Leandro Alejano

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• PhD Mining Engineering
• Professor (Full) at University of Vigo

Stratified rock masses present bedding and cross-joints normal to it that makes them natural heterogeneous and non-isotropic materials difficult to characterize. A successful engineering design of mining rooms with flat roofs in this type of rock masses would benefit from a heuristic perspective and various approaches including analytical (voussoir...

Dry masonry retaining walls are widely used to have available flat surfaces for house building and road construction. A rigorous wall design should consider the impact of shape on wall stability, which may control potential failure mechanisms. The authors carried out a series of tilt tests on empty different-shape small-scale wall models to analyze...

Imperfections in the bonding of bolts to the rock mass (such as anchorage defect and joint) are critical to the time-dependent anchoring performance. The poor load transmission resulted from imperfections may exacerbate the damage resulting from the creep behavior of rock. In this paper, the laboratory experiments were performed to explore the cree...

In this paper, 114 uniaxial compressive strength tests were carried out on specimens of veined gneiss with diameters ranging from 14 mm to 100 mm. The main objective of the study was to investigate the influence of the specimen size on the strength behavior of this metamorphic, heterogeneous rock. This size effect results in an increase in strength...

Singular rock columns or blocks resting on tilted irregular rough joints can be found in rock masses in various geological environments. Their stability can be estimated based on traditional limit equilibrium approaches. However, the geometry of these rock blocks may not be regular, which makes uneasy stability computation tasks. Previous studies h...

This study provides an alternative theoretical approach to analyse the mechanical behaviour of tunnels excavated in time-dependent geomaterials, considering the sequential excavation of tunnels and installation of rockbolts and elastic liner. In the theoretical analyses, the Bolted Rock Mass (BRM) is modelled as a homogeneous material but with high...

In the field of tunnelling applications, it is often found that the rock masses exhibit anisotropy and rheological properties. To optimize the utilization of underground space, the use of noncircular tunnels is often preferred. However, it is important to note that these noncircular tunnels can lead to high-stress concentrations and significant dis...

The characterization of the thermal properties of crushed rock samples is not experimentally straightforward. In the case of thermal conductivity, some authors estimate this property based on solid rock plugs (e.g. optical thermal scanning, split bar, line heat source) what is not a convenient approach for granular materials with variable grain siz...

Sustainable mining development requires structures on or within rock masses that can withstand deformation over a long period without compromising safety. Understanding of time-dependent behaviour of rocks is essential for such a purpose which is commonly investigated under sustained loading or so-called “creep” condition within the laboratory envi...

The present article provides an improvement in the method to correct indirect strain measurements in triaxial compressive strength tests through axial displacement and hydraulic fluid volume change measurements. The improvement focused on reducing the parameters of the formula proposed for indirect volumetric strain in the original method, thereby...

Rock mass classification systems (RMCS) were developed in the seventies of the last century. They were born in response to the need to establish indicative design criteria for tunnel support. But they also focused on rating the quality of the rock, putting numbers in geology that allowed the rock mass to be classified and its parameters computed. R...

The authors analyze strains on triaxial compression tests on jointed granite samples, where global deformations were measured using LVDTs and corrected using an energy approach to estimate the global strains in the jointed specimen. Moreover, some strain gauges were fixed on the intact rock blocks or sections to measure the local strains. Based on...

In this study, the authors compare analytical voussoir-analogue based solutions with nu-merical ones, implemented through 2D distinct-element-method based simulations, in the context of the application of these analyses to the design of underground rooms in bedded rock masses, based on the conditions found in a particular underground room and pilla...

Physical models are a sound tool for verifying some instability mechanisms. The authors apply these physical models to check the stability analysis of traditional dry granite masonry retaining walls as built in NW Spain. Unlike concrete retaining walls, dry masonry ones should be designed to ensure not only general stability but also an intrinsic o...

For many civil and mining engineering structures, rock is the primary construction medium. At engineering scales, the material of interest is the “rockmass,” which contains sections of intact rock separated by a network of pre-existing joints (i.e. fractures). The mechanical behavior of a rockmass is defined by attributes of its intact rock (e.g. s...

The stability of potentially toppling rock blocks has been typically addressed for the case of regular block geometries showing symmetry planes and resting on surfaces aligned with the slope face, i.e., the strike of the slope is parallel to the block sides and their basal planes. However, these simple geometries with ideally oriented blocks are no...

An extensive experimental study is presented including around 140 triaxial compressive strength tests on artificially jointed hard rock. The experiments were performed on cylindrical and jointed specimens with either 1 sub-vertical and 2 sub-horizontal (1 + 2) or 2 sub-vertical and 3-sub-horizontal (2 + 3) joint sets. The specimen diameter consiste...

This study aims to experimentally assess repeatability and reproducibility of direct tensile strength (DTS) tests with deformability measurements on two types of rocks: Blanco Mera granite (Spain) and Cotta sandstone (Germany). The tests were conducted in four rock mechanics laboratories located in different countries (Canada, Germany, Spain and Sw...

The mechanical behavior of block-in-matrix materials is heavily dependent on their block content. This parameter is in most cases obtained through visual analyses of the ground through digital imagery, which provides the areal block proportion (ABP) of the area analyzed. Nowadays, computer vision models have the capability to extract knowledge from...

The profession of a rock engineer is not defined in any academic curriculum. We discuss the professional requirements for civil engineering or mining engineering applications and recommend the necessary classes to form a competent rock engineer. Emphasis is placed on the knowledge about the creation of the appropriate geological and geotechnical mo...

Mountain secondary roads often follows complex land forms with high sub-vertical rock-cuts in outcropping rock prone to rock-fall events. Geo-structural rock mass surveys and collection of discontinuity data provide the basis for rock mass characterization and enable slope stability analysis and rock-fall hazard assessment. With this aim, a multisc...

It is accepted that heat waves, whose occurrence have been increasing throughout the last decades in the Iberian Peninsula, associated with climate change, are one of the main hazards linked to the occurrence of wildfires and the increase of fire risk in the open-pit mining industry. To the best of our knowledge, studies that relate the effect of t...

Las Médulas is an area located in NW-Spain featuring a landscape environment formed by an old Roman gold mining operation. It is thought to be the largest open-pit gold mine in the Roman Empire and it was exploited during I and II centuries AD. The archaeological site and its environment were declared UNESCO World Heritage in 1997, based on its val...

Mechanical properties of rocks with marked weak planes such as foliation, schistosity or bedding, are not isotropic. The deformability of these rocks is transversely anisotropic (TI), and, therefore, different axial strains are observed according to the load direction, being equal in directions within the weakness plane. Their elastic behavior is t...

Field-scale rock formations (i.e. rockmasses) are composed of sections of intact rock separated by a preexisting joint network. As rockmass deforms, strain accumulates within the intact rock and slip occurs along the preexisting joints. However, the magnitude of strain within the intact rock sections are not necessarily equal everywhere throughout...

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 t...

Forested mountain regions in Europe are at risk of wildfires and rockfalls. Almost 600,000 forest fires affecting some 7.5 M ha have been recorded in Spain over the last fifty years. This is a serious problem that threatens to intensify due to the effects of climate change. In addition to the negative consequences associated with the wildfires them...

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-perme-ability rock known as Blanco Mera granite, we have pe...

This study aimed to explore and compare the application of current state-of-the-art machine learning techniques, including bagging (Bag) and rotation forest (RF), to assess landslide susceptibility with the base classifier best-first decision tree (BFT). The proposed two novel ensemble frameworks, BagBFT and RFBFT, and the base model BFT, were used...

The convergence-confinement method (CCM) is a simplified widely utilised tool for assessing the interplay between the rock mass behaviour and the support effect, so it is quite helpful for tunnel support design purposes. However, the direct application of this technique has shown some limitations, many of which are directly related to the three-dim...

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 con...

Toppling of individual rock blocks resting on an inclined surface has often been observed in nature. This instability mechanism has typically been analysed for simple block geometries, considering the contact between the block and the base where it lies is a planar surface. In this study, the authors analyse the case where this contact is a regular...

The main aim of this study is trying to contribute to a better understanding of the role of surface roughness basal planes on toppling-related instability phenomena. In this way, the authors focus on the stability against toppling of a single block resting on a regular rough surface. To do that they have first artificially created sample rock block...

Wildfires and rockfalls are among the major hazards in forested mountainous regions across Europe. Understanding processes and conditions that lead to rockfalls during and after a wildfire in different geological contexts is, therefore, of great relevance. The increase of rockfalls associated with the occurrence of wildfires is connected to several...

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...

Research studies on the scale effect on triaxial strength of intact rocks are scarce, being more common those in uniaxial strength. In this paper, the authors present and briefly interpret the peak and residual strength trends on a series of triaxial tests on different size specimens (30 mm to 84 mm diameter) of an intact granitic rock at confineme...

This study investigates the tensile failure mechanisms in granitic rock samples at different scales by means of different types of tests. To do that, we have selected a granitic rock type and obtained samples of different sizes with the diameter ranging from 30 mm to 84 mm. The samples have been subjected to direct tensile strength (DTS) tests, ind...

Roofing slate was traditionally quarried in Spain for roofing purposes since the Middle Ages. 40 years ago, and due to an increasing market demand from European countries, convenient prices and depletion of old quarries, producers envisaged the underground exploitation of these deposits. Nowadays, there are some underground room and pillar roofing...

RESUMEN Comprender las condiciones que producen los desprendimientos de rocas durante y después de un incendio forestal, es un gran reto al que se expone la comunidad científica, con el fin de precisar el riesgo por este tipo de eventos. El aumento de desprendimientos de rocas asociados con los incendios forestales está relacionado con varios facto...

Highlights A review of the book “Convergence-Confinement Method for Tunnel Design” is provided. The book is put in the context of tunnel design methodologies. The contents of every chapter are briefly summarized. A very positive assessment is eventually issued.

Los diseños geotécnicos se basan en hipótesis y aproximaciones no siempre fiables, por lo que las incertidumbres del comportamiento de estructuras geotécnicas suelen ser mayores que las que se dan en otras estructuras de ingeniería. Así, las observaciones in situ y, en particular, la medición de magnitudes físicas específicas son el mejor antídoto...

An accurate evaluation of the shear strength of discontinuities is frequently a key aspect for determining the safety of mining and civil engineering works and for solving instability issues at rock mass scale. This is usually done by using empirical shear strength criteria in which the basic friction angle (φ b ) is a relevant input parameter. Til...

In numerical modelling, selection of the constitutive model is a critical factor in predicting the actual response of a geomaterial. The use of oversimplified or inadequate models may not be sufficient to reproduce the actual geomaterial behaviour. That selection is especially relevant in the case of anisotropic rocks, and particularly for shales a...

Se presenta en este estudio una caracterización detallada de una pizarra prestando especial atención a su anisotropía en términos de deformabilidad y resistencia a partir de ensayos de resistencia a compresión simple y triaxial en laboratorio. La pizarra es una roca metamórfica que presenta una marcada foliación o esquistosidad. Para realizar el es...

Granite boulders are characteristic geomorphological structures formed in granitic terrains. Due to their formation process associated with typical spheroidal weathering phenomena, they tend to show more or less ellipsoidal shapes prone to instability, and they often lie on small contact surfaces. Analyzing the stability of these boulders is not a...

We present the devlopment of low cost hydraulic fracturing triaxial devics

Prediction of the shear strength of rock discontinuities is usually performed by resorting to empirical shear strength criteria that depend on different inputs, some of which can be estimated through laboratory tests. Even though these tests are usually developed with rock materials, concrete is often used to make joint replicas. A relevant paramet...

Based on the experience gathered by the authors, this article presents a review of the instability phenomena typically associated to natural slopes in granite terrains, focusing on conditions encountered in the northwest of the Iberian Peninsula, particularly in the region of Galicia, characterized by a very humid oceanic climate with high rainfall...

When carrying out compressive tests on rock specimens, a stress plateau is typically attained following peak strength within a strain range a few times larger than the strain at peak strength. This stress level is commonly known as residual strength. A large database of these tests on granitic rock specimens has been compiled and analyzed in detail...

Slates are metamorphic rocks characterized by the pervasive occurrence of cleavage or foliation producing a highly anisotropic mechanical behavior characterized by fissility. Deformability and strength of these rocks are therefore dependent on the cleavage plane orientations relative to the principal stresses. In this study, the failure and deforma...

The basic friction angle of rock joints is usually obtained from tilt tests, being the most common the laboratory tilt tests. This test has been standardized according to the ISRM. However, most of the times when calculating the shear strength of discontinuities, reference tables are used to obtain the basic friction value for the lithology under s...

Scale or size effects of the uniaxial strength response in rock samples have been studied in detail in the past, so a good number of studies on different rocks are available. However, analyses on triaxial strength scale effects in rocks are scarce and they seldom address failure criteria (i.e. Hoek-Brown) evolution with specimen size. This obvious...

Probably, the most relevant issue in stability analysis of rock slopes is the correct identification of the potentially occurring failure mechanism, which should be mechanically analyzed to assess stability, later on. Traditional rock slope stability approaches consider planar, wedge, rotational and toppling failure as potential instability mechani...

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 infrastr...

When carrying out uniaxial, standard triaxial, or true triaxial compressive tests on rock, the strain response of the specimens can be measured directly or indirectly. The most commonly used devices are strain gauges (local direct measurements) and displacement sensors (global indirect measurements). Strain gauges are glued to specimens and directl...

This study investigates the existence and scope of scale effects over several eomechanical and geophysical properties of intact rock: uniaxial compressive strength, tensile strength, static moduli, ultrasonic pulse velocities and dynamic moduli. The study is focused in two relevant rocks of the Forsmark site and includes several experimental survey...

Twelve fracture toughness (KC) tests of specimens in granite to granodiorite (rock type 101057), sampled from a ground surface rock block of the Forsmark future high-level radioactive waste disposal site, have been performed using the ISRM’s SCB suggested method and the results have been compared with the newly developed pCT test methodology. Detai...

Featured Application This review contribute to understand the mechanisms underlying the observed rockfall activity during and after a wildfire, to advance in the solutions and methods to address the study of the problem, and to assess the hazard during and after wildfire, and its impact on not only transportation infrastructure and urban areas, but...

The residual strength of rocks and rock masses is an important parameter to be constrained for analysis and design purposes in many rock engineering applications. A residual strength envelope in principal stress space is typically developed using residual strength data obtained from compression tests on many different specimens of the same rock typ...

In this paper we present a physical modelling approach where the stability of rock blocks against toppling in the field can be estimated using a tilt table, engineered rock models and 3D-printed small-scale versions of a natural rock boulder. To achieve this goal, first, simple geometry rock elements are tilted and results interpreted according to...

The preparation of standardized samples of soft rocks for the development of uniaxial compressive strength (UCS) test is usually difficult, expensive and time-consuming. Needle penetration test (NPT) was originally developed in Japan as an alternative for the indirect estimation of uniaxial compressive strength of soft rocks. The needle penetromete...

Modelling of rock masses is important to assess the geomechanical behaviour of oil & gas reservoirs, especially in fractured tight reservoirs. The presence of discontinuities will significantly influence the general behaviour of the rock masses. In order to achieve realistic simulation process a good knowledge of rock behaviour is required together...

The presence of logan stones or pedestaled boulders is common in granitic environments. There are hundreds of examples of logan stones, many of them being next to inhabited areas, roads, main trails in natural parks and other zones where the fall of these structures could cause major damage. On the other hand, some of these boulders represent a tou...

The main aim of this study is the setting up of a laboratory system capable of testing fissured rock specimen permeability at different stress levels. To achieve this objective, a hydraulic press frame with associated Hoek's cell has been upgraded with servo-controlled pumping, pressure meter and external liquid weighing scales. Accordingly, and on...

Saw-cut rock surfaces, classically utilized to estimate basic friction angle of discontinuities by means of tilt test and other procedures, may seem planar to the naked eye. Nevertheless, they actually present roughness at a micrometric scale. Aiming at characterizing some of these saw-cut rock surfaces and assessing the possible implications betwe...

This study presents a calibration process of three-dimensional particle flow code (PFC3D) simulation of intact and fissured granite samples. First, laboratory stress-strain response from triaxial testing of intact and fissured granite samples is recalled. Then, PFC3D is introduced, with focus on the bonded particle models (BPM). After that, we pres...

Granite boulders are characteristic geomorphological structures formed in granitic terrains. Due to their formation process, they tend to show more or less ellipsoidal shapes prone to instability and they often lie on small contact surfaces. Analyzing the stability of these boulders is not a straight-forward task. First these boulders may topple or...

Various devices can directly or indirectly measure strain and record the deformational response of rock materials in uniaxial compressive strength tests. Strain gauges glued to specimens directly measure electrical resistance, while displacement sensors, typically linear variable differential transformers (LVDTs), indirectly measure linear displace...

The preparation of standardized soft rock specimens to perform unconfined compressive strength (UCS) tests is typically difficult, expensive and time-consuming. Needle penetration test (NPT) was originally developed in Japan as an alternative for the indirect estimation of UCS of soft rocks. The needle penetrometer is a simple, portable and non-des...

Control and monitoring of laboratory tests in the field of rock mechanics are usually expensive due to a wide variety of applications, normally carried out with very specific equipment (UCS and triaxial testing, tilt-test, permeability...). This fact may represent an issue for laboratories located in developing countries, but also for companies or...

This paper presents a case study of the stability analysis of over-tilted benches in an or-namental granite quarry. In order to facilitate quarrying of granite for ornamental purpos-es, the face of the benches of the exploitation are oriented parallel to the strike of the rift plane and to the so-called grain plane. The rift and grain are weakness...

The International Society for Rock Mechanics and Rock Engineering (ISRM) recommends to use the ISRM Suggested Methods (SM) to avoid problems during tests. In any case, fulfilling SM requirements does not ensure a proper result each time they are applied due to the natural variability of the rocks. Between others, there are some requirements regardi...

En este capítulo se muestran las técnicas y sensores que permiten realizar vigilancia y monitoreo de taludes.

In the European Union since 2010, the design of any type of structures must comply with EN-1997 Geotechnical Design (CEN 2004) (EC7) referring to engineering projects in the rock mechanics field. However, the design of debris flow countermeasures in compliance with EC7 requirements is not feasible: EC7 uses partial safety factors for design calcula...

The laboratory equipment is commonly expensive, making its acquisition difficult for laboratories and universities with low budgets. This problem could be solved with the use of open source software and hardware. Last decade, different initiatives were born that promulgate the use of these technologies for the design and construction of low-cost de...

In this work is presented an empirical-analytical method for the design of rock pillars in the underground mining of gold veins in Colombia. The proposal is focused in the observation of the failure mechanisms of existing pillars from real mines, field surveys, experimental rock mechanics and static analysis. The definition of the size of the pilla...

After a recent forest fire, a weathered-granite rock slope located in the northwest of Spain may become increasingly susceptible to rockfalls. This study presents a multi-approach assessment of rockfall hazard, with some features deserving particular attention. First, the geomorphological context represented by a weathered rock mass with multiple d...

Granitic boulders are widespread geomorphological elements, particularly found in humid granitic areas. Although they seldom represent a hazard for people or infrastructures, sometimes their location in steep or natural slopes may jeopardise their stability and potentially affect people or infrastructures. In addition, their complex geometry makes...

The first commercial underground rock caverns for hydrocarbon storage in South East Asia, the Jurong Rock Caverns Project (JRC Project), have recently been completed in Singapore. The storage capacity of 5 caverns is 1.47 million cubic meters and 3.5 million cubic meters of rocks were excavated in this project. Geologically, it was excavated in low...

En este capítulo se describen las técnicas disponibles para proteger al macizo rocoso de las voladuras de producción.

One of the main inputs when estimating the shear strength of rock discontinuities, according to most existing strength criteria, is what is known as the basic friction angle, which is a parameter that responds to the frictional resistance of a planar, unfilled, and nonweathered rock joint. The basic friction angle can be estimated according to vari...

En este capítulo se describen los métodos existentes para estabilizar taludes

En este capítulo se describen los métodos existentes de drenaje de taludes

This paper summarizes a study carried out at the University of Vigo on the mechanical behavior of cylindrical specimens of eight different rocks, focusing on both pre-and post-peak behavior. First, more than 200 intact standard NX-sized specimens were tested under unconfined and confined conditions. Complete stress-strain curves were obtained for e...

En este capítulo se presentan las técnicas disponibles para evaluar el riesgo de accidentes por desprendimientos o caídas de rocas, entre ellas una desarrollada en la Universidad de Vigo específicamente para canteras. También se presenta una metodología sencilla de control de desprendimientos basada en la geometría de los taludes.

En este capítulo se dan las bases de los métodos estadísticos más usados en mecánica de rocas. También se da a conocer el carácter epistémico de algunos de los parámetros usados en mecánica de rocas, lo que dificulta la aplicabilidad del Eurocódigo-7 a la mecánica de rocas.

En este capítulo se trata sobre la aplicación de métodos numéricos en mecánica de rocas. Se da a conocer las bases en las que se fundamentan los distintos métodos y se dan reglas generales para la consecución de modelos numéricos exitosos

A database of post-peak triaxial test results was created for artificially jointed planes introduced in cylindrical compression samples of a Blanco Mera granite. Aside from examining the artificial jointing effect on major rock and rock mass parameters such as stiffness, peak strength and residual strength, other strength parameters related to brit...