Publications

@article{nokey,

title = {Exploring the Limits of Validity of Conventional Equivalent-Continuum Tunnel Analysis in Elasto-Plastic and Post-Yield Weakening Rockmasses using Explicit Structural Models},

author = {C Fischer and MS Diederichs},

year  = {2023},

date = {2023-01-01},

journal = {Canadian Geotechnical Journal},

keywords = {continuum modelling, Post-yield},

pubstate = {forthcoming},

tppubtype = {article}

}

@article{Packulak2022,

title = {Enhancement of Constant Normal Stiffness Direct Shear Testing Protocols for Determining Geomechanical Properties of Fractures},

author = {TR Packulak and JJ Day and MS Diederichs},

doi = {10.1139/cgj-2021-0576},

year  = {2022},

date = {2022-03-03},

journal = {Canadian Geotechnical Journal},

volume = {JustIN},

abstract = {Discontinuity behaviour can have a large impact on geotechnical engineering design; therefore, it is essential to determine their geomechanical properties in order to predict rockmass behaviour and mitigate any potential failure that may affect personnel safety or damage property. Geotechnical numerical software programs that discretely simulate discontinuities rely on direct shear laboratory tests to provide the properties needed as inputs to these tools. This study presents valuable direct shear laboratory test results for the mechanical properties and behaviours of fresh, unweathered, rough fractures in the Pointe du Bois granite. The testing program considers three separate boundary conditions: constant normal stress (CNL*) and two variations of constant normal stiffness (CNS). A new machine stiffness model is proposed to estimate the machine stiffness for tunnelling applications. Measurements of shear strength, and a proposed secant dilation angle are assessed and critically evaluated. It is found in this study that there is no significant difference between shear strength parameters determined from direct shear data from CNL* and CNS boundary conditions when comparing maximum strength and residual strength. In addition, it is found that the proposed secant dilation angle, critical shear displacement, and total dilation potential all have a negative relationship with increasing normal stress.},

keywords = {Constant normal stiffness, Constant normal stress, Dilation, Direct shear testing, Granite, Machine normal stiffness, Rough fractures, Shear strength},

pubstate = {published},

tppubtype = {article}

}

@article{Aubertin2021,

title = {Towards Blast Design Guidelines for Underground},

author = {JD Aubertin and DJ Hutchinson and MS Diederichs},

year  = {2021},

date = {2021-12-14},

journal = {Blasting and Fragmentation},

volume = {13},

number = {2},

pages = {77-101},

keywords = {Blast design, underground excavations},

pubstate = {published},

tppubtype = {article}

}

@article{nokey,

title = {Reliability of excavation damage zone prediction in brittle rocks through continuum modeling},

author = {N Dadashzadeh and MS Diederichs},

year  = {2021},

date = {2021-08-24},

urldate = {2021-08-24},

journal = {Journal of Rock Mechanics and Geotechnical Engineering},

number = {JRMGE_2019_618},

keywords = {Brittle rocks, continuum modelling, excavation damage zone (EDZ)},

pubstate = {published},

tppubtype = {article}

}

@article{FARAHMAND202160,

title = {Calibration of coupled hydro-mechanical properties of grain-based model for simulating fracture process and associated pore pressure evolution in excavation damage zone around deep tunnels},

author = {K Farahmand and MS Diederichs},

url = {https://www.sciencedirect.com/science/article/pii/S1674775520301219},

doi = {https://doi.org/10.1016/j.jrmge.2020.06.006},

issn = {1674-7755},

year  = {2021},

date = {2021-06-20},

journal = {Journal of Rock Mechanics and Geotechnical Engineering},

volume = {13},

number = {1},

pages = {60-83},

abstract = {The objective of this paper is to develop a methodology for calibration of a discrete element grain-based model (GBM) to replicate the hydro-mechanical properties of a brittle rock measured in the laboratory, and to apply the calibrated model to simulating the formation of excavation damage zone (EDZ) around underground excavations. Firstly, a new cohesive crack model is implemented into the universal distinct element code (UDEC) to control the fracturing behaviour of materials under various loading modes. Next, a methodology for calibration of the components of the UDEC-Voronoi model is discussed. The role of connectivity of induced microcracks on increasing the permeability of laboratory-scale samples is investigated. The calibrated samples are used to investigate the influence of pore fluid pressure on weakening the drained strength of the laboratory-scale rock. The validity of the Terzaghi's effective stress law for the drained peak strength of low-porosity rock is tested by performing a series of biaxial compression test simulations. Finally, the evolution of damage and pore pressure around two unsupported circular tunnels in crystalline granitic rock is studied.},

keywords = {Cohesive crack model, Coupled hydro-mechanical properties, excavation damage zone (EDZ), Grain-based model, Stress-dependent permeability, Stress-fracturing model},

pubstate = {published},

tppubtype = {article}

}

@article{ClarkDay2021,

title = {Mineralogical implications for geotechnical properties of intact heterogeneous and veined rocks from the Legacy skarn deposit},

author = {MD Clark and JJ Day},

doi = {10.1016/j.enggeo.2021.106067},

year  = {2021},

date = {2021-02-22},

journal = {Engineering Geology},

volume = {285},

pages = {21},

abstract = {Predicting the geomechanical behaviour of rockmasses is key to the economic success and safety of rock engineering projects including surface and underground excavations. For these projects, unconfined compressive stress (UCS) laboratory testing provides fundamental geomechanical properties of intact rocks. It is currently standard practice for UCS testing to consider only homogeneous specimens that are free of defects and discard heterogeneous specimens such as those that contain intrablock structures (e.g. veins) or extra-granular defects (e.g. phenocrysts). Understanding the complexities of these heterogeneous rocks and rockmasses is critical for excavation projects such as deep cave mines where extensive tunnel networks, caves, and stopes are regularly excavated through heterogeneous rockmasses. This paper presents the test results and analyses of UCS tests conducted on 29 matrix-type and 21 veined drill core specimens from the Legacy Skarn deposit located in northern New Brunswick, Canada. These specimens are sorted into five lithological units: beige, red, and black varieties of quartz-plagioclase granodiorite, calcareous mudstone, and garnet-pyroxene skarn. Mineralogical compositions of these units are determined using field identification techniques and microscopic laboratory methods including petrographic thin section analysis, powdered X-Ray Diffraction, and micro-X-Ray Fluorescence. Significant effects of hydrothermal veining and phenocrysts on the UCS test results are discussed in this study to highlight the significant influence of mineralogy on the variability of geomechanical properties. For example, vein mineralogy dominated by calcite weakened the granodiorites but strengthened the calcareous mudstone. Vein mineralogy dominated by quartz in the skarn unit had a mixed influence on geomechanical properties. Vein thickness primarily influenced geomechanical properties of specimens with single veins, whereas vein density was more useful to characterize specimens that contained vein networks or stockwork. The effects of vein orientation only partially agree with the established Jaeger model for shear failure through critically oriented foliations. The disseminated alteration in the granodiorites (plagioclase phenocrysts) and skarn (garnet crystals) typically increased stiffness and strength as the large grains arrest crack propagation when under load. Lastly, the effects of sample selection on reported UCS test results using four sample selection methods are presented. The results demonstrate the importance of including heterogeneous veined specimens in UCS sample selection and testing programs to capture rock variability and improve the accuracy of numerical geomechanical design. Recommendations are made to improve geotechnical core logging and sample selection protocols when characterizing heterogeneous complex rockmasses.},

keywords = {Drill core sample selection, extra-granular heterogeneous rocks, Geomechanical laboratory testing, hydrothermal veins, Intrablock structures, Unconfined compressive stress},

pubstate = {published},

tppubtype = {article}

}

@article{AUBERTIN2021103985,

title = {Horizontal single hole blast testing – Part 2: Field observations and experimental trends from SHB campaigns at two underground salt mines},

author = {JD Aubertin and DJ Hutchinson and MS Diederichs},

url = {https://www.sciencedirect.com/science/article/pii/S0886779821001760},

doi = {https://doi.org/10.1016/j.tust.2021.103985},

issn = {0886-7798},

year  = {2021},

date = {2021-01-04},

journal = {Tunnelling and Underground Space Technology},

volume = {114},

pages = {103-985},

abstract = {Large scale Single Hole Blast (SHB) testing is used to characterize blasting behavior in a cost-effective manner. SHB testing provides the means to assess the effect of blasting specifications (e.g. burden dimension, explosive used, borehole diameter) on rock cratering and blast efficiency. The observed behavior depends significantly on the testing procedure and measurements recorded. Crater characteristics are commonly described by the displaced volume of rock and breakout shape. Analysis of SHB test results relies on reproducible measurements. This paper proposes a method for analysis of horizontal SHB tests using data collected via terrestrial laser scanning (TLS) surveys. The procedural algorithms, point cloud manipulations, and analysis facilitate systematic SHB testing, including the use of a reference axis aligned with the blasthole orientation. The definition of crater extents, absolute burden measurements, methods for crater slicing, and filtering are developed to maintain consistency with the plane strain assumption. Crater partitioning protocols are elaborated to enhanced details of captured data. A detailed workflow of the analysis is provided with examples from compiled field testing. The conventional SHB measurement approach for crater breakout angle is refined to account for superficial surface roughness, and to capture the full crater shape. Data captured for the craters is represented along the blasthole length to capture the plane-strain component of single blasthole cratering. Comprehensive results from full scale field experiments are presented in a companion paper.},

keywords = {LiDAR, Point cloud processing, Rock blasting, Single hole blast test, terrestrial laser scanning, Underground Mining},

pubstate = {published},

tppubtype = {article}

}

@article{Packulak2021,

title = {New Data Processing Protocols to Isolate Fracture Deformations to Measure Normal and Shear Joint Stiffness},

author = {TR Packulak and JJ Day and MTA Labeid and MS Diederichs},

year  = {2021},

date = {2021-01-01},

urldate = {2021-01-01},

journal = {Rock Mechanics and Rock Engineering},

keywords = {Fracture deformations, Laboratory testing, Normal stiffness, Shear stiffness, Testing protocols},

pubstate = {published},

tppubtype = {article}

}

@article{Hegger2021,

title = {Measuring the full-field strain response of uniaxial compression test specimens using distributed fiber optic sensing},

author = {S Hegger and N Vlachopoulos and T Poles and MS Diederichs},

year  = {2021},

date = {2021-01-01},

urldate = {2021-01-01},

journal = {Rock Mechanics and Rock Engineering},

keywords = {Distributed fiber optic sensing, Strain response, Uniaxial compressive strength of intact rock},

pubstate = {published},

tppubtype = {article}

}

@article{Diederichs2021,

title = {An illustrative study on the sensitivity of EDZ development to layered and nodular sedimentary structure},

author = {MS Diederichs and JJ Day},

year  = {2021},

date = {2021-01-01},

urldate = {2021-01-01},

journal = {Rock Mechanics and Rock Engineering},

keywords = {excavation damage zone (EDZ), Nodular structure, Three-dimensional sensitivity analysis},

pubstate = {published},

tppubtype = {article}

}

@article{CLARK2021106067,

title = {Mineralogical and sample selection implications for geomechanical properties of intact heterogeneous and veined rocks from the Legacy skarn deposit},

author = {MD Clark and JJ Day},

url = {https://www.sciencedirect.com/science/article/pii/S0013795221000788},

doi = {https://doi.org/10.1016/j.enggeo.2021.106067},

issn = {0013-7952},

year  = {2021},

date = {2021-01-01},

journal = {Engineering Geology},

volume = {285},

pages = {106067},

abstract = {Predicting the geomechanical behaviour of rockmasses is key to the economic success and safety of rock engineering projects including surface and underground excavations. For these projects, unconfined compressive stress (UCS) laboratory testing provides fundamental geomechanical properties of intact rocks. It is currently standard practice for UCS testing to consider only homogeneous specimens that are free of defects and discard heterogeneous specimens such as those that contain intrablock structures (e.g. veins) or extra-granular defects (e.g. phenocrysts). Understanding the complexities of these heterogeneous rocks and rockmasses is critical for excavation projects such as deep cave mines where extensive tunnel networks, caves, and stopes are regularly excavated through heterogeneous rockmasses. This paper presents the test results and analyses of UCS tests conducted on 29 matrix-type and 21 veined drill core specimens from the Legacy Skarn deposit located in northern New Brunswick, Canada. These specimens are sorted into five lithological units: beige, red, and black varieties of quartz-plagioclase granodiorite, calcareous mudstone, and garnet-pyroxene skarn. Mineralogical compositions of these units are determined using field identification techniques and microscopic laboratory methods including petrographic thin section analysis, powdered X-Ray Diffraction, and micro-X-Ray Fluorescence. Significant effects of hydrothermal veining and phenocrysts on the UCS test results are discussed in this study to highlight the significant influence of mineralogy on the variability of geomechanical properties. For example, vein mineralogy dominated by calcite weakened the granodiorites but strengthened the calcareous mudstone. Vein mineralogy dominated by quartz in the skarn unit had a mixed influence on geomechanical properties. Vein thickness primarily influenced geomechanical properties of specimens with single veins, whereas vein density was more useful to characterize specimens that contained vein networks or stockwork. The effects of vein orientation only partially agree with the established Jaeger model for shear failure through critically oriented foliations. The disseminated alteration in the granodiorites (plagioclase phenocrysts) and skarn (garnet crystals) typically increased stiffness and strength as the large grains arrest crack propagation when under load. Lastly, the effects of sample selection on reported UCS test results using four sample selection methods are presented. The results demonstrate the importance of including heterogeneous veined specimens in UCS sample selection and testing programs to capture rock variability and improve the accuracy of numerical geomechanical design. Recommendations are made to improve geotechnical core logging and sample selection protocols when characterizing heterogeneous complex rockmasses.},

keywords = {Drill core sample selection, extra-granular heterogeneous rocks, Geomechanical laboratory testing, hydrothermal veins, Intrablock structures, Unconfined compressive stress},

pubstate = {published},

tppubtype = {article}

}

@article{nokeyb,

title = {On the interaction between emitted and reflected pulses as a blast cratering mechanism in rock salt},

author = {JD Aubertin and DJ Hutchinson and MS Diederichs},

year  = {2020},

date = {2020-09-01},

urldate = {2020-09-01},

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

keywords = {blast cratering mechanism, emitted pulses, reflected pulses, Rock salt},

pubstate = {forthcoming},

tppubtype = {article}

}

@article{Innocente2020,

title = {Review of Long-Term Strength and Time-to-Failure of Brittle Rocks: Lab Testing and Interpretation},

author = {J Innocente and MS Diederichs and C Paraskevopoulou},

year  = {2020},

date = {2020-08-01},

journal = {Rock Mechanics and Geotechnical Engineering},

keywords = {Brittle rocks, Laboratory testing, Long-term behaviour},

pubstate = {forthcoming},

tppubtype = {article}

}

@article{OConnor2020,

title = {The geo-mechanical response of axial loaded fully grouted rock bolts using a distributed fiber optic sensor technique},

author = {T O'Connor and N Vlachopoulos and MS Diederichs and B Forbes},

year  = {2020},

date = {2020-08-01},

urldate = {2020-08-01},

journal = {Tunnelling and Underground Space Technology},

keywords = {Distributed fiber optic sensing, Fully grouted rock bolt, Geo-mechanical response},

pubstate = {forthcoming},

tppubtype = {article}

}

@article{DiFrancesco2020,

title = {The implications of M3C2 projection diameter on 3-D semi-automated rockfall extraction from sequential terrestrial laser scanning point clouds},

author = {PM DiFrancesco and D Bonneau and DJ Hutchinson},

doi = {10.3390/rs12111885},

year  = {2020},

date = {2020-06-10},

journal = {Remote Sensing},

volume = {12},

number = {11},

pages = {28},

abstract = {Rockfall inventories are essential to quantify a rockfall activity and characterize the hazard. Terrestrial laser scanning and advancements in processing algorithms have resulted in three-dimensional (3D) semi-automatic extraction of rockfall events, permitting detailed observations of evolving rock masses. Currently, multiscale model-to-model cloud comparison (M3C2) is the most widely used distance computation method used in the geosciences to evaluate 3D changing features, considering the time-sequential spatial information contained in point clouds. M3C2 operates by computing distances using points that are captured within a projected search cylinder, which is locally oriented. In this work, we evaluated the effect of M3C2 projection diameter on the extraction of 3D rockfalls and the resulting implications on rockfall volume and shape. Six rockfall inventories were developed for a highly active rock slope, each utilizing a different projection diameter which ranged from two to ten times the point spacing. The results indicate that the greatest amount of change is extracted using an M3C2 projection diameter equal to, or slightly larger than, the point spacing, depending on the variation in point spacing. When the M3C2 projection diameter becomes larger than the changing area on the rock slope, the change cannot be identified and extracted. Inventory summaries and illustrations depict the influence of spatial averaging on the semi-automated rockfall extraction, and suggestions are made for selecting the optimal projection diameter. Recommendations are made to improve the methods used to semi-automatically extract rockfall from sequential point clouds.},

keywords = {change detection, frequency-magnitude, M3C2, rockfall, spatial averaging, terrestrial laser scanning},

pubstate = {published},

tppubtype = {article}

}

@article{Forbes2020,

title = {An in situ monitoring campaign of a hard rock pillar at great depth within a Canadian mine},

author = {B Forbes and N Vlachopoulos and MS Diederichs and AJ Hyett and A Punkkinen},

doi = {10.1016/j.jrmge.2019.07.018},

year  = {2020},

date = {2020-06-01},

journal = {Journal of Rock Mechanics and Geotechnical Engineering},

volume = {12},

number = {3},

pages = {427-448},

abstract = {A recent research campaign at a Canadian nickel-copper mine involved instrumenting a hard rock sill drift pillar with an array of multi-point rod extensometers, distributed optical fibre strain sensors, and borehole pressure cells (BHPCs). The instrumentation spanned across a 15.24 m lengthwise segment of the relatively massive granitic pillar situated at a depth of 2.44 km within the mine. Between May 2016 and March 2017, the pillar's displacement and pressure response were measured and correlated with mining activities on the same level as the pillar, including: (1) mine-by of the pillar, (2) footwall drift development, and (3) ore body stoping operations. Regarding displacements of the pillar, the extensometers provided high temporal resolution (logged hourly) and the optical fibre strain sensors provide high spatial resolution (measured every 0.65 mm along the length of each sensor). The combination of sensing techniques allowed centimetre-scale rock mass bulking near the pillar sidewalls to be distinguished from microstrain-scale fracturing towards the core of the pillar. Additionally, the influence and extent of a mine-scale schistose shear zone transecting the pillar was identified. By converting measured rock mass displacement to velocity, a process was demonstrated which allowed mining activities inducing displacements to be categorised by time-duration and cumulative displacement. In over half of the analysed mining activities, displacements were determined to prolong for over an hour, predominately resulting in submillimetre cumulative displacements, but in some cases multi-centimetre cumulative displacements were observed. This time-dependent behaviour was more pronounced within the vicinity of the plumb shear zone. Displacement measurements were also used to assess selected support member load and elongation mobilisation per mining activity. It was found that a combined static load and elongation capacity of reinforcing members was essential to maintaining excavation stability, while permitting gradual shedding of stress through controlled pillar sidewall displacements.},

keywords = {Distributed optical fibre strain sensing, Dynamic support, Extensometer, Hard rock pillar, High stress, In situ monitoring, Rock mass bulking, Rockburst},

pubstate = {published},

tppubtype = {article}

}

@article{Forbes2020b,

title = {Augmenting the in-situ rock bolt pull test with distributed optical fiber strain sensing},

author = {B Forbes and N Vlachopoulos and MS Diederichs and JD Aubertin},

url = {https://www.sciencedirect.com/science/article/pii/S1365160919309918},

doi = {https://doi.org/10.1016/j.ijrmms.2019.104202},

issn = {1365-1609},

year  = {2020},

date = {2020-02-01},

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

volume = {126},

pages = {104-202},

abstract = {A high spatial resolution distributed optical fiber strain sensing technology is demonstrated to advance the assessment of support element behaviour during in-situ pull tests. A technique to instrument typical tendon support elements with a fiber optic sensor is discussed and was trialed at an underground salt mine through a series of pull tests on instrumented rebar elements. It is shown that a continuous strain profile can be measured along the length of a support element under pull test load, which, in turn, allows the interfacial shear stress distribution and deformation of the support element to be resolved. In comparison to load and displacement measurements solely at the support element head, which is what is traditionally reported for in-situ pull tests, the optical fiber strain sensor is found to provide significantly more insight into the mechanistic behaviour of the support element by readily measuring highly variable strain distributions and by quantifying the load development length of the support element. The sensor arrangement allowed the conventional handling and installation procedures to be followed without any implication to the integrity of the sensor. Accordingly, an instrumented reinforcement element can be installed with minimal interruption to on-going mining/construction procedures at the given project.},

keywords = {Distributed optical fiber strain sensing, Fully grouted rock bolt, Pull-out testing, Quality assessment, Strain measurement, Support Performance},

pubstate = {published},

tppubtype = {article}

}

@article{Aubertin2020,

title = {Horizontal Single Blasthole Testing – Part 1: Systematic measurements using TLS surveys},

author = {JD Aubertin and DJ Hutchinson and MS Diederichs},

doi = {10.1016/j.tust.2021.103985},

year  = {2020},

date = {2020-01-01},

journal = {Tunnelling and Underground Space Technology},

volume = {114},

number = {103985},

keywords = {terrestrial laser scanning},

pubstate = {published},

tppubtype = {article}

}

@article{nokeyc,

title = {Assessing 3-Dimensional Joint Roughness with Structure-from-Motion Photogrammetry},

author = {D Bonneau and TR Packulak and DJ Hutchinson and MS Diederichs},

year  = {2020},

date = {2020-01-01},

urldate = {2020-01-01},

journal = {International Journal of Geo-information},

keywords = {joint roughness, Photogrammetry, structure-from-motion},

pubstate = {published},

tppubtype = {article}

}

@article{Bonneau2019,

title = {3-Dimensional Rockfall Shape Back-Analysis: Methods and Implications},

author = {D Bonneau and DJ Hutchinson and PM DiFrancesco and M Coombs and Z Sala},

doi = {10.5194/nhess-19-2745-2019},

year  = {2019},

date = {2019-12-04},

journal = {Natural Hazards and Earth System Sciences},

volume = {19},

pages = {2745–2765},

abstract = {Rockfall is a complex natural process that can present risks to the effective operation of infrastructure in mountainous terrain. Remote sensing tools and techniques are rapidly becoming the state of the practice in the characterization, monitoring and management of these geohazards. The aim of this study is to address the methods and implications of how the dimensions of three-dimensional rockfall objects, derived from sequential terrestrial laser scans (TLSs), are measured. Previous approaches are reviewed, and two new methods are introduced in an attempt to standardize the process. The approaches are applied to a set of synthetic rockfall objects generated in the open-source software package Blender. Fifty rockfall events derived from sequential TLS monitoring in the White Canyon, British Columbia, Canada, are used to demonstrate the application of the proposed algorithms. This study illustrates that the method used to calculate the rockfall dimensions has a significant impact on how the shape of a rockfall object is classified. This has implications for rockfall modelling as the block shape is known to influence rockfall runout.},

keywords = {rockfall, terrestrial laser scanning},

pubstate = {published},

tppubtype = {article}

}

@article{deOliveira2019,

title = {Clogging and flow assessment of cohesive soils for EPB tunnelling: Proposed laboratory tests for soil characterisation},

author = {DGG Oliveira and M Thewes and MS Diederichs},

url = {https://www.sciencedirect.com/science/article/pii/S0886779818307879},

doi = {https://doi.org/10.1016/j.tust.2019.103110},

issn = {0886-7798},

year  = {2019},

date = {2019-12-01},

journal = {Tunnelling and Underground Space Technology},

volume = {94},

pages = {103-110},

abstract = {For earth pressure balance (EPB) machines, it is fundamental to characterise the excavated ground in its natural and conditioned states. The characteristics of the excavated material have a direct influence on machine operation, impacting the functions as a support medium maintaining the support pressure ahead of the tunnel face, besides its transportation and disposal. The current available methods to assess the clogging potential focus mainly on sedimentary pure clayey soils, not including mixed soils. Mixed soils exist widely in nature, including a wide variety of residual soils, which are by-products of intense tropical weathering. This paper presents a combined laboratory routine to characterise and evaluate the clogging and fluidity of soils, including mixed soils by considering different clay fractions. This routine still requires tests conducted directly on-site, where the results should be compared with machine operation parameters, such as torque of cutterhead and screw conveyor, temperature, pressure, as well as occurrence of clogging. This testing procedure provides on-site assessment that can also be conducted prior the excavation using borehole material. The intention of this routine is to provide a geological-geotechnical qualitative characterisation of the material to be excavated, and of the effectiveness of the additives that could be added, as a general guidance for EPB soil conditioning, especially of cohesive soils. The advantage of this routine is its simplicity and low cost to be reproducible in different laboratories and jobsites, making feasible the comparison between different soils by different operators, before and during excavation.},

keywords = {Clogging, EPB Machine, Flow behaviour, Fluidity, Mixed soils, Soil conditioning},

pubstate = {published},

tppubtype = {article}

}

@article{Bonneau2019b,

title = {Surface reconstruction for three-dimensional rockfall volumetric analysis},

author = {D Bonneau and PM DiFrancesco and DJ Hutchinson},

doi = {10.3390/ijgi8120548},

year  = {2019},

date = {2019-11-30},

journal = {International Journal of Geo-Information},

volume = {8},

number = {12},

pages = {548},

abstract = {Laser scanning is routinely being used for the characterization and management of rockfall hazards. A key component of many studies is the ability to use the high-resolution topographic datasets for detailed volume estimates. 2.5-Dimensional (2.5D) approaches exist to estimate the volume of rockfall events; however these approaches require rasterization of the point cloud. These 2.5D volume estimates are therefore sensitive to picking an appropriate cell size to preserve resolution while minimizing interpolation, especially for lower volume rockfall events. To overcome the limitations of working with 2.5D raster datasets, surface reconstruction methods originating from the field of computational geometry can be implemented to assess the volume of rockfalls in 3D. In this technical note, the authors address the methods and implications of how the surface of 3D rockfall objects, derived from sequential terrestrial laser scans (TLS), are reconstructed for volumetric analysis. The Power Crust, Convex Hull and Alpha-shape algorithms are implemented to reconstruct a synthetic rockfall object generated in Houdini, a procedural modeling and animation software package. The reconstruction algorithms are also implemented for a selection of three rockfall cases studies which occurred in the White Canyon, British Columbia, Canada. The authors find that there is a trade-off between accurate surface topology reconstruction and ensuring the mesh is watertight manifold; which is required for accurate volumetric estimates. Power Crust is shown to be the most robust algorithm, however, the iterative Alpha-shape approach introduced in the study is also shown to find a balance between hole-filling and loss of detail.},

keywords = {Alpha-shape, Convex Hull, LiDAR, point cloud, Power Crust, rockfall, surface reconstruction, volume estimate},

pubstate = {published},

tppubtype = {article}

}

@article{Dadashzadeh2019,

title = {EDZ prediction and characterization for deep repository engineering based on a 2D random Voronoi grain-based modeling technique},

author = {N Dadashzadeh and MS Diederichs},

year  = {2019},

date = {2019-09-04},

urldate = {2019-09-04},

journal = {Tunnelling and Underground Space Technology},

number = {TUST_2019_1187},

keywords = {2D random Voronoi grain-based modelling, Deep geological repository (DGR), deep re, excavation damage zone (EDZ)},

pubstate = {forthcoming},

tppubtype = {article}

}

@article{nokeyd,

title = {Calibration strategies for brittle fracture simulation at laboratory and in-situ scales using a grain-based distinct element approach},

author = {N Dadashzadeh and MS Diederichs},

year  = {2019},

date = {2019-08-24},

urldate = {2019-08-24},

journal = {Journal of Rock Mechanics and Geotechnical Engineering},

number = {JRMGE_2019_567},

keywords = {Brittle fracturing, grain-based distinct element method, Numerical simulation},

pubstate = {forthcoming},

tppubtype = {article}

}

@article{Garroux2019,

title = {EPB machine excavation of mixed soils – Laboratory characterisation},

author = {D Garroux and DGG Oliveira and M Thewes and MS Diederichs},

url = {https://onlinelibrary.wiley.com/doi/abs/10.1002/geot.201900014},

doi = {https://doi.org/10.1002/geot.201900014},

year  = {2019},

date = {2019-08-01},

journal = {Geomechanics and Tunnelling},

volume = {12},

number = {4},

pages = {373-385},

abstract = {Earth pressure balance (EPB) tunnel boring machines are shield machines that rely on their own excavated material as a support medium to maintain the support pressure at the face. This material also needs to have the necessary properties to be extracted, transported and, finally, disposed of. Whenever the natural material does not fulfil the necessary requirements, additives like water, foam, polymers, and fines, must be added, modifying the excavated ground to the desired conditions. The rheological properties of any excavated material, together with any additives, must be investigated and understood, as they will influence the flow behaviour of this conditioned material, directly affecting the machine operation and tunnel logistics. While studies assessing the flowability related to the EPB excavation of sand or clay soils are available, there is a lack of information on mixed soils. This paper presents the results from a testing campaign with mixed clay-sand samples, aiming to reproduce a simplified tropical weathered mixed soil, investigating its flow behaviour when changing certain controlled variables: clay-sand proportions, clay mineral, size of the clastic grain mixed with clay, water content, and additives (foam and polymers). Results from the tests conducted with a flow table, a slump test, and a rheometer device were compared, providing insights about the flow behaviour of the tested samples and its interaction with an EPB machine.},

keywords = {Earth Pressure Balance Machine, Flow behaviour, Fluidity, mixed sand and clay soils},

pubstate = {published},

tppubtype = {article}

}

@article{nokeye,

title = {Simulation of Fragmental Rockfalls Detected Using Terrestrial Laser Scans from Rock Slopes in South-Central British Columbia, Canada},

author = {Z Sala and DJ Hutchinson and R Harrap and D Gauthier},

doi = {https://doi.org/10.5194/nhess-19-2385-2019},

year  = {2019},

date = {2019-07-25},

journal = {Natural Hazards and Earth System Sciences},

volume = {19},

pages = {2385–2404},

abstract = {Rockfall presents an ongoing challenge to the safe operation of transportation infrastructure, creating hazardous conditions which can result in damage to roads and railways, as well as loss of life. Rockfall risk assessment frameworks often involve the determination of rockfall runout in an attempt to understand the likelihood that rockfall debris will reach an element at risk. Rockfall modelling programs which simulate the trajectory of rockfall material are one method commonly used to assess potential runout. This study aims to demonstrate the effectiveness of a rockfall simulation prototype which uses the Unity 3D game engine. The technique is capable of simulating rockfall events comprised of many mobile fragments, a limitation of many industry standard rockfall modelling programs. Five fragmental rockfalls were simulated using the technique, with slope and rockfall geometries constructed from high-resolution terrestrial laser scans. Simulated change detection was produced for each of the events and compared to the actual change detection results for each rockfall as a basis for testing model performance. In each case the simulated change detection results aligned well with the actual observed change in terms of location and magnitude. An example of how the technique could be used to support the design of rockfall catchment ditches is shown. Suggestions are made for future development of the simulation technique with a focus on better informing simulated rockfall fragment size and the timing of fragmentation},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Day2019,

title = {Brittle overbreak prediction for hydrothermal complex rockmasses with healed structure},

author = {JJ Day},

doi = {10.1007/s10064-019-01578-z},

year  = {2019},

date = {2019-07-24},

journal = {Bulletin of Engineering Geology and the Environment},

volume = {79},

pages = {1041-1060(2020)},

abstract = {In massive rockmasses under high in situ and deviatoric stresses, brittle spalling is the dominant damage process and failure mode and can result in significant depths of overbreak outside the excavation design dimensions during and after construction. Significant work has been done by researchers to develop empirical and mechanistic prediction tools for brittle overbreak in homogeneous rockmasses. Brittle overbreak in heterogeneous rockmasses that contain hydrothermal veins and breccia can behave quite differently than homogeneous rockmasses, with the result that the existing tools for homogeneous rocks are inadequate. In this study, overbreak profiles and excavation observations from part of the undercut level in the New Mine Level project at the El Teniente copper–porphyry mine in Chile and intact laboratory test data from the four local rockmass units are used to develop new functions based on brittle rock mechanics to improve the prediction of the depth of brittle overbreak for similar excavations in heterogeneous rockmasses. The dacite porphyry unit, which has few stockwork veins, most closely resembles the expected homogeneous brittle overbreak development. The stockwork mafic complex unit exhibits overbreak that exceeds the homogeneous prediction because the planar, pervasive quartz veins act as crack attractors and develop maximum crack propagation after initiation and immediate strength loss. The anhydrite breccia unit and a brecciated contact zone contain large clasts of contrasting mineralogy that act as crack arresters, resulting in minimal overbreak. The proposed functions to predict depths of brittle overbreak around tunnels in these heterogeneous rocks can ultimately be used to aid in excavation and ground support design.},

keywords = {Breccia clasts, Brittle failure, Copper–molybdenum porphyry systems, Heterogeneous rockmasses, hydrothermal veins, Rockmass characterization, Tunnel overbreak prediction},

pubstate = {published},

tppubtype = {article}

}

@article{Day2019b,

title = {Composite Geological Strength Index approach with application to hydrothermal vein networks and other healed intrablock structures in complex rockmasses},

author = {JJ Day and MS Diederichs and DJ Hutchinson},

doi = {10.1007/s10706-019-00980-4},

year  = {2019},

date = {2019-06-20},

journal = {Geotechnical and Geological Engineering},

volume = {37},

pages = {5285-5314},

abstract = {Conventional rockmass characterization and analysis methods for geotechnical assessment in mining, civil tunnelling, and other excavations consider only the intact rock properties and the discrete fractures that are present and form blocks within rockmasses. As modern underground excavations go deeper and enter into more high stress environments with complex excavation geometries and associated stress paths, healed structures within initially intact rock blocks such as hydrothermal veins, veinlets and stockwork (termed intrablock structures) are having an increasing influence on rockmass behaviour and should be included in modern geotechnical engineering design. Field observations indicate the conventional Geological Strength Index (GSI) does not accurately estimate rockmass strength and behaviour of complex rockmasses. A modified GSI chart to include intrablock structures and a new Composite Geological Strength Index (CGSI) methodology to combine multiple suites of rockmass structure using a weighted harmonic average are presented as tools to evaluate complex rockmasses that contain multiple suites of structure for application to geomechanical numerical models. CGSI is introduced and numerically validated using implicit and explicit finite element method numerical simulations of an underground excavation and a case study of field observations in an adit at the El Teniente mine in Chile. In both cases, the CGSI approach using the modified GSI chart results in an improved estimate of rockmass behaviour in implicit equivalent continuum numerical models when compared to a conventional GSI approach.},

keywords = {Complex rockmasses, Composite Geological Strength Index, Finite element method numerical models, Geological Strength Index, Healed intrablock structures, Rockmass characterization},

pubstate = {published},

tppubtype = {article}

}

@article{deOliveira2019b,

title = {The Consistency Index and Its Correlation with EPB Excavation of Mixed Clay–Sand Soils},

author = {DGG Oliveira and M Thewes and MS Diederichs and MJ Lato},

url = {https://link.springer.com/article/10.1007%2Fs10706-018-0612-x},

doi = {https://doi.org/10.1007/s10706-018-0612-x},

year  = {2019},

date = {2019-06-18},

journal = {Geotechnical and Geological Engineering},

volume = {37},

pages = {327-345},

abstract = {The behavioural properties of excavated ground have significant influence on the excavation process performed by an Earth Pressure Balance Machine (EPBM), as they are among the main factors responsible for maintaining the pressure ahead of the face, which affects face stability. Therefore, understanding the characteristics of the excavated material along with its flow behaviour is essential for a successful EPB tunnel drive. In scenarios involving the excavation of fine-grained soils containing clay minerals, the consistency index has been widely used as a guideline to define the ideal state of the excavated material. However, there are certain restrictions for the use of this index, the first of which are the Atterberg limits. These limits become more restrictive when mixed soils are involved. This study presents a brief review of the application of the consistency index and Atterberg limits in order to predict the performance of an EPB excavation. This study presents the results of a laboratory testing campaign with artificially mixed clay–sand soils by using a flow table as a preliminary flow assessment of cohesive soils.},

keywords = {Atterberg limits, Consistency index, Earth Pressure Balance Machine, EPB soil conditioning, Flow table, mixed sand and clay soils},

pubstate = {published},

tppubtype = {article}

}

@article{Bonneau2019c,

title = {The Use of Terrestrial Laser Scanning for the Characterization of a Cliff-Talus System in the Thompson River Valley, British Columbia, Canada},

author = {D Bonneau and DJ Hutchinson},

doi = {10.1016/j.geomorph.2018.11.022},

year  = {2019},

date = {2019-02-15},

journal = {Geomorphology},

volume = {327},

pages = {598-609},

abstract = {A postglacial river terrace along the Thompson River in Interior British Columbia, Canada has been monitored using terrestrial laser scanning (TLS) and high-resolution photography for almost a 3-year study to observe the deformation and failure processes, which result in changes in the slope morphology. Change detection using Multiscale Model to Model Cloud Comparison (M3C2) and a multi-scale dimensionality analysis (CANUPO) were performed on the 3-dimensional point cloud data to track the deposition patterns occurring in this active cliff talus system. Changes documented in the analysis of TLS data were verified using the high-resolution photography. Over 1.5 m of valley parallel retreat was captured in a section of the cliff face related to instability of a cobble and boulder horizon beneath a thick fluvial gravel unit. Because of the high-resolution remote sensing data, it was possible to observe a longitudinal sorting of grain sizes (i.e. fall sorting) in this cliff-talus system, whereby the size of individual particles controls the position on the slope. The overall mapped distribution of particle sizes on the slope remained constant for the almost 3-year study period. Flows of granular debris were observed in TLS change detection and the CANUPO analysis was able to display the longitudinal and lateral sorting of grain sizes that occurs during flow. This case history demonstrates that high resolution remote sensing data of large slopes permits us to link the geomorphic processes occurring in the cliff face with mass movement and deposition occurring on the talus slope below.},

keywords = {CANUPO, Grain size mapping, Granular flows, Machine learning, Talus, terrestrial laser scanning},

pubstate = {published},

tppubtype = {article}

}

@article{Vazaios2019,

title = {Assessing fracturing mechanisms and evolution of excavation damaged zone of tunnels in interlocked rock masses at high stresses using a finite-discrete element approach},

author = {I Vazaios and N Vlachopoulos and MS Diederichs},

url = {https://www.sciencedirect.com/science/article/pii/S1674775518303652},

doi = {https://doi.org/10.1016/j.jrmge.2019.02.004},

issn = {1674-7755},

year  = {2019},

date = {2019-02-13},

journal = {Journal of Rock Mechanics and Geotechnical Engineering},

volume = {11},

number = {4},

pages = {701-722},

abstract = {Deep underground excavations within hard rocks can result in damage to the surrounding rock mass mostly due to redistribution of stresses. Especially within rock masses with non-persistent joints, the role of the pre-existing joints in the damage evolution around the underground opening is of critical importance as they govern the fracturing mechanisms and influence the brittle responses of these hard rock masses under highly anisotropic in situ stresses. In this study, the main focus is the impact of joint network geometry, joint strength and applied field stresses on the rock mass behaviours and the evolution of excavation induced damage due to the loss of confinement as a tunnel face advances. Analysis of such a phenomenon was conducted using the finite-discrete element method (FDEM). The numerical model is initially calibrated in order to match the behaviour of the fracture-free, massive Lac du Bonnet granite during the excavation of the Underground Research Laboratory (URL) Test Tunnel, Canada. The influence of the pre-existing joints on the rock mass response during excavation is investigated by integrating discrete fracture networks (DFNs) of various characteristics into the numerical models under varying in situ stresses. The numerical results obtained highlight the significance of the pre-existing joints on the reduction of in situ rock mass strength and its capacity for extension with both factors controlling the brittle response of the material. Furthermore, the impact of spatial distribution of natural joints on the stability of an underground excavation is discussed, as well as the potentially minor influence of joint strength on the stress induced damage within joint systems of a non-persistent nature under specific conditions. Additionally, the in situ stress-joint network interaction is examined, revealing the complex fracturing mechanisms that may lead to uncontrolled fracture propagation that compromises the overall stability of an underground excavation.},

keywords = {Brittle failure, Discrete fracture networks (DFN), excavation damage zone (EDZ), finite–discrete element method (FDEM), tunnelling},

pubstate = {published},

tppubtype = {article}

}

@article{VAZAIOS201912,

title = {Assessment of strain bursting in deep tunnelling by using the finite-discrete element method},

author = {I Vazaios and MS Diederichs and N Vlachopoulos},

url = {https://www.sciencedirect.com/science/article/pii/S167477551830163X},

doi = {https://doi.org/10.1016/j.jrmge.2018.06.007},

issn = {1674-7755},

year  = {2019},

date = {2019-02-01},

journal = {Journal of Rock Mechanics and Geotechnical Engineering},

volume = {11},

number = {1},

pages = {12-37},

abstract = {Rockbursting in deep tunnelling is a complex phenomenon posing significant challenges both at the design and construction stages of an underground excavation within hard rock masses and under high in situ stresses. While local experience, field monitoring, and informed data-rich analysis are some of the tools commonly used to manage the hazards and the associated risks, advanced numerical techniques based on discontinuum modelling have also shown potential in assisting in the assessment of rockbursting. In this study, the hybrid finite-discrete element method (FDEM) is employed to investigate the failure and fracturing processes, and the mechanisms of energy storage and rapid release resulting in bursting, as well as to assess its utility as part of the design process of underground excavations. Following the calibration of the numerical model to simulate a deep excavation in a hard, massive rock mass, discrete fracture network (DFN) geometries are integrated into the model in order to examine the impact of rock structure on rockbursting under high in situ stresses. The obtained analysis results not only highlight the importance of explicitly simulating pre-existing joints within the model, as they affect the mobilised failure mechanisms and the intensity of strain bursting phenomena, but also show how the employed joint network geometry, the field stress conditions, and their interaction influence the extent and depth of the excavation induced damage. Furthermore, a rigorous analysis of the mass and velocity of the ejected rock blocks and comparison of the obtained data with well-established semi-empirical approaches demonstrate the potential of the method to provide realistic estimates of the kinetic energy released during bursting for determining the energy support demand.},

keywords = {Brittle fracturing, Deep tunnelling, Discrete fracture networks (DFN), Finite-discrete element method (FDEM), Hard rock excavations, Rockburst},

pubstate = {published},

tppubtype = {article}

}

@article{nokeyf,

title = {Measuring the in-situ response of tunnel support using high spatial resolution optical fiber strain sensing},

author = {B Forbes and N Vlachopoulos and MS Diederichs},

year  = {2019},

date = {2019-01-01},

urldate = {2019-01-01},

journal = {International Journal of Mining Science and Technology},

keywords = {Distributed optical fiber strain sensing, In-situ response, Tunnel support},

pubstate = {forthcoming},

tppubtype = {article}

}

@article{deOliveira2018b,

title = {EPB tunnelling through clay‐sand mixed soils: Proposed methodology for clogging evaluation},

author = {DGG Oliveira and M Thewes and MS Diederichs and L Langmaack},

url = {https://onlinelibrary.wiley.com/doi/abs/10.1002/geot.201800009},

doi = {https://doi.org/10.1002/geot.201800009},

year  = {2018},

date = {2018-08-01},

journal = {Geomechanics and Tunnelling},

volume = {11},

number = {4},

pages = {375-387},

abstract = {The clogging of Tunnel Boring Machine (TBM) tools by soils has long been investigated, owing to the numerous difficulties arising in shield tunnelling as a result. Its occurrence leads to operation delays owing to the frequent and lengthy interventions required to unblock the soil stuck to the excavation tools and screw conveyor. Several authors have proposed laboratory tests for evaluating the clogging potential, however, those include limitations, such as not considering the clay fraction in a soil. One of these methods is the empirical stickiness evaluation, whereby a mixer and a beater are used to define a clogging evaluation parameter. Following an extended test campaign using soils with different clay contents and minerals, it became clear that this method was not adequate to provide reliable information regarding the tendency of a soil to clog in a tunnel drive. A new device was then implemented, which adds to the first method a kinetic energy impulse via dropping of the beater from a certain height. This combination of methods could provide a reasonable approximation of the potential for clogging to occur along Earth Pressure Balance Machine (EPB) tunnel drives. This paper presents the results of the proposed combined methodology for clogging evaluation, as well as the research evolution that led to the addition of the beater dropping stage.},

keywords = {beater dropping stage, Clogging, clogging evaluation parameter, Earth Pressure Balance Machine, empirical stickiness evaluation, mixed sand and clay soils},

pubstate = {published},

tppubtype = {article}

}

@article{deOliveira2018,

title = {Consistency Index and Its Correlation with EPB Excavation of Mixed Clay–Sand Soils},

author = {DGG Oliveira and M Thewes and MS Diederichs and L Langmaack},

doi = {10.1007/s10706-018-0612-x},

year  = {2018},

date = {2018-06-18},

journal = {Geotechnical and Geological Engineering},

volume = {37},

pages = {327-345},

abstract = {The behavioural properties of excavated ground have significant influence on the excavation process performed by an Earth Pressure Balance Machine (EPBM), as they are among the main factors responsible for maintaining the pressure ahead of the face, which affects face stability. Therefore, understanding the characteristics of the excavated material along with its flow behaviour is essential for a successful EPB tunnel drive. In scenarios involving the excavation of fine-grained soils containing clay minerals, the consistency index has been widely used as a guideline to define the ideal state of the excavated material. However, there are certain restrictions for the use of this index, the first of which are the Atterberg limits. These limits become more restrictive when mixed soils are involved. This study presents a brief review of the application of the consistency index and Atterberg limits in order to predict the performance of an EPB excavation. This study presents the results of a laboratory testing campaign with artificially mixed clay–sand soils by using a flow table as a preliminary flow assessment of cohesive soils.},

keywords = {Atterberg limits, Consistency index, Earth Pressure Balance Machine, EPB soil conditioning, Flow table, mixed sand and clay soils},

pubstate = {published},

tppubtype = {article}

}