bluuebunny/crossref_metadata_2025_split huggingface dataset:
Tunable characteristics of porous silicon optical microcavities by energetic N ion beam interactions
Authors: Verma Chandra Prakash , Adnan Mohammad , Srivastava P , Asokan K , Kanjilal D , Vijaya Prakash G 
Published: September 2021

Abstract
The present study demonstrates the tuning of optical characteristics of porous silicon (PSi)-based microcavities by N ion beam interactions. These optical microcavities are prepared by using electrochemical etching of heavily doped p+-type Si. The PSi microcavities were exposed to N ions of 200 keV and 1 MeV at an optimized ion fluence of 1 × 1015 ions cm−2. A significant red-shifting of 32 ∼ 60 nm in the resonance cavity mode was observed due to ion interaction. The experimental results are in good agreement with the transfer matrix simulations. A substantial modification of the PSi microcavity surface states is visualized through Raman and x-ray photoelectron spectroscopy (XPS) techniques. The Raman spectral results show modifications from crystalline Si to nanostructured Si and subsequently to amorphous Si. The XPS indicates the modification of Si–Si and Si–O bonds and the formation of new Si–N bonds, implying the presence of Si3N4. These experimental observations, along with analytical simulations and transfer-matrix method microcavity modeling, conclusively support the realization of cavity tunability and substantial modification in the optical field intensity and photon confinement within the spacer layer of the microcavity. These results suggest that ion beams are the effective tool to produce wider tunable optical properties in microcavities with highly stable designer optical structures suitable for photonic applications.
Determination of uniaxial tensile strength of brittle materials using tubular samples
Authors: Guerrero-Miguel D J , Alvarez-Fernández M I , Prendes-Gero M B , González-Nicieza C 
Published: September 2021

Abstract
Tensile strength of brittle materials is usually obtained through Brazilian tests. It is accepted that failure is initiated at the centre of the sample and that it propagates through the material, creating a tensile failure plane along the vertical diameter or at the majority of it. Then, the tensile stress developed at the centre of the disc is considered as the tensile strength of the material tested. However, the stress state along the vertical diameter is always biaxial, even in the centre of the sample. This implies that the strength measured using such technique is not the uniaxial tensile strength. In this article, the expressions of the stress state supported by a tubular sample subjected to a novel device to determine the tensile strength of brittle materials are described. Besides, it is noticed that the failure plane contains points with the maximum uniaxial tensile strengths so the testing method is adequate to determine the uniaxial tensile strength of brittle materials.
Determination of thermal conductivity variation through Modified Transient Plane Source (MTPS), and its relationship with porosity variation on thermally treated Prada limestone
Authors: Martínez-Ibáñez V , Garrido M E , Hidalgo Signes C , Tomás R 
Published: September 2021

Abstract
In this research, the variation of thermal conductivity with temperature of a limestone and its relationship with porosity is studied. Samples from Prada formation, a lower Cretaceous limestone from the Catalan Pyrenees (Spain), obtained from the Tres Ponts road tunnel were subjected to temperatures of 105, 300, and 600 °C and then cooled at a slow rate by air-cooling to laboratory temperature. Open porosity tests were determined before and after heating to evaluate the porosity increase and the micro-cracks growth. Complementarity, thermal conductivity was measured in the rock samples before and after the application of a thermal treatment by means of C-Therm TCi device, a Modified Transient Plane Source (MTPS). This is a non-invasive, quick, and precise method, when compared with other steady-state laboratory alternatives, widely used to directly determine thermal properties of rock samples. A clear decrease in the thermal conductivity of above 10% was observed for samples heated at 600 °C, probably due to a dramatic increase in porosity. The obtained results could be of great interest for the incorporation of the effect of temperature on rock in numerical models, to evaluate the potential impacts induced by eventual fires developed inside the Tres Ponts tunnel.
Thermal shock-induced physical changes of granitic rocks of a radioactive waste disposal site
Authors: Németh A , Török Á 
Published: September 2021

Abstract
Medium-and low-level radioactive waste is stored in the subsurface galleries of a granitic formation in Southern Hungary. The main lithology is monzogranite. The present study focuses on the thermal behavior and characteristics of intact rocks and thermally exposed specimens. Cylindrical specimens were heated to 250°C, and 500°C in an electric oven in laboratory conditions. Physical properties (density, ultrasonic pulse velocity) and non-destructive strength tests such as Duroskop rebound value were measured on samples kept at 22°C and on samples exposed to heat. The test procedures followed the guidelines given in EN. Tests show that the bulk density was reduced after the 250 °C treatment but slightly increased due to additional heat up to 500 °C. The ultrasonic pulse velocity rapidly decreases with temperature from 22°C to 500°C. The Duroskop rebound values also show a negative correlation with temperature. Color changes are also observed since the grey specimens became increasingly brownish with increasing temperature. The test results demonstrate that with increasing temperature, the tested monzogranite becomes less dense, and micro-cracks reduce the surface strength.
Comparison of strength-based rock brittleness indices with the brittleness index measured via Yagiz’s approaches
Authors: Yermukhanbetov K , Yazitova A , Yagiz S 
Published: September 2021

Abstract
Rock brittleness is one of the most significant properties of rock having a major impact not only on the failure process of intact rock but also on the response of rock mass to rock excavation. In fact, the brittleness is a combination of rock properties including not only the uniaxial compressive strength (UCS) and Brazilian tensile strength (BTS) but also density and porosity of rocks. Due to that, the brittleness should be examined very carefully for any excavation projects, i.e., mechanized excavation, drilling and blasting. The aim of this paper is to compare the strength-based brittleness indices with both the rock brittleness index (BIo), directly obtained via punch penetration test (PPT) and also estimated via Yagiz’s approach (BI1) as a function of strengths and density of rocks. For the aim, database including more than 45 tunnel cases are used to compute common rock brittleness indices (BI2, BI3, BI4), different combination of UCS and BTS. Further, these indices are compared with both BIo and BI1 as well as each other. It is found that the BIo and BI1 have a significant relations (ranging of determination coefficients (r2) from 0.69 to 0.88 with strength-based brittleness indices commonly used in practice. Also, based on findings, several rock brittleness classifications are also revised herein.
Frictional properties of natural and induced fractures in two types of shales
Authors: Bohloli Bahman , Smith Halvard , Sauvin Guillaume , Cerasi Pierre R. 
Published: September 2021

AbstractThis paper presents results of direct shear tests on two types of shales; Rurikfjellet from Svalbard, Arctic Norway and Draupne from Ling Depression, the North Sea. Rurikfjellet formation is part of a caprock system for the proposed CO2storage site at Svalbard. Draupne shale forms the caprock for deep hydrocarbon reservoirs and also the primary seal for Smeaheia, a candidate site for CO2storage in the North Sea. Four specimens from Rurikfjellet and one specimen from Draupne were tested. Results of the tests shows that the peak friction coefficient for fractures in Rurikfjellet specimens varies between 0.26 and 0.29 while the residual friction coefficient ranges from 0.19 to 0.25. For Draupne shale, peak and residual friction coefficients were equal; i.e. 0.25. Simulation of friction coefficient was performed using the Barton-Bandis model and showed relatively good results in the post-peak and residual parts. The results of these tests provide reliable input data to support analytical and numerical models for assessing stability of fractures and faults under various loading conditions.
Determination of the basic friction angle ϕb of joints using the field tilt test: results of various “fast” tests on outcrops
Authors: Jordá-Bordehore L , Alejano L , Tomás R , Loaiza S C , García M T , Galindo R Á , Pérez-Rey I , Riquelme-Guill A , Cano M , Borja-Bernal C P , Medinaceli Torrez R 
Published: September 2021

Abstract
The basic friction angle of rock joints is usually obtained from tilt tests, being the most common the laboratory tilt tests. This test has been standardized according to the ISRM. However, most of the times when calculating the shear strength of discontinuities, reference tables are used to obtain the basic friction value for the lithology under study. These tables omit some lithologies complicating the search of adequate references. An alternative, straightforward and economical way to obtain ϕb
is through the field tilt test, which is carried out by sliding two blocks aside a joint. It is a well-known test, but there are few references to its implementation. In this test, unlike the laboratory tilt test, the samples are not “polished” and it is necessary to evaluate the roughness of the joint and the normal component to the weight of the upper blocks. The idea is to calculate the term of ϕb
from the Barton-Bandis’ equation and include the tilt angle α. Various tilt-test measurements were carried out with field blocks on both sides of the same joint, considering different lithologies (granite, limestone, andesite, dacite, coal and slate) and block sizes, evaluating the ideal ranges of applicability of the test.
Descriptive and quantitative analysis of fracture systems in a carbonate rock mass complex
Authors: Gallas J , Backers T 
Published: September 2021

Abstract
The study area is located in the Franconian Alb in Southern Germany and is an Upper Jurassic, karstified and fractured, regularly bedded carbonate rock mass with thin marl interlayers. Structurally, these deposits are heterogeneous and a classification into structural types is striven for in this study. The structural classification is based on discontinuity and fault characteristics gained from field work. The study area is considered an analogue for Germanys most productive deep geothermal reservoir horizon in the South German Molasse Basin. The aim of the field study is to describe and quantitatively analyse the different structural types, and to optimize the scanline method for a specific geological setting to gain comprehensive information with regard to fracture permeability and rock mass behaviour. The structural types are described in terms of discontinuity orientation and density, rock strength, and fault characteristics. To optimize the scanline method for the field study additional discontinuity attributes were added. One of these accessory attributes, the existence of discontinuity lags, will be discussed. It occurs when vertical and sub-vertical fractures cross sedimentary layers and continue with a small horizontal displacement in the next sedimentary layer. The results of this study are used to improve derived fracture networks with respect to thermo-hydro-mechanical models in the geothermal sector. Following article discusses the first results of the above-mentioned field study.
Fracture density analysis at Stromboli Volcano, Italy: implications to flank stability
Authors: Alcock T , Vinciguerra S , Benson P , Vagnon F 
Published: September 2021

AbstractStromboli volcano has experienced four sector collapses over the past 13,000 years, resulting in the formation of the Sciara del Fuoco (SDF); a horseshoe-shaped flank collapse scarp where episodes of instability are continuously observed and recorded. A NE / SW striking rift zone across the SDF and the western sector of the island is inferred to be a potential weakness zone for further instability episodes. This study reports new data of fracture density using remote sensing imagery, across within and outside the rift zone, to identify areas of damage that could reduce the edifice strength and promote fracturing. Pleiades satellite data of 0.5 m resolution was processed to highlight 23635 distinct linear features, determine fracture density across the island, and identify key areas of macro-scale weakness on the volcano. These data suggest that the SW sector of the island, including the summit area and the slopes of SDF, have an average fracture density between 1.18 – 2.73 × 10−5m−2in contrast to the rest of the volcano that has an average fracture density of 4.56 × 10−6m−2. Analysis was also conducted on the orientation of fracture strikes across the volcanic edifice by analysing fracture data specifically associated with areas of intrusions and fissures: the NW / SE rift zone and the SDF. Preliminary results show that the average fracture strike ranged from between 030 – 047 NE/SW and thus broadly parallel to the inferred rift axis.
Acoustic emission and digital image correlation for damage evolution in brittle rocks under time-dependent tensile loading
Authors: Moradian Omid , Wu Rui , Li Ying , Leith Kerry , Loew Simon 
Published: September 2021

Abstract
Time-dependent rock deformation is considered to precede dynamic failure in many rock-engineering projects and natural geohazards. In order to understand long-term performance of brittle rocks, we gather mechanical load, strain, acoustic emission (AE) and digital image correlation (DIC) data to describe the evolution of damage and cracking in response to tensile loading during multi-stage relaxation experiments on inverted single edge notch bending (iSENB) specimens. The source locations of the AEs correspond to a process zone ahead and around the notch indicating the evolution of the microcracks. The results showed that the cracks first start aseismicaly under subcritical growth until 10mm from the tip of the notch and then they grow seismically by showing seismic signals in the form of acoustic emissions. It was observed that the process zone obtained by DIC is smaller than the cloud of the AE locations. This can be partially because DIC only shows surface deformation and partially because of the errors associated with the AE source locations such as ignoring anisotropic velocity, sampling rate, sensor locations, etc. Moment tensor analyses of the AE signals showed that both tensile and shear cracks are involved in the micro-scale although in the macroscopic scale the damage process is mostly considered as tensile. The results showed that microcracks start as tensile, and then continue as shear, especially at the end of the crack where the specimen experiences compression loading.
Discrete Element Modelling of Rock Creep in Deep Tunnels using Rate Process Theory
Authors: Gutiérrez-Ch J G , Senent S , Zeng P , Jimenez R 
Published: September 2021

Abstract
Rock creep behaviour is a key aspect of many engineering projects, such as deep tunnels in which squeezing problems could occur. Many theories have been published in the literature to reproduce rock creep behaviour; however, most of them are not able to capture the last phase of creep (i.e., tertiary creep, or the accelerating strains that occur prior to failure). In this work, the Distinct-Element Method (DEM) approach is employed, in conjunction with Rate Process Theory (RPT), to simulate the effect of rock creep in deep tunnels. To do that, the DEM models are constructed using particles, whose interactions are simulated with a hybrid mixture of the Flat Joint Contact Model (FJCM) and the Linear Model (LM) contact models; the RPT is implemented into DEM models using a Visual C++ function. Results show that the DEM plus RPT combination can suitably reproduce the tunnel convergences due to rock creep.
Geomechanical substantiation of the Oleniy Ruchey deposit underground mining in a protective pillar of the Niorkpakhk open pit
Authors: Zemtsovskii A V , Semenova I E 
Published: September 2021

Abstract
The location of significant volumes of the lower level reserves close to an open pit which produces the adjacent Niorkpakhk deposit considerably complicates underground mining of the Oleniy Ruchey rockburst-hazardous deposit. The progress of underground excavations into the under-pit space is permitted if the undermined rock thickness and open pit walls remain stable. 3D numerical studies of stress-strain state have indicated particularities in deformation such as increase in undermined thickness stability under high tectonic stresses. The parameters of safe mining of temporary inactive reserves were scientifically substantiated. The boundaries of maximal development of underground mining were determined. The stability of overlying rocks and open pit walls is maintained by forming an advance of overlying sublevels relative underlying ones under 45° angle and providing the monitoring for the undermined rock mass. The mining method in a protective pillar the authors propose allows increasing reserves of the first mining stage by 76.9% and avoiding decrease in production volumes when mining operations terminate.
The integrated usage of ground-based and satellite SAR, along with 3D structural modelling in Titania: creating a link between short and long - term slope stability hazard management
Authors: Botsialas K , Ravde V , Falomi A , Meloni F , Boldrini N , Bellotti F , Leoni L , Coli N 
Published: September 2021

Abstract
Mining is a high risk business and for every modern mining industry, the main aim of its open pit design is to create walls that will be stable for the life of the open pit, which in some cases may extend beyond the closure. As a result, any kind of instability should be manageable and if possible, it should not develop to instabilities. This paper focuses on 300.000 tons instability that began in 2008 and continues until today in Titania. The hazard associated with this instability was a constant threat for the continuation of the production and the safety of people and machinery. In order to manage the hazard in short- and long-term, it was evident that data from different sources should be combined and analyzed. Data from ground-based and satellite SAR were used to delineate the unstable area through a period of 10 years. At the same time advanced implicit modelling techniques were used to integrate borehole and surface structural data in a 3D structural model. This 2 stage workflow, led to a set of preventive and remedial measures that allowed the continuation of the production the last ten years and will ensure the continuation of the production for, at least, other ten years.
Considerations on the deformation of Ridracoli dam foundation based on the analysis of monitoring data
Authors: Lusini E , Boldini D , Graziani A 
Published: September 2021

Abstract
The behaviour of the Ridracoli arch-gravity dam in the 2002-2020 operation years has been analysed, by applying “statistical” models of increasing complexity to the time series of pendulum and long-base extensometer measurements. The modelling approach has proved robust. A satisfactory estimate of the reservoir load, thermal and irreversible drift components has been obtained for most of the instruments. As expected, the influence of temperature is lower for the instruments deeply embedded in the rock mass. The deformations recorded on the left and right bank of the dam have shown a minor influence of the anisotropic proprieties of the rock mass, well characterized by the mechanical tests performed at the time of dam construction.
Application of SBAS-DInSAR to monitoring landslides along the northern Black Sea coast in Bulgaria
Authors: Yamaguchi M , Yastika P E , Shimizu N , Milev N , Vrkljan I 
Published: September 2021

AbstractThe Black Sea coast of Bulgaria is well known as an active landslide area across which various landslides extend. Monitoring the real behavior of landslides has not often been conducted due to technical difficulties and cost issues, although it is essential to reveal the mechanism of these landslides and to solve the problems they cause. In this paper, SBAS-DInSAR is applied to monitor the landslide displacements along the northern Black Sea coast. The results are compared with the field observation results described in the official annual reports of landslides issued in Bulgaria and other published papers. It is found that the SBAS-DInSAR results show a good agreement with the actual behavior and verify its applicability for monitoring landslides in extensive areas along the northern Black Sea coast.
Review of U.S. subsidence monitoring using conventional and satellite based methods
Authors: Maleki H , McKenzie J 
Published: September 2021

Abstract
Tracking of surface deformations is typically achieved using periodic measurements of both vertical and horizontal deformations using conventional, Ground Positioning Satellite (GPS), and or photographic techniques. Within the last decade, satellite based methods have also found limited applications over some underground coal mines and commercial applications for open pit mines. In this paper, the authors will review the subsidence monitoring over one of the Colorado operations utilizing precise GPS measurements. This case study will address geologic setting, vertical and horizontal displacements, the influence of topography and gate pillar designs on surface subsidence and fracturing, upon longwall extraction of the Upper D Seam. In addition, we will review the potential use of satellite based, remote sensing methods. InSAR technologies are finding new interest in the U.S. mining industry for (1) investigating the utility of InSAR in discriminating different types of seismic events including underground explosions, natural earthquakes and mine collapses (2) tracking surface subsidence for satisfying permitting requirements and (3) potential use in the area of mine safety. The combination of satellite InSAR imaging and GPS measurements is suggested for enhancing the quality of ground movement analysis including assessment of horizontal deformations and effects on surface resources. Satellite data availability, and the improvements in interpretation and processing tools, are very promising.
A new parameter for TBM data analysis based on the experience of the Brenner Base Tunnel excavation
Authors: Heikal G , Erharter G H , Marcher T 
Published: September 2021

Abstract
Tunnel boring machine (TBM) operational data can be seen as a function of three main influences: the machinery of the TBM itself, the way the TBM is operated, and the excavated rockmass. Whereas the processing of TBM data must be done by computer-aided methods, the interpretation is typically done visually and is highly dependent on the user’s prior experience. One way is to inspect the raw data itself, and another is to inspect computed parameters (specific penetration, specific energy or torque ratio). Either way, the goal is to find distinctive patterns that indicate changes in the rock mass conditions, and therefore it is crucial to find parameters that bear as much information as possible. The goal of this paper is to introduce the new parameter “theoretical advance force” (FNtheo
) that was developed in the course of systematic analysis of TBM operational data from the exploratory tunnel Ahrental Pfons (part of the Brenner Base tunnel project). FNtheo
is back-calculated from the measured cutterhead torque and the measured penetration. The theoretical advance force shows very promising results with the data at hand, yielding more pronounced and well-defined patterns that correlate better with the encountered rockmass conditions than several other common parameters.