Publications

@article{Lato2011,

title = {Evaluating roadside rockmasses for rockfall hazards using LiDAR data: optimizing data collection and processing protocols},

author = {MJ Lato and MS Diederichs and DJ Hutchinson and R Harrap},

url = {https://link.springer.com/article/10.1007/s11069-011-9872-y},

doi = {https://doi.org/10.1007/s11069-011-9872-y},

year  = {2011},

date = {2011-06-18},

journal = {Natural Hazards},

volume = {60},

pages = {831–864},

abstract = {Highways and railroads situated within rugged terrain are often subjected to the hazard of rockfalls. The task of assessing roadside rockmasses for potential hazards typically involves an on-site visual investigation of the rockmass by an engineer or geologist. At that time, numerous parameters associated with discontinuity orientations and spacing, block size (volume) and shape distributions, slope geometry, and ditch profile are either measured or estimated. Measurements are typically tallied according to a formal hazard rating system, and a hazard level is determined for the site. This methodology often involves direct exposure of the evaluating engineer to the hazard and can also create a potentially non-unique record of the assessed slope based on the skill, knowledge and background of the evaluating engineer. Light Detection and Ranging (LiDAR)–based technologies have the capability to produce spatially accurate, high-resolution digital models of physical objects, known as point clouds. Mobile terrestrial LiDAR equipment can collect, at traffic speed, roadside data along highways and rail lines, scanning continual distances of hundreds of kilometres per day. Through the use of mobile terrestrial LiDAR, in conjunction with airborne and static systems for problem areas, rockfall hazard analysis workflows can be modified and optimized to produce minimally biased, repeatable results. Traditional rockfall hazard analysis inputs include two distinct, but related sets of variables related to geological or geometric control. Geologically controlled inputs to hazard rating systems include kinematic stability (joint identification/orientation) and rock block shape and size distributions. Geometrically controlled inputs include outcrop shape and size, road, ditch and outcrop profile, road curvature and vehicle line of sight. Inputs from both categories can be extracted or calculated from LiDAR data, although there are some limitations and special sampling and processing considerations related to structural character of the rockmass, as detailed in this paper.},

keywords = {Characterization, Hazard, LiDAR, Risk, rockfall, Rockmass},

pubstate = {published},

tppubtype = {article}

}

@article{Fekete2010614,

title = {Geotechnical and operational applications for 3-dimensional laser scanning in drill and blast tunnels},

author = {S Fekete and MS Diederichs and MJ Lato},

url = {https://www.sciencedirect.com/science/article/pii/S0886779810000763},

doi = {https://doi.org/10.1016/j.tust.2010.04.008},

issn = {0886-7798},

year  = {2010},

date = {2010-09-01},

journal = {Tunnelling and underground space technology},

volume = {25},

number = {5},

pages = {614-628},

abstract = {Three-dimensional laser scanning (Lidar) techniques have been applied to a range of industries while their application to the geological environment still requires development. Lidar is a range-based imaging technique which collects a very accurate, high resolution 3-dimensional image of its surroundings. While the use of Lidar in underground environments has been primarily limited to as-built design verification in the past, there is great value in the scan data collected as the excavation advances. The advantages of employing a static Lidar system for geotechnical and operational applications have been demonstrated at a drill and blast tunnel operation at the Sandvika–Asker Railway Project near Oslo, Norway as well as in two other test tunnels in Oslo. The increased scanning rate of newer systems makes it possible to remotely obtain detailed rockmass and excavation information without costly delays or disruption of the construction workflow with a simple tripod setup. Tunnels are non-traditional environments for laser scanners and add limitations to the scanning process as well as the in-office interpretation process; these are discussed. Operational applications of the data include: calculation of shotcrete thickness, as-built bolt spacing, and regions of potential leakage. The authors find that Lidar data, when correctly interpreted, can also provide detailed 3-dimensional characterization of the rockmass. Geometrical characterization of discontinuity surfaces including location, orientation, frequency and large-scale roughness can be obtained. Discontinuity information may be synthesized for a much more representative geomechanical understanding of the rockmass than was previously impossible with traditional hand mapping limited by face accessibility. The alignment of Lidar scans from successive exposed faces offers additional interpretation and recording advantages, particularly where shotcrete is subsequently applied behind the face. In aligning scans, larger scale features can be readily identified and rockmass trends over several rounds may be identified. Discontinuity geometries and characteristics may be input into kinematic and numerical models for further analysis.},

keywords = {Laser scanning, LiDAR, Remote sensing, Rockmass characterization, Structural evaluation, tunnelling},

pubstate = {published},

tppubtype = {article}

}

@article{Lato2010b,

title = {Geomechanical feature extraction and analysis using LiDAR data: IOC Mine},

author = {MJ Lato and DJ Hutchinson and MS Diederichs},

year  = {2010},

date = {2010-03-01},

journal = {CIM Bulletin},

volume = {4},

number = {8},

pages = {10},

keywords = {Bias, Corridor analysis, geomechanical feature extraction, hazard assessment, LiDAR, Mining, Monitoring, Risk, rockfall},

pubstate = {published},

tppubtype = {article}

}

@article{Lato2010,

title = {Bias Correction for View-limited Lidar Scanning of Rock Outcrops for Structural Characterization},

author = {MJ Lato and MS Diederichs and DJ Hutchinson},

doi = {10.1007/s00603-010-0086-5},

year  = {2010},

date = {2010-02-26},

journal = {Rock Mechanics and Rock Engineering},

volume = {43},

pages = {615-628},

abstract = {Lidar is a remote sensing technology that uses time-of-flight and line-of-sight to calculate the accurate locations of physical objects in a known space (the known space is in relation to the scanner). The resultant point-cloud data can be used to virtually identify and measure geomechanical data such as joint set orientations, spacing and roughness. The line-of-sight property of static Lidar scanners results in occluded (hidden) zones in the point-cloud and significant quantifiable bias when analyzing the data generated from a single scanning location. While the use of multiple scanning locations and orientations, with merging of aligned (registered) scans, is recommended, practical limitations often limit setup to a single location or a consistent orientation with respect to the slope and rock structure. Such setups require correction for measurement bias. Recent advancements in Lidar scanning and processing technology have facilitated the routine use of Lidar data for geotechnical investigation. Current developments in static scanning have lead to large datasets and generated the need for automated bias correction methods. In addition to the traditional bias correction due to outcrop or scanline orientation, this paper presents a methodology for correction of measurement bias due to the orientation of a discrete discontinuity surface with respect to the line-of-sight of the Lidar scanner and for occlusion. Bias can be mathematically minimized from the analyzed discontinuity orientation data.},

keywords = {Bias, Characterization, Discontinuity, Joints, LiDAR, Mapping, Remote sensing, Rockmass},

pubstate = {published},

tppubtype = {article}

}

@article{Quinn2010,

title = {Regional-scale landslide susceptibility mapping using the weights of evidence method: an example applied to linear infrastructure},

author = {PE Quinn and DJ Hutchinson and MS Diederichs and RK ROwe},

url = {https://doi.org/10.1139/T09-144},

doi = {https://doi.org/10.1139/T09-144},

year  = {2010},

date = {2010-01-01},

journal = {Canadian Geotechnical Journal},

volume = {47},

number = {8},

pages = {905-927},

abstract = {Large landslides are common in the gently sloping clay plains of the Saint Lawrence Lowlands of eastern Canada. These tend to occur along rivers carved into the marine soils deposited in the former Champlain Sea, which occupied the area roughly 10 000 years ago. This paper presents a landslide susceptibility model, developed at the regional scale using a bivariate statistical method: the weights of evidence method. The analysis considers the association of existing large landslides in a portion of the study area with key terrain features, such as ground elevation, flow accumulation in adjacent streams, soil type, soil thickness, and land use. The resulting model identifies three different levels of susceptibility: low, low to moderate, and moderate to high. These descriptors are related statistically to the probability of encountering existing large landslides within 500 m, 1 or 2 km, respectively. The model is tested along primary railway corridors and isolates 8% of the total length for further consideration of landslide hazard. Reconnaissance level air photo survey results further reduce the length of corridor with elevated susceptibility to 2% of the total length, thus focusing the application of additional resources to a very small proportion of the total inventory.},

keywords = {Hazard, landslide, Risk, susceptibility, weight of evidence},

pubstate = {published},

tppubtype = {article}

}

@article{Diederichs2010b,

title = {Practical Rock Spall Prediction in Tunnels},

author = {MS Diederichs and TG Carter and D Martin},

url = {https://www.eoas.ubc.ca/courses/eosc547/lecture-material/Part3-SupplementaryUpdate_Diederichs-et-al.pdf},

year  = {2010},

date = {2010-01-01},

journal = {International Tunnelling Association},

pages = {1e8},

abstract = {Spalling is a mode of damage and overbreak in tunnels at depth in hard rocks (low porosity). 

Spalling is defined as the development of visible extension fractures under compressive loading near the boundary of an excavation. Varying levels of spall damage are illustrated in Figure 1. 

 

It is important to note that spalling associated with hard rock excavations, while brittle in nature, need not be violent. This process dominates rock damage and failure processes in crystalline rocks near excavation boundaries under high stress. Spalling can be violent or non-violent and in some cases can be time dependent. In unsupported conditions and under an anisotropic in situ stress field, the process of spalling can form notch geometries often confused with wedge fallout. 

 

Strain bursting is often confused with spalling. Strain bursting is the violent rupture of a volume of wall rock under high stress. In spalling rocks, the spalling damage (extension fractures) can happen before the actual rockburst or strain burst. It is the instability created (example: buckling) by the formation of parallel and thin spall slabs that provide the kinematics for the sudden energy release. While even weak rocks can spall, the ability to store energy, typical of strong rocks, is normally required for strain bursting. Typical examples are shown in Figure 2. 

 

Extensive research over the last few decades (See [1] for a complete history and references) has demonstrated that brittle non-porous rocks exhibit an maximum long term tunnel wall strength of no more than half of the laboratory test value for unconfined compressive strength (UCS). Damage monitoring [3] indicates that this lower bound strength threshold is less sensitive to confining stress than the peak lab envelope such that the limit for major principal stress is approximately 

 σ1max = CI + (1 to 2)σ3 

 

Where CI is the Crack Initiation Threshold (typically 35-50% of UCS) obtained through laboratory testing as discussed presently in this paper. Back analysis of observed tunnel breakout [4.5] indicates that this threshold only applies a low confinements. At higher confining stress the strength envelope makes a transition up to the envelope defined by the yield or Crack Damage Threshold, CD, obtained from testing. Uniaxial (unconfined) CD is typically 70-90% of UCS. 

 

The envelope for insitu damage of massive rocks is limited in tension by the true tensile strength of the rock, T. The full spalling envelope and the zonal significance is illustrated in Figure 3. Below the Lower bound field strength envelope (CI) no damage occurs within the rock. Above this envelope, micro-cracks initiate at the grain scale. Above CI but at high confinements these initiating micro-cracks quickly stabilize as they propagate away from the nucleation site. Upper bound strength (CD envelope) is controlled by shear fractures formed by microcrack coalescence. Acoustic emissions can occur in this range above the CI threshold and even minor joint slip events as small asperities locking up structure become weakened. At low confinement, such as that near an excavation wall, rock that is stressed above CI will incur spalling damage as new extension cracks and old cracks are allowed to propagate in an unstable fashion. In situ strength in this spalling zone falls significantly short of that predicted by lab testing},

keywords = {Brittle damage, Crack initiation threshold, Hard rockmasses, spalling, tunnelling},

pubstate = {published},

tppubtype = {article}

}

@article{Kalenchuk2009,

title = {Application of spatial prediction techniques to defining three-dimensional landslide shear surface geometry},

author = {KS Kalenchuk and DJ Hutchinson and MS Diederichs},

doi = {https://doi.org/10.1007/s10346-009-0168-1},

year  = {2009},

date = {2009-10-01},

journal = {Landslides},

volume = {6},

pages = {321-333},

abstract = {This study explores the application of interpolating and non-interpolating spatial prediction algorithms to interpreting shear surface geometries. A number of spatial prediction techniques have been tested, and the most appropriate algorithms for the Downie Slide dataset have been selected based on the root mean squared error (RMSE) determined from cross-validation. Visual assessment of reasonable spatial patterns has allowed for final selection of algorithms that produce geologically realistic results. Through this process, the performance of a number of interpolation algorithms has been tested in terms of accuracy and the development of reasonable spatial patterns. The goal of this study has been: (a) to develop a methodology for interpolating three-dimensional shear surface geometries and (b) to assess which interpolation methods are most appropriate for the interpretation of the Downie Slide basal slip surface geometry, based quantitatively on RMSE and qualitatively on the geological “trueness” of the geometric output.},

keywords = {Downie slide, Shear surface geometry, Three-dimensional landslide model},

pubstate = {published},

tppubtype = {article}

}

@article{Lato2009,

title = {Engineering monitoring of rockfall hazards along transportation corridors: using mobile terrestrial LiDAR},

author = {MJ Lato and DJ Hutchinson and MS Diederichs and D Ball and R Harrap},

url = {https://nhess.copernicus.org/articles/9/935/2009/},

doi = {https://doi.org/10.5194/nhess-9-935-2009},

year  = {2009},

date = {2009-06-23},

journal = {Natural Hazards and Earth System Sciences},

volume = {9},

number = {3},

pages = {935-946},

abstract = {Geotechnical hazards along linear transportation corridors are challenging to identify and often require constant monitoring. Inspecting corridors using traditional, manual methods requires the engineer to be unnecessarily exposed to the hazard. It also requires closure of the corridor to ensure safety of the worker from passing vehicles. This paper identifies the use of mobile terrestrial LiDAR data as a compliment to traditional field methods. Mobile terrestrial LiDAR is an emerging remote data collection technique capable of generating accurate fully three-dimensional virtual models while driving at speeds up to 100 km/h. Data is collected from a truck that causes no delays to active traffic nor does it impede corridor use. These resultant georeferenced data can be used for geomechanical structural feature identification and kinematic analysis, rockfall path identification and differential monitoring of rock movement or failure over time. Comparisons between mobile terrestrial and static LiDAR data collection and analysis are presented. As well, detailed discussions on workflow procedures for possible implementation are discussed. Future use of mobile terrestrial LiDAR data for corridor analysis will focus on repeated surveys and developing dynamic four-dimensional models, higher resolution data collection. As well, computationally advanced, spatially accurate, geomechanically controlled three-dimensional rockfall simulations should be investigated.},

keywords = {Corridor analysis, LiDAR, Mobile terrestrial LiDAR, rockfall, Static LiDAR},

pubstate = {published},

tppubtype = {article}

}

@article{Vlachopoulos2009,

title = {Improved longitudinal displacement profiles for convergence confinement analysis of deep tunnels},

author = {N Vlachopoulos and MS Diederichs},

doi = {10.1007/s00603-009-0176-4},

year  = {2009},

date = {2009-04-01},

journal = {Rock Mechanics and Rock Engineering},

volume = {42},

number = {2},

pages = {131-146},

abstract = {Convergence-confinement analysis for tunneling is a standard approach for preliminary analysis of anticipated wall deformation and support design in squeezing ground. Whether this analysis is performed using analytical (closed form) solutions or with plane strain numerical models, a longitudinal displacement profile (LDP) is required to relate tunnel wall deformations at successive stages in the analysis to the actual physical location along the tunnel axis. This paper presents a new and robust formulation for the LDP calculation that takes into account the significant influence of ultimate (maximum) plastic radius. Even after all parameters are appropriately normalized, the LDP function varies with the size of the ultimate plastic zone. Larger yield zones take a relatively longer normalized distance to develop, requiring an appropriately calculated LDP. Failure to use the appropriate LDP can result in significant errors in the specification of appropriate installation distance (from the face) for tunnel support systems. Such errors are likely to result in failure of the temporary support. The equations presented here are readily incorporated into analytical solutions and a graphical template is provided for use with numerical modeling.},

keywords = {Convergence-confinement, displacement, ground reaction, squeezing, tunnelling},

pubstate = {published},

tppubtype = {article}

}

@article{Carranza-Torres2009,

title = {Mechanical analysis of circular liners with particular reference to composite supports. For example, liners consisting of shotcrete and steel sets},

author = {C Carranza-Torres and MS Diederichs},

url = {https://www.sciencedirect.com/science/article/abs/pii/S0886779809000145},

doi = {https://doi.org/10.1016/j.tust.2009.02.001},

issn = {0886-7798},

year  = {2009},

date = {2009-02-04},

journal = {Tunnelling and Underground Space Technology},

volume = {24},

number = {5},

pages = {506-532},

abstract = {This paper describes a methodology for the mechanical analysis of composite supports, such as liners consisting of shotcrete and steel sets. The methodology presented here is based on an established technique of structural analysis commonly referred to as the ‘equivalent section’ approach. This technique consists in treating the composite section of a straight beam as a homogenized section of equivalent mechanical properties. The equations presented in this paper have been derived from application of the theory of elastic shells (or curved beams) and therefore are more appropriate for the analysis of circular tunnel liners. The proposed methodology for the design of liners is based on the construction of capacity diagrams, another established technique of structural analysis and concrete design that can be conveniently extended to the analysis of composite sections for tunnel liners. When applying the theory of elastic shells to derive the equations that conform to the proposed methodology, the problem of determining the mechanical response of semi-circular arches treated with the theory of thin and thick formulations has been re-visited. Observations of practical interest arising from the comparison of results obtained with both approaches are discussed.},

keywords = {Beam analysis, Capacity diagrams, Convergence-confinement method, Elasticity, Rock-support interaction, shotcrete lining, Steel sets, Theory of shells, Tunnel support},

pubstate = {published},

tppubtype = {article}

}

@article{Kalenchuk2008,

title = {Block geometry and rockmass characterization for prediction of dilution potential into sub-level cave mine voids},

author = {KS Kalenchuk and S McKinnon and MS Diederichs},

url = {https://www.sciencedirect.com/science/article/pii/S1365160907001748},

doi = {https://doi.org/10.1016/j.ijrmms.2007.10.006},

isbn = {1365-1609},

year  = {2008},

date = {2008-09-01},

journal = {International Journal of Rock Mechanics and Mining Sciences},

volume = {45},

number = {6},

pages = {929-940},

abstract = {When sub-level caving is used as an underground mining method for the exploitation of diamondiferous kimberlite pipes, a deep, steep-sided pipe is created that is susceptible to sloughage. Pipe wall sloughage allows waste rock to mix with and dilute the caved kimberlite ore. Using the Koala Kimberlite Pipe at Ekati Diamond Mine as a case study, a method has been developed, using rockmass and rock structure characterization integrated with discrete block (DEM) simulation, for comparative assessment of dilution potential and the classification and mapping of dilution source zones around the kimberlite pipe. The assessment process involves the development of a geomechanical model to delineate the structural fabric within the host rockmass and characterize the size and shape distributions of discrete rock blocks defined by intersecting discontinuities. Combining the slope geometry with the structural geology model allows for a zone-by-zone numerical analysis of pipe wall stability under gravitational loading. A final dilution map is developed in order to target problem areas where the highest levels of slope instability are anticipated.},

keywords = {Block geometry, Caving, Dilution, discrete elements, Pit stability, Rockmass characterization, Rockmass failure},

pubstate = {published},

tppubtype = {article}

}

@article{Lato2008,

title = {Optimization of LiDAR scanning and processing for automated structural evaluation of discontinuities in rockmasses},

author = {MJ Lato and MS Diederichs and DJ Hutchinson and R Harrap},

url = {https://www.sciencedirect.com/science/article/pii/S1365160908000804},

doi = {https://doi.org/10.1016/j.ijrmms.2008.04.007},

issn = {1365-1609},

year  = {2008},

date = {2008-06-16},

journal = {International Journal of Rock Mechanics and Mining Sciences},

volume = {46},

number = {1},

pages = {194-199},

abstract = {Terrestrial light detection and ranging (LiDAR) can be used for the delineation and evaluation of geomechanically controlled hazards. The United States Geological Survey [1] has adopted the use of LiDAR through numerous projects, as discussed in [2]. Other examples of the use of LiDAR surveys for geological data collection include discussion of the process of acquiring digital outcrop models for stratigraphic modelling [3], mapping basalt flow units [4], structural mapping of a large landslide [5], and evaluation of rockfall source and accumulation zones [6], [7]. In non-geological-based applications, LiDAR has been used for projects ranging from volumetric analysis in open pit mines [8], to recording and cataloguing archaeological digs in ancient ruins [9]. The equipment mobility, accuracy, and rate of data collection, in comparison to conventional surveying and stereophotogrammetric methods, have allowed existing surface analysis projects to proceed at unprecedented levels of detail and have promoted new applications. 

 

The use of terrestrial (ground based) LiDAR as a structural analysis and measurement tool has been investigated in detail by Kemeny and Post [10], Feng and Röshoff [11], Pringle et al. [12], Slob et al. [13] and others. Once the data is acquired and the primary 3D model is generated (as x, y, z data points with intensity scalars or mapped colourization via photo coupling), the analytical process can proceed in a similar fashion to modern photogrammetric techniques such as those applied by Haneberg et al. [14]. Both applications can replace traditional field mapping processes including the use of a compass or inclinometer to measure orientation, photos and notebooks to keep records, and manual data entry. Further, the conventional measurement of geo-structure is restricted to accessible and safe rock faces while these modern techniques can sample the visible structure remotely and safely. 

 

Automated procedures for structural data reduction have been developed [10], [15] specifically for Lidar applications. The objective of this research is to provide guidance for the optimization of automated structural discontinuity analysis based on LiDAR point cloud data collected from static terrestrial equipment. This paper deals primarily with issues pertaining to the data collection location, scan orientation, and data interpretation procedures involving interpolated surface development and mesh density. Scan occlusion effects are also discussed. Insights pertaining to future work and recommendations complete this paper.},

keywords = {data collection, Geomechanically controlled hazards, LiDAR, structural data reduction},

pubstate = {published},

tppubtype = {article}

}

@article{Carter2008,

title = {Application of modified Hoek-Brown transition relationships for assessing strength and post yield behaviour at both ends of the rock competence scale},

author = {TG Carter and MS Diederichs and JL Carvalho},

url = {http://www.scielo.org.za/pdf/jsaimm/v108n6/03.pdf},

issn = {2411-9717},

year  = {2008},

date = {2008-06-01},

journal = {Journal of the Southern African Institute of Mining and Metallurgy},

volume = {108},

number = {6},

pages = {325-338},

abstract = {upport system design for tunnels and underground excavations has for many years relied heavily on the use of rock mass classification systems and the Hoek-Brown failure criterion as a means for characterizing rock mass behaviour. Because of their development, both the GSI system and the Hoek-Brown criterion admirably characterize most 'normal' rockmasses from the viewpoint of their behaviour for rock excavations. They, however, run into difficulties when applied at the two ends of the rock competence scale. This is largely because block size and incipient strength are such that rock mass behaviour in these domains tends not to be controlled by interblock shear strength but rather by material strength. At the low end of the rock competence scale (UCSi << 15 MPa and GSI generally <30) discontinuities play less of a role and rock mass strength tends to matrix strength. Similarly, at the high end of the scale (GSI >> 65, mi >> 15), because discontinuities are now widely spaced, block size becomes so significant that again, intact material behaviour rather than the fracturing becomes the dominant factor controlling rock mass strength. 

In this paper several case examples are presented to illustrate the application of the high-end (spalling) and low-end (weak ground) transition Hoek-Brown relationships proposed by Carter, Diederichs and Carvalho (2007) as a basis for better defining rock mass behaviour at the extreme ends of the rock competence scale.},

keywords = {Discontinuity, Rockmass, spalling, Support, Weak rock},

pubstate = {published},

tppubtype = {article}

}