20,416 research outputs found
A fractal fragmentation model for rockfalls
The final publication is available at Springer via http://dx.doi.org/10.1007/s10346-016-0773-8The impact-induced rock mass fragmentation in a rockfall is analyzed by comparing the in situ block size distribution (IBSD) of the rock mass detached from the cliff face and the resultant rockfall block size distribution (RBSD) of the rockfall fragments on the slope. The analysis of several inventoried rockfall events suggests that the volumes of the rockfall fragments can be characterized by a power law distribution. We propose the application of a three-parameter rockfall fractal fragmentation model (RFFM) for the transformation of the IBSD into the RBSD. A discrete fracture network model is used to simulate the discontinuity pattern of the detached rock mass and to generate the IBSD. Each block of the IBSD of the detached rock mass is an initiator. A survival rate is included to express the proportion of the unbroken blocks after the impact on the ground surface. The model was calibrated using the volume distribution of a rockfall event in Vilanova de Banat in the CadĂ Sierra, Eastern Pyrenees, Spain. The RBSD was obtained directly in the field, by measuring the rock block fragments deposited on the slope. The IBSD and the RBSD were fitted by exponential and power law functions, respectively. The results show that the proposed fractal model can successfully generate the RBSD from the IBSD and indicate the model parameter values for the case study.Peer ReviewedPostprint (author's final draft
Unsupervised Classification of Intrusive Igneous Rock Thin Section Images using Edge Detection and Colour Analysis
Classification of rocks is one of the fundamental tasks in a geological
study. The process requires a human expert to examine sampled thin section
images under a microscope. In this study, we propose a method that uses
microscope automation, digital image acquisition, edge detection and colour
analysis (histogram). We collected 60 digital images from 20 standard thin
sections using a digital camera mounted on a conventional microscope. Each
image is partitioned into a finite number of cells that form a grid structure.
Edge and colour profile of pixels inside each cell determine its
classification. The individual cells then determine the thin section image
classification via a majority voting scheme. Our method yielded successful
results as high as 90% to 100% precision.Comment: To appear in 2017 IEEE International Conference On Signal and Image
Processing Application
Towards the optimal Pixel size of dem for automatic mapping of landslide areas
Determining appropriate spatial resolution of digital elevation model (DEM) is a key step for effective landslide analysis based on remote sensing data. Several studies demonstrated that choosing the finest DEM resolution is not always the best solution. Various DEM resolutions can be applicable for diverse landslide applications. Thus, this study aims to assess the influence of special resolution on automatic landslide mapping. Pixel-based approach using parametric and non-parametric classification methods, namely feed forward neural network (FFNN) and maximum likelihood classification (ML), were applied in this study. Additionally, this allowed to determine the impact of used classification method for selection of DEM resolution. Landslide affected areas were mapped based on four DEMs generated at 1m, 2m, 5m and 10m spatial resolution from airborne laser scanning (ALS) data. The performance of the landslide mapping was then evaluated by applying landslide inventory map and computation of confusion matrix. The results of this study suggests that the finest scale of DEM is not always the best fit, however working at 1m DEM resolution on micro-topography scale, can show different results. The best performance was found at 5m DEM-resolution for FFNN and 1m DEM resolution for results. The best performance was found to be using 5m DEM-resolution for FFNN and 1m DEM resolution for ML classification
Yielding of rockfill in relative humidity-controlled triaxial experiments
The final publication is available at Springer via http://dx.doi.org/10.1007/s11440-016-0437-9The paper reports the results of suction controlled triaxial tests performed on compacted samples of two well graded granular materials in the range of coarse sand-medium gravel particle sizes: a quartzitic slate and a hard limestone. The evolution of grain size distributions is discussed. Dilatancy rules were investigated. Dilatancy could be described in terms of stress ratio, plastic work input and average confining stress. The shape of the yield locus in a triaxial plane was established by different experimental techniques. Yielding loci in both types of lithology is well represented by approximate elliptic shapes whose major axis follows approximately the Ko line. Relative humidity was found to affect in a significant way the evolution of grain size distribution, the deviatoric stress-strain response and the dilatancy rules.Peer ReviewedPostprint (author's final draft
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Predicting Landslides Using Locally Aligned Convolutional Neural Networks
Landslides, movement of soil and rock under the influence of gravity, are
common phenomena that cause significant human and economic losses every year.
Experts use heterogeneous features such as slope, elevation, land cover,
lithology, rock age, and rock family to predict landslides. To work with such
features, we adapted convolutional neural networks to consider relative spatial
information for the prediction task. Traditional filters in these networks
either have a fixed orientation or are rotationally invariant. Intuitively, the
filters should orient uphill, but there is not enough data to learn the concept
of uphill; instead, it can be provided as prior knowledge. We propose a model
called Locally Aligned Convolutional Neural Network, LACNN, that follows the
ground surface at multiple scales to predict possible landslide occurrence for
a single point. To validate our method, we created a standardized dataset of
georeferenced images consisting of the heterogeneous features as inputs, and
compared our method to several baselines, including linear regression, a neural
network, and a convolutional network, using log-likelihood error and Receiver
Operating Characteristic curves on the test set. Our model achieves 2-7%
improvement in terms of accuracy and 2-15% boost in terms of log likelihood
compared to the other proposed baselines.Comment: Published in IJCAI 202
Quantification of sub-resolution porosity in carbonate rocks by applying high-salinity contrast brine using X-ray microtomography differential imaging
Characterisation of the pore space in carbonate reservoirs and aquifers is of utmost importance in a number of applications such as enhanced oil recovery, geological carbon storage and contaminant transport. We present a new experimental methodology that uses high-salinity contrast brine and differential imaging acquired by X-ray tomography to non-invasively obtain three-dimensional spatially resolved information on porosity and connectivity of two rock samples, Portland and Estaillades limestones, including sub-resolution micro-porosity. We demonstrate that by injecting 30 wt% KI brine solution, a sufficiently high phase contrast can be achieved allowing accurate three-phase segmentation based on differential imaging. This results in spatially resolved maps of the solid grain phase, sub-resolution micro-pores within the grains, and macro-pores. The total porosity values from the three-phase segmentation for two carbonate rock samples are shown to be in good agreement with Helium porosity measurements. Furthermore, our flow-based method allows for an accurate estimate of pore connectivity and a distribution of porosity within the sub-resolution pores
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