1,720,991 research outputs found
How rock block shape can influence the kinematics and direction of slope displacement: Results from the San Leo rock plateau, Italy
No full textThe kinematic behavior of slope failures in fractured rock masses is strongly influenced by the presence of discontinuities. Block size and shape are controlled by fracture orientation, intensity and length. A preliminary analysis of these parameters was conducted in the north-eastern cliff of the San Leo plateau (Italy). Classical stereographic projection analysis, coupled with GIS, and a limit equilibrium approach were applied to analyze the blocks shape and the block kinematic constraint and thereby define the expected movement directions of selected rock wedges. Our analyses provided further insights into the instability mechanisms involving the sub-vertical cliff faces. The data are also useful in the interpretation of the data collected by the slope monitoring system. By deriving the expected direction of movements, its effectiveness can be improved. The size distribution and the shape of the blocks in the landslide deposit were mapped and classified, providing the constraint for more advanced geomechanical analyses
Using pre-failure and post-failure remote sensing data to constrain the three-dimensional numerical model of a large rock slope failure
No full textFactors governing rock slope stability include lithology, geological structures, hydrogeological conditions, and landform evolution. When certain conditions are met, rock slopes may become unstable, inducing deformation and failure. In the present study, an integrated remote sensing-numerical modeling approach investigates the deformation mechanisms leading to the 1965 Hope Slide, BC, Canada and the effect of slope kinematics on the longterm evolution of the slope. Pre- and post-failure datasets were used to perform a large-scale geomorphic and structural characterization, including kinematic and block-theory analyses. Extensive data collection was also undertaken using state-of-the-art remote sensing techniques, including digital photogrammetry (Structure-from-Motion), laser scanning (aerial and terrestrial), and infrared thermography. New evidence is provided that one or more prehistoric failures caused the removal of a key-block, and the initiation of long-term slope deformation and cumulative slope damage ultimately resulting in the catastrophic 1965 event. Detailed characterization of the rock slope has allowed the first three-dimensional, distinct element numerical model of the Hope Slide to be conducted. The results of the numerical simulations involving gradual reduction of the rupture surface shear strength indicate that 1965 slope failure may represent the outcome of a long-term, progressive failure mechanism that initiated after a prehistoric landslide. This combined field mapping–remote sensing– numerical modeling study clearly highlights the role of 3D slope kinematics on the geomorphic evolution of the slope, along with the associated failure mechanisms
A new approach for defining Slope Mass Rating in heterogeneous sedimentary rocks using a combined remote sensing GIS approach
No full textEngineering rock mass classification is usually the first stage in the analysis and characterization of rock slopes. However, when dealing with sedimentary/heterogeneous rock masses, the use of existing classification methods can be difficult and often misleading, especially when used to define rockfall risk areas and appropriate slope mitigation works. In this research, we describe a novel approach for geomechanical rock slope analysis based on the combined use of remote sensing, geographic information systems (GIS), and the Slope Mass Rating (SMR) classification system. The Montagna dei Fiori area (Italian central Apennines), which is characterized by the sedimentary rocks of the Umbria Marche heterogeneous succession, is used as a case study to demonstrate the application of the proposed approach. Conventional geomechanical scanlines are integrated with photogrammetric techniques to increase the amount of data collected, especially in inaccessible areas. In particular, a new fast and low-cost method of georeferencing 3D photogrammetric models is presented. GIS are used to manage all the data acquired using remote sensing techniques and geomechanical analyses, and a semi-automatic tool developed to allow calculation of the SMR along a major highway, the SP52, which crosses the study area. Finally, a modification of the SMR procedure is proposed to enable definition of the most appropriate mitigation works in folded heterogeneous sedimentary rock masses comprising alternating marls and limestones. © 2018, Springer-Verlag GmbH Germany, part of Springer Nature
Modelling discontinuity control on the development of Hell’s Mouth landslide
Full text linkThis paper focuses on numerical modelling and back analysis of the Hell’s Mouth landslide to provide improved understanding of the evolution of a section of the north coast of Cornwall, UK. Discontinuity control is highlighted through the formation of a ‘zawn’ or inlet, the occurrence of two successive landslides and evidence of ongoing instability through opening of tension cracks behind the cliff top. Several integrated remote sensing (RS) techniques have been utilised for data acquisition to characterise the slope geometry, landslide features and tension crack extent and development. In view of the structural control on the rock slope failures, a 3D distinct element method (DEM) code incorporating a discrete fracture network and rigid blocks has been adopted for the stability analysis. The onset and opening of tension cracks behind the modelled slope failure zones has also been studied by analysing the displacements of two adjoining landslide blocks, between which, a joint-related tension crack developed. In addition, a sensitivity analysis has been undertaken to provide further insight into the influence of key discontinuity parameters (i.e. dip, dip direction, persistence and friction angle) on the stability of this section of the coastline. Numerical modelling and field observations indicate that block removal and preferential erosion along a fault resulted in the formation of the inlet. The development of the inlet provides daylighting conditions for discontinuities exposed on the inlet slope wall, triggering the initial landslide which occurred on 23rd September 2011. Numerical modelling, and evidence from a video of the initial landslide, suggests that the cliff instability is characterised by a combination of planar sliding, wedge sliding and toppling modes of failure controlled by the discrete fracture network geometr
A remote sensing approach for the derivation of numerical modelling input data: insights from the Hope Slide, Canada
No full textIn this paper, we describe an integrated remote sensing approach for the collection of geomechanical data to be used as input for continuum, discontinuum, and hybrid numerical analyses. Ground-based and aerial remote sensing techniques, including terrestrial digital photogrammetry (TDP), terrestrial laser scanning (TLS), structure-frommotion photogrammetry (SfM), and terrestrial infrared thermography (IRT) may be used for collecting rock mass data appropriate for input into varied numerical modelling approaches. To demonstrate our suggested approach, we have used the 1965 Hope Slide, British Columbia, Canada. We present the mapping of rock discontinuities for numerical modelling using a hierarchical geological structure order. Large-scale geological structures which were identified and mapped on the pre-failure and present-day topography are used in a preliminary analysis of the rock slope to investigate their influence on kinematic freedom and in bounding keyblocks. Detailed geomechanical mapping is performed on three-dimensional TDP models. IRT data is used to characterize surface water seepage. Unmanned aerial vehicle (UAV) SfM imagery of the landslide debris was used to analyse the block size distribution. Preliminary numerical discontinuum 3D-DEM modelling based on this data and assigned mechanical properties shows that with detailed planning and systematic field data collection techniques, the geological engineer can obtain the data necessary to reduce both model and parameter uncertainty and allow more reliable and realistic numerical slope simulations
The Importance of Rock Mass Damage in the Kinematics of Landslides
Full text linkThe stability and kinematics of rock slopes are widely considered to be functions of lithological, structural, and environmental features. Conversely, slope damage features are often overlooked and considered as byproducts of slope deformation. This paper analyzes and discusses the potential role of slope damage, its time-dependent nature, and its control on both the stability of rock slopes and their kinematics. The analysis of several major landslides and unstable slopes, combined with a literature survey, shows that slope damage can play an important role in controlling short- and long-term slope stability. Seasonal and continuously active events cause permanent deformation within the slope due to the accumulation of slope damage features, including rock mass dilation and intact rock fracturing. Rock mass quality, lithology, and scale control the characteristics and complexity of slope damage, as well as the failure mechanism. The authors propose that the role of slope damage in slope kinematics should always be considered in slope stability analysis, and that an integrated characterization–monitoring–numerical modelling approach can enhance our understanding of slope damage, its evolution, and the controlling factors. Finally, it is emphasized that there is currently a lack of guidelines or frameworks for the quantitative assessment and classification of slope damage, which requires a multidisciplinary approach combining rock mechanics, geomorphology, engineering geology, remote sensing, and geophysics
Rock Slides and Topples
No full textDifferent types of rock slides and toppling failure modes can occur in rock slope. Structural geological controls, rainfall, groundwater and earthquakes are among the factors that can contribute or triggers these rock slope failure modes. Scale (geological structure and slope), time, and damage can also play a role in the development of rock slides and topples. Rock slope analysis methods used for rock slides and topples are summarized with examples, including initial stereographic kinematic analysis, 2D/3D limit equilibrium analysis, and 2D/3D continuum, discontinuum and hybrid-lattice spring modelling
Improvements in the integration of remote sensing and rock slope modelling
No full textThis is the author accepted manuscript. The final version is available from Springer Verlag via the DOI in this record.Over the last two decades, the approach to the investigation of landslides has changed dramatically. The advent of new technologies for engineering geological surveys and slope analyses has led to step-change increases in the quality of data available for landslide studies. However, the use of such technologies in the survey and analysis of slopes is often complex and may not always be either desirable or feasible. In this context, this paper aims to improve the understanding of the use of remote sensing techniques for rock mass characterization and provide guidance and on how and when the data obtained from these techniques can be used as input for stability analyses. Advantages and limitations of available digital photogrammetry and laser scanning techniques will also be discussed in relation to their cost and the quality of data that can be obtained. A critique of recent research data obtained from remote sensing techniques is presented together with a discussion on use of the data for slope stability analysis. This highlights how data use may be optimized to reduce both parameter and model uncertainty in future slope analyses
Remote Sensing and Geovisualization of Rock Slopes and Landslides
Full text linkOver the past two decades, advances in remote sensing methods and technology have enabled larger and more sophisticated datasets to be collected. Due to these advances, the need to effectively and efficiently communicate and visualize data is becoming increasingly important. We demonstrate that the use of mixed- (MR) and virtual reality (VR) systems has provided very promising results, allowing the visualization of complex datasets with unprecedented levels of detail and user experience. However, as of today, such visualization techniques have been largely used for communication purposes, and limited applications have been developed to allow for data processing and collection, particularly within the engineering–geology field. In this paper, we demonstrate the potential use of MR and VR not only for the visualization of multi-sensor remote sensing data but also for the collection and analysis of geological data. In this paper, we present a conceptual workflow showing the approach used for the processing of remote sensing datasets and the subsequent visualization using MR and VR headsets. We demonstrate the use of computer applications built in-house to visualize datasets and numerical modelling results, and to perform rock core logging (XRCoreShack) and rock mass characterization (EasyMineXR). While important limitations still exist in terms of hardware capabilities, portability, and accessibility, the expected technological advances and cost reduction will ensure this technology forms a standard mapping and data analysis tool for future engineers and geoscientists
Response of a large deep-seated gravitational slope deformation to meteorological, seismic, and deglaciation drivers as measured by InSAR
Full text linkWe analyze the sensitivity of a large (area extent ∼3 km2), deep-seated gravitational slope deformation (Fels slide, Alaska Range) to three specific drivers: (i) liquid surface water input from ERA-5 reanalysis snow melt and rainfall; (ii) locally projected seismic activity of Alaskan earthquakes; and (iii) lowering of Fels Glacier at the slide toe estimated from topographic data. A surface displacement map-series is derived from 1991 to 2016 spaceborne multi-sensor InSAR data (ERS, RADARSAT-1/2, ALOS, TerraSAR-X) using adaptive demodulation to unwrap interferograms of variable spatial resolution and quality. On this series we use independent component analysis (ICA) to uncover five displacement patterns that map to independently moving domains of the slide and then correlate the corresponding temporal pattern intensities with the suspected drivers. We find significant sub-annual correlation between displacement pattern intensities and seasonal water input variations. The correlation can be optimized, for each ICA pattern, by choosing appropriate values of temporal smoothing and lag to create depth-propagated versions of the water input driver. Lag time results ranging from one to 3 weeks relate to shallower and deeper propagations of water input, driving the different deformation patterns. For two of the deformation patterns, seasonal sensitivity to water input was strongly amplified by the 2002 Mw7.9 Denali earthquake. Sensitivity of these patterns remained high for 4 years until abruptly dropping to below pre-earthquake values, which suggests a highly non-linear modulation by the seismic driver. Other deformation patterns show a steady intensity increase that appears linked to the deglaciation driver. Despite these observations, the inter-annual variations in ICA pattern intensities show no clear predictability by individual drivers or driver combinations. This suggests that the mechanical and hydraulic evolution of the slide, especially after damaging events such as earthquakes or heavy rainfall, is a crucial factor not adequately modeled in our approach. Despite this limitation, our analysis provides the first direct evidence that the Fels slide comprises several independently moving domains that respond differently to the suspected drivers as is suggestive of a complex slope deformation
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