Issue 189 by Leandro R. Alejano
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.
Papers by Leandro R. Alejano
IOP conference series, 2023
There are not many studies on jointed rock specimens, which can be considered small scale rock ma... more There are not many studies on jointed rock specimens, which can be considered small scale rock mass analogs. On the other hand, the scale effects in the mechanical properties of such samples have seldom been studied. With the aim of continuing previous research on intact granite rocks, the authors have carried out sets of 25 stress-strain triaxial compressive tests on 1 sub-vertical and 2 sub-horizontal 38 mm, 54 mm and 84 mm diameter jointed granite specimens at various confinements. Peak and residual strength values were obtained and compared to those recovered form intact rock samples. Results suggest that peak strength follows similar trends with scale to those observed on intact rock, even if lower strength values are logically recorded. Regarding residual strength, the obtained results are in line with those observed trends for standard size samples, showing a similar trend for all cases independently of scale, even if we observe larger variability for jointed samples. The authors have also compared the values fitting the generalized Hoek-Brown criterion for rock masses to better understand the behavior in relation to sample size. So scale effects clearly appear on jointed rock peak strength of jointed sample; even if residual strength seems hardly affected by scale.
Rock Mechanics and Rock Engineering
Understanding size effects is important to rigorously analyse the behaviour of rocks and rock mas... more Understanding size effects is important to rigorously analyse the behaviour of rocks and rock masses at different scales and for different applications. A number of empirical and numerical studies have included size effects on the uniaxial compressive strength of different rocks, but only few have focussed on the triaxial compressive strength. In this study, several triaxial tests were conducted on granite samples at different confinements (from 0.2 to 15 MPa) and sizes (from 30 to 84 mm in diameter). The most relevant strength parameters were recovered including peak and residual strengths, orientation and frictional response of shear bands. Size effects were observed to be less dominant at high confining pressures for both peak and residual strengths. The resulting data were analysed in the context of size-dependent rock strength theories. For peak strength analyses, the unified size effect law (USEL) and the improved unified size law (IUSEL) were used, in which the double trends,...
Geomechanics and Geophysics for Geo-Energy and Geo-Resources
We have designed and built a versatile testing device to perform hydraulic fracturing experiments... more We have designed and built a versatile testing device to perform hydraulic fracturing experiments under true triaxial conditions. The device, based on a stiff biaxial frame that can be installed in a servocontrolled press, can accommodate cube rock samples of up to 150 mm-edge. Using a low-permeability rock known as Blanco Mera granite, we have performed a series of tests across a range of confining pressures including hydrostatic, normal, and strike-slip regimes. We have verified the applicability of two simple fracture mechanics-based models for the interpretation of experimental results, and we have determined the value of tensile strength of the rock from the injection curves recorded. The orientation of the hydraulically-triggered fractures with respect to the applied stress has also been analyzed. Although the models proposed by Rummel and Abou-Sayed provided reasonably satisfactory results, especially for hydrostatic and strike-slip tests, the presence of heterogeneities and ...
Journal of Rock Mechanics and Geotechnical Engineering
Rock Mechanics and Rock Engineering
Large granitic boulders resting on steep slopes represent considerable safety hazards that largel... more Large granitic boulders resting on steep slopes represent considerable safety hazards that largely depend on the location of the contact surface characterized by the impression d, denoting the parallel distance between the contact surface and the original rock surface. On the other hand, this impression reflecting the often convex nature of the contact between boulders and resting platforms, cannot be measured precisely, so Factors of Safety (FoS) computed with this input may have significant uncertainties. Using geometric 3D analysis, here, we present the concept of computing FoS as a function of the impression d, admitting a much more reliable estimate of the actual hazards. Beyond introducing the FoS functions, we also identify all failure modes, some of which have not yet been investigated. We compute the FoS functions for the boulder Pena do Equilibrio, located in Spain. Our computations for FoS against sliding match all earlier results. However, we also compute FoS against top...
espanolEl angulo de friccion basico (ɸb) es un parametro esencial para la estimacion de la resist... more espanolEl angulo de friccion basico (ɸb) es un parametro esencial para la estimacion de la resistencia al corte de juntas de roca, de acuerdo a la ecuacion de Barton y a otros criterios sugeridos. Este parametro se puede obtener en laboratorio mediante el ensayo de inclinacion o tilt test. Sin embargo, aun no existe una metodologia sugerida o procedimiento generalizado para la obtencion de este parametro de manera experimental. En el presente estudio se investiga el efecto del desgaste, consecuencia de las sucesivas repeticiones del ensayo sobre la misma superficie de roca, asi como la posible influencia de la velocidad de rotacion de la mesa de inclinacion sobre los resultados. Se han estudiado cinco velocidades distintas, con cinco juntas para cada velocidad y cinco ensayos para cada junta, para el caso de un granito medianamente meteorizado. Los resultados indican que, si bien la velocidad de rotacion no afecta de manera significativa a los resultados, el efecto del desgaste jueg...
International Journal of Rock Mechanics and Mining Sciences, 2021
Tunnelling and Underground Space Technology, 2021
IOP Conference Series: Earth and Environmental Science, 2021
Debris flows are dangerous natural processes that cause extensive damages to infrastructures and ... more Debris flows are dangerous natural processes that cause extensive damages to infrastructures and urbanized areas and can lead to loss of human lives. Their unpredictability, their extremely high motion and their magnitude are the main causes of these harms. Mitigation measures are fundamental for reducing the associated risk and protecting infrastructures in mountainous areas. Their design is still an open issue: there are many formulations to evaluating impact pressure. Moreover, the uncertainties in the determination of flow characteristics (velocity and thickness) are significantly high and difficult to quantify. In the European Union, the design of any type of structures involved in rock mechanics field must comply with EN-1997 Geotechnical Design (CEN 2004) (EC7). For debris flow countermeasures, EC7 requirements are very difficult to apply in practice since partial safety factors are not provided for these phenomena. However, the basic philosophy of reliability-based design (R...
IOP Conference Series: Earth and Environmental Science, 2021
Rock Mechanics and Rock Engineering, 2020
International Journal of Rock Mechanics and Mining Sciences, 2019
Procedia Engineering, 2017
Journal of Rock Mechanics and Geotechnical Engineering, 2014
Rock Mechanics for Resources, Energy and Environment, 2013
In 2010, the Eurocode for Geotechnical Design, EN-1997-1:2004 (CEN, 2004), informally known as Eu... more In 2010, the Eurocode for Geotechnical Design, EN-1997-1:2004 (CEN, 2004), informally known as Eurocode 7 or EC7, became the Reference Design Code (RDC) for geotechnical design - including rock eng ...
Harmonising Rock Engineering and the Environment, 2011
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Issue 189 by Leandro R. Alejano
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.
Papers by Leandro R. Alejano
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.