The use of digital images and the correlation of them in time is commonly used in geotechnical la... more The use of digital images and the correlation of them in time is commonly used in geotechnical laboratory experiments to measure surface variables in a non-invasive and massive way. Digital image correlation-based methods provide a measure of the motion of soil. More recently, measurements of the degree of saturation on soil surface using digital images have also been developed, although its application and validation are still limited. This methodology is based on the fact that almost all soils become darker (less light reflective) due to wetting. This article uses image-based analysis techniques to evaluate the behaviour during wetting of a small-scale dam made of compacted fine sand. With the aim of validating the measurements from images, soil moisture sensors were installed in the dam. The tested soil was previously calibrated to determine the correlation of light reflectance and the degree of saturation covering from dry to fully saturated range. Measurements of velocity, displacements, deformations and the degree of saturation in time are evaluated during the experiment based on images recorded in the visual and shortwave infrared (SWIR) light range. The methodology is described step-by-step including camera and lighting system, sample preparation, image acquisition and image analysis. The techniques used allow the changes in the degree of saturation in soil in motion and the failure mechanisms associated with the wetting process to be observed. The results obtained through image analyses show good agreement with the parameters obtained in point measurements with conventional sensors. The results also show some limitations of the method, mainly associated with the accumulation of errors in the tracking of soil particles during large displacements.
Dam maintenance and rehabilitation ii-fachbuch As dams age, they are subject to a series of exter... more Dam maintenance and rehabilitation ii-fachbuch As dams age, they are subject to a series of external agents and processes which tend to deteriorate the qualities with which they were originally conceived to stand Dam maintenance and rehabilitation ii th edition COUPON: Rent Dam Maintenance and Rehabilitation II th edition by Romeo Garc a eBook (9781136818394) and save up to 80% on online textbooks at Chegg.com now! Dam maintenance and rehabilitation ii: amazon.
The paper describes first the theoretical framework of a "single layer" three phase material. The... more 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 Mohr-Coulomb elastoplastic soil formulated in terms of net stress and suction. Three aspects of the behaviour of landslides are discussed: first time failures in over-consolidated 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.
Mechanical and hydraulic compacted soil properties for a given soil mineralogy are essentially co... more Mechanical and hydraulic compacted soil properties for a given soil mineralogy are essentially controlled by the attained dry density, water content and microstructure. Basic compaction conditions (wet or dry of optimum, higher or lower energy of compaction) result in changes in microstructure. The paper attempts to provide a procedure of increasing accuracy to translate compaction concepts, rooted in common practice, into a modelling framework capable of explaining the behaviour of compacted soils. The approach developed is divided into the following stages: a) The classical compaction variables are interpreted in terms of two stress-like variables. They are regarded as the initial state for a given elasto-plastic constitutive model. The usefulness of this approach is discussed with some examples. b) A proper constitutive framework should introduce explicitly density effects in order to capture a swelling-collapse transition during wetting, a particularly important case in practice since embankments or dams usually experience a wetting increase path after initial compaction. The paper shows how the double structure model introduced by the authors is capable of including density effects in a natural manner. c) Further affects of microstructure are introduced through a different approach namely by defining an appropriate effective stress in terms of a microstructural parameter. This idea enhances the capabilities of previous frameworks.
Rain induced instabilities are a common geotechnical problem specially in partially saturated soi... more Rain induced instabilities are a common geotechnical problem specially in partially saturated soils. A large number of steep, natural or cut slopes remain stable for a long time and then fail during heavy rainstorms or after a long period of rain. In this work, the Material Point Method (MPM) is used to model the whole instability process. The MPM theoretical framework regarding a
International Society for Soil Mechanics and Geotechnical Engineering Online Library: 13th International Symposium on Landslides ( XIII ISL), 2020
The paper discusses some factors that control the shearing soil behaviour and the dynamics of lan... more The paper discusses some factors that control the shearing soil behaviour and the dynamics of landslides: strain-, strain rate-, and temperature effects. The strain rate effect on residual strength is discussed through shearing tests reported in the literature on saturated samples at velocities ranging from 10-5 mm/min to 10 4 mm/min. Such range covers from very slow to very rapid landslides according to landslide classification. The analysis of available data is presented and provides a framework which helps to define the constitutive law and phenomena further selected for the landslide analyses. Some recent experimental published works are also discussed to show the temperature effect on shear strength. It is concluded that temperature effects are strain-rate dependent. The available data on that is limited and it may have a relevant effect in shallow landslides in which the sliding surface suffers the influence of weather induced temperature changes. The second part of the article focusses on the analysis of landslides including several factors affecting the available shearing strength of the soils involved in instabilities. The motion from triggering to the final re-established equilibrium of slow and rapid landslides is analyzed through academic and simple examples as well as documented real cases. Under some hypotheses to simplify the problems, governing equations are solved analytically or in a simple numerical way to facilitate the discussion and to perform sensitivity analyses. With the interest of evaluating more realistic cases, some simplified hypotheses are relaxed and complex geometries and conditions are taken into account through numerical modeling. The material point method is selected. The MPM numerical codes, recently developed, can deal with strain-and strain-rate dependent shearing strength and include coupled effects likely developed during motion in landslides. Strain-softening of shear strength causing progressive phenomenon is firstly discussed not only because of its effect on triggering first failures, but also for the estimation of landslide run-out. Compound landslides are specifically analyzed to discuss the progressive phenomena developed along internal shearing planes. Peak and residual strength envelopes control the landslide acceleration. The magnitude of the strength drop correlates well with the run-out. Including a strain rate hardening component to the strength allows the assessment of creeping landslides. Weakening phenomena inducing the acceleration of landslides are not directly included as an intrinsic feature. The loss of residual strength that may lead to a rapid landslide is explained by invoking thermal water pressurization. Both effects, strain rate hardening and hydro-thermal coupled weakening, are probably present during motion. Soil properties, landslide features, and external conditions will determine the landslide motion. This interaction is discussed in terms of run-out and velocity of landslides subjected to static conditions, as well as seismic actions. Normalized residual shear stress (V=0.01-0.025 mm/min) Displacement rate (mm/min) Brown London clay-Petley et al. (1966) Muscovite <6um Kenney et al. (1967) Na-Hydrous mica 0.5 M.-Kenney et al. (1967) Na montmorillonite 0M. <2um-Kenney et al. (1967) Na montmorillonite 0M.<0.1um-Kenney et al. (1967) Ca montmorillonite 0M. <2um-Kenney et al. (1967) Selnes quick clay-Kenney et al. (1967) Kaolinite-Kenney et al. (1967) Vajont < 60um-Kenney et al. (1967) Boom clay-De Beer (1967) Boom clay-De Beer (1967) Silty clay-Ramiah et al. (1967) Pepper Shale-La Gatta (1970) Crushed cucaracha shale-La Gatta (1970) Blue London clay-La Gatta (1970) Bearpaw shale-La Gatta (1971) Clay-Bucher (1975) San Francisco mudstone-Pyles (1984) Clayey sandy silt-Salt (1988) Velocity scale Soils exhibiting positive rate effect-Tika et al. (1989a, 1989b) Soils exhibiting negative rate effect-Tika et al. (1989a, 1989b) Soils exhibiting neutral rate effect-Tika et al. (1989a, 1989b) Shiraishi Landslide-Wang et al. (2010) Clayey siltstone, siltstone neutral effect-Lemos (1986) Clayey siltstone, siltstone negative effect-Lemos et al. (1989) Fiji (A)-Lupini (1981) Lower cromer till-Lupini (1981)
&amp;lt;p&amp;gt;The available strength on slip surfaces in landslide after a significant... more &amp;lt;p&amp;gt;The available strength on slip surfaces in landslide after a significant displacement and at motion is the residual strength. The residual strength depends on the soil properties including both solid skeleton (mineralogy, particle shape and size, index properties) and pore fluid (chemical and rheological properties). The available strength also depends, as extensively reported in the literature, on several factors that may not remain constant in time and affect the landslide stability and dynamics: applied stress, accumulated displacement and shear strain rate. With a less extensive literature related to, the effect of temperature on the residual strength have been also observed.&amp;lt;/p&amp;gt;&amp;lt;p&amp;gt;This work reports on the results of a large number of ring shear tests under controlled rate and temperature performed on different types of soils. The results are interpreted in terms of the influence of mineralogy, clay content and plasticity on temperature effects on residual strength.&amp;lt;/p&amp;gt;
El artículo analiza el comportamiento de deslizamientos en rocas caracterizadas por el predominio... more El artículo analiza el comportamiento de deslizamientos en rocas caracterizadas por el predominio de su componente arcillosa y por una tipología de movimientos que se explican por el agotamiento de la resistencia al esfuerzo cortante en superficies o bandas de pequeño espesor. El artículo se centra en primeras roturas y, posteriormente, en el efecto de los planos de corte internos que se desarrollan por compatibilidad de movimiento. Las primeras roturas en materiales que exhiben un comportamiento de reblandecimiento bajo tensión están generalmente precedidas por un mecanismo de rotura progresiva seguido de un movimiento acelerado. El tipo de solicitación exterior (carga, descarga, cambio en presiones intersticiales) controla el mecanismo de rotura y su evolución. Ello se ilustra en varios ejemplos de roturas (Selborne, Viladesens, Sabadell, Aznalcóllar). Por otro lado, mediante análisis de sensibilidad utilizando el “método del punto material”, se muestra que el desplazamiento esper...
Landslides and Engineered Slopes. Experience, Theory and Practice, 2018
Rain induced instabilities are a common geotechnical problem specially in partially saturated soi... more Rain induced instabilities are a common geotechnical problem specially in partially saturated soils. A large number of steep, natural or cut slopes remain stable for a long time and then fail during heavy rainstorms or after a long period of rain. In this work, the Material Point Method (MPM) is used to model the whole instability process. The MPM theoretical framework regarding aPeer Reviewe
This paper presents a centrifuge model of a silty clay slope. The increase of the gravity accel-e... more This paper presents a centrifuge model of a silty clay slope. The increase of the gravity accel-eration is applied to the slope under unsaturated conditions. The slope is wetted in flight by means of water injection from the bottom. The deformation of the slope and the subsequent failure is analyzed. In order to avoid difficulties in the installation of sensors in the prototype, the model was built in a box of transparent walls and the slope behavior during the flight was recorded using a digital camera. The images were analyzed using the PIV method (Particle Image Velocimetry) and processed by means of the methodology called PIV-NP with the aim of obtaining accumulated displacements and strains. This methodology is able to provide the strains from PIV measurements following an Eulerian scheme even in case of large defor-mations. The experimental results indicate that the wetting-induced volumetric strains (col-lapse) occurred in the wetting front and the soil located above settled ...
Thermal effects induced by the own motion of an unstable mass have been included in the analysis ... more Thermal effects induced by the own motion of an unstable mass have been included in the analysis of the post-failure behavior in early works, most of them with the aim of looking for the causes of the rapid acceleration of Vajont landslide (Italy, 1963). Some limitations of these contributions, including recently published papers, lies in the fact that (a) the analyzed landslide geometries are simple and (b) the plastic work dissipation, inducing heat, is concen-trated in a shear band defined by the contacts between rigid bodies. This contribution general-izes previous ideas and presents a numerical approach capable of including thermally induced pore water pressure in landslide analyses. Special attention is given to the effect of the shear band thickness, which becomes relevant in numerical simulations.
La ocurrencia de deslizamientos rapidos se ha ligado a la perdida de resistencia efectiva a lo la... more La ocurrencia de deslizamientos rapidos se ha ligado a la perdida de resistencia efectiva a lo largo de la superficie de rotura debido a excesos de presion de agua inducidos por el calor generado durante el propio movimiento. La simulacion numerica de estos procesos se ha enfocado resolviendo la ecuacion de la dinamica del movimiento de forma acoplada con la resolucion de las ecuaciones de balance de masa y temperatura a la escala de la banda de corte. Para ello se debe definir a priori la geometria y la posicion de la superficie de rotura. En este articulo se presenta la simulacion numerica de deslizamientos incluyendo los efectos termicos utilizando el Metodo del Punto Material, metodo numerico bien adaptado a la simulacion de grandes desplazamientos. Ello permite simular de manera general el proceso de inestabilidad y el comportamiento post-rotura sin la necesidad de definir a priori la posicion de la superficie de rotura critica. Las ecuaciones de equilibrio dinamico y las de ba...
One of the factors causing the acceleration of landslides is the loss of strength of the soil inv... more One of the factors causing the acceleration of landslides is the loss of strength of the soil involved in the potential unstable mechanism. The travelled distance and the landslide velocity, a key factor in risk analysis, will be determined by the loss of resistant forces. Brittle behaviour, commonly associated with cemented soils, overconsolidated plastic clay formations and sensitive clays, lead to the progressive failure phenomenon explained by the reduction of the strength with increasing strain. In the present study, this phenomenon has been analysed in the case of a saturated slope which becomes unstable by increasing the boundary pore water pressure. A Mohr-Coulomb model with strain softening behaviour induced by increasing deviatoric plastic strain is used. The paper focusses not only on the stability of the slope but also on the post failure behaviour (run-out and sliding velocity). A coupled hydro-mechanical formulation of the Material Point Method has been used to simulate the whole instability process. The influence of the brittleness of the material on the triggering of instability and runout is evaluated by means of a parametric study varying peak and residual strength. The onset of the failure and the failure geometry are controlled by both peak and residual values. Good correlations between run-outs and brittleness are found. The decay of the strength determines the acceleration of the landslides and the travelled distance.
The use of digital images and the correlation of them in time is commonly used in geotechnical la... more The use of digital images and the correlation of them in time is commonly used in geotechnical laboratory experiments to measure surface variables in a non-invasive and massive way. Digital image correlation-based methods provide a measure of the motion of soil. More recently, measurements of the degree of saturation on soil surface using digital images have also been developed, although its application and validation are still limited. This methodology is based on the fact that almost all soils become darker (less light reflective) due to wetting. This article uses image-based analysis techniques to evaluate the behaviour during wetting of a small-scale dam made of compacted fine sand. With the aim of validating the measurements from images, soil moisture sensors were installed in the dam. The tested soil was previously calibrated to determine the correlation of light reflectance and the degree of saturation covering from dry to fully saturated range. Measurements of velocity, displacements, deformations and the degree of saturation in time are evaluated during the experiment based on images recorded in the visual and shortwave infrared (SWIR) light range. The methodology is described step-by-step including camera and lighting system, sample preparation, image acquisition and image analysis. The techniques used allow the changes in the degree of saturation in soil in motion and the failure mechanisms associated with the wetting process to be observed. The results obtained through image analyses show good agreement with the parameters obtained in point measurements with conventional sensors. The results also show some limitations of the method, mainly associated with the accumulation of errors in the tracking of soil particles during large displacements.
Dam maintenance and rehabilitation ii-fachbuch As dams age, they are subject to a series of exter... more Dam maintenance and rehabilitation ii-fachbuch As dams age, they are subject to a series of external agents and processes which tend to deteriorate the qualities with which they were originally conceived to stand Dam maintenance and rehabilitation ii th edition COUPON: Rent Dam Maintenance and Rehabilitation II th edition by Romeo Garc a eBook (9781136818394) and save up to 80% on online textbooks at Chegg.com now! Dam maintenance and rehabilitation ii: amazon.
The paper describes first the theoretical framework of a "single layer" three phase material. The... more 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 Mohr-Coulomb elastoplastic soil formulated in terms of net stress and suction. Three aspects of the behaviour of landslides are discussed: first time failures in over-consolidated 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.
Mechanical and hydraulic compacted soil properties for a given soil mineralogy are essentially co... more Mechanical and hydraulic compacted soil properties for a given soil mineralogy are essentially controlled by the attained dry density, water content and microstructure. Basic compaction conditions (wet or dry of optimum, higher or lower energy of compaction) result in changes in microstructure. The paper attempts to provide a procedure of increasing accuracy to translate compaction concepts, rooted in common practice, into a modelling framework capable of explaining the behaviour of compacted soils. The approach developed is divided into the following stages: a) The classical compaction variables are interpreted in terms of two stress-like variables. They are regarded as the initial state for a given elasto-plastic constitutive model. The usefulness of this approach is discussed with some examples. b) A proper constitutive framework should introduce explicitly density effects in order to capture a swelling-collapse transition during wetting, a particularly important case in practice since embankments or dams usually experience a wetting increase path after initial compaction. The paper shows how the double structure model introduced by the authors is capable of including density effects in a natural manner. c) Further affects of microstructure are introduced through a different approach namely by defining an appropriate effective stress in terms of a microstructural parameter. This idea enhances the capabilities of previous frameworks.
Rain induced instabilities are a common geotechnical problem specially in partially saturated soi... more Rain induced instabilities are a common geotechnical problem specially in partially saturated soils. A large number of steep, natural or cut slopes remain stable for a long time and then fail during heavy rainstorms or after a long period of rain. In this work, the Material Point Method (MPM) is used to model the whole instability process. The MPM theoretical framework regarding a
International Society for Soil Mechanics and Geotechnical Engineering Online Library: 13th International Symposium on Landslides ( XIII ISL), 2020
The paper discusses some factors that control the shearing soil behaviour and the dynamics of lan... more The paper discusses some factors that control the shearing soil behaviour and the dynamics of landslides: strain-, strain rate-, and temperature effects. The strain rate effect on residual strength is discussed through shearing tests reported in the literature on saturated samples at velocities ranging from 10-5 mm/min to 10 4 mm/min. Such range covers from very slow to very rapid landslides according to landslide classification. The analysis of available data is presented and provides a framework which helps to define the constitutive law and phenomena further selected for the landslide analyses. Some recent experimental published works are also discussed to show the temperature effect on shear strength. It is concluded that temperature effects are strain-rate dependent. The available data on that is limited and it may have a relevant effect in shallow landslides in which the sliding surface suffers the influence of weather induced temperature changes. The second part of the article focusses on the analysis of landslides including several factors affecting the available shearing strength of the soils involved in instabilities. The motion from triggering to the final re-established equilibrium of slow and rapid landslides is analyzed through academic and simple examples as well as documented real cases. Under some hypotheses to simplify the problems, governing equations are solved analytically or in a simple numerical way to facilitate the discussion and to perform sensitivity analyses. With the interest of evaluating more realistic cases, some simplified hypotheses are relaxed and complex geometries and conditions are taken into account through numerical modeling. The material point method is selected. The MPM numerical codes, recently developed, can deal with strain-and strain-rate dependent shearing strength and include coupled effects likely developed during motion in landslides. Strain-softening of shear strength causing progressive phenomenon is firstly discussed not only because of its effect on triggering first failures, but also for the estimation of landslide run-out. Compound landslides are specifically analyzed to discuss the progressive phenomena developed along internal shearing planes. Peak and residual strength envelopes control the landslide acceleration. The magnitude of the strength drop correlates well with the run-out. Including a strain rate hardening component to the strength allows the assessment of creeping landslides. Weakening phenomena inducing the acceleration of landslides are not directly included as an intrinsic feature. The loss of residual strength that may lead to a rapid landslide is explained by invoking thermal water pressurization. Both effects, strain rate hardening and hydro-thermal coupled weakening, are probably present during motion. Soil properties, landslide features, and external conditions will determine the landslide motion. This interaction is discussed in terms of run-out and velocity of landslides subjected to static conditions, as well as seismic actions. Normalized residual shear stress (V=0.01-0.025 mm/min) Displacement rate (mm/min) Brown London clay-Petley et al. (1966) Muscovite <6um Kenney et al. (1967) Na-Hydrous mica 0.5 M.-Kenney et al. (1967) Na montmorillonite 0M. <2um-Kenney et al. (1967) Na montmorillonite 0M.<0.1um-Kenney et al. (1967) Ca montmorillonite 0M. <2um-Kenney et al. (1967) Selnes quick clay-Kenney et al. (1967) Kaolinite-Kenney et al. (1967) Vajont < 60um-Kenney et al. (1967) Boom clay-De Beer (1967) Boom clay-De Beer (1967) Silty clay-Ramiah et al. (1967) Pepper Shale-La Gatta (1970) Crushed cucaracha shale-La Gatta (1970) Blue London clay-La Gatta (1970) Bearpaw shale-La Gatta (1971) Clay-Bucher (1975) San Francisco mudstone-Pyles (1984) Clayey sandy silt-Salt (1988) Velocity scale Soils exhibiting positive rate effect-Tika et al. (1989a, 1989b) Soils exhibiting negative rate effect-Tika et al. (1989a, 1989b) Soils exhibiting neutral rate effect-Tika et al. (1989a, 1989b) Shiraishi Landslide-Wang et al. (2010) Clayey siltstone, siltstone neutral effect-Lemos (1986) Clayey siltstone, siltstone negative effect-Lemos et al. (1989) Fiji (A)-Lupini (1981) Lower cromer till-Lupini (1981)
&amp;lt;p&amp;gt;The available strength on slip surfaces in landslide after a significant... more &amp;lt;p&amp;gt;The available strength on slip surfaces in landslide after a significant displacement and at motion is the residual strength. The residual strength depends on the soil properties including both solid skeleton (mineralogy, particle shape and size, index properties) and pore fluid (chemical and rheological properties). The available strength also depends, as extensively reported in the literature, on several factors that may not remain constant in time and affect the landslide stability and dynamics: applied stress, accumulated displacement and shear strain rate. With a less extensive literature related to, the effect of temperature on the residual strength have been also observed.&amp;lt;/p&amp;gt;&amp;lt;p&amp;gt;This work reports on the results of a large number of ring shear tests under controlled rate and temperature performed on different types of soils. The results are interpreted in terms of the influence of mineralogy, clay content and plasticity on temperature effects on residual strength.&amp;lt;/p&amp;gt;
El artículo analiza el comportamiento de deslizamientos en rocas caracterizadas por el predominio... more El artículo analiza el comportamiento de deslizamientos en rocas caracterizadas por el predominio de su componente arcillosa y por una tipología de movimientos que se explican por el agotamiento de la resistencia al esfuerzo cortante en superficies o bandas de pequeño espesor. El artículo se centra en primeras roturas y, posteriormente, en el efecto de los planos de corte internos que se desarrollan por compatibilidad de movimiento. Las primeras roturas en materiales que exhiben un comportamiento de reblandecimiento bajo tensión están generalmente precedidas por un mecanismo de rotura progresiva seguido de un movimiento acelerado. El tipo de solicitación exterior (carga, descarga, cambio en presiones intersticiales) controla el mecanismo de rotura y su evolución. Ello se ilustra en varios ejemplos de roturas (Selborne, Viladesens, Sabadell, Aznalcóllar). Por otro lado, mediante análisis de sensibilidad utilizando el “método del punto material”, se muestra que el desplazamiento esper...
Landslides and Engineered Slopes. Experience, Theory and Practice, 2018
Rain induced instabilities are a common geotechnical problem specially in partially saturated soi... more Rain induced instabilities are a common geotechnical problem specially in partially saturated soils. A large number of steep, natural or cut slopes remain stable for a long time and then fail during heavy rainstorms or after a long period of rain. In this work, the Material Point Method (MPM) is used to model the whole instability process. The MPM theoretical framework regarding aPeer Reviewe
This paper presents a centrifuge model of a silty clay slope. The increase of the gravity accel-e... more This paper presents a centrifuge model of a silty clay slope. The increase of the gravity accel-eration is applied to the slope under unsaturated conditions. The slope is wetted in flight by means of water injection from the bottom. The deformation of the slope and the subsequent failure is analyzed. In order to avoid difficulties in the installation of sensors in the prototype, the model was built in a box of transparent walls and the slope behavior during the flight was recorded using a digital camera. The images were analyzed using the PIV method (Particle Image Velocimetry) and processed by means of the methodology called PIV-NP with the aim of obtaining accumulated displacements and strains. This methodology is able to provide the strains from PIV measurements following an Eulerian scheme even in case of large defor-mations. The experimental results indicate that the wetting-induced volumetric strains (col-lapse) occurred in the wetting front and the soil located above settled ...
Thermal effects induced by the own motion of an unstable mass have been included in the analysis ... more Thermal effects induced by the own motion of an unstable mass have been included in the analysis of the post-failure behavior in early works, most of them with the aim of looking for the causes of the rapid acceleration of Vajont landslide (Italy, 1963). Some limitations of these contributions, including recently published papers, lies in the fact that (a) the analyzed landslide geometries are simple and (b) the plastic work dissipation, inducing heat, is concen-trated in a shear band defined by the contacts between rigid bodies. This contribution general-izes previous ideas and presents a numerical approach capable of including thermally induced pore water pressure in landslide analyses. Special attention is given to the effect of the shear band thickness, which becomes relevant in numerical simulations.
La ocurrencia de deslizamientos rapidos se ha ligado a la perdida de resistencia efectiva a lo la... more La ocurrencia de deslizamientos rapidos se ha ligado a la perdida de resistencia efectiva a lo largo de la superficie de rotura debido a excesos de presion de agua inducidos por el calor generado durante el propio movimiento. La simulacion numerica de estos procesos se ha enfocado resolviendo la ecuacion de la dinamica del movimiento de forma acoplada con la resolucion de las ecuaciones de balance de masa y temperatura a la escala de la banda de corte. Para ello se debe definir a priori la geometria y la posicion de la superficie de rotura. En este articulo se presenta la simulacion numerica de deslizamientos incluyendo los efectos termicos utilizando el Metodo del Punto Material, metodo numerico bien adaptado a la simulacion de grandes desplazamientos. Ello permite simular de manera general el proceso de inestabilidad y el comportamiento post-rotura sin la necesidad de definir a priori la posicion de la superficie de rotura critica. Las ecuaciones de equilibrio dinamico y las de ba...
One of the factors causing the acceleration of landslides is the loss of strength of the soil inv... more One of the factors causing the acceleration of landslides is the loss of strength of the soil involved in the potential unstable mechanism. The travelled distance and the landslide velocity, a key factor in risk analysis, will be determined by the loss of resistant forces. Brittle behaviour, commonly associated with cemented soils, overconsolidated plastic clay formations and sensitive clays, lead to the progressive failure phenomenon explained by the reduction of the strength with increasing strain. In the present study, this phenomenon has been analysed in the case of a saturated slope which becomes unstable by increasing the boundary pore water pressure. A Mohr-Coulomb model with strain softening behaviour induced by increasing deviatoric plastic strain is used. The paper focusses not only on the stability of the slope but also on the post failure behaviour (run-out and sliding velocity). A coupled hydro-mechanical formulation of the Material Point Method has been used to simulate the whole instability process. The influence of the brittleness of the material on the triggering of instability and runout is evaluated by means of a parametric study varying peak and residual strength. The onset of the failure and the failure geometry are controlled by both peak and residual values. Good correlations between run-outs and brittleness are found. The decay of the strength determines the acceleration of the landslides and the travelled distance.
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