bluuebunny/crossref_metadata_2025 huggingface dataset:
Exploring the accretion-ejection geometry of GRS 1915+105 in the obscured state with future X-ray spectro-polarimetry
Authors: Ratheesh A. , Matt G. , Tombesi F. , Soffitta P. , Pesce-Rollins M. , Di Marco A.
Published: September 2021

Context. GRS 1915+105 has been in a bright flux state for more than two decades, but in 2018 a significant drop in flux was observed, partly due to changes in the central engine along with increased X-ray absorption.

Aims. The aim of this work is to explore how X-ray spectro-polarimetry can be used to derive the basic geometrical properties of the absorbing and reflecting matter. In particular, the expected polarisation of the radiation reflected off the disc and the putative outflow is calculated.

Methods. We used NuSTAR data collected after the flux drop to derive the parameters of the system from hard X-ray spectroscopy. The spectroscopic parameters were then used to derive the expected polarimetric signal, using results from a Monte Carlo radiative transfer code, both in the case of neutral and fully ionised matter.

Results. From the spectral analysis, we find that the continuum emission becomes softer with increasing flux, and that in all flux levels the obscuring matter is highly ionised. This analysis, on the other hand, confirms that spectroscopy alone is unable to put constraints on the geometry of the reflectors. Simulations show that X-ray polarimetric observations, such as those that will be provided soon by the Imaging X-ray Polarimetry Explorer (IXPE), will help to determine the geometrical parameters which are left unconstrained by the spectroscopic analysis.
Stereoscopy of extreme UV quiet Sun brightenings observed by Solar Orbiter/EUI
Authors: Zhukov A. N. , Mierla M. , Auchère F. , Gissot S. , Rodriguez L. , Soubrié E. , Thompson W. T. , Inhester B. , Nicula B. , Antolin P. , Parenti S. , Buchlin É. , Barczynski K. , Verbeeck C. , Kraaikamp E. , Smith P. J. , Stegen K. , Dolla L. , Harra L. , Long D. M. , Schühle U. , Podladchikova O. , Aznar Cuadrado R. , Teriaca L. , Haberreiter M. , Katsiyannis A. C. , Rochus P. , Halain J.-P. , Jacques L. , Berghmans D.
Published: September 2021

Context. The three-dimensional fine structure of the solar atmosphere is still not fully understood as most of the available observations are taken from a single vantage point.

Aims. The goal of the paper is to study the three-dimensional distribution of the small-scale brightening events (“campfires”) discovered in the extreme-UV quiet Sun by the Extreme Ultraviolet Imager (EUI) aboard Solar Orbiter.

Methods. We used a first commissioning data set acquired by the EUI’s High Resolution EUV telescope on 30 May 2020 in the 174 Å passband and we combined it with simultaneous data taken by the Atmospheric Imaging Assembly (AIA) aboard the Solar Dynamics Observatory in a similar 171 Å passband. The two-pixel spatial resolution of the two telescopes is 400 km and 880 km, respectively, which is sufficient to identify the campfires in both data sets. The two spacecraft had an angular separation of around 31.5° (essentially in heliographic longitude), which allowed for the three-dimensional reconstruction of the campfire position. These observations represent the first time that stereoscopy was achieved for brightenings at such a small scale. Manual and automatic triangulation methods were used to characterize the campfire data.

Results. The height of the campfires is located between 1000 km and 5000 km above the photosphere and we find a good agreement between the manual and automatic methods. The internal structure of campfires is mostly unresolved by AIA; however, for a particularly large campfire, we were able to triangulate a few pixels, which are all in a narrow range between 2500 and 4500 km.

Conclusions. We conclude that the low height of EUI campfires suggests that they belong to the previously unresolved fine structure of the transition region and low corona of the quiet Sun. They are probably apexes of small-scale dynamic loops heated internally to coronal temperatures. This work demonstrates that high-resolution stereoscopy of structures in the solar atmosphere has become feasible.
Diabetestherapie im Krankenhaus
Authors: Ritter Michael Matthias
Published: September 2021

Eine strukturierte und standardisierte Diabetestherapie im Krankenhaus war noch nie so wichtig wie heute. Die Nebendiagnose Diabetes ist so häufig geworden, dass jede Abteilung sich damit auseinandersetzen muss. Eine Vernachlässigung der Erkrankung hat eine Zunahme von Komplikationen, eine Verlängerung des stationären Aufenthaltes und eine verstärkte Nutzung von teuren Intensivkapazitäten zur Folge. Die Zunahme von Häufigkeit der Erkrankung, Komplexität der vorhandenen Medikamente und häufig erforderlichen Insulintherapie spricht für den Einsatz von ärztlichen und nicht-ärztlichen Fachkräften auf allen Stationen in einem Krankenhaus. Dies kann durch die zentrale Verantwortlichkeit einer Serviceeinheit „Diabetologie“ erreicht werden – so wie es das Zertifikat „Krankenhaus für Diabetiker geeignet“ der Deutschen Diabetes Gesellschaft fordert und fördert.
Kinetic Resolution by Lithiation: Highly Enantioselective Synthesis of Substituted Dihydrobenzoxazines and Tetrahydroquinoxalines
Authors: Coldham Iain , El-Tunsi Ashraf , Carter Nicholas , Yeo Song-Hee , Priest Joshua D. , Choi Anthony , Kobras Carolin M. , Ndlovu Soneni , Proietti Silvestri Ilaria , Fenton Andrew K.
Published: September 2021

Kinetic resolution provided a highly enantioselective method to access a range of 3-aryl-3,4-dihydro-2H-1,4-benzoxazines using n-butyllithium and the chiral ligand sparteine. The enantioenrichment remained high on removing the tert-butoxycarbonyl (Boc) protecting group. The intermediate organolithium undergoes ring opening to an enamine. The kinetic resolution was extended to give enantiomerically enriched substituted 1,2,3,4-tetrahydroquinoxalines and was applied to the synthesis of an analogue of the antibiotic levofloxacin that was screened for its activity against the human pathogen Streptococcus pneumoniae.
Outcomes of Palliative Radiotherapy in Metastatic Epidural Spinal Cord Compression in Lung Cancer—A Prospective Observational Study from Tata Memorial Hospital
Authors: Tibdewal Anil , Sharma Alisha , Gurram Lavanya , Mummudi Naveen , Agarwal Jaiprakash
Published: September 2021

Background Metastatic epidural spinal cord compression (MESCC) secondary to lung cancer (LC) is a debilitating complication associated with poor prognosis and is commonly treated with radiotherapy (RT). There is no consensus for RT dose fractionation in spinal cord compression.

Methods Forty consecutive patients of LC with radiological evidence of MESCC treated with palliative RT were evaluated for functional outcomes (pain, ambulation, and sphincter function) at 2-, 4-, and 24-week post RT completion. Pain assessment was done using visual analogue scale (VAS) and response was categorized according to international consensus criteria, ambulation status (AS) using Tomita’s scale, and sphincter function by the presence or absence of a catheter. Overall survival (OS) was assessed using Kaplan-Meier method and compared using log-rank test. Impact of potential prognostic factors on survival was also analyzed and p-value ≤0.05 was considered significant.

Results Sixteen, 22, and two patients received 8 Gy single fraction (SF), 20 Gy in five fractions (20/5), and 30 Gy in 10 fractions (30/10), respectively. At 2 weeks, overall response (OR) rates of pain, ambulation, and sphincter control were 73, 81, and 81%, respectively. At 4 and 24 weeks, 93.7, 84.3, 87.5% and 88, 94, 76.5% had OR, respectively. Median OS was 4 months. Six- and 12-months OS was 50 and 37.5%. Nonsignificant difference in OS was seen between SF and 20/5 fractions (median 2.2 vs. 7.1 months, p = 0.39). Age ≤50 years was the only significant factor (p <0.05) in univariate analysis for OS.

Conclusion Radiotherapy provided equivalent pain control, ambulation, and sphincter function compared with reported literature in MESCC. Nonsignificant difference in OS exists between SF and multifraction RT regimens.
Influence of Screw-Hole Defect Size on the Biomechanical Properties of Feline Femora in an Ex Vivo Model
Authors: Hoon QiCai Jason , Wang Tian , Hall Evelyn , Walsh William R. , Johnson Kenneth A.
Published: September 2021

Objective The study aims to evaluate the biomechanical properties of feline femora with craniocaudal screw-hole defects of increasing diameter, subjected to three-point bending and torsion to failure at two different loading rates.

Study Design Eighty femoral pairs were harvested from adult cat cadavers. For each bending and torsional experiment, there were five groups (n = 8 pairs) of increasing craniocaudal screw-hole defects (intact, 1.5 mm, 2.0 mm, 2.4 mm, 2.7mm). Mid-diaphyseal bicortical defects were created with an appropriate pilot drill-hole and tapped accordingly. Left and right femora of each pair were randomly assigned to a destructive loading protocol at low (10 mm/min; 0.5 degrees/s) or high rates (3,000 mm/min; 90 degrees/s) respectively. Stiffness, load/torque-to-failure, energy-to-failure and fracture morphology were recorded.

Results Defect size to bone diameter ratio was significantly different between defect groups within bending and torsional experiments respectively (intact [0%; 0%], 1.5 mm [17.8%; 17.1%], 2.0 mm [22.8%; 23.5%], 2.4 mm [27.8%; 27.6%], 2.7 mm [31.1%; 32.4%]) (p < 0.001). No significant differences in stiffness and load/torque-to-failure were noted with increasing deficit sizes in all loading conditions. Screw-hole (2.7 mm) defects up to 33% bone diameter had a maximum of 20% reduction in bending and torsional strength compared with intact bone at both loading rates. Stiffness and load/torque-to-failure in both bending and torsion were increased in bones subjected to higher loading rates (p < 0.001).

Conclusion Screw-hole defects up to 2.7 mm did not significantly reduce feline bone failure properties in this ex vivo femoral study. These findings support current screw-size selection guidelines of up to 33% bone diameter as appropriate for use in feline fracture osteosynthesis.
Consistent solution of Einstein–Cartan equations with torsion outside matter
Authors: Morawetz Klaus
Published: September 2021

The Einstein–Cartan equations in first-order action of torsion are considered. From Belinfante–Rosenfeld equation special consistence conditions are derived for the torsion parameters relating them to the metric. Inside matter the torsion is given by the spin which leads to an extended Oppenhaimer–Volkov equation. Outside matter a second solution is found besides the torsion-free Schwarzschild one with the torsion completely determined by the metric and vice versa. This solution is shown to be of non-spherical origin and its uniqueness with respect to the consistence is demonstrated. Unusual properties are discussed in different coordinate systems where the cosmological constant assumes the role of the Friedman parameter in Friedman–Lamaître–Robertson–Walker cosmoses. Parameters are specified where wormholes are possible. Transformations are presented to explore and map regions of expanding and contracting universes to the form of static metrics. The autoparallel equations are solved exactly and compared with geodesic motion. The Weyl tensor reveals that the here found solution is of Petrov-D type.
Simplified approach to estimation of organ absorbed doses for patients undergoing abdomen and pelvis CT examination
Authors: Sookpeng S , Martin C J , López-González M R
Published: September 2021

The volumetric computed tomography (CT) dose index (CTDIvol) is the measure of output displayed on CT consoles relating to dose within a standard phantom. This gives a false impression of doses levels within the tissues of smaller patients in Southeast Asia. A size-specific dose estimate (SSDE) can be calculated from the CTDIvol to provide an assessment of doses at specific positions within a scan using size-specific conversion factors. SSDE is derived using the water equivalent diameter (D
w) of the patient, but calculation of D
w requires sophisticated computer software. This study aimed to evaluate relationships between D
W and effective diameter (D
Eff), which can be measured more readily, in order to estimate SSDE at various positions within a routine clinical abdomen and pelvis CT examination for Thai patients. An in-house ImageJ algorithm was developed to measure D
w, effective diameter (D
Eff), and SSDE on CT slices located at the heart, liver, kidneys, colon, and bladder, on 181 CT examinations of abdomen and pelvis. Relationships between D
Eff and D
w were determined, and values of organ absorbed dose using D
Eff were estimated. This approach was validated using a second cohort of 54 patients scanned on a different CT scanner. The results revealed that ratios between D
Eff and D
w at the heart level were 1.11–1.13 and those for the others were about 1.00. Additionally, the SSDE/CTDIvol ratio was estimated for each organ in terms of exponential functions using the relationships between D
w and D
Eff for individual organs. In summary, this study proposed a simple method for estimation of organ absorbed doses for Southeast Asian patients undergoing abdomen and pelvis CT examinations where sophisticated computer software is not available.
The social cost of carbon dioxide under climate-economy feedbacks and temperature variability
Authors: Kikstra Jarmo S , Waidelich Paul , Rising James , Yumashev Dmitry , Hope Chris , Brierley Chris M
Published: September 2021

A key statistic describing climate change impacts is the ‘social cost of carbon dioxide’ (SCCO2), the projected cost to society of releasing an additional tonne of CO2. Cost-benefit integrated assessment models that estimate the SCCO2 lack robust representations of climate feedbacks, economy feedbacks, and climate extremes. We compare the PAGE-ICE model with the decade older PAGE09 and find that PAGE-ICE yields SCCO2 values about two times higher, because of its climate and economic updates. Climate feedbacks only account for a relatively minor increase compared to other updates. Extending PAGE-ICE with economy feedbacks demonstrates a manifold increase in the SCCO2 resulting from an empirically derived estimate of partially persistent economic damages. Both the economy feedbacks and other increases since PAGE09 are almost entirely due to higher damages in the Global South. Including an estimate of interannual temperature variability increases the width of the SCCO2 distribution, with particularly strong effects in the tails and a slight increase in the mean SCCO2. Our results highlight the large impacts of climate change if future adaptation does not exceed historical trends. Robust quantification of climate-economy feedbacks and climate extremes are demonstrated to be essential for estimating the SCCO2 and its uncertainty.
Rise and fall of vegetation annual primary production resilience to climate variability projected by a large ensemble of Earth System Models’ simulations
Authors: Zampieri Matteo , Grizzetti Bruna , Toreti Andrea , de Palma Pierluca , Collalti Alessio
Published: September 2021

Climate change is affecting natural ecosystems and society. Anticipating its impacts on vegetation resilience is critical to estimate the ecosystems’ response to global changes and the reliability of the related ecosystem services, to support mitigation actions, and to define proper adaptation plans. Here, we compute the Annual Production Resilience Indicator from gross primary production (GPP) data simulated by a large ensemble of state-of-the-art Earth System Models involved in the last Coupled Model Intercomparison Project (CMIP6) of the Intergovernmental Panel on Climate Change. In theSustainability (Taking the Green Road)andMiddle of the Roadscenarios (ssp126 and ssp245), the areas where vegetation shows increasing GPP resilience are wider than the areas with decreasing resilience. The situation drastically reverses in theFossil-fuel Development (Taking the Highway)scenario (ssp585). Among the larger countries, Brazil is exposed to the highest risk of experiencing years with anomalously low GPP, especially in theTaking the Highwayscenario.
Causes of increased dissolved inorganic carbon in the subsurface layers in the western shelfbreak and high latitudes basin in the Arctic Pacific sector
Authors: Chu Gangzhi , Luo Xiaofan , Zheng Zijia , Zhao Wei , Wei Hao
Published: September 2021

The expansion of dissolved inorganic carbon (DIC)-rich water carried by the Pacific inflow creates a DIC maximum layer and exerts important influences on ocean acidification in the subsurface Arctic Ocean. This study analyzed shifts in the DIC distribution of the subsurface Arctic Ocean during 1998–2015 through hindcast simulation using a three-dimensional ocean-sea ice-biogeochemical model. For this purpose, the study was divided into two time periods (1998–2007 and 2008–2015). The results showed that the lower boundary layer of the Pacific Winter Water, defined as an isopycnal of 27 kg m−3, became deeper by ∼50 m in the central Canada Basin and expanded northward during 2008–2015 relative to 1998–2007. Accordingly, the subsurface DIC maximum layer deepened and expanded northwards into the Makarov Basin at high latitudes around 85° N. During 2008–2015, DIC concentrations, averaged over a 50–250 m water column, increased significantly in the Chukchi-East Siberian Shelfbreak and Makarov Basin. The DIC increase over the shelfbreak is mainly attributable to increased local biological degradation and the transportation of DIC-rich water from the Chukchi Shelf through Barrow Canyon. Estimates of the DIC budget indicated that advection controlled the increase in DIC content in the Makarov Basin during 2008–2015. This is attributed to the shift of the ocean circulation pattern, in which the ocean current along the Chukchi-East Siberian Slope to the Makarov Basin became stronger during 2008–2015, promoting the transport of DIC-rich Pacific Water into the Makarov Basin.
Rock engineering challenges in post-mining
Authors: Alber M
Published: September 2021

A legacy of environmental challenges with abandoned mines remains for many generations. The challenges include among others: (i) danger from sinkholes above shallow old mine workings and (ii) effects of rising water level in deep mines. Abandoned shallow mines show after > 20 years no damaging subsidence. Sinkholes, however, may still develop by structurally controlled failure. Main contributing factors are the geometry of an underground opening. Geological factors include the resource type (orebody or seam), height of rock overburden and cohesive soil, water flow and discontinuity spacing. The latter determines the bulking factor of the displaced roof and thus the maximum caving height. For steeply inclined openings it must be considered whether the caved rock moves down the dip and prevents self-stabilization. Rising water levels in deep abandoned mines may induce seismic events. Despite significant progress in monitoring and numerical methods there is still no appropriate geological or rock mechanical basis for explaining or predicting water pressure induced seismic events. Some research topics are suggested to approach this issue.
Reduction of natural disaster in Bulgaria by adopting DInSAR as a landslide monitoring approach
Authors: Milev N
Published: September 2021

1. Extended abstract

Monitoring the actual behavior of landslides is essential for assessing and predicting the risk of disaster. However, since the target area is usually huge, monitoring has not often been conducted due to technical difficulties and cost problem.

Synthetic Aperture Radar (SAR) is a high-resolution radar device that is mounted on an artificial satellite. It transmits pulse waves to the Earth’s surface and receives the reflections. Differential Interferometric SAR (DInSAR) is a technique for detecting the displacements of the Earth’s surface using SAR data and it has the potential to be an efficient, effective, and economical method for monitoring the landslide behavior in extensive areas. The great advantage of DInSAR is that it can monitor huge areas without the use of any sensors on the ground surface.

The author is now conducting a project of application of DInSAR to monitor the landslide behavior in the northern Black Sea coast in Bulgaria as an international collaboration with Bulgaria, Japan, Indonesia and Croatia by members of ISRM.

The distribution maps and the time-transition of the displacements in that area were obtained over a period of six years starting in 2014. DInSAR was able to detect the typical landslide behavior in northern Black Sea coast. The results agreed well with the actual behavior described in the Bulgarian official report of landslides. This study can suggest that DInSAR will be a useful tool for long-term continuous landslide monitoring in the northern Black Sea coast. The SAR application project will continue.
Crack Initiation Evolution Under Triaxial Loading Conditions
Authors: Mutaz E , Serati M , Williams D J
Published: September 2021

In response to high demands for minerals and in the light of rapid advancement in instrumentation and testing facilities, mines, tunnels, and infrastructures are getting deeper at an annual increasing rate. For instance, Australia’s deepest Gwalia gold mine near Leonora is extending beyond 2 km depth in the hunt for more ore. In Europe, the Gotthard sub-alpine base tunnels exceeding 10 m wide are excavated at depths greater than 2 km. At depth, explosion-like fractures occur which are known as stress spalling, slabbing, or rock bursting due to high-pressure environment, high temperature, and low porosity. Although rockburst and spalling failures have both been observed in the past 50 years and investigated by numerous researchers, this phenomenon is yet mysterious and the physics behind is still not fully understood. Recent researches have suggested that the spalling strength can be related to the crack initiation point. Various methods have therefore been proposed to identify the crack initiation at laboratory scales based on stress-strain response. Limited models are also available based on applied stresses, but only under triaxial conditions. This study aims to compare the volumetric strain method (as a strain-based technique) with the improved Griffith and Hoek-Brown criterion (G-HB) (as a stress-based method) to determine the crack initiation stress threshold under triaxial loading conditions.
Development of a direct shear testing method using true triaxial apparatus
Authors: Asahina D , Takemura T , Kawakita S , Li Y
Published: September 2021

Instability of faults and weak joints of rock mass is affected by underground three-dimensional loading conditions as well as hydrostatical fluid pressure within pores and cracks. This paper presents a direct shear testing method to characterize the shear behavior of Kimachi sandstones under various pore pressures and joint roughnesses. The direct shear test was conducted under three mutually perpendicular loads and with various levels of pore pressure through effective utilization of a true triaxial loading system. An overview of the experimental method, its advantages, and results showing the usefulness of the experiment were presented. Sample permeability in the direction parallel to the joint was measured during the shear test.
UCS field estimation of intact rock using the Schmidt hammer: A new empirical approach
Authors: Bolla A , Paronuzzi P
Published: September 2021

In the present work we discuss the results of a number of Schmidt hammer tests (total number of impacts N > 2,400) that were performed in situ on rock outcrops of different lithology (marl, calcareous marl, limestone, sandstone, quartz sandstone and rhyolite) that occur in Italy. Firstly, a specific field procedure to choose the reference value of the rebound index adopted to calculate UCS of intact rock is suggested. A relationship between L and N hammer rebound index values (RL and RN, respectively) is subsequently assessed. Considering the experimental datasets provided by a Schmidt hammer construction company and other research available in literature, a new exponential equation for the correlation between RL and UCS of intact rock has been derived. Considering the here-proposed RL-RN relationship, a new exponential correlation between RN and UCS has also been defined. The newly proposed procedure and relationships were successfully utilised to determine the intact rock strength of different rocks. The calculated UCS values are very similar when using both types of Schmidt hammer (L and N) and are generally in line with previous determinations from experimental data available in literature.
Effects of Excavation Damage on the Physical Properties of Rock Matrix
Authors: Kiuru R , Jacobsson L , Király D , Suikkanen J
Published: September 2021

Posiva Oy has conducted investigations into excavation damage, including comprehensive laboratory testing of physical properties of rock specimens from excavation damaged rock mass. Laboratory testing was conducted on drill core specimens extracted from the excavated surface of a tunnel located at approximately 345 m depth in Olkiluoto, Finland. A total of 141 drill core specimens of three main rock types, a structurally isotropic coarse-grained pegmatoid (PGR) and structurally anisotropic veined gneiss (VGN) and diatexitic gneiss (DGN), were subjected to petrophysical testing, rock mechanics testing and petrographic analyses. Results from the various tests were subjected to rigorous statistical analysis in order to reveal the effects excavation damage has on the physical properties of the rock mass. Results of the study revealed changes that are credited to excavation damage in resistivity, S-wave velocity and various elastic properties of the rock specimens. Effects of excavation damage and the depth of the excavation damaged zone seem to be different to gneiss compared to pegmatoid. On microscopic level, the extent of excavation damaged zone appears to be 0.2 – 0.4 m depending on the measured property. This means that the deeper excavation damaged layer observed by geophysical surveys may be caused by larger scale fractures.
Analysis of size effects on the Hoek-Brown failure criterion of intact granite samples
Authors: González-Fernández M A , Estévez-Ventosa X , Alonso E , Alejano L R
Published: September 2021

Scale or size effects of the uniaxial strength response in rock samples have been studied in detail in the past, so a good number of studies on different rocks are available. However, analyses on triaxial strength scale effects in rocks are scarce and they seldom address failure criteria (i.e. Hoek-Brown) evolution with specimen size. This obvious lack of data can be attributed to the difficulties of having available Hoek’s cell of different sizes. With the aim of filling this void, the authors have carried out sets of around 25 stress-strain triaxial tests on intact 30, 38, 54 and 84 mm diameter granite specimens, with various confinements (0.2 to 15 MPa), so reliable estimates of Hoek-Brown strength were obtained for every scale. We compare results with previous studies on UCS scale effects, showing a good correlation. Results suggest the studied granite undergoes a reverse size effect in terms of strength at low confinements. Indeed, the UCS increases as sample diameter increases up to around 50 mm, but decreases thereafter. However, results obtained put forward that this strength variation with scale tends to be mitigated for higher confinements where the scale effect may not be clearly recognised. So increased confinement can be associated with a decreased scale dependency component of strength.
Geomechanical characterization of an Italian complex formation with a block-in-matrix fabric
Authors: Napoli M L , Barbero M , Scavia C
Published: September 2021

Melanges are chaotic and heterogeneous geological mixtures of strong rock blocks embedded in a weaker finer-grained matrix. These complex formations, often referred to as “bimrocks” (block-in-matrix rocks) and “bimsoils” (block-in-matrix soils), are characterized by a high spatial, dimensional and lithological variability. Such a variability, together with the presence of rock inclusions of different lithologies and dimensions, makes the collection of representative high-quality specimens for laboratory tests very challenging. As a consequence, the determination of the geomechanical properties of such geomaterials is extraordinarily problematic. In this paper a preliminary characterization of an Italian sedimentary chaotic melange is performed by means of several laboratory tests. In dry conditions it looks like a bimrock but it is very sensitive to water and will transform into a bimsoil if it comes into contact with water. Since conventional drilling methods could not be employed to collect the specimens, a manual coring had to be used. The irregular lumps obtained were then cut with a specially made cutting machine. Point load tests and uniaxial compression tests were performed on the melange specimens. Atterberg limits, grading curves and mineralogical analyses were further carried out on the matrix material, in order to characterize it. The paper comments on both the procedure of these tests and the results obtained.
Lithology, physical and mechanical characterization of Chinese Porphyry
Authors: Valido J A , Laz M M , Cáceres J M
Published: September 2021

A thorough characterisation of porphyry from China (Province of Fujian) was made, regarding three chromatic variants: red, brown and grey. The properties object of study are: petrographic, chemical and mineralogical analysis, real and apparent density as well as open and total porosity, water absorption at atmospheric pressure, resistance to salt crystallization, rupture energy, compressive strength, flexural strength, abrasion resistance and slip resistance. The achieved results remain into the expected ones for this kind of stone. Nevertheless, small differences were found according to the colour of the sample. Finally, those properties which are covered in the CE marking were compared with the representative values of commercial samples from countries as Italy, Argentina and Mexico.
A New Double Shearing Testing Equipment for the Shear Behaviour of Rocks and Discontinuities under Static and Shock Loads
Authors: Aydan ömer , Kodate Shinya , Iwata Naoki
Published: September 2021

The dynamic mechanical behaviour and characteristics of rocks have been investigated using different techniques to evaluate the engineering structures under dynamic loads. The authors devised a new experimental apparatus to investigate the behaviour of rocks under shock waves. A new double shearing jig shown in figure 1 was developed and it was used to study the shearing of rocks and discontinuities under static and impact loading conditions using the device. Double shearing tests involve various rocks and discontinuities. The authors describe the experimental results under shock load and static loading and the results are compared with each other and their implications are discussed in rock mechanics and rock engineering. Although the system is quite simple, it is shown that it is very practical to study the shear behaviour of both intact rocks and discontinuities.
Q-slope application to coal mine stability
Authors: Bar N , McQuillan A
Published: September 2021

The Q-slope classification system is used to assess the stability of excavated rock slopes and provide an indication of long-term stable, reinforcement-free slope angles. Q-slope is based on over 500 rock slope case studies from mines, road and rail cuts hosted in igneous, sedimentary and metamorphic rocks around the world. Q-slope has successfully been applied to slopes ranging from less than 5 m to more than 250 m in height in both civil and mining environments since its introduction in 2015. This paper describes the application of Q-slope to excavated coal mine slopes which are often hosted in complex, interbedded sedimentary strata. Q-slope application to coal mine slopes is compared to the likelihood of failure calculated by the Slope Stability Assessment Methodology (SSAM). A relationship between Q-slope and SSAM is also provided.
Effect of sampling interval on the output statistics of large 3D discontinuity surfaces generated by a multiscale random field model
Authors: Jeffery M , Huang J , Fityus S , Giacomini A , Buzzi O
Published: September 2021

The scale effect is known to hinder reliable shear strength estimation of large-scale discontinuities. Recently, a stochastic approach was proposed to predict shear strength of large discontinuities directly at problem scale, thereby bypassing the scale effect. One aspect of the stochastic approach seeks to use the available roughness information from the 1D profile of a discontinuity to create a series of statistically representative 3D synthetic rock surfaces, via a rigorous random field model. The application procedure for producing such synthetic surfaces was validated at small scale; however, preliminary large-scale applications were not quite satisfactory. It was found that the absence of consideration for the multiscale nature of discontinuity roughness contributed to the issues encountered. This paper presents the details of the revised multiscale-based 2D LAS approach for producing representative large-scale synthetic surfaces with an emphasis on the effect of sampling interval, called segment length, on the statistics of the synthetic surfaces.
Methods for sampling discontinuity traces on rock mass 3D models: state of the art
Authors: Umili G
Published: September 2021

Discontinuities are an intrinsic characteristic of rock masses, and they appear at every scale of a technical survey. Issues related to the procedure’s duration and the operator’s safety during the survey have encouraged the development of non-contact methods: images and digital models serve as representations of the rock mass for surveying the geometric features of discontinuities. In particular, various automatic and semi-automatic trace sampling methods were developed in the last decade, focused on estimating persistence and the degree of fracturing. A review of these methods is presented in this paper, highlighting their strengths and disadvantages.
The Unseen: A Case Study of Innovative Methods for Investigating Historic Mine Workings
Authors: Hartzenberg A , Joaquim A , Gibbons O , Coleman T
Published: September 2021

Canadian mining operations have long been key contributors to economic vitality. This has resulted in Canada standing at the forefront of implementing best practices that relate to mine closure projects. In the case of closing historic mines this can be a particularly challenging task as often the level of information available is much less than active mines preparing to close. Closing historic mines provides an opportunity to apply new, and innovative methods to collect the data required to design and execute a successful mine closure plan. The site discussed in this study is in northern Canada and used interconnecting open pit and underground mining methods while in operation but has been closed for over half a century. Historic documents indicate that the mine was closed after a failure occurred at depth and some backfill material was lost. A pond currently exists where the open pit was located. This study is Rock Mechanics focused and discusses the methods used to assess the geometry and stability of the historic mine workings. The need for innovation stemmed from the limited historic plans and documentation that existed. Empirical methods suggested that the crown pillar at the site was unstable and should have failed, which did not align with on-site observations. Therefore, an alternative method of assessing the stability was required which involved undertaking bathymetric and three-dimensional sonar surveys to gain a better spatial understanding of the open pit and underground environment. The surveys confirmed that there were no visible signs of instability in the areas where the surveys were done. Advantages and limitations exist for the methods used to complete the survey and use the survey results during this investigation. These will be discussed in this paper.
Mitigation measures for the protection of coastal railways in the Flysch of Western Liguria
Authors: Foria F , Giordano R , Avancini G , Miceli G
Published: September 2021

In the countries bordered by the sea, it’s common to have an infrastructure in proximity or on the coastlines. The strategic value of transportation systems along the sea is still fundamental for commercial, emergency and touristic purposes. The sea level and the action of the sea waves are relevant issues for the safety and protection of the infrastructure. The Genova-Ventimiglia railway runs along the coast of the Liguria region of Italy. The meteoric events and the sea storms between November 2019 and June 2020 caused different issues along a stretch of the line. The paper presents the study, the planning and the design of the mitigation measures. An investigation campaign involved both the existing structures and the geological context. The structures on the sea are investigated with GPRs analyses and specific tests performed by rock-climbers during the night disruptions of the line. The geotechnical-geomechanical tests revealed a scenario with the western Liguria Flysch in different facies. ETS Srl has also implemented and deployed a marine Unmanned Surface Vehicle (USV) for the bathymetric survey. The processed data are integrated with the topographic survey to obtain a 3D reconstruction of both the above-sea and undersea surface. The aforementioned data are used for the study, the characterization of the materials and the design of the solution to reinforce the existing structures and mitigate the erosion effect near the line.
Analysis of heaving phenomenon in mountain tunnel and consideration to shallow shaped invert as countermeasures
Authors: Nakano K , Kuremochi N , Matsuda M , Kunimura S , Isago N
Published: September 2021

Heaving in some mountain tunnels after completion occurs in roadbeds that were built without an inverted arch structure because the ground was relatively stable during construction. The stress-release by excavation, along with subsequent swelling by groundwater, cause the roadbed to lose strength, allowing upheaval of the road surface. In this study, we analysed geological degradation characteristics and the state of past tunnels in cases where inverts were installed. We also analysed measurement data for axial forces of inverts. The necessary performance was discussed through the result obtained by numerical analysis to compare support effectiveness of the invert shape and consider a shallow structure.
Seismic activity of hard coal longwall mining in protective shaft pillar near closed room and pillar panel
Authors: Konicek P. , Kajzar V. , Schreiber J.
Published: September 2021

Monitoring of seismic activity during mining in the Upper Silesian Coal Basin is a part of rockburst prevention system. System is composed from two parts - seismological (SL) and seismoacoustic (SA) monitoring. Evaluation of data from both systems allows describing stress deformation process during mining and evaluation of rockburst mitigation techniques effectiveness. Described longwall was mining in a protective pillar after two trial room and pillar (R&P) testing panels were completed.

Evaluation of seismic activity was carried out by special software tool which allows simulating daily advance of mining and registered seismic activity. Different mining stages were identified for evaluation of seismic activity (e.g. weekly and daily summary graph of seismic activity, Benioff graph, event rate graph, energy vs time graph etc.). Evaluation of seismic activity provides many interesting results, mainly in the area of longwall panel termination when one pillar of the R&P trial was impacted by the longwall. This work presents seismic activity analysis, detailed site conditions and implemented active rockburst measures and its effectiveness. Analysis of seismic activity allows to formulate conclusions for longwall mining operations and evaluation of seismic activity in unfavourable geomechanical conditions within the area of protective shaft pillar border.
The role of joint spacing on the stability analysis of wedge failures
Authors: Pérez-Rey I , Moreno J , Muñiz-Menéndez M
Published: September 2021

Kinematic analyses of wedge failures in rock slopes are usually carried out based on stereographic techniques. Nevertheless, this methodology presents several limitations that could lead to poorly accurate conclusions. In line with this idea, the main objective of this work is to evaluate the effect of joint spacing in the estimation of the factor of safety of rock slopes affected by potential wedge failures. For this purpose, a 3D numerical distinct-element code (3DEC) was selected to carry out a good number of simulations in which the factor of safety a slope, affected by different discontinuity sets, was studied by using the Shear Strength Reduction (SSR) method. Different values of joint spacing, cohesion and friction angles were considered, combined with two angles of the slope face under study. The joint spacing has been found to relevantly affect the values of the factor of safety, which showed variations of up to 40% in comparison with those obtained from limit-equilibrium methods for rock slopes with similar structural features. This work provides an insight into a more realistic interpretation of rock slope analyses against wedge failures, and particularly to more accurate estimations of the factor of safety.
A Hybrid FEM/DEM Approach to Estimating Rock Block Breakage due to Gravity Free-Fall
Authors: Veltin K , Elmo D , Rogers S
Published: September 2021

An understanding of the fragmentation of rock blocks from gravity free-fall has applications to rock fall analysis as well as block cave mining. In the case of a rock fall, blocks splitting mechanics can reduce the overall block energy and therefore reduce the travel distance of the blocks. Conversely, splitting may result in a larger number of smaller fragments that may still pose a risk despite their reduced dimensions. In the case of block caving, splitting of blocks it is believed to aid the flow of the ore column, to reduce the potential of hang-ups, and to allow for easier extraction and processing of the ore. Traditional methods for block fragmentation analysis use empirical relationships and rule-based approaches that heavily rely on the block geometry, rather than block-to-block interactions. In this paper we present a study of fragmentation processes using a hybrid finite-element/discrete-element method (FEM/DEM). The approach is capable to account for the numerical instability generally associated with the simulation of high velocity surface interactions and subsequent fracturing. To date the analysis has focused on the simulation of free-falling blocks onto a fixed surface. The initial and final block breakage has been compared against parameters including the roughness and curvature of the impacted surface, and the rock block orientation in space during free fall. We believe the results could provide useful insight into designing catchments for rock fall, as well as an increased understanding of the complexities of secondary fragmentation estimates and the range of fragmentation that could be expected in block caving.
Investigation into the influence of macro-scale geometry on the stability of underground excavations in layered rock masses
Authors: Ingham J , Vazaios I , Paraskevopoulou C
Published: September 2021

Underground excavations for the development of infrastructure, mining operations, waste management etc. require support measures to ensure stability both during their construction and operational phases, which highly depends on the rock mass strength and deformability. Discontinuities within the rock mass are intrinsic features which determine said strength and deformability and affect the excavation stability. Several defining parameters demonstrate that rock mass variability has significant control in the material response during an excavation, especially in sedimentary rocks. In this paper, the Thornhill Sandstone is examined by applying numerical analysis and its mechanical response is investigated under several scenarios with varying excavation geometries, stress conditions while incorporating the influence of discontinuities explicitly within the numerical model. A two-dimensional parametric analysis is performed by applying the Finite Element Method (FEM) and integrating Discrete Fracture Networks (DFNs). More specifically, four different excavation geometries and three different in situ stress regimes are investigated. Drawing on the results, this paper provides insights for tunnel design optimisation when layered rock masses are encountered during an excavation in various underground stress environments with different opening geometries.
A Discrete Element Framework for the modelling of rock-filled gabions
Authors: Marigo Nicola , Gabrieli Fabio , Pol Antonio , Bisson Alberto , Brezzi Lorenzo
Published: September 2021

Gabions are steel mesh cages filled with stones. Recently, they have had a great diffusion for numerous applications such as erosion control and soil retention along cuts and natural slopes. The study of their mechanical behaviour under different loading conditions is a fundamental prerequisite for an improved understanding of their overall performance and in a design perspective. In this respect, the Discrete Element Method (DEM) appears a robust and effective technique. The DEM is particularly suited for modelling granular materials, and recently it has efficiently been applied for modelling deformable structures such as welded meshes. This work presents a discrete framework for the modelling of rock-filled gabions. The gabion module is modelled as an assembly of deformable cylindrical elements, while the filling material is represented using rigid aggregates of spherical particles. The tensile behaviour of the gabion elements is set in order to fit the mechanical response of the steel bars adopted in practice. The model is applied to analyse a uniaxial compression test on a single gabion.
Investigation of hydro-mechanical processes in fluid-saturated fractured rock based on numerical model generation
Authors: Pollmann N , Gallas J , Brandenburg M Ch , Witte L , Backers T
Published: September 2021

To realistically simulate fluid flow in fractured rock mass, a scheme to represent the discrete fracture networks (DFN) in the numerical model is of utmost importance. In this paper we discuss a workflow to implement a field-measurement based DFN into an FEM code (COMSOL Multiphysics) by means of a MATLAB routine. This workflow is involved in the ZoKrateS project which aims at showing the feasibility to enhanced fractured carbonate Rock Mass by proppant placement for geothermal application.

The model generation is based on analytical geometry including the equations for dip, azimuth and spacing of lines. The spacing between the discontinuities and the characteristic fracture length and aperture as well as orientation serve as input parameters for the model. It is possible to generate periodic models to be able to include periodic boundary conditions in simulations. In 2D the fractures are modeled as poroelastic ellipses in a poroelastic square-matrix. We investigate hydro-mechanically triggered fluid transport in stationary fractures that are mechanically and hydraulically active.

An extension to 3D fracture networks requires an algorithm based on analytical geometry including the equations for azimuth, dip and spacing of planes. To decrease the numerical costs of the 3D simulation a diffuse interface approach is strived for, including a modified model generation.

With the numerical model generator (NUMOG) a workflow is developed which allows numerical investigations of (thermo-) hydro-mechanically triggered fluid transport in a geothermal reservoir.