bluuebunny/crossref_metadata_2025 huggingface dataset:
Cellular irradiations with laser-driven carbon ions at ultra-high dose rates
Authors: Chaudhary Pankaj , Milluzzo Giuliana , McIlvenny Aodhan , Ahmed Hamad , McMurray Aaron , Maiorino Carla , Polin Kathryn , Romagnani Lorenzo , Doria Domenico , McMahon Stephen J , Botchway Stanley W , Rajeev Pattathil P , Prise Kevin M , Borghesi Marco
Published: January 2023

Objective. Carbon is an ion species of significant radiobiological interest, particularly in view of its use in cancer radiotherapy, where its large Relative Biological Efficiency is often exploited to overcome radio resistance. A growing interest in highly pulsed carbon delivery has arisen in the context of the development of the FLASH radiotherapy approach, with recent studies carried out at dose rates of 40 Gy s−1. Laser acceleration methods, producing ultrashort ion bursts, can now enable the delivery of Gy-level doses of carbon ions at ultra-high dose rates (UHDRs), exceeding 109 Gy s−1. While studies at such extreme dose rate have been carried out so far using low LET particles such as electrons and protons, the radiobiology of high-LET, UHDR ions has not yet been explored. Here, we report the first application of laser-accelerated carbon ions generated by focussing 1020 W cm−2 intense lasers on 10–25 nm carbon targets, to irradiate radioresistant patient-derived Glioblastoma stem like cells (GSCs). Approach. We exposed GSCs to 1 Gy of 9.5 ± 0.5 MeV/n carbon ions delivered in a single ultra-short (∼400-picosecond) pulse, at a dose rate of 2 × 109 Gy s−1, generated using the ASTRA GEMINI laser of the Central Laser Facility at the Rutherford Appleton Laboratory, Didcot, Oxfordshire, UK. We quantified carbon ion-induced DNA double strand break (DSB) damage using the 53BP1 foci formation assay and used 225 kVp x-rays as a reference radiation. Main Results. Laser-accelerated carbon ions induced complex DNA DSB damage, as seen through persistent 53BP1 foci (11.5 ± 0.4 foci/cell/Gy) at 24 h and significantly larger foci (1.69 ± 0.07 μm2) than x-rays induced ones (0.63 ± 0.02 μm2). The relative foci induction value for laser-driven carbon ions relative to conventional x-rays was 3.2 ± 0.3 at 24 h post-irradiation also confirming the complex nature of the induced damage. Significance. Our study demonstrates the feasibility of radiobiology investigations at unprecedented dose rates using laser-accelerated high-LET carbon ions in clinically relevant models.
Pre-conceptual studies of a travelling wave array antenna for the EAST
Authors: Li Jiahao , Ragona R , Hillairet J , Zhang Wei , Chen Zhaoxi , Zhang Xinjun , Yang Qingxi
Published: January 2023

One of the primary problems of ion cyclotron range of frequency (ICRF) systems in magnetic confinement experiments is the coupling of a large amount of radio frequency wave power through the plasma cut-off layer within the voltage limits of the antenna system. Travelling wave array (TWA) antennas have higher coupling than conventional ICRF antennas, which is manifested in a sharp and optimized k
// spectrum. As a pre-study of TWA applications in tokamaks, a TWA antenna with six consecutive straps and double-fin capacitors was conceptually designed for the experimental advanced superconducting tokamak (EAST). The antenna geometry was optimized to seek a low reflection coefficient for EAST ICRF heating scenarios. The design and simulation results of the TWA antenna are briefly presented. The results of the frequency sweep in vacuum show that a bandwidth of approximately 3 MHz with S
11 < −30 dB can be obtained. The peak of the k
// power spectrum is adjusted to ∼3–4 m−1 at the frequency of 34–36 MHz. In addition, the properties of the power flow and the characteristics of the wave field are also discussed by modelling the plasma facing the TWA antenna using a cold plasma medium. The results in this study may provide some reference and guidance for the study of TWA antennas and other ICRF antennas in magnetic-confined fusion devices like EAST or the Chinese Fusion Engineering Test Reactor.
Wave propagation in rotating magnetised plasmas
Authors: Gueroult Renaud , Rax Jean-Marcel , Fisch Nathaniel J
Published: January 2023

Wave propagation properties in a medium are fundamentally affected when this medium is moving instead of at rest. In isotropic dielectric media rotation has two noteworthy contributions: one is a mechanically induced circular birefringence, which materialises as a rotation of the polarisation, the other is image rotation, which corresponds to a rotation of the transverse structure of a wave. Here, we review the effect of rotation in a magnetised plasma. We also point out applications to both astrophysical phenomena and laboratory devices. We first show that the mechanical effect of rotation on polarisation is in a magnetised plasma superimposed onto the classical Faraday rotation and that failing to account for this new contribution could lead to errors in the interpretation of polarimetry data. We also demonstrate that image rotation is recovered in plasmas for a number of low-frequency magnetised plasma waves carrying orbital angular momentum and that this phenomenon holds promise for the development of new rotation diagnostic tools in plasmas.
Anti-de Sitter neutron stars in the theory of gravity with nonminimal derivative coupling
Authors: Kashargin Pavel E. , Sushkov Sergey V.
Published: January 2023

We consider neutron star configurations in the scalar-tensor theory of gravity with the coupling between the kinetic term of a scalar field and the Einstein tensor (such the model is a subclass of Horndeski gravity). Neutron stars in this model were studied earlier for the special case with a vanishing “bare” cosmological constant, Λ0 = 0, and a vanishing standard kinetic term, α = 0. This special case is of interest because it admits so-called stealth configuration, i.e. vacuum configuration with nontrivial scalar field and the Schwarzschild metric. However, generally one has Λ0 ≠ 0 and α ≠ 0 and in this case a vacuum configuration is represented as an asymptotically anti-de Sitter (AdS) black hole solution with the nontrivial scalar field. We construct neutron star configurations in this general case and show that resulting diagrams describing the relation between mass and radius of the star essentially differ from those obtained in GR or the particular model with α = Λ0 = 0. Instead, the mass-radius diagrams are similar to those obtained for so-called bare strange stars when a star radius decreases monotonically with decreasing mass. We show also that neutron stars in the theory of gravity with nonminimal derivative coupling are more compact comparing to those in GR or the particular model with α = Λ0 = 0 and suggest a way to estimate possible values of the parameter of nonminimal coupling ℓ. At last, using the Regge-Wheeler method, we discuss briefly the stability of obtained neutron star configurations.
Analysis methods for in-beam PET images in proton therapy treatment verification: a comparison based on Monte Carlo simulations
Authors: Moglioni M. , Kraan A.C. , Berti A. , Carra P. , Cerello P. , Ciocca M. , Ferrero V. , Fiorina E. , Mazzoni E. , Morrocchi M. , Pennazio F. , Retico A. , Rosso V. , Sportelli G. , Vitolo V. , Bisogni G.
Published: January 2023

Background and purpose: in-beam Positron Emission Tomography (PET) is one of the modalities that can be used for in-vivo non-invasive treatment monitoring in proton therapy. PET distributions obtained during various treatment sessions can be compared in order to identify regions that have anatomical changes. The purpose of this work is to test and compare different analysis methods in the context of inter-fractional PET image comparison for proton treatment verification.

Methods: for our study we used the FLUKA Monte Carlo code and artificially generated CT scans to simulate in-beam PET distributions at different stages during proton therapy treatment. We compared the Beam-Eye-View method, the Most-Likely-Shift method, the Voxel-Based-Morphology method and the gamma evaluation method to compare PET images at the start of treatment, and after a few weeks of treatment. The results were compared to the CT scan.

Results and conclusions: three-dimensional methods like VBM and gamma are preferred above two-dimensional methods like MLS and BEV if much statistics is available, since the these methods allow to identify the regions with anomalous activity. The VBM approach has as disadvantage that a larger number of MC simulations is needed. The gamma analysis has the disadvantage that no clinical indication exist on tolerance criteria. In terms of calculation time, the BEV and MLS method are preferred. We recommend to use the four methods together, in order to best identify the location and cause of the activity changes.
Development of the radiation and magnetic field tolerant DC/DC converter system for the ATLAS ITk Strip Detector
Authors: Dyndał M. , Cieśla K. , Dąbrowski W. , Górnicki E. , Guguła K. , Kopeć R. , Koperny S. , Korba A. , Krzempek D. , Stanecka E. , Wiącek P. , Wolter M.
Published: January 2023

The radiation and magnetic field tolerant step-down DC/DC converter system is developed to supply low-voltage power for the ATLAS ITk Strip Detector. The system is modular and consists of custom designed crates with embedded cooling plates, backplane, and DC/DC converter modules. Each converter module comprises two or four power channels. Each channel comprises a 48-to-11 V DC/DC converter, hardware overcurrent and overvoltage protection circuits, correction circuitry to compensate for voltage drops along the cables, and control and monitoring functionality based on the AMACStar chip. We present the design and performance of such a DC/DC converter system, including evaluation of its radiation tolerance.
Evaluation of mercury (II) iodide dosimeter for digital quality assurance in intracavitary radiotherapy
Authors: Jung Jae-Hoon , Han Moo-Jae , Yang Seung-Woo , Shin Yong-Il , Park Sung-Kwang
Published: January 2023

In intracavitary radiotherapy, it is essential to verify the correct location of radiation source among quality control items because an incorrect location will irradiate an unnecessary dose to normal tissues. As a basic study of digital line dosimeters, this study fabricated a unit cell dosimeter based on polycrystalline mercury (II) iodide (HgI2) and compared its performance with a diode. The study result showed that for reproducibility, the relative standard deviation (RSD) was 1.21%, satisfying the RSD evaluation criterion of within 1.5%. Considering linearity, the coefficient of determination R2 showed an excellent result of 0.9997. Regarding the evaluation of distance dependence, it showed a similar trend in general with a difference of 0.035 cm for intensity 50% when compared with the inverse square value. The angular dependence gradually decreased in intensity as the angle increased, showing a difference of up to 25%. This study suggests the applicability of a digital dosimeter for brachytherapy quality control by evaluating the performance of the HgI2 dosimeter. However, to develop it into a quality assurance (QA) dosimeter, correction factor for sensitivity according to angle should be applied. This study on dosimeter for candidate photoconductor materials can be used as basic data in all areas using radiation.
Quantitative comparison of planar coded aperture imaging reconstruction methods
Authors: Meißner T. , Rozhkov V. , Hesser J. , Nahm W. , Loew N.
Published: January 2023

Imaging distributions of radioactive sources plays a substantial role in nuclear medicine as well as in monitoring nuclear waste and its deposit. Coded Aperture Imaging (CAI) has been proposed as an alternative to parallel or pinhole collimators, but requires image reconstruction as an extra step. Multiple reconstruction methods with varying run time and computational complexity have been proposed. Yet, no quantitative comparison between the different reconstruction methods has been carried out so far.
This paper focuses on a comparison based on three sets of hot-rod phantom images captured with an experimental γ-camera consisting of a Tungsten-based MURA mask with a 2 mm thick 256 × 256 pixelated CdTe semiconductor detector coupled to a Timepix© readout circuit.
Analytical reconstruction methods, MURA Decoding, Wiener Filter and a convolutional Maximum Likelihood Expectation Maximization (MLEM) algorithm were compared to data-driven Convolutional Encoder-Decoder (CED) approaches. The comparison is based on the contrast-to-noise ratio as it has been previously used to assess reconstruction quality. For the given set-up, MURA Decoding, the most commonly used CAI reconstruction method, provides robust reconstructions despite the assumption of a linear model. For single image reconstruction, however, MLEM performed best of all analytical reconstruction methods, but took on average 45 times longer than MURA Decoding. The fastest reconstruction method is the Wiener Filter with a run time 4.3 times faster compared to MURA Decoding and a mediocre quality. The CED with a specifically tailored training set was able to succeed the most commonly used MURA decoding on average by a factor between 1.37 and 2.60 and an equal run time.
Dual unitary circuits in random geometries
Authors: Kasim Yusuf , Prosen Tomaž
Published: January 2023

Recently introduced dual unitary brickwork circuits have been recognised as paradigmatic exactly solvable quantum chaotic many-body systems with tunable degree of ergodicity and mixing. Here we show that regularity of the circuit lattice is not crucial for exact solvability. We consider a circuit where random 2-qubit dual unitary gates sit at intersections of random arrangements of straight lines in two dimensions (mikado) and analytically compute the variance of the spatio-temporal correlation function of local operators. Note that the average correlator vanishes due to local Haar randomness of the gates. The result can be physically motivated for two random mikado settings. The first corresponds to the thermal state of free particles carrying internal qubit degrees of freedom which experience interaction at kinematic crossings, while the second represents rotationally symmetric (random euclidean) space-time.
Estimating the Hydraulic Conductivity of jointed rock mass using Genetic Programming
Authors: Doan Luong T A , Karakus Murat , Nguyen Giang D , Smith Scott , Chester Chris , Hawker Robert
Published: January 2023

Ground engineering through injection of cementitious grouts or polymer resins is an integral part of fractured rock mass stabilisation by improving its maximum load carrying capacity, stiffness, cohesiveness and reduction in permeability. To optimise product delivery and achieve a high penetrability of product into the rock mass, it is imperative to understand the permeability characteristics or hydraulic conductivity of the rock mass. The hydraulic conductivity of the rock mass also dictates the type of polyurethane (PU) or cement-based products to be injected. For this purpose, a Packer test has to be conducted to measure the hydraulic conductivity of a rock formation which is an expensive and time-consuming process. Alternatively, a number of empirical methods that use rock mass classifications and rock joint properties Rock Quality Designation (RQD), Q-system (Q), Geological Strength Index (GSI), Joint Spacing (JS), Joint Aperture (a) proposed by a number of researchers that are capable of predicting hydraulic conductivity (HC). In this research, a predictive model between rock mass properties and HC is proposed using new approach - genetic programming (GP). For this purpose, a database of rock mass parameters including RQD, Q, GSI, JS, Joint Aperture (a), Second Permeability Index (SPI) and Packer test results available in the literature is established. The database is split into randomly selected training and testing sets. To assess the fitting quality, the sum of the absolute difference is used, while maximum depth on trees is set to control the bloat of the model. The performance is assessed with four statistical criteria and three GP models using different input combinations are proposed. These models have been converted into simple mathematical equations to calculate HC based on collected input data. In summary, two out of three models have successfully predicted HC with high correlation to the actual HC (R2 of testing sets ≈ 0.92). Therefore, this study has shown the feasibility of applying GP models into future prediction of HC for the initial phase of rock grouting design.
Detection of geometric properties of discontinuities on the Špičunak rock slope (Croatia) using high-resolution 3D Point Cloud generated from Terrestrial Laser Scanning
Authors: Lukačić H , Krkač M , Gazibara S Bernat , Arbanas Ž , Arbanas S Mihalić
Published: January 2023

Rock mass characterization is a very important part of engineering geological investigation. For a better understanding of the rock mass behaviour, it is crucially important to obtain as much as possible information about the discontinuity network, especially about orientation and the number of dominant discontinuity sets. The traditional methodology includes field mapping which dominantly produces a limited amount of data and consequently only a rough estimate about discontinuity network. To increase the number of measurements and to eliminate orientation bias, rock mass on the Špičunak rock slope in Gorski kotar, Croatia, was analysed using a combination of 3D Point Cloud and Textured Mesh Model generated from 3D Point Cloud by Poisson surface reconstruction. Both models were obtained from Terrestrial Laser Scanning. Two considerably different parts of a rock slope, with different weathering conditions and different degrees of fracturing were mapped. Discontinuities were mapped in the field and on the models using manual mapping techniques and semi-automated methods. Manual mapping on a 3D Point Cloud and Textured Mesh Model was done by Compass plugin and by Trace a polyline tool in Cloud Compare software version V2.12 and semi-automated mapping methods were done by Discontinuity Set Extractor and qFacet Fast Marching plugin for Cloud Compare software version V2.12. This study was used to show how the application of different methodologies, for the detection of geometric properties of discontinuities, influences the result. Statistical analyses were performed on the collected data to determine differences in the accuracy between the mapping techniques. Manual mapping on the 3D Point Cloud and high-resolution Textured Mesh Model showed good agreement with field measurements, apart from the higher number of discontinuities mapped by remote sensing methods. On the other hand, significant deviations were found between manual and semi-automated mapping techniques. Semiautomated methods did not correctly detect certain discontinuities, especially bedding planes that are perpendicular to a rock face. Also, semi-automated methods overestimate the number of discontinuity sets, especially in a highly weathered and highly fractured rock mass. These differences between methods can influence kinematic analysis results. Based on the results, an appropriate methodology was proposed to utilize the advantages of both manual and semiautomated methods. The proposed approach presents a powerful tool to accurately map and measure discontinuity orientation with results comparable to the field measurements.
Rapid tunnel scanning using a 360-degree camera and SfM photogrammetry
Authors: Janiszewski Mateusz , Prittinen Markus , Torkan Masoud , Uotinen Lauri
Published: January 2023

Photogrammetric scanning can be employed for the digitization of underground spaces, for example for remote mapping, visualization, or training purposes. However, such a technique requires capturing many photos, which can be laborious and time-consuming. Previous research has demonstrated that the acquisition time can be reduced by capturing the data with multiple lenses or devices at the same time. Therefore, this paper demonstrates a method for rapid scanning of hard rock tunnels using Structure-from-Motion (SfM) photogrammetry and a 360-degree camera. The test was performed in the Underground Research Laboratory of Aalto University (URLA). The tunnel is located in granitic rocks at a depth of 20 m below the Otaniemi campus in Espoo, Finland. A 10 m long and 3.5 m high tunnel section with exposed rock was selected for this study. Photos were captured using the 360-degree camera from 27 locations and 3D models were reconstructed using SfM photogrammetry. The accuracy, speed, and resolution of the 3D models were measured and compared with models scanned with a digital single-lens reflex (DSLR) camera. The results show that the data capture process with a 360-degree camera is 6x faster compared to a conventional camera. In addition, the orientation of discontinuities was measured remotely from the 3D model and the digitally obtained values matched the manual compass measurements. Even though the quality of the 360-degree camerabased 3D model was visually inferior compared to the DSLR model, the point cloud had sufficient accuracy and resolution for semi-automatic discontinuity measurements. The quality of the models can be improved by combining 360-degree and DSLR photos which result in a point cloud with 3x higher resolution and 2x higher accuracy. The results demonstrated that 360-degree cameras can be used for the rapid digitization of underground tunnels.
A novel method for automated trace discontinuity mapping at the Kemano hydroelectric tunnels in Western Canada
Authors: Morgenroth Josephine , Taylor Samantha , Yee Shelby
Published: January 2023

Mapping of geological structures, as well the subsequent generation of as-built drawings of mine and infrastructure tunnels, is a crucial step in the evaluation of excavation performance during and after construction. Mapping is typically a tedious paper-based process, which is occasionally done with the support of rugged tablets. In either case, geotechnical data is collected manually and then transcribed to a compatible format based on the software that is being used for post-processing or visualization. These traditional data collection practices offer limited quality control, decreased accuracy, and minimal standardization across geotechnical personnel. This paper presents an extension of a geotechnical mapping application, 3-Dimensial Axis Mapping (3DAM), for trace mapping using the RockMass Mapper to the drill and blast and TBM tunnels at the Kemano hydroelectric facility near Kitimat, Canada.

The aim of this study is to use the Mapper to capture trace discontinuities in TBM and blasted tunnels, and to integrate the data into industry-standard CAD software that is already used by construction teams to generate drawings. This new application of the 3DAM method will assist in obtaining more accurate geotechnical data in a digital form, allowing for quicker data analysis and more reliable excavation design in the long term.
Effect of roughness and pore pressure on shear behavior of rock joint under true triaxial loading conditions
Authors: Asahina D , Takemura T , Li Y
Published: January 2023

This paper presents the direct shear test to investigate the effect of the joint roughness and pore pressure on the shear behavior of rock joints. Recently, we have developed an experimental method for the direct shear test using true triaxial apparatus that can control three mutually perpendicular loads and pore pressure independently. The morphological properties of the joints were quantified using a non-contact 3D laser scanner to investigate the change in surface roughness due to shear and the effect of pore pressure. In addition, the time variation of shear load, normal displacement, and flow rate on the joint during shear sliding were measured, and the relationship with the change of the discontinuous surface after the experiment was discussed.
An experimental study on division of fracture ligament and evolution of fracture process zone in sandstone
Authors: Qiao Y , Zhang Z-X , Zhang Sh , Li Y-P , Chi L-Y
Published: January 2023

Fracture process zone (FPZ) is an irreversible deformation and damage zone in the front of a crack tip in rock. Only a few of them experimentally focused on the size development of FPZ during the loading process. Therefore, the DIC technology was used to monitor the development of FPZ in three-point bending beam rock specimens. The far-field displacements and strains were measured during the whole loading process. By analyzing the strains, the displacements and derivative distributions in the far-field, the fractured ligament is divided into three zones: Intact Zone, Crack Propagation Zone and Fracture Process Zone (FPZ). The FPZ first appears at the 60% pre-peak load, and its initial length is 4-6 mm. The length of the FPZ increases rapidly from the 90% pre-peak load to the 95% pre-peak load, and the increased length at this period occupies 47% of its full length. The length of the FPZ increases slowly near the peak load, and it reaches a maximum (15.5 mm) at the peak load.
Degradation of Fracture Characteristics on Coconino Sandstone Due to Water Content
Authors: Ko T Y
Published: January 2023

The water content of a rock affects its fracture characteristics, such as strength and fracture toughness. In this study, the effect of water content on the fracture characteristics, such as strength, fracture toughness and subcritical crack growth index under shear loading for Coconino sandstone was investigated. Here, experiments were conducted in two cases: completely dry and fully saturated. In particular, a short-beam compression specimen was employed to examine the fracture characteristics due to shear; in addition, the shear strength, mode II fracture toughness, and subcritical crack growth index under shear stress were obtained. Consequently, the shear strength and mode II fracture toughness decreased as the water content increased; however, the subcritical crack growth index remained almost the same without significant alterations. The effect of water on the strength reduction of rocks is related to chemical and physical corrosion, pore pressure increase, and frictional reduction. Previous investigations on the deterioration of strength by water have yielded similar results in this research. Under saturated conditions, the shear strength decreased by 15.5%, and the fracture toughness decreased by 11.8%, compared with dry conditions. Regardless of the dry or saturated condition, the subcritical crack growth indexnexhibited similar values.
Development and verification of a long-distance survey ahead of the tunnel face using excavation blasting as seismic source
Authors: Yamagami M , Ichiki T , Ito S , Murata K
Published: January 2023

In mountain tunnelling, it is important from the point of construction safety and effectiveness to obtain information about the ground ahead of excavation, such as the positions of fracture zones and possible water inflows which may pose problems during construction. Seismic reflection surveys are used to survey the ground ahead of the face. While the maximum surveyable distance of conventional methods is 100-150 m, the authors are working on extending this ability to provide a long-distance outlook for tunnelling work and have developed a method known as Blast Excavation Prospecting (T-BEP). As a result of comparing conventional method in a verification experiment, it is found that T-BEP can detect a fracture zone with a width of 35 m about 350 m ahead of the face with an error of about 40 m..
Effect of anisotropy of fracture surface on fluid flow
Authors: Torkan Masoud , Khorasgani Amir Hosseini , Uotinen Lauri , Bagbanan Alireza , Rinne Mikael
Published: January 2023

Characterization of fluid flow through rough fractures is an important issue in designing underground excavations, such as nuclear repositories or geothermal applications. Fluid flow could be influenced by several parameters such as contact areas, aperture, hydraulic and mechanical conditions. Contact area and aperture could be two crucial geometrical factors which control hydraulic and mechanical behaviors of fractures. These factors are rarely isotropic, and anisotropy is observed in different directions. In this research, photogrammetry, as a high precision method, was used to analyze morphology of a tensile fracture induced in granite. Experimental and numerical stress-flow tests on rock fracture were conducted in two different directions with diverse normal stresses and water pressures. Analyzing the regenerated 3D model of the fracture and hydromechanical tests predicts the anisotropy in flow rates in different directions. Numerical and experimental results are well fitted particularly in low-stress conditions. The obtained results show that anisotropy affects permeability since outlet flow rates in the different directions with the same initial water pressures differ by 7 % in experiments and 4% in numerical modeling.
Geomechanical characterization and analysis of the influence of durability tests on metabasalts
Authors: dos Santos Lemos Carolina Crissafe , de Souza Pires Costa Carolina , de Faria Silva Natália , Marques Eduardo Antonio Gomes , Jaques Daniel Silva
Published: January 2023

Laboratory tests are essential to provide knowledge on rock matrix properties, to predict field behaviour and to plan and execute improved engineering design. The paper presents the results of several laboratory tests performed on samples of a basic rock from N4 mine, located at Carajás Complex, on sound and cycled (artificially weathered) rock material. Carajás complex is located in Carajás sierra, Amazon region, North of Brazil, and is currently known as the biggest mineral province of the world. This region has great geological and economical importance and, on this context, studies related to rock mechanics are essential to evaluate open pit stability on long term periods. This study comprises a mineralogical, physical and geomechanical characterization of a metamorphised basalt rock, throughout a comprehensive laboratory test campaign encompassing the following tests: thin section description (including micropetrographic and weathering indices determination), physical properties, uniaxial compressive strength, point load strength, P wave propagation velocity, Schmidt hammer and durability test (accelerated cycling). Results from other works in the literature are presented to provide a basis for comparison. Petrographic analyses allowed classifying the rock as a hydrothermalized metabasalts. Micropetrographic index has shown that rock presents low weathering, with a higher quantity of sound minerals. Porosity, dry and saturated specific weight and water absorption capacity were calculated for samples with and without cycling and the results show that the number of water – salt cycles were not sufficient to cause a significant change on these physical indices. Wave propagation velocities were determined and the results are similar to the ones found in literature for similar rocks. Schmidt hammer were used to determine uniaxial compressive strength (UCS) trough Miller abacus. Another strength tests performed on rock samples were point load test, and the results were also used to correlate with UCS and other studies results. All these results were later compared with uniaxial compressive strength tests data and the values were similar. Furthermore, data from UCS tests were also used to calculate elasticity (Young) modulus and the material has shown a highly elastic behaviour.
Characterisation of Fine Particles Generated at Draw points During Sub-Level Cave Mining for Assessment of Mud Inrush Hazard
Authors: Musolino Matthew , Karakus Murat , Cox David , Chester Chris , Balog Glen , Nguyen Giang
Published: January 2023

The inundation of mud, known in the industry as ‘mud inrush’ is a hazard associated with caving mining methods. Ineffective inrush management strategies can result in sections of the mine lost, or in some cases, fatalities. Previous studies have focused on water and various percentages of fines (particles <2mm - <5cm) in draw points as risk indicators for the hazard. Standardised material tests were conducted on samples collected from a sub-level caving operation in Australia. Concrete slump tests were carried out on two in-situ mud samples based on their observed mobility. The immobile sample had 6% more material below 300μm and required a 2% higher moisture content to begin slumping and turn from plastic to soft flow. Shear strength tests reflected the higher plasticity of the immobile sample with a cohesive strength of 23.08 kPa compared to the second mobile sample of 9.16 kPa. The elemental assay revealed the mobile sample had lower iron oxide, and higher silicon oxide content than the immobile sample. The work presented in this paper indicates that fine fractions <0.6mm noticeably affect laboratory test results that are hypothesised to relate mud flowability and potential hazard.
Geometrical aspects in the consideration of actual opposed surface along shearing direction in rock joints
Authors: Guerrero-Miguel Diego-José , Prendes-Gero María-Belén , Álvarez-Fernández Martina-Inmaculada , González-Nicieza Celestino , Conde-Fenández Lucía
Published: January 2023

Shear behaviour of rock joints is strongly influenced by the roughness of its surface as the different failure mechanisms will be conditioned by the shape and distribution of the asperities and undulations in it. Currently, this surface can be digitalized using scanning methods directly in the field or in representative laboratory samples. After that, the surface is digitally reproduced using triangulation methods. This allows to analyse it using stablished parameters that do not depend on the arbitrariness of the technician. Despite the fact that 2D roughness parameters are still of great importance, these techniques are nowadays provoking a tendency to implement 3D measuring methods that allow to treat all the surface simultaneously and thus gathering valuable information of the rock joint as a whole. The vast majority of the 3D most powerful methods consider the area of the surface that is opposed against the shearing direction in order to determine the roughness, anisotropy and peak shear strength of the rock joint. However, not always the whole surface of each triangle that faces against shearing direction should be considered. In this work, a new methodology to consider the actual area of each triangular element that is involved in the shearing process is mathematically derived. Therefore, improving the accuracy of current methods, as well as the truthfulness of the mechanical characterization of rock joints.
A new approach to reduce blasting-induced vibration in tunnel blasting by utilizing the initiation time scatter of detonator
Authors: Yoon Y , Baek J , Jeong M S , Jeon S
Published: January 2023

The charge weight per delay is one of the major variables in empirical models for predicting the peak particle velocity in tunnel blasting. In many instances, the corresponding initiation times of the detonators often overlaps. The overlaps occur because of the initiation time scatter of each of the detonators. The overlap, in turn, causes an increased charge weight per delay, which consequently causes an increase in the blast-induced vibration. In this study, a novel technique is introduced for development of a blasting pattern exploiting the initiation time scatter of the detonators. The initiation time of 423 detonators was measured using a vibration monitoring instrument and a high-speed camera. From the data obtained, a standard deviation of the initiation times of the detonators was determined. The probability of overlap of the initiation times of the detonators was calculated using a Monte Carlo simulation. After simulating both a new blasting pattern utilizing the initiation time scatter of the detonator and the conventional blasting pattern 10,000 times each, it was determined that, in the new blasting pattern, the number of sets in which four or more blastholes initiated simultaneously decreased from 17,595 to 1604. Moreover, the probability that four or more blastholes initiated simultaneously in a blasting round decreased from approximately 70% to 12%.
An investigation on relations between dissipated energy and dynamic compressive strength of Kemi-peridotite at high strain rates
Authors: Ozoji T M , Zhang Z X , Aladejare A E , Zhang N , Guan X
Published: January 2023

Dynamic properties of rocks are essential for planning sustainable engineering structures in regions prone to dynamic loading as well as effective fragment size distributions during quarrying activities. Due to the vast application of dynamic rock properties, several studies have been conducted on the context. However, studies on relations between dissipated energy and dynamic compressive strength are scanty. The aim of the study is to investigate relations between dynamic compressive strength and dissipated energy during fragmentation of Kemi-peridotites at high strain rates. To achieve this, cored specimen was prepared according to recommendations of the International Society for Rock Mechanics and fractured using the split Hopkinson’s pressure bar. Results indicate that the dissipated energy during rock fracture generally increases at high dynamic compressive stress. However, the regression square of dissipated energy and dynamic compressive strength plots suggest poor relations between both variables. Further evaluation of measured strain at maximum dynamic compressive stress indicates that strain in specimen continued significantly after maximum dynamic compressive stress was attained. However, evaluations on relations between dissipated energy and strain indicates that energy dissipation continued along a significant portion of the measured strain during rock fracture at high strain rates. Visual evaluation of broken fragments also indicates good relations between dissipated energy and fragmentation results of Kemi-peridotites at high strain rates. Based on study findings, dissipated energy provides improved indices for evaluating strain and fragment size distribution while dynamic compressive stress provides indices on maximum stress required for rock failure.
Virtual reality learning system for remote rock mass mapping
Authors: Janiszewski Mateusz , Zhang Xiaoyun , Uotinen Lauri , Rinne Mikael
Published: January 2023

Rock mass quality mapping is essential in rock engineering and mining projects. However, the current manual mapping approach and its teaching are restricted due to the dangerous nature of work near rock walls and the constraints of resources. Therefore, a virtual reality learning system for teaching remote mapping of rock mass quality was developed at Aalto University. Two rock wall sections of an underground tunnel and a roadside rock-cut were scanned using photogrammetry and imported as high-resolution textured 3D models. The user wears a head-mounted display and performs mapping using a pointing device. The system collects the measurements automatically and assists the user in rock mass mapping. Along with the development of the system, qualitative research was conducted to evaluate user performance in a gamified learning system. The results demonstrate that with proper game elements implemented, the learning system can be used to steer student behaviour towards the target range. Once set up, the VR system is a tireless, user-paced aid in training and teaching.
Assessing the tunnel stability in brittle rocks based on strain bursting assessment
Authors: Aujmaya Lans , Vazaios Ioannis , Paraskevopoulou Chrysothemis
Published: January 2023

Strain bursting is a phenomenon associated with deep underground excavations and tunnelling in brittle hard rocks that result in a sudden and violent failure, posing high risks and damage. This work aims to assess the strain bursting and the energy response characteristics and develop a guideline that can be utilized in the preliminary investigation stage. The obtained results are intended to enable predicting different brittle behaviours in deep geological environments. Elastic stress analysis using the DISL approach based on boundary element method is established (EX3-software) for the assessment of two tunnel geometries (circular, horseshoe) in granitic rock mass. Two different stress states are modelled to simulate the potential stress regime. The analysis’ results demonstrate that different geometries affect the energy storage capacity and result in different behaviour regarding the bursting potential of the rock mass.
Use of flow-back and pressure rebound data improves the minimum stress estimation in a tight claystone formation
Authors: de Lesquen C , Armand G
Published: January 2023

Andra is in charge of the long-term management of all radioactive waste in France. It has acquired between 2000 and 2008 a vast amount of stress data around the area selected to host the French deep geological repository for high activity and long-lived radioactive waste. The minimum principal stress was estimated from hydraulic fracturing tests and the fracture closure pressure was interpreted during the shut-in phase. However, in the Callovo-Oxfordian claystone, this method results in a minimum horizontal stress that is much larger than the vertical stress even when vertical fractures were clearly generated. As the uncertainty on the weight of the overlying sediments is low, the validity of this technique in a tight claystone formation with very limited leak-off is questioned. Several tests were reinterpreted using the flow-back data and the pressure rebounds when they were recorded. The new interpretation gives consistent results between the wells drilled around the Meuse/Haute-Marne underground research laboratory and the magnitude of the minimum principal stress matches well the actual orientation of the induced fractures. These data support the use of flowback tests as the preferred stress determination technique in tight formations.
Predicting rockburst damage scale in seismically active mines using a classifier ensemble approach
Authors: Toksanbayev N , Adoko A C
Published: January 2023

Rockburst still remains one of the most important sources of hazards in underground mine industry. This phenomenon results in many accidents and casualties in many underground mine projects around the world. Despite the scientific achievements in rock mechanics and engineering, the accurate prediction of rockburst damage potential is still challenging due to the complexity of seismic event occurrence. Hence, this paper aims to develop a reliable classifier ensemble to rockburst intensity in underground mine excavations subjected to seismicity. High quality rockburst database consisting of 254 case histories was used for the study. The classifier ensemble was developed through aggregation of several commonly used machine learning classifiers using the weighted voting. The performance of the classifier ensemble was evaluated using several indicators, namely: accuracy, recall, precision, and F1-score. The overall results indicate that the proposed classifier ensemble achieved good performance metrics and outperformed some existing empirical methods. It is concluded that the classifier ensemble could assist engineers to properly assess rockburst damage and contribute to selecting adequate ground control measures.
Effects of the initial stress and spalling strength on spalling around deposition holes and tunnels
Authors: Figueiredo B , Vatcher J , Sjöberg J , Ivars D Mas
Published: January 2023

Spalling in the deposition holes and tunnel stability are of concern for the design of deep geological repositories for spent nuclear fuel. A 3D numerical stress model, including a single deposition tunnel and multiple deposition holes to analyse the potential for spalling resulting from the excavation phase, was developed for the proposed repository location at the Forsmark site. Several potential initial stress field cases and spalling strengths of the intact rock were considered. The magnitudes of the factor of safety, the spalling depth, the minor principal stress, and the differential stress were evaluated. The results showed that no spalling in the central deposition hole is indicated for the most likely stress field, and the occurrence of spalling and the spalling depth are minimised for a maximum horizontal stress aligned approximately parallel to the tunnel axis. For spalling occurrence and depth of spalling, the magnitude of the maximum horizontal stress is more critical than its orientation, and the spalling strength is more critical than the magnitude of the maximum horizontal stress. No instability problems were indicated in the vicinity of the roof for all analysed stress cases.
An advanced constitutive model for transversely isotropic rock - Evaluation of two different regularization approaches
Authors: Mader Thomas , Schreter Magdalena , Hofstetter Günter
Published: January 2023

The mathematical description of the material behavior of rock is a demanding task in engineering practice. Rock is classified as a frictional cohesive material characterized by highly nonlinear mechanical behavior with irreversible deformation, strain hardening, strain softening and degradation of stiffness. In addition, depending on the origin of a particular rock type, the orientation of minerals and grains as well as the formation of stratification planes lead to inherent anisotropic behavior. Especially in stratified rock types like shales or phyllites, often the special case of transversely isotropic material behavior is encountered. In a previous work, a novel continuum-based material model for describing both, the highly nonlinear and transversely isotropic material behavior of rock, denoted as TI-RDP model, was presented. By means of the linear mapping of the Cauchy stress tensor into a fictitious isotropic configuration, an established isotropic damage plasticity model for rock was extended. In this contribution two different regularization approaches, which are well established for isotropic models, i.e., the mesh-adjusted softening modulus and the implicit gradient-enhancement, are adopted for the TI-RDP model. Based on uniaxial tension and triaxial compression tests considering different orientations of the principal material directions with respect to the direction of axial loading, their capabilities are assessed in terms of predicting the direction-dependent mechanical behavior in a mesh-insensitive manner.
Weakening of tensile strength of granitic rock by HV-HF-AC actuation of piezoelectric properties of Quartz: a 3D numerical study
Authors: Saksala T , Ruiz R A Rubio , Kane A , Hokka M
Published: January 2023

High-voltage and high-frequency alternating current (HV-HF-AC) excitation of piezoelectric properties of Quartz is a potential method to induce cracks in granite. This was recently shown in a numerical feasibility study [6], where cracking was induced on cylindrical rock samples made of granite by sinusoidal AC excitation at the frequency of ~100 kHz and the amplitude of ~10 kV. However, this study did not investigate the weakening effect due to this cracking on the tensile strength of the sample. The present study addresses this topic numerically. For this end, a numerical method based on 3D embedded discontinuity finite elements for rock fracture and an explicit time stepping scheme to solve the coupled piezoelectro-mechanical problem is adopted. Rock heterogeneity and anisotropy are accounted for at the mineral mesotructure level. A preliminary numerical simulation demonstrates that the HV-HF-AC treatment reduces the tensile strength of a cylindrical granite sample by 12 %, making it thus a potential non-conventional pre-treatment method in comminution and excavation of Quartz bearing rocks and ores.