-ray spectroscopy to characterise micro-structural features and detect clayey and non-clayey constituents. Results showed cumulative and irreversible swelling of the samples with the application of relative humidity cycles. Regarding shear stiffness, an important reduction (around 80%) was observed at the end of the hydraulic paths applied. Evidence of rock degradation at macro-scale was linked to structural modifications at micro-level.

  • Failure mechanisms in brittle soils: a dam failure revisited with the material point method

     Alonso Pérez de Agreda, Eduardo; Zabala, Francisco
    International conference of IACMAG (International Association for Computer Methods and Advances in Geomechanics)
    p. 377-380
    Presentation's date: 2011-05
    Presentation of work at congresses

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    The material Point Method (MPM) combines features of Finite Element and Discrete Particle methods. It is well suited to analyze geotechnical problems which involve large displacements and dynamic response. An explicit coupled hydro-mechanical formulation has been developed to analyze cases controlled by general loading and pore pressure generation and dissipation. The procedure has been successfully applied to reproduce the failure conditions of Aznalcóllar dam. The failure was explained by a combination of a slow dissipation of pore water pressures in impervious, high plasticity brittle clay and by a progressive failure mechanism. It was also found that the initial state of stress controlled the development and position of the failure surface. Taking Aznalcóllar as a reference case, the following aspects have been investigated: The response of brittle and non-brittle soils; the effect of a sudden loss of effective cohesion at peak strength conditions and the construction sequence and the dam geometry. The analysis of results provides a valuable insight into the significance of the set of aspects outlined above.

  • Simulating particle breakage and relative humidity effects in rockfill behaviour

     Alonso Pérez de Agreda, Eduardo; Tapias Camacho, Mauricio Alberto; Gili Ripoll, Jose Antonio
    International Symposium on Computational Geomechanics
    p. 1-10
    Presentation's date: 2011-04
    Presentation of work at congresses

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    The paper presents an analysis of the mechanical behaviour of rockfill using the discrete element method. A background reference is the set of results of a few large scale triaxial tests performed at the UPC geotechnical laboratory. In those tests Relative Humidity (RH) was controlled by means of a vapour equilibrium technique. RH is a fundamental aspect in the behaviour of rockfill which has received limited attention in the past. The Relative Humidity within the large pores between rock fragments controls the velocity of crack propagation within the particles. An increase in RH means faster crack propagation and eventually breakage of some particles and subsequent re-arrangement of the granular structure. The basic tool used to simulate some of the tests is the computer code PFC3D. Rockfill particles (they have the size of gravels, typically ranging from 1 cm to 4 cm) were simulated as breakable clusters of 3D balls. Particle breakage occurs in time according to fracture mechanic’s laws. In a parallel study, the development of cracks in time has been examined. This information was taken into account in the numerical analysis to derive criteria for particle breakage. The paper describes the preliminary results of the work in progress. The actual shape of rock gravels has been approximated by means of clusters of spherical particles. Several arrangements, comprising a different number of particles, have been numerically tested. The results of the modelling exercise are encouraging and test results are reasonably well reproduced. The model is fairly general and it has a number of interesting capabilities.

  • A study of the effects of suction and roughness on the mechanical behaviour of rock joints

     Zandarín Iragorre, Maria Teresa; Alonso Pérez de Agreda, Eduardo; Olivella Pastalle, Sebastian
    International Symposium on Computational Geomechanics
    p. 1-9
    Presentation's date: 2011-04
    Presentation of work at congresses

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    The experimental investigation focused on the effects of suction on the mechanical behaviour of rock joints. Available experimental data on the effect of moisture on joint behaviour is very scarce. Laboratory tests were performed in a direct shear cell equipped with suction control. Suction was imposed using a vapour forced convection circuit connected to the cell and controlled by an air pump. Artificial joints of Lilla claystone were prepared. Joint roughness of varying intensity was created by carving the surfaces in contact in such a manner that rock ridges of different tip angles were formed. Several tests were performed for different values of suction (20, 100 and 200 MPa) and for different values of vertical stress (30, 60 and 150 kPa). A constitutive model including the effects of suction and joints roughness is proposed to simulate the unsaturated behaviour of rock joints. The new constitutive law was incorporated into the FE computer code Code-Bright and experimental results were numerically simulated.