A New Method for Automatic Extraction and Analysis of Discontinuities Based on TIN on Rock Mass Surfaces

Light detection and ranging (LiDAR) can quickly and accurately obtain 3D point clouds on the surface of rock masses, and on the basis of this, discontinuity information can be extracted automatically. This paper proposes a new method to automatically extract discontinuity information from 3D point clouds on the surface of rock masses. This method first applies the improved K-means algorithm based on the clustering algorithm by fast search and find of density peaks (DPCA) and the silhouette coefficient in the cluster validity index to identify the discontinuity sets of rock masses, and then uses the hierarchical density-based spatial clustering of applications with noise (HDBSCAN) algorithm to segment the discontinuity sets and to extract each discontinuity from a discontinuity set. Finally, the random sampling consistency (RANSAC) method is used to fit the discontinuities and to calculate their parameters. The 3D point clouds of the typical rock slope in the Rockbench repository is used to extract the discontinuity orientations using the new method, and these are compared with the results obtained from the classical approach and the previous automatic methods. The results show that, compared to the results obtained by Riquelme et al. in 2014, the average deviation of the dip direction and dip angle is reduced by 26% and 8%, respectively; compared to the results obtained by Chen et al. in 2016, the average deviation of the dip direction and dip angle is reduced by 39% and 40%, respectively. The method is also applied to an artificial quarry slope, and the average deviation of the dip direction and dip angle is 5.3° and 4.8°, respectively, as compared to the manual method. Furthermore, the related parameters are analyzed. The study shows that the new method is reliable, has a higher precision when identifying rock mass discontinuities, and can be applied to practical engineering.

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Canopy Parameter Estimation of Citrus grandis var. Longanyou Based on LiDAR 3D Point Clouds

Remote Sensing ◽

10.3390/rs13091859 ◽

2021 ◽

Vol 13 (9) ◽

pp. 1859

Author(s):

Xiangyang Liu ◽

Yaxiong Wang ◽

Feng Kang ◽

Yang Yue ◽

Yongjun Zheng

Keyword(s):

Convex Hull ◽

Clustering Algorithm ◽

Plant Protection ◽

Point Clouds ◽

Biomass Estimation ◽

Reconstruction Method ◽

Volume Calculation ◽

Alpha Shape ◽

3D Point Clouds ◽

Canopy Volume

The characteristic parameters of Citrus grandis var. Longanyou canopies are important when measuring yield and spraying pesticides. However, the feasibility of the canopy reconstruction method based on point clouds has not been confirmed with these canopies. Therefore, LiDAR point cloud data for C. grandis var. Longanyou were obtained to facilitate the management of groves of this species. Then, a cloth simulation filter and European clustering algorithm were used to realize individual canopy extraction. After calculating canopy height and width, canopy reconstruction and volume calculation were realized using six approaches: by a manual method and using five algorithms based on point clouds (convex hull, CH; convex hull by slices; voxel-based, VB; alpha-shape, AS; alpha-shape by slices, ASBS). ASBS is an innovative algorithm that combines AS with slices optimization, and can best approximate the actual canopy shape. Moreover, the CH algorithm had the shortest run time, and the R2 values of VCH, VVB, VAS, and VASBS algorithms were above 0.87. The volume with the highest accuracy was obtained from the ASBS algorithm, and the CH algorithm had the shortest computation time. In addition, a theoretical but preliminarily system suitable for the calculation of the canopy volume of C. grandis var. Longanyou was developed, which provides a theoretical reference for the efficient and accurate realization of future functional modules such as accurate plant protection, orchard obstacle avoidance, and biomass estimation.

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2D quantitative analysis of fractures from high-resolution photos for the geomechanical characterization of rock masses

10.5194/egusphere-egu21-2589 ◽

2021 ◽

Author(s):

Emmanuel Wyser ◽

Lidia Loiotine ◽

Charlotte Wolff ◽

Gioacchino Francesco Andriani ◽

Michel Jaboyedoff ◽

...

Keyword(s):

High Resolution ◽

Point Clouds ◽

Mitigation Measures ◽

Future Perspective ◽

Rock Masses ◽

Sampling Errors ◽

Discontinuity Sets ◽

Adverse Weather ◽

Geomechanical Characterization

The identification of discontinuity sets and their properties is among the key factors for the geomechanical characterization of rock masses, which is fundamental for performing stability analyses, and for planning prevention and mitigation measures as well. In practice, discontinuity data are collected throughout difficult and time-consuming field surveys, especially when dealing with areas of wide extension, difficult accessibility, covered by dense vegetation, or with adverse weather conditions. Consequently, even experienced operators may introduce sampling errors or misinterpretations, leading to biased geomechanical models for the investigated rock mass. In the last decades, new remote techniques such as photogrammetry, Light Detection and Ranging (LiDAR), Unmanned Aerial Vehicle (UAV) and InfraRed Thermography (IRT) have been introduced to overcome the limits of conventional surveys. We propose here a new tool for extracting information on the fracture pattern in rock masses, based on remote sensing methods, with particular reference to the analysis of high-resolution georeferenced photos. The first step consists in applying the Structure from Motion (SfM) technique on photos acquired by means of digital cameras and UAV techniques. Once aligned and georeferenced, the orthophotos are exported in a GIS software, to draw the fracture traces at an appropriate scale. We developed a MATLAB routine to extract information on the geostructural setting of rock masses by performing a quantitative 2D analysis of the fracture traces, based on formulas reported in the literature. The code was written by testing few experimental and simple traces and was successively validated on an orthophoto from a real case study. Currently, the script plots the fracture traces as polylines and calculates their orientation (strike) and length. Subsequently, it detects the main discontinuity sets by fitting an experimental composite Gaussian curve on histograms showing the number of discontinuities according to their orientation, and splitting the curve in simpler Gaussian curves, with peaks corresponding to the main discontinuity sets. Then, for each set, a linear scanline intersecting the highest number of traces is plotted, and the apparent and real spacing are calculated. In a second step, a grid of circular scanlines covering the whole area where the traces are located is plotted, and the mean trace intensity, trace density and trace length estimators are calculated. It is expected to test the presented tools on other case studies, in order to optimize them and calculate additional metrics, such as persistence and block sizes, useful to the geomechanical characterization of rock masses. As a future perspective, a similar approach could be investigated for 3D analyses from point clouds.

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Surface Subsidence Prognosis above an Underground Longwall Excavation and Based on 3D Point Cloud Analysis

Minerals ◽

10.3390/min10010082 ◽

2020 ◽

Vol 10 (1) ◽

pp. 82 ◽

Cited By ~ 3

Author(s):

Andrej Pal ◽

Janez Rošer ◽

Milivoj Vulić

Keyword(s):

Rock Mass ◽

Longwall Mining ◽

Underground Mining ◽

Point Clouds ◽

Surface Subsidence ◽

Protection Measures ◽

Engineering Research ◽

3D Point Clouds ◽

Research Activities ◽

And Control

Impacts of underground mining have been reduced by continuous environmental endeavors, scientific, and engineering research activities, whose main object is the behavior and control of the undermined rock mass and the subsequent surface subsidence. In the presented Velenje case of underground sublevel longwall mining where coal is being exploited both horizontal and vertical, backfilling processes and accompanying fracturing in the coal layer, and rock mass are causing uncontrolled subsidence of the surface above. 3D point clouds of the study were acquired in ten epochs and at excavation heights on the front were measured at the same epochs. By establishing a sectors layout in the observational area, smaller point clouds were obtained, to which planes were fitted and centroids of these planes then calculated. Centroid heights were analyzed with the FNSE model to estimate the time of consolidation and modified according to excavation parameters to determine total subsidence after a certain period. Proposed prognosis approaches for estimating consolidation of active subsidence and long term surface environmental protection measures have been proposed and presented. The C2C analysis of distances between acquired 3D point clouds was used for identification of surface subsidence, reclamation areas and sink holes, and for validation of feasibility and effectiveness of the proposed prognosis.

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Automatic characterization of rock mass discontinuities using 3D point clouds

Engineering Geology ◽

10.1016/j.enggeo.2019.05.008 ◽

2019 ◽

Vol 259 ◽

pp. 105131 ◽

Cited By ~ 6

Author(s):

Xiaojun Li ◽

Ziyang Chen ◽

Jianqin Chen ◽

Hehua Zhu

Keyword(s):

Rock Mass ◽

Point Clouds ◽

3D Point Clouds

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Clustering Mixed Data by Fast Search and Find of Density Peaks

Mathematical Problems in Engineering ◽

10.1155/2017/5060842 ◽

2017 ◽

Vol 2017 ◽

pp. 1-7 ◽

Cited By ~ 4

Author(s):

Shihua Liu ◽

Bingzhong Zhou ◽

Decai Huang ◽

Liangzhong Shen

Keyword(s):

Clustering Algorithm ◽

New Method ◽

Mixed Data ◽

Fast Search ◽

Density Peaks ◽

Categorical Attributes

Aiming at the mixed data composed of numerical and categorical attributes, a new unified dissimilarity metric is proposed, and based on that a new clustering algorithm is also proposed. The experiment result shows that this new method of clustering mixed data by fast search and find of density peaks is feasible and effective on the UCI datasets.

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Mechanical Characteristics and Failure Modes of Low-Strength Rock Samples with Dissimilar Fissure Dip Angles

10.3233/atde210291 ◽

2021 ◽

Author(s):

Y L Wang ◽

D S Liu ◽

K Li ◽

X M Hu ◽

D Chen

Keyword(s):

Rock Mass ◽

Mechanical Characteristics ◽

Failure Modes ◽

High Strength ◽

Rock Masses ◽

Deformation And Failure ◽

Deformation Features ◽

Low Strength ◽

Dip Angle ◽

Strength Rock

The mechanical characteristics and failure modes of low-strength rock sample with various fissure dip angles were investigated by conventional uniaxial compression test and three-dimensional (3D) crack reconstruction. The results indicated that compared with high-strength rock masses, cracks had different influences on the low-strength rock mass mechanical deformation features. Thereinto, the dip angle of fissures can cause post-peak failure stage of stress-strain curve change from swift decline to multi-step down, showing obvious ductility deformation and failure characteristics. Peak strength and elastic modulus owned an anti-S-shaped growth tendency with the growth of fissure dip angle, which was positively correlated and greatest subtle to the fissure dip angle α < 21° and α > 66.5°. The axial peak strain reduced first and enlarged rapidly with growing fissure dip angle, suggesting a V-shaped change trend. Increasing the fissure dip angle will change the sample failure mode, experienced complete tensile failure to tensile-shear composite failure, and ultimately to typical shear failure. Also, the crack start angle decreased with enlarging fissure dip angle, larger than that the high-strength rock mass fissure dip angle. The above research findings can complement and improve the study of fissured rock masses.

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Numerical Modeling on Dynamic Characteristics of Jointed Rock Masses Subjected to Repetitive Impact Loading

Shock and Vibration ◽

10.1155/2021/5274602 ◽

2021 ◽

Vol 2021 ◽

pp. 1-13

Author(s):

Jie Liu ◽

Yan-Bin Song ◽

Yue-Mao Zhao

Keyword(s):

Rock Mass ◽

Impact Loading ◽

Jointed Rock ◽

Stress Waves ◽

Rock Masses ◽

Jointed Rock Masses ◽

Numerical Tests ◽

Repetitive Impact ◽

Dip Angle ◽

Energy Dissipated

A discrete element method code was used to investigate the damage characteristics of jointed rock masses under repetitive impact loading. The Flat-Joint Contact Model (FJCM) in the two-dimensional particle flow code (PFC2D) was used to calibrate the microparameters that control the macroscopic behavior of the rock. The relationship between macro- and microparameters by a series of uniaxial direct tension and compression numerical tests based on an orthogonal experimental design method was obtained to calibrate the microparameters accurately. Then, the Synthetic Rock Mass (SRM) method that incorporates joints into the calibrated particle model was used to construct large-scale jointed rock mass specimens, and the repetitive drop hammer impact numerical tests on SRM specimens with different numbers of horizontal joints and dip angle joints were carried out to study the damage evolution, stress wave propagation, and energy dissipation characteristics. The results show that the greater the number of joints, the greater the number of cracks generated, the greater the degree of damage, and the more energy dissipated for rock masses with horizontal joints. The greater the dip angle of joints, the less the number of cracks generated, the less the degree of damage, and the less energy dissipated for rock masses with different dip angles of joints. The impact-induced stress waves will be reflected when they encounter preexisting joints in the process of propagation. When the reflected stress waves meet with subsequent stress waves, the stress waves will change from compressional waves to tensile waves, producing tensile damage inside rock masses.

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Using open-source software for extracting geomechanical parameters of a rock mass from 3D point clouds: Discontinuity set extractor and SMRTool

Rock Mechanics and Rock Engineering: From the Past to the Future ◽

10.1201/9781315388502-190 ◽

2016 ◽

Cited By ~ 3

Author(s):

A Riquelme ◽

R Tomás ◽

M Cano ◽

A Abellán

Keyword(s):

Rock Mass ◽

Open Source ◽

Open Source Software ◽

Point Clouds ◽

3D Point Clouds ◽

Geomechanical Parameters

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Discontinuity Characterization of Rock Masses through Terrestrial Laser Scanner and Unmanned Aerial Vehicle Techniques Aimed at Slope Stability Assessment

Applied Sciences ◽

10.3390/app10082960 ◽

2020 ◽

Vol 10 (8) ◽

pp. 2960

Author(s):

Marco Pagano ◽

Biagio Palma ◽

Anna Ruocco ◽

Mario Parise

Keyword(s):

Laser Scanning ◽

Economic Value ◽

Laser Scanner ◽

Point Clouds ◽

Rock Masses ◽

First Case ◽

Discontinuity Sets ◽

Aerial Vehicle ◽

Automatic Methods ◽

Geomechanical Characterization

Stabilization projects of rock masses cannot be performed without a proper geomechanical characterization. The classical approaches, due to logistic issues, typically are not able to cover extensively the areas under study. Geo-structural analysis on point cloud from terrestrial laser scanning and photogrammetry from unmanned aerial vehicles are valid tools for analysis of discontinuity systems. Such methodologies provide reliable data even in complex environmental settings (active cliffs) or at inaccessible sites (excavation fronts in tunnels), offering advantages in terms of both safety of the operators and economic and time issues. We present the implementation of these techniques at a tuff cliff over the Santa Caterina beach (Campania) and at the main entrance of Castellana Caves (Apulia). In the first case study, we also perform an integration of the two techniques. Both sites are of significant tourist and economic value, and present instability conditions common to wide areas of southern Italy: namely, retrogressive evolution of active cliffs along the coast, and instability at the rims of natural and/or artificial sinkholes. The results show the reliability of the data obtained through semi-automatic methods to extract the discontinuity sets from the point clouds, and their agreement with data collected in the field through classical approaches. Advantages and drawbacks of the techniques are illustrated and discussed.

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