bluuebunny/crossref_metadata_2025_split huggingface dataset:
Rock Engineering in Canadian Mining – Highlights, Challenges and Contributions
Authors: Falmagne Véronique 
Published: August 2024

ABSTRACT:
Recent years have been characterized by some significant world events and the continuing evolution of mining in a mature jurisdiction, such as Canada. Topics that will be discussed include managing Covid-19 and social expectations; expanding Canadian mining into harsh environments, in the Arctic and at great depth; and the need to extract more value from every drill hole in the context of rising costs and the push to reduce uncertainty.
From March 2020 to the second half of 2022, the mining industry had to manage through the Covid 19 pandemic and is now navigating a period of inflationary pressures in addition to meeting social expectations in terms of inclusion and collaboration with local populations and environmental excellence. In the Canadian Arctic, the Covid-19 pandemic represented a tremendous challenge to maintain operations without putting workers and local populations in remote communities at risk. The response from both mine management and individuals was overwhelming in its seriousness, inventiveness, and teamwork. The measures that were put in place in record time ensured workers and community safety and demonstrated true leadership in Canada's most remote regions.
Mining in the Canadian Arctic presents a host of challenges and opportunities which lend themselves to the development of technical solutions. For example, these include managing groundwater when mining below the permafrost, introducing the first paste backfill system operating in the Arctic and optimizing cemented rockfill in sub-zero temperatures.
At the other end of the spectrum, Canadian operations are reaching unprecedented depths, mining down to 3.4 km in environments where the stress around excavations exceeds the uniaxial compressive strength of the rock. Managing seismic and rockfall risks in such environments requires robust risk management systems based on continuous monitoring and analysis, design review and research. The risk management framework for seismically active mines is presented, highlighting successes and areas of continuous improvements.
Geotechnical models are the foundation of all rock engineering hazard assessment and risk management programs. Geological and structural models form the basis of any geotechnical characterization program. With rising costs and the need to reduce uncertainty there is growing pressure to extract greater value from every opportunity to look at the rock. In most cases, this means increasing the quality and the quantity of data extracted from drill cores and drill holes. Technological advances in core scanning and borehole geophysics are leveraged to enhance geotechnical databases and models.
Experimental Research on Characteristics of CO2-CH4 Transport in Water-Bearing Carbonate Gas Reservoirs
Authors: Huang Yize , Elsworth Derek , Li Xizhe , Hu Yong , Wu Zhenkai , Guo Qimin , Pei Xiangyang 
Published: August 2024

ABSTRACT:
We investigate the transport properties of CO2-CH4 under high pressure conditions in both dry and variably saturated porous and fractured carbonates containing native H2O and CH4. The specific focus is on determining optimal CO2 injection rates for maximizing CH4 recovery. A series of experiments involving fluid displacement at the core scale is conducted, considering various initial H2O and CH4 saturations and CO2 injection rates. Examination of the resulting residence time distribution (RTD) curves reveals several findings: (1) the larger pores support advective transfer with diffusion from the smaller pores contributing to tailing in the RTD; (2) the porous medium to free phase diffusion coefficient ratio (D’) in dry samples is related to porosity (φ) as D’ = φ3; (3) the presence of formation water increases heterogeneity, reduces effective porosity and decreases the Peclet number of saturated samples by two orders of magnitude and transforms D’; (4) displacement by CO2, alleviates water blockage in the removal of CH4 and switches transport to that of gas-phase convection. This research enhances our understanding of fundamental phenomena governing multiphase-component transport in porous and fractured media, contributing valuable insights to enhanced gas recovery and carbon storage in variably saturated carbonate reservoirs.

1. INTRODUCTION
Injecting captured CO2 into depleted reservoirs is an essential technology to decrease carbon emissions and may concomitantly enhance recovery of heavy or condensed hydrocarbons (Oldenburg et al., 2001; Liu et al., 2013; Liu et al., 2019). Despite this clear utility, such reinjection methods have been seldom used in carbonate gas reservoirs due to unknown response. Currently, the large number of water-bearing gas reservoirs with low recovery urgently require more effective techniques to improve gas production (Honari et al., 2016; Mohammed et al., 2021; Pan et al., 2023). Successful implementation of the injection of CO2 for enhanced recovery of hydrocarbons and concurrent CO2 storage holds great promise if the fundamental response can be defined and thus potential benefits established (Pooladi-Darvish et al., 2008; Pentyala et al., 2021; Cheng et al., 2022).
We explore the transport characteristics of CO2-CH4 at high pressure (32MPa) in both dry and variably-saturated porous and fractured carbonates containing native H2O and CH4 – in particular the role of water saturation on the CO2 breakthrough profile and subsequent gas recovery. Injection rates are varied to examine both diffusive and advective response and afterward define CO2 injection rates that optimize CH4 recovery. We conduct a series of core-scale fluid displacement experiments for a spectrum of initial H2O and CH4 saturations and CO2 injection rates. Subsequently, experimental data and analytical model are fitted.
Coupling Between Weathering and Fracture: Finite Element Modeling of Granite Weathering Using Cohesive Elements
Authors: Xu Tingting , Arson Chloé 
Published: August 2024

ABSTRACT:
This research examines the initiation of fracture propagation by weathering and explores how an escalation in fracture density accelerates weathering rates. By integrating cohesive zone elements into an ABAQUS FEM software through user-defined subroutines, we simulate arbitrary fracture paths and examine the effect of weathering on stress redistribution and fracture propagation in the bedrock. The weathering rate is scaled based on the magnitude of fracture opening displacements, which control fluid exchanges. Simulations in a topographical setting reveal that weathering significantly affects cohesive fracture propagation, particularly in the upper 30 meters where weathering accelerates both fracture propagation and the depletion of reactant mass, in particular unweathered biotite. These findings underscore the potential of the proposed methodology for predicting the interplay between weathering and fracture development, and thus explaining the formation of landscapes as a result of climatic events and ensued environmental processes.

1 INTRODUCTION
Fractures play a crucial role in enhancing the connectivity of pore spaces, thereby significantly increasing rock permeability. This facilitation of fluid flow is instrumental in accelerating mineral dissolution processes, as evidenced by Hu et al. (2011). Fracture systems increase the specific surface of the bedrock, which escalates the likelihood of chemical reactions (St. Clair et al., 2015), thereby altering rock structure through the interplay of chemical, mechanical, and hydrological processes. Such transformations are pivotal in promoting further weathering, as was demonstrated in studies that document the coupling between bedrock weathering and fracture propagation (Navarre-Sitchler et al., 2015). Reversely, weathering enhances rock permeability (Worthington et al., 2016). A simplified homogenization model was recently introduced (Lebedeva and Brantley, 2023) to explain the impact of reactive flow in fractured rock.
Despite these developments, the feedback mechanisms between weathering and bedrock porosity evolution via microcracks and metric fractures remain under-explored. In order to address this gap, Cohesive Zone (CZ) elements are inserted within the Finite Element Method (FEM) model initially developed by Xu et al. (2022). The fracture represented by the CZ elements, comparable in length to the volume elements, are significantly larger than the microcracks depicted in the damage variable of the homogenization model implemented in the Finite Elements (FEs), offering a novel approach to examining the intricate feedback effects between weathering and porosity evolution in bedrock. The homogenization approach is summarized in Section 2. The coupling between the CZ tractionseparation law and the continuum variables of the homogenization model is explained in Section 3. Numerical results are presented in Section 4, and conclusions are drawn in Section 5.
A New Evaluation Method for Drillability of Hot Dry Rock Considering In-Situ Temperature in Formation
Authors: Li Kun , Sun Zhaowei , Wang Zikang , Wu Xiaoguang , Ye Shanlin , Liu Muchen , Wang Xiangyang 
Published: August 2024

ABSTRACT:
Traditional assessment approach of rock drillability is limited in deep geothermal drilling, especially in Hot Dry Rock (HDR), due to the ultra-high abrasive resistance and temperature conditions. This paper proposed a new evaluation method to assess the drillability of HDR. A series of drilling tests were conducted on Gonghe granites under in-situ high temperature conditions. The effect of five key parameters, including bit weight, RPM, torque, penetration depth and rock temperature on rate of penetration (ROP) was investigated by HDR drilling experiments. Then, an unsupervised clustering method was employed to classify the ROP and its correlated parameters reasonably. Finally, the HDR drillability levels correlated with ROP were specified. Results showed that the ROP increases with a growth in rock temperature, which is conductive to promote the bit penetration. HDR is assigned a rating from 1 to 4 taking into account the effects of rock temperature, with a higher rating corresponding greater ease of drilling. The ROP may be classified into four modes: slow (0.28-2.39mm/min), slow-medium (0.56-3.09mm/min), medium (3.31-8.93mm/min) and fast (5.63-15.93mm/min). Our works are expected to provide a theoretical basis for the optimization drilling performance in HDR.

1. INTRODUCTION
Hot dry rock (HDR) possesses the attributes of being environmentally friendly, highly efficient, and stable, making it a significant alternative energy source for the future. Efficient exploitation of geothermal resources in HDR is of great significance to the global energy transition. Drilling is the dominant technology for development HDR resources, accounting for approximately 35% to 60% of the overall engineering investment. This technology necessitates drilling holes into the high-temperature reservoirs composed of exceptionally hard crystalline rock formations, such as granite. However, the mechanical properties of HDR, i.e., high temperature, high hardness and abrasive resistance, significantly decrease the rock drillability (Kelkar et al., 2016; Lu and Wang., 2015; Zeng, 2015), resulting in bit wear and low drilling efficiency in real operations (Si et al., 2019; Wang et al., 2019). Hence, it is essential to develop an evaluation method for drillability of HDR, which is respected to enhance the drilling performance and reduce the operation costs in HDR resource excavation.
On Sweet Spot in Percussive Drilling: Single Impact Experiments
Authors: Borges Dos Santos J. V. , Richard T. , Kovalyshen Y. 
Published: August 2024

ABSTRACT:
This work presents results of research on down-the-hole percussive drilling and investigates the origin of the observed non-monotonic dependency of the rate of penetration (ROP) on the applied weight-on-bit (WOB). Field experiments were carried out at a mining site with a drilling rig that was instrumented with a tailored monitoring system. The field data clearly shows in several instances that the ROP is maximized for specific values of WOB; this phenomenon is commonly referred to as Sweet Spot. In order to investigate whether the Sweet Spot is intrinsic to the bit-rock interface or stems from the system dynamics, laboratory experiments were conducted with a novel apparatus that drills shallow holes with discrete events (one impact at a time); prior to each impact of the piston on the drill bit, the initial conditions are guaranteed to be re-established. The effect of drilling parameters can be studied independently with the experimental setup, such as WOB, piston impact energy, and angular displacement of the bit between successive impacts. Preliminary results show no intrinsic dependency of the rate of penetration with the applied WOB.

1 INTRODUCTION
Down-the-hole (DTH) percussive drilling is a widely employed technique in mining and civil engineering. In DTH drilling, a pneumatically or hydraulically activated piston (or hammer) strikes the drill bit, which fragments the rock surface and propagates the borehole. Concurrently, the drill bit rotates, and either compressed air or water is used to flush out rock debris and maintain bit cooling (Hustrulid and Fairhurst, 1971; Amjad, 1996; Zhao et al., 2014; Depouhon, 2014).
In the context of DTH percussive drilling, several laboratory and field experimental studies have reported the existence of optimal operating conditions that result in the highest drilling efficiency and effectiveness (Cheetham and Inett, 1953; Lundquist, 1968; Hustrulid and Fairhurst, 1972; Unger and Fumanti, 1972; Amjad, 1996; Schunnesson, 1998; Kivade et al., 2015; Ghosh et al., 2017; Shen et al., 2022). The rate of penetration (ROP) increases with the increase of weight-on-bit (WOB) up to a point and then starts to decrease with a further increase in WOB (refer to Figure 1). This phenomenon is commonly referred to in the literature as the Sweet Spot (Depouhon, 2014); in this paper, however, it will be referred to as Optimum Drilling State (ODS). Despite numerous studies investigating potential causes of the Optimum Drilling State (ODS), there remains a lack of consensus or definitive explanation for its occurrence. This absence of a precise understanding regarding the correlation between drilling parameters and the manifestation of the ODS impedes the development of optimization and control algorithms aimed at maximizing the Rate of Penetration (ROP) amidst changing borehole conditions (Song et al., 2019).
Numerical Simulation Study of Proppant Migration and Settlement Behavior in Complex Fractures
Authors: Kangjia Zhao , Jie Wang , Hualei Xu , Houshun Jiang 
Published: August 2024

ABSTRACT:
Hydraulic fracturing is one of the main technologies for developing unconventional oil and gas resources. Effective placement of proppant in the fracture has an important impact on the formation of channels with high conductivity. In order to study the migration and settlement law of proppant in complex fracture, computational fluid dynamics (CFD) is used to simulate the migration process of proppant in fracture, and drag and lift models are added in the simulation process. The proppant migration and settlement law under different impact factors is analyzed from three dimensions: sand dune length ratio, maximum height ratio of sand dune and sand dune area ratio. The simulation results show that the proppant tends to enter and settle in the branch fracture close to the entrance of the main fracture. When the main-branch fracture angle is smaller, the proppant is more likely to be carried into the branch fracture for settlement. When the fracture is inclined downward, the sand dune pattern in the main fracture moves to the depth of the fracture as a whole, which is not conducive to the effective filling of proppant near the wellbore. Increasing the viscosity and injection rate of fracturing fluid, the proppant migration trends in the main fracture and branch fracture are different. The numerical simulation results and conclusions will provide reference for the optimization of fracturing construction in the field.

1. INTRODUCTION
Unconventional oil and gas resources have gradually become the focus of development (Liao et al., 2022). The unconventional oil and gas resources are mainly shale oil and gas, tight sandstone oil and super heavy oil (Meng et al., 2023; Ardakani et al., 2022). The rock properties of shale and sandstone make sand fracturing technology as the preferred measure for reservoir stimulation (Hou et al. 2014; Zhao et al., 2012). Successful sand fracturing requires effective fluid flow channels in the fracture (Yao et al., 2022). At the same time, a large amount of proppant is injected into the fracture to support the fracture and prevent it from closing.The migration and settlement trend of proppant directly affects the hydrofracture morphology and conductivity after fracturing. Therefore, it is necessary to study the impact of different factors on proppant placement during fracturing.
Mechanical Responses and Dynamic Seepage Evolution Laws of Rock Mass Containing Inclined Rough Fracture Under Three-Dimensional Stress
Authors: Tang J. Z. , Zhao G. M. , Chang J. C. , Yin Z. Q. , Duan M. K. , Wang T. 
Published: August 2024

ABSTRACT:
The stress-seepage tests are conducted on sandstone samples that containing inclined rough fracture under three-dimensional stress conditions. The surface scanners are utilized to scan and analyze the morphology of the fractures before and after the tests, studying the relationship between morphology and mechanical and seepage characteristics. The research results demonstrate that: (i) Confining pressure has a significantly strengthening effect on the peak stress and crack damage threshold, while pore pressure has the opposite effect; (ii) As the confining pressure increases, the JRC in vertical (JRCV) and absolute difference between JRC in vertical and horizontal (|JRCV−JRCH|) nonlinear decreases, this trend can be described by power function properly; (iii) A revised permeability calculation formula for a rough single fracture was proposed by introducing the fractal dimension D. The negative correlation between the fractal dimension of fracture surface and permeability, which confirms the validity of the revised formula; (iv) Based on gray threshold segmentation methods, the seepage channels have been identified and segmented, the ratio of the area of seepage channels to the entire fracture surface area, defined as connectivity ratio Ф, exhibited a basic positive correlation with permeability. During the compression, the permeability dynamic evolution can be divided into two modes.

1. INTRODUCTION
In rock engineering fields such as water conservancy and underground resource exploitation, the coupling effect between the seepage field and stress field of fractured rock masses has a significant impact on the response of rock masses under engineering actions (Snow 1969, Tsang and Tsang 1987). The hydraulic conductivity of fractures is much greater than the intact rock matrix, fractures are the main pathways for water movement in rock masses. The complex fracture network system is composed of interconnected individual fractures, and the study of the groundwater movement mechanism within individual fractures forms the foundation of research on complex fracture network systems (Ju et al. 2013, Zhao et al. 2017, 2021, Khanal et al. 2019, Li et al. 2022).
Time-Dependent Fracturing in Granite Under Uniaxial Compression
Authors: Zafar Sana , Hedayat Ahmadreza , Moradian Omid 
Published: August 2024

ABSTRACT:
Time-dependent processes in rock govern its long-term behavior; hence, understanding these processes is very important, especially for long-lasting surface and underground structures. A series of laboratory-based uniaxial compression tests coupled with acoustic emission (AE) monitoring was conducted to explore the influence of control mode and loading rate on AE characteristics and the damage processes of granite. The experiments were carried out under axial displacement controlled and load controlled modes at varying displacement and loading rates. The stress-strain behavior, strength, AE characteristics, and failure modes were analyzed. The loading and displacement rate in the two control modes significantly affected the mechanical properties of the rock specimen. Results indicated a decrease in rock strength by 15% when the displacement rate reduced from 1μm/s to 0.05 μm/s, and in load-controlled mode, the strength reduced by 20% as the loading rate decreased from 0.55 kN/s to 0.02 kN/s. With the increase in the loading and displacement rates, a noticeable decrease in the time of failure was observed. Acoustic emission (AE) results showed that initially, the loading rates had minimal effect on the damage source parameters, whereas during crack propagation, their influence became substantial. Explosive or tensile events were obtained as the dominant failure mechanism. Under a high displacement rate, the proportion of the explosive events was higher; as the displacement rate reduced, the proportion of the explosive events reduced, and shear events increased. Load-controlled experiments showed insignificant variation in the proportions of the different fracturing mechanisms by changing the loading rate. Decreasing b-value indicated the evolution of large-magnitude events under high rates of loading. This study offers fundamental insights into how brittle rocks undergo damage evolution under various loading and displacement rates, whether in load-controlled or displacement-controlled conditions.

1. INTRODUCTION
Understanding the mechanisms of microcracking in rocks over time is crucial for assessing the long-term stability of various rock engineering structures, including tunnels, mining chambers, rock slopes, and nuclear waste repositories. This understanding is essential for evaluating the long-term stability of rock engineering structures such as tunnels, mining rooms and pillars, rock slopes, and nuclear waste repositories (Diederichs and Kaiser 1999, Nara et al. 2010, Paraskevopoulou et al. 2018, Zhang et al. 2020, and Zhao et al. 2022). Furthermore, time-dependent factors also significantly influence the exploration and utilization of resources such as oil and gas reservoirs and enhanced geothermal systems (EGS), as noted by Demarest (1976) and Cornet (2007).