Mark S. Diederichs

Queen's University | QueensU · Department of Geological Sciences and Geological Engineering

The use of acoustic emission (AE) monitoring in brittle rock laboratory testing is one of the most accurate methods for measuring damage evolution and failure. In this study, AE data was collected from two separate laboratory testing programs. The first program consists of a series of unconfined compressive strength (UCS) tests completed on moderat...

The tensile strength of rock is a critical material property in rock engineering design. In many cases, anisotropic rocks make up the intact part of the rockmass that practitioners encounter during site investigation and construction of critical infrastructure including, for example, excavations for hydropower, rapid transit development, mining of...

Brazilian tensile strength (BTS) testing in standard practice is a practical method to approximate tensile strength for rock core using the conversion of axial compressive vertical and diametral loading to horizontal tensile stress in the centre of the core disk. The method, however, routinely inflates tensile strength, using peak tensile stress ca...

There has been a wide effort to develop constitutive models to aid prudent engineers or scientists in understanding materials' behaviour in rock mechanics. Hoewever, there is still a lot of work to be done when considering time-dependent behaviour that can lead to instabilities and progressive failures which cannot be captures when considered the c...

In laboratory direct shear testing of rock fractures, it is current practice to shear an ellipsoidal specimen in the direction of its longest axis, as this allows for the greatest amount of data collection and is assumed to be the direction of shear displacement for unoriented boreholes with inclined, planar joints. However, it is unclear where the...

Brazilian tensile strength (BTS) testing is crucial for hard rock engineering projects. Despite being uncommon, there is growing interest in monitoring strain during the test to assess true tensile strength, analyze geological effects, and study fracture development. Given the heterogeneous strain fields in BTS tests, obtaining full-field strain ma...

As mining operations pursue deeper and larger excavations, the accurate assessment of the risk of excessive rock deformations caused by brittle fracturing and dilation/bulking near excavation boundaries becomes increasingly important. To address this, the bonded-block modeling (BBM) approach such as UDEC-Voronoi has been widely used to simulate the...

The tensile strength of rock and rock-like materials is a critical material property in rock engineering design and the prediction of rockmass behaviour to mitigate any potential failure that may affect personnel safety or damage property. This study presents new instrumentation guidelines to the Brazilian Tensile Strength (splitting tensile streng...

The tensile strength of rock and rock-like materials is a critical material property in rock engineering design and the prediction of rockmass behaviour to mitigate any potential failure that may affect personnel safety or damage property. This study presents new instrumentation guidelines for the Brazilian Tensile Strength (splitting disc tensile...

The tensile strength of rock and rock-like materials is a critical material property in rock engineering design and the prediction of rockmass behaviour to mitigate any potential failure that may affect personnel safety or damage property. This study presents new instrumentation guidelines to the Brazilian Tensile Strength (splitting tensile streng...

The excavation of tunnels in brittle rocks with high in-situ strengths under large deviatoric stresses has been shown to exhibit brittle failure at the periphery of tunnels parallel to the maximum in-situ stress. This failure can either occur instantaneously or after several hours due to the strength degradation that is implicitly and indirectly co...

Ultra-long-term storage of spent nuclear fuel and other waste products is most likely to be accomplished through the construction and safe closure of deep geological repositories (DGRs). Around the world, numerous countries are planning, designing and in some cases, building such repositories in sound rock between 400 and 1000 m below surface. In O...

The importance of discontinuity geomechanical properties is increasing as the use of numerical models with explicit or discrete rock mass structure becomes the state of practice. Joint normal stiffness and joint shear stiffness are two parameters that characterize the deformation behaviour of discontinuities. This paper presents practical guideline...

The uniaxial compressive strength (UCS) test is crucial in determining the strength and stiffness behavior of intact rock and is frequently utilized by industry to determine project site characteristics. A fundamental procedure of UCS testing is strain response measurement. Conventionally, discrete strain measuring devices such as extensometers and...

Discontinuity behaviour can have a large impact on geotechnical engineering design; therefore, it is essential to determine their geomechanical properties to predict rockmass behaviour and mitigate any potential failure that may affect personnel safety or damage property. Geotechnical numerical software programmes that discretely simulate discontin...

The uniaxial compressive strength (UCS) test is a key tool used by the geotechnical industry to determine the strength and stiffness behavior of intact rock. A fundamental procedure in the process of these experiments is strain response measurement. The standard method of measuring UCS test strain response is to use discrete strain measuring device...

Two fundamental fracturing mechanisms act as the primary drivers for burden removal in rock blasting: the propagation of radial cracks from the borehole due to the internal detonation pressure and the tensile failure relatively close to a free surface associated with spalling. A third mechanism may also influence cratering when the emitted compress...

Direct shear testing is a common laboratory method used to define peak and residual shear strengths of rock discontinuities. Current procedures for laboratory direct shear testing outline two techniques: (1) single stage, and (2) multi-stage direct shear testing. Multi-stage direct shear testing is the practice of repeatedly shearing the same rock...

The long-term strength and time-to-failure of brittle rocks has become increasingly important with the increased interest in the storage of used nuclear fuel in deep geological repositories. This paper critically reviews and analyzes the currently available time-to-failure data for various brittle rock types. The current best approach on estimating...

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...

This results presented in this paper follow the basic principles and methodology developed for horizontal Single Hole Blast (SHB) testing using terrestrial laser scanning (TLS), introduced in Part 1, and shows specific SHB test applications as a mean to investigate rock blasting behavior. Part 1 introduced a detailed procedure for consistent and sy...

Numerical modelling of excavations in rock has advanced considerably in recent decades. While continuum numerical models form their basis in methods which can be verified by analytical solutions, discontinuum and hybrid numerical modelling software are challenging to verify. This necessitates the development of processes that can verify individual...

Salt blasting involves significant differences when compared with hard rock blasting, due to the distinct geomechanical properties. Rock salt is characterized by moderately high stiffness (20-40 GPa) and very low resistance in tension (~1 MPa). Energy losses near the blasthole in rock salt are at least an order of magnitude higher than in typical h...

Excavation damage zone (EDZ) Grain-based model (GBM) calibration Stress-fracturing of rock Cohesive crack model Stress-dependent permeability a b s t r a c t 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...

Discontinuity geomechanical properties are becoming increasingly more important to measure as the use of numerical models with explicit structure becomes the state of practice. Joint normal stiffness and joint shear stiffness are two parameters that characterize the deformation behaviour of discontinuities, and in many cases when determined from la...

The uniaxial compression test is crucial in determining the strength and stiffness behavior of intact rock and is heavily relied upon in industry and research. A fundamental procedure in the process of these experiments is the strain-response measurement which is most often measured using discrete strain measuring devices such as extensometers and...

Time-dependency manifests as several different mechanisms, namely creep, swelling, consolidation, stress relaxation, and dilatancy. Creep is an important mechanism to consider in the design of projects with ultra-long lifespans or for projects developed in rocks that readily creep, such as rock salt. Creep models are typically calibrated at the lab...

The construction of any geotechnical project relies heavily on the in-situ geomaterial’s geomechanical properties which are determined through laboratory testing. The uniaxial compression test is crucial in determining the strength and stiffness behaviour of intact rock and is relied upon heavily in industry and research. A fundamental procedure in...

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 fiber strain sensors, and borehole pressure cells. The instrumentation spanned across a 15.24 m lengthwise segment of the relatively massive granitic pillar that was sit...

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...

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 wi...

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 transp...

Today the Geotechnical Baseline Report (GBR) and the Geotechnical Database Report, (GDR), are becoming standard contractual documents in any underground project to describe the expected geological and geotechnical conditions. The GBR contains a synthesis of all the acquired geotechnical data listed in the more comprehensive and purely factual GDR,...

Joint roughness directly affects the behaviour of discontinuities at the laboratory scale and the rockmass at the excavation scale. For the design of large underground infrastructure projects (e.g. deep base tunnels for transportation and deep geological repositories for the storage of nuclear waste), laboratory testing is required to measure geome...

The primary function of rock bolts is to stabilize the weakened ground around the periphery of the tunnel by transferring the load from the weakened rock to the more stable rock deeper into the rock mass. Through the use of a fiber optic sensor technology that has been developed by the authors, axial strain along the fully grouted rock bolt can be...

While many researchers have reported unstable sliding, or stick-slip movement, of smooth joints in direct shear testing, there is no consensus on the physical mechanisms that cause this phenomenon. Some researchers relate this behaviour to an increased static friction gained in stationary contact of the joint surfaces, while others describe it as a...

The Finite Discrete Element Method (FDEM) can be used for forward modelling of tunnels in brittle rock. This method does however pose challenges with respect to verification. To improve confidence in forward modelling, a process to upscale micro-mechanical properties from calibrated lab test simulations, to tunnel scale models must be developed. Th...

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 necess...

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 wi...

Intrablock structures such as hydrothermal veins and stockwork have been observed to control additional or delayed development of ground failures in deep mines and tunnels. Key geomechanical parameters for excavation design are typically measured using unconfined compressive strength (UCS) laboratory tests of intact rock, but it is currently standa...

Unlined underground pressure tunnels and shafts have been the standard design in Norway since the 1960s, and in some cases, shotcrete is used as both temporary and permanent support. For low-porosity rocks in such an environment, the geomechanical response of the host rock with respect to water saturation under unconfined and confined loading remai...

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 mechan...

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...

Mechanical scaling consists of removing hazardous and loose rock from surfaces, following excavation by blasting. Mechanical scaling using heavy machinery involves scraping surfaces systematically to effectively cover most of the excavation and mitigate risks associated with loose materials. Quality control and performance assessment of mechanical...

Halite, commonly referred to as Rock Salt, presents remarkable and often unique mechanical behavior. Rock salt exhibits pronounced time dependent deformation under deviatoric stresses, denoted as creep. Rock salt also requires unconventional blasting methods due to its low blast wave impedance and very weak tensile strength. The mechanical behavior...

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...

Mine development and operation in North and South America as well as Australia and Asia manage rockbursting conditions as a routine but always complex and difficult challenge. The hazard and the associated risks can be managed based on local experience, monitoring, informed data rich modelling and holistic understanding in a mature mining operation...

Rock salt exhibits a strain and time dependent response under deviatoric stresses. The practical implications of this creeping behavior have been studied extensively for the design of underground excavations. Advanced constitutive models combined with modern computing capabilities can be used for the analysis of rock salt behavior under complex str...

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 ha...

In this study, a step-by-step methodology on how to simulate sparsely to moderately fractured, highly interlocked rockmasses is demonstrated, depicting the necessary steps from the discontinuity data collection stage to the rockmass scale numerical modelling. For this purpose, the first step involves the use of LiDAR to collect field joint data in...

The main objective of this paper is to examine the influence of the applied confining stress on the rock mass modulus of moderately jointed rocks (well interlocked undisturbed rock mass with blocks formed by three or less intersecting joints). A synthetic rock mass modelling (SRM) approach is employed to determine the mechanical properties of the r...

A monitoring program employed to measure the support performance of spiles in a recent Canadian tunnel project is presented. Of novelty in this research is the use of a distributed optical strain sensing technique to measure the load distribution of individual spile support members at a spatial resolution of 0.65mm. The distinct challenges and tech...

The convergence-confinement method (CCM) is a method that has been introduced in tunnel construction that considers the ground response to the advancing tunnel face and the interaction with installed support. One limitation of the CCM is due to the numerically or empirically driven nature of the longitudinal displacement profile and the incomplete...

While laboratory direct shear testing of rock fractures in constant normal stress (CNL*) conditions are well established in practice, testing in constant normal stiffness (CNS) boundary conditions is less common and few recommendations on CNS testing are available regarding appropriate laboratory testing conditions. This paper provides practical gu...

Clogging occurrence has long been an issue for EPB drives, through not only pure clay soils, but also in mixed soils with sufficient clay content for clogging to happen. It occurs when clay particles adhere to metal surfaces of excavation tools because of the attractive forces of the clay particles and the presence of water between the clay-metal s...

The construction of an underground opening leads to changes in the in situ stress regime surrounding the excavation. The opening influences the rock mass owing to the redistribution of the stresses and results in the disturbance of the surrounding ground. At great depths, massive to slightly or moderately fractured rock masses are usually encounter...

The stress at onset of yielding for the walls of deep underground excavations in hard rock is significantly less than the laboratory strength of intact rock samples. The wall stability is rather controlled by the microfracturing strength of the rock (i.e. crack propagation (CD) and initiation (CI) thresholds). Factors such as loading and unloading...

Managing rockbursting conditions in mine development and operational environments is a complex and difficult challenge. The hazard and the associated risks can be managed based on local experience, monitoring, and informed data-rich analysis. On the other hand, blind development for deep tunnelling is being carried out around the world at depths in...