A combined remote sensing–numerical modelling approach to the stability analysis of Delabole Slate Quarry, Cornwall, UK

The final publication is available at Springer via http://dx.doi.org/10.1007/s00603-015-0805-zRock slope geometry and discontinuity properties are among the most important factors in realistic rock slope analysis yet they are often oversimplified in numerical simulations. This is primarily due to the difficulties in obtaining accurate structural and geometrical data as well as the stochastic representation of discontinuities. Recent improvements in both digital data acquisition and incorporation of discrete fracture network data into numerical modelling software have provided better tools to capture rock mass characteristics, slope geometries and digital terrain models allowing more effective modelling of rock slopes. Advantages of using improved data acquisition technology include safer and faster data collection, greater areal coverage, and accurate data geo-referencing far exceed limitations due to orientation bias and occlusion. A key benefit of a detailed point cloud dataset is the ability to measure and evaluate discontinuity characteristics such as orientation, spacing/intensity and persistence. This data can be used to develop a discrete fracture network (DFN) which can be imported into the numerical simulations to study the influence of the stochastic nature of the discontinuities on the failure mechanism. We demonstrate the application of digital terrestrial photogrammetry in discontinuity characterization and distinct element simulations within a slate quarry. An accurately georeferenced photogrammetry model is used to derive the slope geometry and to characterize geological structures. We first show how a discontinuity dataset, obtained from a photogrammetry model can be used to characterize discontinuities and to develop discrete fracture networks. A deterministic three dimensional distinct element model is then used to investigate the effect of some key input parameters (friction angle, spacing and persistence) on the stability of the quarry slope model. Finally, adopting a stochastic approach, discrete fracture networks are used as input for 3D distinct element simulations to better understand the stochastic nature of the geological structure and its effect on the quarry slope failure mechanism. The numerical modelling results highlight the influence of discontinuity characteristics and kinematics on the slope failure mechanism and the variability in the size and shape of the failed blocks

Multi Scale Numerical Modelling Related to Hydrofracking for Deep Geothermal Energy Exploitation

Prediction of fracture propagation through rock masses is investigated in this paper by adopting the Distinct Element Method (DEM) and the Voronoi tessellation. A microstructure-based model was created. Microparameters governing Voronoi sub-blocks contacts behaviour were calibrated against laboratory tests results for different rocks. An upscaling procedure is proposed to build reliable and representative numerical models at in situ scale to study fracture propagation for deep geothermal wells

Dynamic numerical modelling of co-seismic landslides using the 3D distinct element method: Insights from the Balta rockslide (Romania)

peer reviewedAncient landslides of unknown origin can be found in large numbers in mountainous regions; some represent valid markers of (pre-)historic natural regimes referring to either long-term evolution or short-term peak events of climatic and seismotectonic nature. An example is represented by the Balta rockslide in the Romanian Carpathian Mountains. Its location in the seismically active Vrancea-Buzau region, as well as its morphological features, deep-seated rupture surface and large debris volume, raise the question of its failure history with regard to a possible co-seismic triggering. A 3D volume based reconstruction of the slope morphology together with field measurements of elasto-plastic in-situ rock properties allow to estimate pre-failure conditions of the slope, with special regards to the geological, i.e. flysch bedrock of poor to fair rock quality, and structural settings, i.e. anti-dip slope bedding crossed by the main joint family. The reconstructed slope behaviour was tested under static and dynamic forces with the 3D distinct element code 3DEC, subsequently used to simulate a failure scenario with a 120 s long real earthquake record that leads to the realistic post-failure morphology of Balta. For the latter, we observe a principally joint-controlled failure combined with internal fracturing of the undamaged rock mass. After 230 s of simulated time, the landslide debris reaches the valley bottom with maximum displacements of 1350 m and is marked by a lateral expansion to a broader extent than the source zone width, as observed in the field. Extension of this work to other pre-historic slope failures in the valleys of Vrancea-Buzau yield valuable new information for future seismic hazard estimations of the region

Dynamic Numerical Modelling of Co-Seismic Landslides Using the 3D Distinct Element Method: Insights from the Balta Rockslide (Romania)

peer reviewedAncient landslides of unknown origin can be found in large numbers in mountainous regions; some represent valid markers of (pre-)historic natural regimes referring to either long-term evolution or short-term peak events of climatic and seismotectonic nature. The Balta rockslide in the Romanian Carpathian Mountains represents such a site: its location in the seismically active Vrancea-Buzau region, and its morphological features, deep-seated shape and large debris volume, raise the question of its failure history with regard to a possible co-seismic triggering. A 3D volume based reconstruction of the slope morphology together with field measurements of elasto-plastic in-situ rock properties allow to estimate pre-failure conditions of the slope, with special regards to the geological, i.e. flysch bedrock of poor to fair rock quality, and structural settings, i.e. anti-dip slope bedding crossed by the main joint family. The reconstructed slope behaviour was tested under static and dynamic forces with the 3D distinct element code 3DEC, subsequently used to simulate a failure scenario with a 120 s long real earthquake record that leads to the realistic post-failure morphology of Balta. For the latter, we observe a principally joint-controlled failure combined with internal fracturing of the intact rock mass. After 230 s of simulated time, the landslide debris reaches the valley bottom with maximum displacements of 1350 m and is marked by a lateral expansion to a broader extent than the source zone width, as observed in the field. Extension of this work to other pre-historic slope failures in the valleys of Vrancea-Buzau yield valuable new information for future seismic hazard estimations of the region

Energy loss for electrons in the Heliosphere and local interstellar spectrum for solar modulation

Galactic Cosmic Rays (GCR) entering the Heliosphere are affected by the solar modulation, which is a combination of diffusion, convection, magnetic drift, and adiabatic energy losses usually seen as a decrease of the flux at low energies (less than 10 GeV). We improved a quasi time-dependent 2D Stochastic Simulation code describing such effects. We focused our attention on the electron modulation, adding energy losses mechanisms in the Heliosphere that can be neglected for protons and ions: inverse Compton, ionization, synchrotron, and bremsstrahlung. These effects have been evaluated in the region affected by the solar magnetic field, up to 100 AU, where the environment conditions are not constant, especially the magnetic field intensity, and the photon density. In our calculation the inverse compton energy losses are dominant, but they contribute only a few percent in comparison with the adiabatic losses. We also compared the Local Interstellar Spectrum (LIS) of primary electrons with experimental data collected in the past years at energies 20 GeV. We found that, inside one standard deviation, LIS fits the data and can be used in a Monte carlo code reproducing CR propagation in the Heliosphere

Impact of constitutional TET2 haploinsufficiency on molecular and clinical phenotype in humans

Clonal hematopoiesis driven by somatic heterozygous TET2 loss is linked to malignant degeneration via consequent aberrant DNA methylation, and possibly to cardiovascular disease via increased cytokine and chemokine expression as reported in mice. Here, we discover a germline TET2 mutation in a lymphoma family. We observe neither unusual predisposition to atherosclerosis nor abnormal pro-inflammatory cytokine or chemokine expression. The latter finding is confirmed in cells from three additional unrelated TET2 germline mutation carriers. The TET2 defect elevates blood DNA methylation levels, especially at active enhancers and cell-type specific regulatory regions with binding sequences of master transcription factors involved in hematopoiesis. The regions display reduced methylation relative to all open chromatin regions in four DNMT3A germline mutation carriers, potentially due to TET2-mediated oxidation. Our findings provide insight into the interplay between epigenetic modulators and transcription factor activity in hematological neoplasia, but do not confirm the putative role of TET2 in atherosclerosis.Peer reviewe

Evaluation of a hybrid FEM/DEM approach for determination of rock mass strength using a combination of discontinuity mapping and fracture mechanics modelling, with particular emphasis on modelling of jointed pillars

EThOS - Electronic Theses Online ServiceGBUnited Kingdo

The Bologna Interpretation of Rock Bridges

One can only know where a rock bridge is once one measures it. In addition, to measure it, you need the rock mass to fail. This critical problem is ignored by many, and engineers continue to refer to rock bridges as geometrical distances between non-persistent fractures. This paper argues that this rather simplistic approach can lead to non-realistic failure mechanisms. We also raise the critical question of whether the inappropriate functioning of strength equations centred on the measurement of rock bridge percentages could result in misinterpreting the risk of failure. We propose a new interpterion, aptly called the Bologna Interpretation, as an analogy to the Copenhagen Interpretation of quantum mechanics, to highlight the indeterministic nature of rock bridges and to honour the oldest university in Europe (Bologna University). The Bologna Interpretation does not negate the existence of rock bridges. What rock bridges look like, how many there are, and where they are, we do not know; we can assume their existence and account for their contribution to rock mass strength using a potential analogue

Why Engineers Should Not Attempt to Quantify GSI

In the past decade, there has been an increasing trend of digitalizing rock engineering processes. However, this process has not been accompanied by a critical analysis of the very same empirical methods that many complex numerical and digital methods are founded upon. As engineers, we are taught to use and trust numbers. Indeed, we would not be able to define the factor of the safety of a structure without numbers. However, what happens when those numbers are nothing but numerical descriptions of qualitative assessments? In this paper we present a critical review of the many attempts presented in the literature to quantify GSI (geological strength index). To the authors’ knowledge, this paper represents the first time that all the different GSI tables and quantification methods that have been proposed over the past two decades are collated and compared critically. In our critique, we argue against the paradigm whereby the quantification process adds the experience factor for inexperienced engineers. Furthermore, we discuss the limitations of the notion that GSI quantification methods could transform subjectivity into objectivity since the parameters under considerations are not quantitative measurements. Relying on empirically defined quantitative equivalences raises important questions, particularly when these quantitative equivalences are being used to define so-called accurate rock mass classification input for design purposes.Applied Science, Faculty ofMining Engineering, Keevil Institute ofReviewedFacultyGraduat