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The importance of characterizing slope damage in rock slopes
No full textThe stability of high rock slopes is controlled by many geological factors including the orientation, size, and location of geological structures, lithology, rock mass strength, hydrogeological setting, and slope topography. Together, these “inherited” factors often control the location, the extent, and the volume of the potential rock mass involved in a rock slope failure. Rock slopes can remain stable for many thousands of years before a de-stabilizing event or “trigger”, causes the slope to fail. However, often the failure of a rock slope is the final outcome of a slow and progressive degradation of the rock mass causing a gradual reduction in slope stability.
Many authors have investigated the role of so-called “exogenic” and “endogenic” factors on the evolution of rock slope stability. Exogenic factors may lead to damage in the rock mass at the surface of rock slopes (i.e. weathering, erosion, etc.). Conversely, endogenic factors cause the weakening of the rock mass from within the Earth’s crust (earthquakes, volcanism, etc.). The action of the above factors, extending over thousands of years, and the interaction with the aforementioned inherited factors, causes the formation of rock slope damage features such as tension cracks, rock mass dilation and brittle fracture resulting in “progressive failure” of the slope.
In the course of this research, several landslide sites were visited, both in North America (the Downie Slide and the Hope Slide, British Columbia, Canada) and Italy (San Leo landslide). At each site, slope damage was investigated using an integrated remote sensing and numerical modelling approach. It was noted that the accumulation of slope damage was driven and controlled by a complex interaction of factors and geomorphic processes, including glacial and fluvial erosion, steepening and undermining of the slope, debuttressing, slope deformations and fatigue. In this paper we provide clear evidence of how mapping and characterization of slope damage features using state-of-the-art remote sensing methods can provide new insights on the style of slope deformation and the factors that control the stability and failure of rock slopes. Finally, it is recommended that the analysis of rock slope damage should be an important component in the workflow to ensure comprehensive rock slope characterization
Multidisciplinary approach (geology, geomorphology, geomechanics, geomatics) for the characterization of the Blais Creek DsGSD (Monashee Mountains, BC, Canada)
No full textField investigations, including detailed geological and geomorphological mapping have been coupled with stratigraphic
and structural studies of the Blais Creek Deep-seated Gravitational Slope Deformations (DsGSD),
Monashee Mountains, British Columbia (BC). To reconstruct the DsGSD evolutionary stages and to evaluate its
controlling factors, a complex methodology has been applied, integrating orthophotos, stereo models and 3D models
of the DsGSD with field and literature data concerning tectonic and glacial history of the Seymour Valley.
General geomechanical properties of the deforming rock mass has been then evaluated for using in numerical
models of the failure mechanism at Blais Creek and to define a broad geomechanical characterization of different
portions of the DsGSD.
The combination between the aerial and terrestrial photogrammetry was appropriate in terms of the quality of
the information obtained more than the quantitative information. Several Ground Control Points (GCPs) and Tie
Points (TPs) were selected from the original DEM received by the BC Government. The use of a multitemporal
aerial triangulation gave the possibility to minimize the error relative to every single block of images. Couples of
oriented photos were used to create stereoscopic models. Multitemporal variations of the Blais Creek slope were
observed and compared to the actual situation of the slope.
The use of terrestrial photogrammetry through Adamtech software confirmed some of the qualitative data obtained
from aerial interpretation and from field survey. The limited use of terrestrial photogrammetry was due to the impossibility
of orienting the 3D terrestrial models. Anyway these models were also useful to confirm one of the
possible mechanisms used to describe the evolution of Blais Creek.
Geomechanical analysis was performed through field work and laboratory tests to characterize the entire slope
and to produce some of the values useful for a possible numerical analysis of Blais Creek. It showed interesting
differences in geomechanical properties between the calc-silicate and quartzite/gneiss.
The kinematic analysis showed very the different instability areas along the slope, even if variations in landforms
and rock masses volume weren’t widespread along Blais Creek slope during the time span covered by aerial photographs
(1973-2007). Indeed, the multitemporal analysis outlined very active instability along the large upper
trench and the lateral active slopes of Blais Creek. Even without significant level of risks in the area, considering
the remote area involved in this instability, some relevant hazards could occur, related to the possible collapse of
SE side of Blais Creek DsGSD.
Regarding the long term evolution of the DsGSD, the extensive network of linear features at Blais Creek is of a
large deforming rock mass. Movement probably began with the retreat of valley glaciers during deglaciation when
the oversteepened valley sides were debuttressed. By these evidences it is possible to theorize that the post-glacial
retreat of the rock face and removal of the ice buttress from both the Seymour and the Blais Creeek Valleys lowered
the factor of stability of the mass as a whole, allowing a deep-seated shear surface to develop gradually over time
by progressive creep
Characterising the kinematics of the Joffre Peak landslides using a combined numerical modeling-remote sensing approach
No full textGeological structure and kinematics are often the most important factors controlling the stability of high rock slopes; their characterization can provide insights that are instrumental in understanding the behaviour of a slope in addition to its evolution with time. In this research, we used a combined remote sensing-numerical modelling approach to characterize the Joffre Peak landslides (British Columbia, Canada), two rock avalanche events that occurred on May, 13th and 16th 2019. The May 13th event involved a volume of 2-3million m3, and resulted in a runout distance of 6 km. The May 16th event involved a volume of 2-3 million m3, and a runout distance of 4 km. The failure was likely promoted by permafrost degradation and reduction in shear strength along geological structures (in our simulation checked in dry condition). Using a wide range of techniques, including Structure-from-Motion photogrammetry, virtual outcrop discontinuity mapping, GIS analysis, and 3D distinct element numerical modelling, we investigated the important role that structural geology and slope kinematics played prior to and during the Joffre landslide events. In particular, we demonstrate that i) a very persistent, sub-vertical geological structures formed the lateral and rear release surfaces of the rock mass volume that failed as two discrete landslide events. The landslide blocks were separated by one such sub-vertical structure, which remains visible in the fresh landslide scar; ii) the first block, failed on May 13th 2019, involving planar sliding failure mechanism, possibly promoted by progressive failure and propagation of discontinuities along the basal surface. The detachment of this block enhanced the kinematic freedom of the second landslide block, which, on May 16th, failed as wedge/toppling mechanism; iii) the first landslide block acted as a key block; its displacement and failure provided the kinematic freedom for the occurrence of the second landslide. In this paper we show that combining remote sensing mapping and 3D numerical modelling allows for the identification of the structural geological features controlling the stability and evolution of high rock slopes in alpine environments. We also show that constraining and validating the numerical modelling results using historical data is of paramount importance to ensure that the correct failure mechanism of the landslides is simulated
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
A complex rock slope failure investigated by means of numerical modelling based on laser scanner technique.
No full textOn March 12, 2005 in the Scascoli Gorges (Savena Valley, Northern Apennines, Italy) a rock (siltstones and arenites) slope failure occurred damming the torrent below. The geometry of the collapsed rock mass was characterized by a failure surface progressively changing from over-steepened at the top to concave at the bottom. Terrestrial laser scanner technique (TLS) has been applied to obtain high resolution topography of the rock slope. Mechanism and kinematics of the rock slope failure has been investigated by distinct-element code (UDEC). As distinct elements simulation in rock masses largely depends on joint pattern and orientation, accurate discontinuities orientation, spacing and location of discrete surface features have been directly gathered from data provided by TLS. The paper describes the stability analyses carried on simulating the progressively developing damage of the rock mass by reducing the GSI initial value and using an Hoek & Brown constitutive model
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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