Rib/snook design in mechanised depillaring of rectangular/square pillars

This is the author accepted manuscript. The final version is available from Elsevier via the DOI in this record.A field study at different mechanised depillaring (MD) operations in Indian coalfields (with depth ranging from 60 to 377 m and caveability Index variation from 2300 to 10500) found mixed performances of adopted sizes of the ribs/snooks. Formation of an irregular shaped rib/snook during MD of the existing square/rectangular pillars by a continuous miner and uniqueness of the existing geo-mining conditions limit scope of application of the conventional rib/snook design approaches. Taking guidance from the field studies, a parametric investigation is conducted in laboratory on the calibrated simulated models using FLAC3D. An analysis of stress redistribution for different stages of the MD in simulated models provided a different characteristic of an irregular shaped ribs/snooks failure. Presence of moderate roof strata is found to be, relatively, more significant for the rib/snook design. Based on the simulation results, an attempt is made to provide a model for the rib/snook design in MDCSIR-CIMF

Evaluation of coal longwall caving characteristics using an innovative UDEC Trigon approach

Author version of article. The version of record is available from the publisher via DOI: 1016/j.compgeo.2013.09.020Copyright © 2013 Elsevier Ltd. All rights reserved.The paper presents an innovative numerical approach to simulate progressive caving of strata above a longwall coal mining panel. A proposed Trigon logic is incorporated within UDEC to successfully capture the progressive caving of strata which is characterized by fracture generation and subsequent propagation. A new damage index, D, is proposed that can quantify regions of both compressive shear and tensile failure within the modelled longwall. Many features of progressive caving are reproduced in the model and found to fit reasonably well with field observations taken from a case study in the Ruhr coalfield. The modelling study reveals that compressive shear failure, rather than tensile failure, is the dominant failure mechanism in the caved strata above the mined-out area. The immediate roof beds act like beams and can collapse in beam bending when vertical stress is dominant or in beam shear fracture when horizontal stress is dominant. The proposed numerical approach can be used to guide the design of longwall panel layout and rock support mechanisms

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

A legacy slope failure in Penlee Quarry - a warning to others

PublishedArticlePenlee Quarry is a large quarry in West Cornwall that has been in operation since the late 1880s. It was a major producer of aggregate, but since 2003 under new ownership, quarry operations have concentrated on maintenance and preparatory works for the recovery of armourstone and the eventual construction of a marina. The western face of this quarry was excavated between the 1950s and 1970s and is akin to other legacy slopes found at several older British quarries. The slope is up to 90m in height, has little benching and has shown increasing signs of instability since 2005. Initially instability was evidenced by rockfall and more recently by serious collapses that have indicated the need for appropriate geotechnical design of a new replacement slope. This paper sets out background and historical data and then considers investigations into the underlying mechanisms and rock structures that have contributed to instability and are relevant to the design of measures to overcome the potential for future significant ground movements. Methods to remotely assess the controlling joint sets are discussed and the rationale behind the excavated solution to facilitate future workings is outlined. High, over-steep rock faces with limited, ineffective benching and excessive bench heights that may be found in some older quarries, as at Penlee, are likely to become a matter of increasing concern. In addition the potential for major air blast or flow slide phenomena needs further investigation in these legacy slopes some of which are present in Southwest England

The Benefits of Laser Scanning & 3D Modelling in Accident Investigation: In a Mining Context

PublishedArticleThis is the author’s final accepted version of the article: M. L. Eyre, P. J. Foster, J. Jobling-Purser and J. Coggan. "The benefits of laser scanning and 3D modelling in accident investigation: in a mining context." Mining Technology 2015; 124(2), 73-77. DOI: 10.1179/1743286315Y.0000000004Accurate reconstruction of the facts and causes surrounding accidents is critical if the mining industry is to learn from incidents and prevent future events. Effective accident investigation and training are essential in order to accomplish this, while providing a record of the incident in order to help in explaining the situation to people unconnected to the event itself. Over a number of years there have been considerable innovations in survey instrumentation and software used to record data. However, the final deliverable data has remained the same, with surveyors tasked to represent a 3D environment using 2D deliverables. This paper explores the benefits that can be obtained using 3D data capture and representation with regard to accident investigation with discussion on accuracy, time, witness verification and reduction in human error

The Role of Visual and Semantic Properties in the Emergence of Category-Specific Patterns of Neural Response in the Human Brain

Brain-imaging studies have found distinct spatial and temporal patterns of response to different object categories across the brain. However, the extent to which these categorical patterns of response reflect higher-level semantic or lower-level visual properties of the stimulus remains unclear. To address this question, we measured patterns of EEG response to intact and scrambled images in the human brain. Our rationale for using scrambled images is that they have many of the visual properties found in intact images, but do not convey any semantic information. Images from different object categories (bottle, face, house) were briefly presented (400 ms) in an event-related design. A multivariate pattern analysis revealed categorical patterns of response to intact images emerged ∼80–100 ms after stimulus onset and were still evident when the stimulus was no longer present (∼800 ms). Next, we measured the patterns of response to scrambled images. Categorical patterns of response to scrambled images also emerged ∼80–100 ms after stimulus onset. However, in contrast to the intact images, distinct patterns of response to scrambled images were mostly evident while the stimulus was present (∼400 ms). Moreover, scrambled images were able to account only for all the variance in the intact images at early stages of processing. This direct manipulation of visual and semantic content provides new insights into the temporal dynamics of object perception and the extent to which different stages of processing are dependent on lower-level or higher-level properties of the image

Selectivity for mid‐level properties of faces and places in the fusiform face area and parahippocampal place area

Regions in the ventral visual pathway, such as the fusiform face area (FFA) and parahippocampal place area (PPA), are selective for images from specific object categories. Yet images from different object categories differ in their image properties. To investigate how these image properties are represented in the FFA and PPA, we compared neural responses to locally-scrambled images (in which mid-level, spatial properties are preserved) and globally-scrambled images (in which mid-level, spatial properties are not preserved). There was a greater response in the FFA and PPA to images from the preferred category relative to their non-preferred category for the scrambled conditions. However, there was a greater selectivity for locally-scrambled compared to globally-scrambled images. Next, we compared the magnitude of fMR adaptation to intact and scrambled images. fMR-adaptation was evident to locally-scrambled images from the preferred category. However, there was no adaptation to globally-scrambled images from the preferred category. These results show that the selectivity to faces and places in the FFA and PPA is dependent on mid-level properties of the image that are preserved by local scrambling

The Use of Remote Sensing Techniques for Monitoring and Characterization of Slope Instability

This is the author accepted manuscript. The final version is available from Elsevier via the DOI in this record.Understanding changes in slope geometry and knowledge of underlying engineering properties of the rock mass are essential for the safe design of man-made slopes and to reduce the significant risks associated with slope failure. Recent advances in the geomatics industry have provided the capability to obtain accurate, fully geo-referenced three-dimensional datasets that can be subsequently interrogated to provide engineering-based solutions for monitoring of deformation processes, rock mass characterization and additional insight into any underlying failure mechanisms. Importantly, data can also be used to spatially locate and map geological features and provide displacement or deformation rate information relating to movement of critical sections or regions of a slope. This paper explores the benefits that can be obtained by incorporating different remote sensing techniques and conventional measurement devices to provide a comprehensive database required for development of an effective slope monitoring and risk management program. The integration of different techniques, such as high accuracy discrete point measurement at critical locations, which can be used to complement larger scale less dense three-dimensional survey will be explored. Case studies using a combination of aerial and terrestrial laser scanning, unmanned aerial vehicle and hand-held scanning devices will demonstrate their ability to provide spatial data for informing decision making processes and ensuring compliance with Regulations

Modelling the Influence of Geological Structures in Paleo Rock Avalanche Failures Using Field and Remote Sensing Data

This paper focuses on the back analysis of an ancient, catastrophic rock avalanche located in the small city of Lettopalena (Chieti, Italy). The integrated use of various investigation methods was employed for landslide analysis, including the use of traditional manual surveys and remote sensing (RS) mapping for the identification of geological structures. The outputs of the manual and RS surveys were then utilised to numerically model the landslide using a 2D distinct element method. A series of numerical simulations were undertaken to perform a sensitivity analysis to investigate the uncertainty of discontinuity properties on the slope stability analysis and provide further insight into the landslide failure mechanism. Both numerical modelling and field investigations indicate that the landslide was controlled by translational sliding along a folded bedding plane, with toe removal because of river erosion. This generated daylighting of the bedding plane, creating kinematic freedom for the landslide. The formation of lateral and rear release surfaces was influenced by the orientation of the discrete fracture network. Due to the presence of an anticline, the landslide region was constrained in the middle-lower section of the slope, where the higher inclination of the bedding plane was detected. The landslide is characterized by a step-path slip surface at the toe of the slope, which was observed both in the modelling and the field. This paper highlights the combined use of a geological model and numerical modelling to provide an improved understanding of the origin and development of rock avalanches under the influence of river erosion, anticline structures, and related faults and fractures

Petrographic features as an effective indicator for the variation in strength of granites

AcceptedArticlethis is the author’s version of a work that was accepted for publication in Engineering Geology. A definitive version was subsequently published in Engineering Geology, http://dx.doi.org/10.1016/j.enggeo.2016.01.001The textural characteristics of four different granites from the lower Himalayan regime in north-western Pakistan have been examined in relation to their effect on the mechanical nature of rock. Detailed petrographic examination and subsequent quantitative QEMSCAN analysis provide better understanding of the difference between their textures. Three of the granite types are slightly altered (Grade-II) whereas the other has a higher degree of alteration and corresponds to alteration Grade-III. The mechanical properties determined for each granite type include: unconfined compressive and tensile strength, elastic modulus, P-wave velocity, Schmidt hardness and dry density. Statistical analyses, combined with post-test petrography, demonstrate textural control on mechanical properties. The important petrographic characteristics influencing mechanical behaviour include modal concentration and grain size of individual minerals, mean grain size of rock and distribution of grain size within a rock. Recrystallization of minerals along boundaries has a pronounced effect on increased strength of granites. Texture, however, has a significant influence on the variation of strength of granites with similar alteration grade.Commonwealth Scholarship Commission, U