bluuebunny/crossref_metadata_2025_split huggingface dataset:
Optimizing the flatness of 4H-silicon carbide wafers by tuning the sequence of lapping
Authors: Zhang Xi , Liu Xiaoshuang , Wang Yazhe , Zhu Ruzhong , Zhang Xuqing , Zhang Yiqiang , Wang Rong , Yang Deren , Pi Xiaodong 
Published: January 2023

Abstract
In this letter, we optimize the flatness of 4H silicon carbide (4H-SiC) wafers by tuning the sequence of single-sided lapping, enlightened by the different mechanical properties of the Si face and C face of 4H-SiC. After wire sawing, the coarse lapping and fine lapping are carried out to rapidly remove the surface damage and optimize the flatness of 4H-SiC wafers. From the point of view of controlling the values of the bow and warp of 4H-SiC wafers, the coarse-lapping sequence of the C-face lapping followed by Si-face lapping is beneficial, while the preferred fine-lapping sequence is Si-face lapping followed by C-face lapping. Nanoindentation tests indicate that the C face has higher hardness and lower fracture toughness than the Si face. This gives rise to thicker surface damage at the C face after the wire sawing. After removing the same amount of wire-sawing induced surface damage, the thickness of residual surface damage of the C face is higher than that of the Si face after the coarse lapping. The fine lapping basically removes all the surface damage and creates the near-perfect C face and Si face. The higher amount of surface damage of the C face after the coarse lapping and the higher fracture toughness of the near-perfect Si face after the fine lapping can tolerate more plastic deformations, which gives rise to the superior flatness of the C-face-followed-by-Si-face coarse lapped and the Si-face-followed-by-C-face fine lapped 4H-SiC wafers, respectively.
Assessment of the creep behavior of siltstone for the Snowy 2.0 hydropower station using multistage uniaxial creep tests
Authors: Kheir S Abou , Bamford B , Brogiato A , Carli G De , Lambrughi A 
Published: January 2023

Abstract
Multistage uniaxial creep tests with durations up to four months were performed to investigate the time-dependent behavior of the siltstone rock formations into which the Snowy 2.0 hydropower station will be excavated. Short term experimental tests are used to determine the stress levels of the creep tests and to assess the effect of creep on the short-term parameters of the siltstone. The samples have been collected from boreholes at a depth of about 650-850 meters beneath the surface where the power station complex will be constructed. The samples are extracted from the Ravine Beds unit formation and the main lithology is composed of siltstones with interlaminated to interbedded sandstones. The relative percentage of siltstone/sandstone within the rock mass ranges from 80/20% to 50/50% and on average is 70/30%. The siltstone features a medium strength matrix, a very stiff matrix, and a very low porosity. During the creep tests, the results show consistently negligible secondary creep deformations after the full development of the primary stage, and this finding was found to be valid regardless of the initial water content of the specimens. Additionally, a tertiary creep is observed on some of the tests under failure stress levels, where the tertiary creep of the siltstone is described with sudden brittle creep deformations. Ultimately, empirical and rheological creep models are used to interpret and fit the creep deformations. The results of the models are compared to creep deformations measured in the laboratory.
Cross-scale rockmass characterization by high resolution seismic imaging around tunnels
Authors: Cosma Calin , Enescu Nicoleta 
Published: January 2023

Abstract
Reflection seismic surveys are relevant to the detailed characterisation of crystalline bedrock. Relatively small-scale features, even single fractures, can demonstrably be detected. Integrated analysis and modelling of geological, hydrogeological and geophysical data is instrumental in the interpretation of reflection seismic data. This requires the inference of the nature of the reflectors, e.g. lithological contacts or deformation zones and resolving the orientation ambiguity of the reflectors. Brittle deformation zones and large fractures may be heterogeneous in their detailed structure, making their characterization a challenging task. Several examples of structure characterization ahead and around tunnels are presented, with focus on the safety assessment for engineering and mining applications. Seismic imaging techniques adapted for tunnels and galleries are presented with examples from high resolution seismic surveys carried out at ONKALO (Finland) and Äspö HRL (Sweden). Studies performed over a span of several years demonstrate that large fractures identified initially through geological mapping, can also be found, positioned and characterized by seismics at the small scale of tunnels and/or boreholes. We show that reflection seismic surveys are relevant to the detailed characterization of crystalline bedrock. The detection of some distinctive features, even large-scale, can be uncertain if the survey layout is spatially constrained. Combinations of borehole and tunnel measurements using measuring arrays with diverse orientations helped reduce the location ambiguities and are recommended to be used in mining and tunneling rock characterization surveys wherever possible.
Method to obtain 3D point clouds of tunnels using smartphone LiDAR and comparison to photogrammetry
Authors: Torkan Masoud , Janiszewski Mateusz , Uotinen Lauri , Rinne Mikael 
Published: January 2023

Abstract
Remote sensing methods, for example, photogrammetry and laser scanning can be employed to scan rock masses by digitizing underground spaces or slopes. To reconstruct a 3D model by photogrammetry, plenty of photos should be captured. This process is time-consuming and can be dangerous when the rock mass is unstable. Therefore, rapid capturing methods are needed to reduce the acquisition time. This can be achieved with LiDAR scanners that capture a 3D point cloud with a high-speed pulsed laser beam. However, the cost of laser scanners is high, which limits their usability. Apple’s iPhone 12 Pro Max smartphone is equipped with a LiDAR sensor and is much cheaper than conventional laser scanners. Several mobile applications for 3D models using the smartphone Lidar have been developed, making the scanning process easy. Therefore, smartphones can be used for rapid scanning of unstable surfaces of tunnels and slopes. In this study, 3D point clouds (3DPC) of a tunnel wall of the Underground Research Laboratory of Aalto University (URLA) are obtained by a high-resolution digital camera and smartphone LiDAR. The models are analyzed and compared. The results show the quality of the smartphone LiDAR sensor is adequate for generating 3D models of underground spaces.
Influence of Temperature and Deviatoric Stress on Creep Behavior of Rock Salt
Authors: Moslehy A , Alshibli K A 
Published: January 2023

AbstractRock salt deposits are used as depositories for hazardous wastes and oil due to their excellent mechanical properties for depositories such as low permeability and self-healing. The creep behavior of rock salt plays a major role in the long-term stability of rock salt depositories. Temperature and deviatoric stress significantly impact the creep behavior of rock salt. This paper studies the influences of temperature and deviatoric stress on the creep behavior of natural single-crystal rock salt specimens using creep experiments. A special triaxial thermal cell was developed to conduct the experiments. Prismatic specimens were cut out of a large mass of a sample that was acquired from Windsor Salt Mine, Ontario, Canada. The prepared specimens were tested in one-dimensional creep experiments at 20, 100, and 150° C temperatures and under 1 MPa confining pressure. Constant deviatoric stresses (σd) of 4, 10, and 12 MPa were applied to the specimens. Increasing the applied deviatoric stress and temperature caused an increase in the accumulated strain during the experiments and resulted in higher steady-state strain rates. Although the transient strain rate is increased at elevated temperatures, it appears to be insensitive to the applied deviatoric stress.
Coupled Thermo-Mechanical Study of Crack Initiation Stress Threshold in Porous Sandstone
Authors: Moravej S , Mutaz E , Serati M , Williams D J 
Published: January 2023

Abstract
The increasing depth of tunnels and underground mining operations worldwide has resulted in the rise of deep mines at temperatures well above 50°C. Such unwanted thermal gradients not only adversely impact the physical and mechanical behaviours of the rock mass but could also affect the safety of underground mines leading to temporarily and permanently shutting down the operation. The combination of high temperature and high-stress conditions further culminates in explosion-like fractures like rockburst and spalling, which are the main problems in deep mining and tunnel constructions. Spalling is identified as an abrupt explosion-like rock failure that occurs spontaneously and can endanger tunnelling and mining operations, causing injuries and fatalities, and necessitating investigation of the effect of temperature on rock behaviour. It is known that the spalling strength is correlated with the internal crack initiation in low-porosity and brittle crystalline rocks. This paper investigates this phenomenon and examines the influence of coupled thermo-mechanical conditions on the crack initiation stress level of sandstone samples. True triaxial compression tests were carried out on 50 mm sandstone cubes from room temperature (25°C) to 100°C using a high temperature true triaxial testing facility. The results suggest that temperature can have a significant impact on crack initiation and the spalling strength of rock, particularly at low confinement.
Experimental Device for the Determination of Fracture Toughness at High Pressure
Authors: Muñoz-Ibáñez A , Herbón-Penabad M , Delgado-Martín J 
Published: January 2023

Abstract
Mode I fracture toughness (KIC
) is a relevant property in many applications involving rock mechanics. However, the conventional methods for its determination only consider ambient pressure conditions. Although the available experimentation on high pressure fracture toughness shows that KIC
tends to increase with confining pressure not all the published results provide with the same evidence. Among the available methodologies for KIC
testing, the pseudo-compact tension (pCT) test approach provides with a number of operational advantages over other alternatives and makes it a good candidate for its extension to high pressure research. Based on it, we have designed and constructed a simple high-pressure cell that may be easily installed in any conventional compression frame without modifications to test pCT specimens. The cell may accommodate either a gas or liquid as confining fluids and work with samples of up to 50 mm (~2”) diameter. In order to verify the expected performance, we have conducted different calibration tests, including leak rate and the assessment of axial friction. For the demonstration and validation of the experimental approach presented, we have selected virtually impervious poly-methacrylate (PMMA) and Corvio sandstone samples. Results obtained at room conditions and at high pressure are compared and discussed.
Laboratory block model tests simulating rock anchoring in rock mass
Authors: Grindheim B , Aasbø K S , Li C C , Høien A H 
Published: January 2023

Abstract
Rock anchors are used to stabilise large scale infrastructures. Failure of rock anchors could threaten the stability and lead to severe economic and social consequences. The design of rock anchors is based on four principal failure modes, which are breakage of the steel tendon, tendon-grout interface failure, grout-rock interface failure and rock mass failure around the anchor. The current dimensioning methods are uncertain due to limited knowledge of the grout-rock bond strength and the rock mass failure. The dimensioning method against rock mass failure is based upon the weight of the overlying rock mass in an inverted cone and the shear strength of the rock mass along the inverted cone, which results in conservative design of rock anchors. A small laboratory model was developed to evaluate the rock mass failure of a rock anchor at maximum pullout load. The model contained small concrete blocks set in a staggered pattern representing the rock mass. The loading of the model showed that the load was transferred to the sides by rotation and lifting of the blocks, which created a small load bearing arch in each layer during loading. This resulted in the model being able to carry much higher loads than what was calculated with the dimensioning methods. Back calculation of the results from the physical tests in UDEC showed the same arching effect in each layer during loading. The testing has improved the knowledge on the concept of how the load transfer from a rock anchor to the rock mass.
Interpreting ultrasonic pulse velocities and elastic properties of lac du bonnet granite under compression
Authors: McDonald M R , Gaines S N , Diederichs M S 
Published: January 2023

Abstract
The measurement of ultrasonic velocities in rock core is a straightforward, non-destructive, economic method to estimate rock material properties conducted by emitting high frequency acoustic waves through the rock core. The velocities of compressional and shear waves (P- and S-waves, respectively) are influenced by the unique microstructural characteristics of the rock. Once wave velocities and bulk density for each sample have been determined, the dynamic elastic material constants such as Young’s modulus, Poisson’s ratio, and shear modulus can be calculated. In theory, it is expected that the dynamic properties would be similar to the static properties calculated in uniaxial compression strength (UCS) tests. In UCS tests, elastic parameters are estimated using stress-strain relationships at approximately 50% of the peak strength. However, dynamic properties from the UPV method often do not match static properties. In this study, dynamic testing of the rock core is completed under two broad stress conditions: no compression and axial compression (UCS). This allows for a direct comparison between dynamic UPV testing data, and static data, and should produce a closer match between the dynamic and static testing data when dynamic UPV testing is conducted under stress conditions similar to the static testing stress state.
High-speed train induced vibration measurements in fresh tunnel shotcrete layer
Authors: Siren T , Dahlström M , Cronvall T 
Published: January 2023

Abstract
Existing coastal railway track has been undergoing for renovation and improvement work aiming to raise train speed and shorten the travel time between Turku and Helsinki. The track has 16 existing tunnels of which 14 has been renovated between 2019 and 2021. Majority of the tunnels have been reinforced by system and shotcrete and rock bolts. The water seepage control has been solved by using PE sheets with additional 100 mm fibre shotcrete layer as fire protection layer. After the track and tunnel improvements, the track was test driven with two different trains: a high speed SM train unit and a two storey intercity train unit. The speeds used were higher than the current allowed speeds aiming to study the potential to increase the travel speed. One of the most restrictive parameters for the increase is the pressure shock of high speed train entering the tunnel. Too high pressure shock will cause inconvenience for the passengers and can cause damage in tunnel lining structures. Also currently no clear guideline exists what speed limits need to be used for trains entering tunnels with curing shotcrete. To study these matters the test run train units were instrumented including with pressure sensors. The conclusions about the pressure shocks are investigated briefly in the paper.
Intact rock deformation bimodularity: an experimental study
Authors: Muñiz-Menéndez Mauro , Pérez-Rey Ignacio 
Published: January 2023

Abstract
Rock deformability under tensile stresses plays an important role in different scenarios like, e.g., in the mechanical behaviour of roofs in underground openings, hydraulic fracturing, dilatometer tests performed in massive rock masses or in tensile strength tests. Different authors have proved that the tensile deformation modulus of the intact rock can be significantly different than that obtained under compressive load, being this so-called ‘bimodularity’ often ignored. In this work, we present preliminary results from uniaxial compressive and tensile strength tests carried out in three rocks with a testing apparatus recently modified to be able to perform both types of tests. Experimental results show that the deformational behaviour of the rocks studied is dependent on the type of load applied. The present work aims at contributing to a better understanding of the deformational behaviour of rocks, in particular when subjected to uniaxial tensile loads as well as in dealing with future updates of existing test methodologies.
Comparison of different methods to characterise the abrasivity potential and mechanical properties of carbonates with respect to its relevance for practical purposes in excavation technologies
Authors: Aderhold M , Disselkamp C , Formanski R , Grimberg M , Grineisen A M , Kroenert L M , Ogan M S , Romahn H , Sandkühler R , Skonetzki C , Ullah F , Zinke B H , Duda M , Witte L C , Brajer C , Backers T 
Published: January 2023

Abstract
The characterisation of the abrasivity potential of carbonates plays an important role for drilling-based excavation technologies, for example in tunneling or geothermal exploration. Although carbonates are known to have a rather low abrasivity, they have been associated with severe excavation performance reductions. We compared different methods to characterise the abrasivity potential of carbonates with respect to its applicability for practical purposes in excavation technologies. In this study, seven carbonate rocks were investigated which differ with respect to their microstructural properties and degrees of dolomitisation. These carbonate rock samples were selected from different lithological units in Germany (Jurassic: Kelheimer limestone, Wachenzell dolomite, Solnhofen limestone, Pappenheim limestone, Treuchtlingen limestone; Devonian: Wülfrath limestone, Brilon limestone). Rock samples were characterised with respect to basic physical properties (density, ultrasound velocity), microstructure (thin section analysis, XRD), mechanical properties (uniaxial compressive strength UCS, splitting tensile strength STS) and commonly applied abrasivity indices (Cerchar abrasivity index test CAI, LCPC test) as well as derived indices (equivalent quartz content eQu). Our results confirm that the tested carbonate rocks show low abrasivity indices in terms of CAI, LCPC and eQu with an increase in abrasivity potential with increasing dolomite content. The microstructural properties play an important role for the abrasiveness of purely calcitic carbonates. Uniaxial compressive strength and splitting tensile strength were high and can additionally be, as has been shown before, particularly sensitive to sample preparation. We conclude that carefully determining the mechanical properties of carbonate rock samples in combination with common approaches to determine the abrasivity potential is key to properly predict tool wear, and required to derive information on performance in carbonate rocks. This study is the outcome of a research-oriented teaching program at Ruhr-University Bochum within the Geoscience curriculum for students with focus on Engineering Geology. Student authors are listed in alphabetical order (Aderhold to Zinke).
Effect of anisotropic creep on the convergence of deep drifts in Callovo-Oxfordian claystone
Authors: Jung Sophie , Vu Minh Ngoc , Ghabezloo Siavash , Pouya Amade 
Published: January 2023

Abstract
The long term behavior of the lining support in deep drifts is a crucial issue for nuclear waste underground repository project. In order to demonstrate the feasibility of the project, the French Radioactive Waste Management Agency (Andra) has built an Underground Research Laboratory (URL) at Bure. The underground structure is composed of a network of galleries whose drilling generates stress redistribution, damage and fracture in the surrounding medium. The damage and fracturing of this excavation damage zone have a direct effect on the displacement field and on the interaction between the formation and the lining support. The design of the support system request, in order to be as efficient as possible, a precise knowledge of the stress and displacement fields around the drift. For viscoplastic rock formation, the stress field around the drift and its effect on the support system must be determined for at least a couple hundred years. This is why we have studied the long term behavior of drifts using an elasto-viscoplastic constitutive law. The laboratory test data and field observations have shown that the Callovo-Oxfordian claystone has a slightly anisotropic behaviour for its elasticity, failure criterion and also creep properties. This anisotropy is largely increased by the presence of the fractures, which we take into account with transverse isotropic models. Homogenization techniques are used to establish a macroscopic expression of the viscous deformation depending on the behavior of the rock matrix and of the fractures. The macroscopic viscous deformation depends on the orientation and density of fractures, which is why based on investigation campaign, we divide the fractured zone, in our numerical models, into zones with fractures of different density and orientation to describe the behavior of the fractured zone as closely to the reality as possible. The model is then applied to the simulation of the convergences of GCS drift. The so called GCS drift belong to the network of monitored drift of the URL and was excavated in the direction of the major principal horizontal stress.
Evaluation of progressive damage of discontinuity asperities due to shearing by means photogrammetric survey
Authors: Carriero M T , Ferrero A M , Migliazza M R , Umili G 
Published: January 2023

Abstract
It is well known that the mechanical behaviour of rock discontinuities strongly influences the stability of slopes and fractured rock walls. With this end, particular attention must be paid to the analysis of the roughness of natural discontinuities, which represents a peculiar geometric feature strongly influencing their shear strength. The paper describes an experimental procedure carried out at laboratory scale on natural rock discontinuities to measure the shear strength and the roughness of their surfaces to analyse the progressive damage of the asperities during shearing process. The direct shear tests along discontinuities were coupled to photogrammetric surveys of the surfaces carried out before the tests (natural surfaces), after the first cycle and at the end of the last cycle. This allowed the reconstruction of the digital surface models of the intact and degraded surfaces. Through analytical procedures, the data obtained were processed to obtain geometric descriptors and adequately estimate the Joint Roughness Coefficient (JRC), analysing several profiles extracted along the direction in which the mechanical tests were conducted. The comparison between the experimental results and the roughness surface direct measure showed that discontinuities, even at the small scale, have an inhomogeneous roughness and that discontinuity degree of damage is a progressive process influenced by the state of confinement applied during the tests.