Leandro Alejano | Universidade de Vigo (original) (raw)
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Papers by Leandro Alejano
During the last decade different researchers on the field of rock mechanics have stated that a se... more During the last decade different researchers on the field of rock mechanics have stated that a series of typical average rock masses behave in a strain-softening manner. However, it is not easy to obtain all the parameters needed to study this behavior. In this paper we attempt to give some guidelines on how to reasonably characterize a more or less average quality rock mass so as to obtain all the parameters needed to correctly estimate its stress-strain behavior. The characterisation process is based on drawing together recently published approaches and our own estimates based on practical experience. © 2010 Taylor & Francis Group, London.
A proper selection of the distance to the face to install support is of paramount interest in tun... more A proper selection of the distance to the face to install support is of paramount interest in tunneling. This selection can be based on the Longitudinal Deformation Profile (LDP), in the frame of the Convergence Confinement Method (CCM). However, obtaining the actual LDP of a tunnel is not a simple matter. Elastic approaches have been widely used in the past. Recently, new techniques accounting for perfect plasticity have been proposed. The aim of this study is to assess the influence of considering strain-softening behavior on the longitudinal deformation profiles for tunnels by means of simple numerical techniques. The obtained results show that the fact of accounting for strain-softening behavior does not significantly affect LDPs. © 2010 Taylor & Francis Group.
The aim of this paper is to perform a simplified numeric model of the labours in the Tinyag under... more The aim of this paper is to perform a simplified numeric model of the labours in the Tinyag underground mining exploitation (sublevel caving method), in order to estimate the possible behaviour of the rock mass affected by the labours, and to detect possible failure mechanisms (circular failure, toppling, etc.). The model is also interesting to identify the subsidence mechanisms associated and to have an approximate vision of the existent geomechanical risks. We have performed this model using UDEC.
Journal of Rock Mechanics and Geotechnical Engineering, 2014
With respect to constitutive models for continuum modeling applications, the post-yield domain re... more With respect to constitutive models for continuum modeling applications, the post-yield domain remains the area of greatest uncertainty. Recent studies based on laboratory testing have led to the development of a number of models for brittle rock dilation, which account for both the plastic shear strain and confining stress dependencies of this phenomenon. Although these models are useful in providing an improved understanding of how dilatancy evolves during a compression test, there has been relatively little work performed examining their validity for modeling brittle rock yield in situ. In this study, different constitutive models for rock dilation are reviewed and then tested, in the context of a number of case studies, using a continuum finite-difference approach (FLAC). The uncertainty associated with the modeling of brittle fracture localization is addressed, and the overall ability of mobilized dilation models to replicate in situ deformation measurements and yield patterns is evaluated.
Rock Engineering and Rock Mechanics: Structures in and on Rock Masses, 2014
Rock Engineering and Rock Mechanics: Structures in and on Rock Masses, 2014
Rock Engineering and Rock Mechanics: Structures in and on Rock Masses, 2014
The stress-strain response of some intact metamorphic rocks (amphibolite, gneiss and marble) has ... more The stress-strain response of some intact metamorphic rocks (amphibolite, gneiss and marble) has been studied based on around 60 compressive uniaxial and triaxial strength tests. The results have been interpreted to obtain peak and residual strength, and post-peak parameters. Particular attention has been given to the study of dilation. The dilation angle of these intact rocks has been fitted to recently developed models for plastic shear strain and confinement-stress-dependent dilation. Even if the dilative response of these rocks has shown to follow similar trends to those observed in other hard rocks, in the case of foliated ones the peak dilation angle attain is not as high as that of more homogeneous (granite, marble). This is attributed to the fact that the final fracturing of the samples partially follows already existing weakness planes, which show less dilation than newly developed shear bands.
Proceedings of the International Symposium of the International Society for Rock Mechanics, Eurock 2006, Liège, Belgium, 9-12 May 2006, 2006
Proceedings of the ISRM Workshop W1, Madrid, Spain, 6-7 July 2007, 2007
Tunnelling and Underground Space Technology, 2005
This paper presents a study of bifurcation in the problem of unloading a circular excavation in a... more This paper presents a study of bifurcation in the problem of unloading a circular excavation in a strain-softening rock mass. The analysis focuses on how bifurcation affects the calculation of ground reaction curves for tunnels.To begin with, the most important issues in strain-softening behaviour are discussed, with the concepts of bifurcation and localisation presented by reviewing physical observations of these
Rock Engineering and Rock Mechanics: Structures in and on Rock Masses, 2014
Rock Mechanics for Resources, Energy and Environment, 2013
DYNA, 2015
We statistically analysed the chemical components present in waste water from mines in Galicia (N... more We statistically analysed the chemical components present in waste water from mines in Galicia (NW Spain). These elements pose a risk to public health and the environment, most particularly in the event of a failure in the containment structure of a pond or dam. The statistical processing of the data, which started with an analysis of the typical contaminants present in mining ponds and dams, pointed to the potential limitations of using non-spatial models for spatially structured data. Our results indicate the greater potential of the generalized linear spatial model over the generalized linear model for analysis of spatially structured data. We also show how a misspecification of the model for analysing spatial data can lead to misleading conclusions, which might lead, in turn, to poorly designed protective or corrective measures.
Rock Mechanics for Resources, Energy and Environment, 2013
Harmonising Rock Engineering and the Environment, 2011
The ISRM Suggested Methods for Rock Characterization, Testing and Monitoring: 2007-2014, 2012
Rock Engineering and Rock Mechanics: Structures in and on Rock Masses, 2014
Journal of Rock Mechanics and Geotechnical Engineering, 2013
Tunnel with an aureole of a different material a b s t r a c t Fast methods to solve the unloadin... more Tunnel with an aureole of a different material a b s t r a c t Fast methods to solve the unloading problem of a cylindrical cavity or tunnel excavated in elasto-perfectly plastic, elasto-brittle or strain-softening materials under a hydrostatic stress field can be derived based on the self-similarity of the solution. As a consequence, they only apply when the rock mass is homogeneous and so exclude many cases of practical interest. We describe a robust and fast numerical technique that solves the tunnel unloading problem and estimates the ground reaction curve for a cylindrical cavity excavated in a rock mass with properties depending on the radial coordinate, where the solution is no longer self-similar. The solution is based on a continuation-like approach (associated with the unloading and with the incremental formulation of the elasto-plastic behavior), finite element spatial discretization and a combination of explicit sub-stepping schemes and implicit techniques to integrate the constitutive law, so as to tackle the difficulties associated with both strong strain-softening and elasto-brittle behaviors. The developed algorithm is used for two practical ground reaction curve computation applications. The first application refers to a tunnel surrounded by an aureole of material damaged by blasting and the second to a tunnel surrounded by a ring-like zone of reinforced (rock-bolted) material.
Harmonising Rock Engineering and the Environment, 2011
Resources Policy, 2011
Mining activities are compatible with other activities in space and time if they are developed to... more Mining activities are compatible with other activities in space and time if they are developed together and adapted to each other. If permits are required for two projects that are not considered to be compatible, the authorities will be forced to decide which one has ...
During the last decade different researchers on the field of rock mechanics have stated that a se... more During the last decade different researchers on the field of rock mechanics have stated that a series of typical average rock masses behave in a strain-softening manner. However, it is not easy to obtain all the parameters needed to study this behavior. In this paper we attempt to give some guidelines on how to reasonably characterize a more or less average quality rock mass so as to obtain all the parameters needed to correctly estimate its stress-strain behavior. The characterisation process is based on drawing together recently published approaches and our own estimates based on practical experience. © 2010 Taylor & Francis Group, London.
A proper selection of the distance to the face to install support is of paramount interest in tun... more A proper selection of the distance to the face to install support is of paramount interest in tunneling. This selection can be based on the Longitudinal Deformation Profile (LDP), in the frame of the Convergence Confinement Method (CCM). However, obtaining the actual LDP of a tunnel is not a simple matter. Elastic approaches have been widely used in the past. Recently, new techniques accounting for perfect plasticity have been proposed. The aim of this study is to assess the influence of considering strain-softening behavior on the longitudinal deformation profiles for tunnels by means of simple numerical techniques. The obtained results show that the fact of accounting for strain-softening behavior does not significantly affect LDPs. © 2010 Taylor & Francis Group.
The aim of this paper is to perform a simplified numeric model of the labours in the Tinyag under... more The aim of this paper is to perform a simplified numeric model of the labours in the Tinyag underground mining exploitation (sublevel caving method), in order to estimate the possible behaviour of the rock mass affected by the labours, and to detect possible failure mechanisms (circular failure, toppling, etc.). The model is also interesting to identify the subsidence mechanisms associated and to have an approximate vision of the existent geomechanical risks. We have performed this model using UDEC.
Journal of Rock Mechanics and Geotechnical Engineering, 2014
With respect to constitutive models for continuum modeling applications, the post-yield domain re... more With respect to constitutive models for continuum modeling applications, the post-yield domain remains the area of greatest uncertainty. Recent studies based on laboratory testing have led to the development of a number of models for brittle rock dilation, which account for both the plastic shear strain and confining stress dependencies of this phenomenon. Although these models are useful in providing an improved understanding of how dilatancy evolves during a compression test, there has been relatively little work performed examining their validity for modeling brittle rock yield in situ. In this study, different constitutive models for rock dilation are reviewed and then tested, in the context of a number of case studies, using a continuum finite-difference approach (FLAC). The uncertainty associated with the modeling of brittle fracture localization is addressed, and the overall ability of mobilized dilation models to replicate in situ deformation measurements and yield patterns is evaluated.
Rock Engineering and Rock Mechanics: Structures in and on Rock Masses, 2014
Rock Engineering and Rock Mechanics: Structures in and on Rock Masses, 2014
Rock Engineering and Rock Mechanics: Structures in and on Rock Masses, 2014
The stress-strain response of some intact metamorphic rocks (amphibolite, gneiss and marble) has ... more The stress-strain response of some intact metamorphic rocks (amphibolite, gneiss and marble) has been studied based on around 60 compressive uniaxial and triaxial strength tests. The results have been interpreted to obtain peak and residual strength, and post-peak parameters. Particular attention has been given to the study of dilation. The dilation angle of these intact rocks has been fitted to recently developed models for plastic shear strain and confinement-stress-dependent dilation. Even if the dilative response of these rocks has shown to follow similar trends to those observed in other hard rocks, in the case of foliated ones the peak dilation angle attain is not as high as that of more homogeneous (granite, marble). This is attributed to the fact that the final fracturing of the samples partially follows already existing weakness planes, which show less dilation than newly developed shear bands.
Proceedings of the International Symposium of the International Society for Rock Mechanics, Eurock 2006, Liège, Belgium, 9-12 May 2006, 2006
Proceedings of the ISRM Workshop W1, Madrid, Spain, 6-7 July 2007, 2007
Tunnelling and Underground Space Technology, 2005
This paper presents a study of bifurcation in the problem of unloading a circular excavation in a... more This paper presents a study of bifurcation in the problem of unloading a circular excavation in a strain-softening rock mass. The analysis focuses on how bifurcation affects the calculation of ground reaction curves for tunnels.To begin with, the most important issues in strain-softening behaviour are discussed, with the concepts of bifurcation and localisation presented by reviewing physical observations of these
Rock Engineering and Rock Mechanics: Structures in and on Rock Masses, 2014
Rock Mechanics for Resources, Energy and Environment, 2013
DYNA, 2015
We statistically analysed the chemical components present in waste water from mines in Galicia (N... more We statistically analysed the chemical components present in waste water from mines in Galicia (NW Spain). These elements pose a risk to public health and the environment, most particularly in the event of a failure in the containment structure of a pond or dam. The statistical processing of the data, which started with an analysis of the typical contaminants present in mining ponds and dams, pointed to the potential limitations of using non-spatial models for spatially structured data. Our results indicate the greater potential of the generalized linear spatial model over the generalized linear model for analysis of spatially structured data. We also show how a misspecification of the model for analysing spatial data can lead to misleading conclusions, which might lead, in turn, to poorly designed protective or corrective measures.
Rock Mechanics for Resources, Energy and Environment, 2013
Harmonising Rock Engineering and the Environment, 2011
The ISRM Suggested Methods for Rock Characterization, Testing and Monitoring: 2007-2014, 2012
Rock Engineering and Rock Mechanics: Structures in and on Rock Masses, 2014
Journal of Rock Mechanics and Geotechnical Engineering, 2013
Tunnel with an aureole of a different material a b s t r a c t Fast methods to solve the unloadin... more Tunnel with an aureole of a different material a b s t r a c t Fast methods to solve the unloading problem of a cylindrical cavity or tunnel excavated in elasto-perfectly plastic, elasto-brittle or strain-softening materials under a hydrostatic stress field can be derived based on the self-similarity of the solution. As a consequence, they only apply when the rock mass is homogeneous and so exclude many cases of practical interest. We describe a robust and fast numerical technique that solves the tunnel unloading problem and estimates the ground reaction curve for a cylindrical cavity excavated in a rock mass with properties depending on the radial coordinate, where the solution is no longer self-similar. The solution is based on a continuation-like approach (associated with the unloading and with the incremental formulation of the elasto-plastic behavior), finite element spatial discretization and a combination of explicit sub-stepping schemes and implicit techniques to integrate the constitutive law, so as to tackle the difficulties associated with both strong strain-softening and elasto-brittle behaviors. The developed algorithm is used for two practical ground reaction curve computation applications. The first application refers to a tunnel surrounded by an aureole of material damaged by blasting and the second to a tunnel surrounded by a ring-like zone of reinforced (rock-bolted) material.
Harmonising Rock Engineering and the Environment, 2011
Resources Policy, 2011
Mining activities are compatible with other activities in space and time if they are developed to... more Mining activities are compatible with other activities in space and time if they are developed together and adapted to each other. If permits are required for two projects that are not considered to be compatible, the authorities will be forced to decide which one has ...