bluuebunny/crossref_metadata_2025 huggingface dataset:
A triple star in disarray
Authors: Kasper M. , Santhakumari K. K. R. , Herbst T. M. , van Boekel R. , Menard F. , Gratton R. , van Holstein R. G. , Langlois M. , Ginski C. , Boccaletti A. , Benisty M. , de Boer J. , Delorme P. , Desidera S. , Dominik C. , Hagelberg J. , Henning T. , Heidt J. , Köhler R. , Mesa D. , Messina S. , Pavlov A. , Petit C. , Rickman E. , Roux A. , Rigal F. , Vigan A. , Wahhaj Z. , Zurlo A.
Published: November 2020

Aims. T Tauri remains an enigmatic triple star for which neither the evolutionary state of the stars themselves, nor the geometry of the complex outflow system is completely understood. Eight-meter class telescopes equipped with state-of-the-art adaptive optics provide the spatial resolution necessary to trace tangential motion of features over a timescale of a few years, and they help to associate them with the different outflows.

Methods. We used J-, H-, and K-band high-contrast coronagraphic imaging with VLT-SPHERE recorded between 2016 and 2018 to map reflection nebulosities and obtain high precision near-infrared (NIR) photometry of the triple star. We also present H2 emission maps of the ν = 1-0 S(1) line at 2.122 μm obtained with LBT-LUCI during its commissioning period at the end of 2016.

Results. The data reveal a number of new features in the system, some of which are seen in reflected light and some are seen in H2 emission; furthermore, they can all be associated with the main outflows. The tangential motion of the features provides compelling evidence that T Tauri Sb drives the southeast–northwest outflow. T Tauri Sb has recently faded probably because of increased extinction as it passes through the southern circumbinary disk. While Sb is approaching periastron, T Tauri Sa instead has brightened and is detected in all our J-band imagery for the first time.
Coordinated Ionospheric Reconstruction CubeSat Experiment (CIRCE), In situ and Remote Ionospheric Sensing (IRIS) suite
Authors: Attrill Gemma D. R. , Nicholas Andrew C. , Routledge Graham , Miah Junayd A. , Kataria Dhiren O. , Mitchell Cathryn N. , Watson Robert J. , Williams James , Agathanggelou Alex , Brown Charles M. , Budzien Scott A. , Carman Tobias , Chaudery Rahil , Dymond Kenneth F. , Finne Ted T. , Fortnam Alex , Fritz Bruce , Hands Alex , Marquis Peter J. , Murphy Sean , Pinto-Jayawardena Talini , Rust Duncan , Ryden Keith A. , Schofield Dave , Stephan Andrew W. , Wiggins Kevin , Underwood Craig
Published: November 2020

The UK’s Defence Science and Technology Laboratory (Dstl) is partnering with the US Naval Research Laboratory (NRL) on a joint mission to launch miniature sensors that will advance space weather measurement and modelling capabilities. The Coordinated Ionospheric Reconstruction Cubesat Experiment (CIRCE) comprises two 6U cube-satellites that will be launched into a near-polar low earth orbit (LEO), targeting 500 km altitude, in 2021. The UK contribution to CIRCE is the In situ and Remote Ionospheric Sensing (IRIS) suite, complementary to NRL sensors, and comprising three highly miniaturised payloads provided to Dstl by University College London (UCL), University of Bath, and University of Surrey/Surrey Satellite Technology Ltd (SSTL). One IRIS suite will be flown on each satellite, and incorporates an ion/neutral mass spectrometer, a tri-band global positioning system (GPS) receiver for ionospheric remote sensing, and a radiation environment monitor. From the US, NRL have provided two 1U Triple Tiny Ionospheric Photometers (Tri-TIPs) on each satellite (Nicholas et al., 2019), observing the ultraviolet 135.6 nm emission of atomic oxygen at night-time to characterize the two-dimensional distribution of electrons.
Behavior of ring polymers under 1D confinement
Authors: Kim Meeri
Published: November 2020

Although they show some similarity to their linear counterparts, ring polymers have a larger maximum of self-density that develops with increasing ring size.
Defect suppression in wet-treated etched-and-regrown nonpolar m-plane GaN vertical Schottky diodes: A deep-level optical spectroscopy analysis
Authors: Aragon Andrew , Monavarian Morteza , Pickrell Greg , Crawford Mary , Allerman Andrew , Feezell Daniel , Armstrong Andrew M.
Published: November 2020

Steady-state photocapacitance (SSPC) was conducted on nonpolar m-plane GaN n-type Schottky diodes to evaluate the defects induced by inductively coupled plasma (ICP) dry etching in etched-and-regrown unipolar structures. An ∼10× increase in the near-midgap Ec – 1.9 eV level compared to an as-grown material was observed. Defect levels associated with regrowth without an etch were also investigated. The defects in the regrown structure (without an etch) are highly spatially localized to the regrowth interface. Subsequently, by depth profiling an etched-and-regrown sample, we show that the intensities of the defect-related SSPC features associated with dry etching depend strongly on the depth away from the regrowth interface, which is also reported previously [Nedy et al., Semicond. Sci. Technol. 30, 085019 (2015); Fang et al., Jpn. J. Appl. Phys. 42, 4207–4212 (2003); and Cao et al., IEEE Trans. Electron Devices 47, 1320–1324 (2000)]. A photoelectrochemical etching (PEC) method and a wet AZ400K treatment are also introduced to reduce the etch-induced deep levels. A significant reduction in the density of deep levels is observed in the sample that was treated with PEC etching after dry etching and prior to regrowth. An ∼2× reduction in the density of Ec – 1.9 eV level compared to a reference etched-and-regrown structure was observed upon the application of PEC etching treatment prior to the regrowth. The PEC etching method is promising for reducing defects in selective-area doping for vertical power switching structures with complex geometries [Meyers et al., J. Electron. Mater. 49, 3481–3489 (2020)].
The effect of collisions on the rotational angular momentum of diatomic molecules studied using polarized light
Authors: Arndt P. T. , Huennekens J. , Packard C. , Tran V. , Carey J. , Livingston R. , Marcune V. M. , Rowe B. A. , Ng J. , Qi J. , Lyyra A. M. , Ahmed E. H.
Published: November 2020

We report results of an experimental study of the changes in the alignment of the rotational angular momentum of diatomic molecules during elastic collisions. The experiment involved collisions of diatomic lithium molecules in the A1Σu+ excited electronic state with noble gas atoms (helium and argon) in a thermal gas phase sample. Polarized light for excitation was combined with the detection of polarization-specific fluorescence in order to achieve magnetic sublevel state selectivity. We also report results for rotationally inelastic collisions of Li2 in the lowest lying rotational levels of the A1Σu+v=5 vibrational state with noble gas atoms.
Effect of molecular constitution and conformation on positron binding and annihilation in alkanes
Authors: Swann A. R. , Gribakin G. F.
Published: November 2020

The model-potential approach previously developed by the authors to study positron interactions with molecules is used to calculate the positron binding energy for n-alkanes (CnH2n+2) and the corresponding cycloalkanes (CnH2n). For n-alkanes, the dependence of the binding energy on the conformation of the molecule is investigated, with more compact structures showing greater binding energies. As a result, thermally averaged binding energies for larger alkanes (n ≳ 9) show a strong temperature dependence in the range of 100 K–600 K. This suggests that positron resonant annihilation can be used as a probe of rotational (trans-gauche) isomerization of n-alkanes. In particular, the presence of different conformers leads to shifts and broadening of vibrational Feshbach resonances in the annihilation rate, as observed with a trap-based low-energy positron beam.
Smoothed particle hydrodynamics simulation of underwater explosions with dynamic particle refinement
Authors: Zhuang Tieshuan , Dong Xiangwei
Published: November 2020

The underwater explosion is a very complex multiphase phenomenon that poses a threat to the safety of ocean structures. Numerical simulation is of great significance in understanding the underlying mechanisms of hydrodynamics and structural damages due to underwater explosions. In this study, a mesh-free method, smoothed particle hydrodynamics (SPH), is used to establish the numerical model of underwater explosions. The computational domain consists of water and explosive gas, which is initially discretized into a series of uniformly distributed particles. To overcome the resolution difference between two phases due to the gas expansion, the dynamic particle refinement algorithm is first combined into the SPH. The particle resolution can be automatically adjusted by particle splitting techniques, thereby reducing the computation error of the gas–liquid interface. Robustness, concision, and validity of the model are validated by simulating the shock wave propagation and the bubble expansion. This study provides an effective numerical model for underwater explosion problems involving free surface flow, fluid–structure interaction, and large deformation.
High thermoelectric figure of merit in monolayer Tl2O from first principles
Authors: Huang Qingjun , Ma Jinlong , Xu Dongwei , Hu Run , Luo Xiaobing
Published: November 2020

The thermoelectric properties of monolayer Tl2O are studied using first-principles calculations with all involved electrical and thermal transport properties calculated in the parameter-free frameworks. It is found that monolayer Tl2O possesses remarkably high thermoelectric figure of merit, zT, due to its ultralow lattice thermal conductivity and fairly good power factor. The room temperature zT can be as high as 1.4 and 1.2 for n- and p-type systems, respectively, whereas the maximum zT values can reach up to 5.3 and 4.2 as the temperature increases to 800 K. In addition, it is clarified that the mobilities of monolayer Tl2O are orders of magnitude smaller than previous estimation from simplified semiempirical models. The room temperature electron and hole mobilities are only about 56 and 11cm2V−1s−1, respectively, due to the heavy effective mass along with strong polar optical phonons coupling scattering. Nonetheless, the intrinsically ultrahigh zT from entire first-principles calculations stimulate that the further experimental verification and exploration for practical application are worthwhile.
Effects of fire frequency and microhabitat on the ground layer in a grassy woodland
Authors: Watson Penny J. , Morris E. Charles
Published: November 2020

Grassy woodlands worldwide are vertically structured by trees, a ground layer of grasses and forbs, and a variable mid-storey. In Western Sydney’s Cumberland Plain Woodland this mid-storey is increasingly dominated by the prickly shrub Bursaria spinosa Cav. subsp. spinosa. We investigated whether tree and shrub vegetation affects species richness and composition of ground layer microhabitats in this woodland, and whether fire frequency directly affects the ground layer in addition to any indirect effects via overstorey vegetation. Replicate sites were located in areas that had burnt with a frequency that was high, moderate or low. All sites had a similar time since last fire. Three microhabitats (open, under Bursaria, around tree) within each site were sampled for species richness and composition of native and exotic species. Native species richness was not significantly affected by either microhabitat or fire frequency, for total species, grasses or forbs; however the relative abundance of native grasses decreased significantly as fire frequency declined, while the relative abundance of native forbs increased. Exotic species richness was lowest at high fire frequency and significantly higher at low fire frequency. Species composition was significantly affected by both microhabitat and fire frequency combining independently. Planned burning at relatively short intervals can help managers retain grassy habitat for open patch species, habitat for ground layer species that do best under frequent fire, and a robust Themeda triandra Forssk. sward antagonistic to weeds.
Factors associated with self-reported hepatitis B virus vaccination status among men who have sex with men in the Netherlands
Authors: Den Daas C. , Adam P. C. G. , Vermey K. , Zuilhof W. , de Wit J. B. F.
Published: November 2020

Background
Reducing the number of new acute hepatitis B virus (HBV) infections to zero by 2022 is an important goal in the Netherlands. Free HBV vaccination is available for population groups at higher risk of infection, including men who have sex with men (MSM). Identifying correlates of HBV vaccination among MSM can guide the development of health promotion interventions to increase coverage of HBV vaccination. Methods: We assessed factors associated with the HBV vaccination status of 4270 MSM in the Netherlands. Data were collected through the 2018 online Men & Sexuality survey. Results: Multinomial regression analysis showed that lower education level, having never tested for HIV, not recently diagnosed with a sexually transmissible infection, recently having had sex abroad and unknown HBV testing status were associated with higher odds of being unvaccinated as opposed to fully vaccinated. Living in Amsterdam and testing HBV negative were associated with lower odds of being unvaccinated as opposed to fully vaccinated. Age (25–39 years vs younger ages), living in Amsterdam and using pre-exposure prophylaxis decreased the odds to be partly vaccinated as opposed to fully vaccinated; having a migration background increased these odds. Conclusions: HBV vaccination rates among MSM will not reduce HBV transmission to zero. HBV promotion should focus on MSM outside of Amsterdam who are likely less connected with sexual health services and may be at lower (perceived) risk. The factors identified related to HBV vaccination status provide guidance for health promotion interventions to increase uptake and vaccination completion among MSM.
Structural basis for GLP-1 receptor activation by LY3502970, an orally active nonpeptide agonist
Authors: Kawai Takahiro , Sun Bingfa , Yoshino Hitoshi , Feng Dan , Suzuki Yoshiyuki , Fukazawa Masanori , Nagao Shunsuke , Wainscott David B. , Showalter Aaron D. , Droz Brian A. , Kobilka Tong Sun , Coghlan Matthew P. , Willard Francis S. , Kawabe Yoshiki , Kobilka Brian K. , Sloop Kyle W.
Published: November 2020

Significance

Glucagon-like peptide-1 receptor agonists have become established as a leading class of diabetes medications. However, these peptide-based drugs are administered by subcutaneous injection or, in one case, by a complex oral dosing regimen. We now report the discovery of LY3502970, a potent and selective small-molecule GLP-1R agonist. LY3502970 exhibits preclinical pharmacology equivalent to a marketed injectable GLP-1R agonist and possesses pharmacokinetic properties compatible with oral dosing in humans. Cryoelectron microscopy (cryo-EM) studies reveal an ECD-driven receptor binding mode for LY3502970 that provides a favorable pharmacological profile.
Localization and culturalization for a history-based game
Authors: Hsu Hao
Published: November 2020

Released in 2017, the game Detention by the Taiwanese indie developer Red Candle Games gained
great domestic success and made a name for itself among gamer communities worldwide. Providing an English-language localization
upon its release, the 2D point-and-click horror game is set in the 1960s during Taiwan’s “White Terror” era. The story follows a
ghost girl bound to the school she attended and unravels her tragic story. With such a specific temporal and spatial background,
the game has a wide range of cultural references, potentially preventing non-Taiwanese players from being immersed in the game.
This paper aims to examine industry practices within the theoretical framework of translation studies and understand, with the
case of Detention, how culturalization operates at different levels. Through the lens of loss and gain, this
paper also discusses how certain cultural connotations are lost in localization to retain the immersive game experience as an
overall gain.
Thermal Stability Evaluation Method Based on Pile’s Bearing Capacity in a Permafrost Region
Authors: Chunxiang Guo , Weijia Zhang , Laiku Jiang , Yaping Wu , Daijun Jiang , Yalong Zhou
Published: November 2020

Pile foundations are widely adopted in the Qinghai–Tibet Railway. The pile’s bearing capacity must be influenced the trends of global warming, rising foundation soil temperatures, expanding active layers, ground ice melting, etc. Thus, the pile’s long-term bearing capacity must be understood, and methods for evaluating its stability in permafrost regions must be developed. The bearing capacity of a pile foundation in a permafrost region is caused by the freezing strength of the pile–soil interface and support force at the pile bottom. Based on the formation mechanism of the bearing capacity of pile foundations in permafrost regions, the stability ratio of the freezing area and the freezing strength between the pile and soil are proposed to evaluate the thermal stability of the pile’s bearing capacity in permafrost. Using the method, a bearing capacity study on a single pile in typical moist permafrost and two piles in a permafrost region where warm groundwater is underground is performed. Compared with the field-measured value, the evaluation method proves to be correct and effective. Using the two parameters dependent on the soil–pile interface temperature, the effect of the thermal stability of pile bearing capacity may be described intuitively. Thus, both parameters are conducive to the analysis of pile bearing capacity formation mechanism in permafrost.
Dynamics of Organic Matter of Soil Profiles with Different Vegetation Conditions from the Chinese Loess Plateau: δ13C and δ15N Approaches
Authors: Li Long-Bo , Wang Xiao-Dan , Zhang Ping , Zhu Yao-Qiang , Ren Ming-Qiang , Cai Da-Wei
Published: November 2020

To understand the biogeochemical processes associated with soil organic matter (SOM) decomposition, we analyzed the SOM contents, the δ13C and δ15N values of the dominant species foliage, litter and SOM from soil samples for five soil profiles with different vegetation conditions in the Loess Plateau, Northwestern China. Results showed that the amounts of soil organic carbon (SOC) and total nitrogen (TN) mainly concentrated on the surface soil and differentiated according to the vegetation conditions in the following order: broad-leaved forest > coniferous woodland > shrub forest > grassland > wasteland. SOC and TN contents decreased with depth and varied in the ranges of 1.1–31.2 g/kg and 0.3–3.7 g/kg, respectively. Compared with the other regions, the 13C and 15N were enriched and the δ13C and δ15N values of topsoil SOM respectively increased in the ranges of 0.5%o–3.2%o and 0.7%o–4.6%o during litter degradation to SOM on the surface soil, which was controlled by SOM turnover rates. This result indicates that the effect of isotopic fractionation was obvious during the transformation of SOM from plant debris to SOM in topsoil, which resulted in great increments of SOM δ13C and δ15N. Litter inputs lowered the surface soil δ13C and δ15N values while decomposition increased δ13C and δ15N values in deeper soil. Foliage and litter inputs averaged 1.0% and 1.3% δ15N and -28.3% and -27.0% δ13C, respectively. The five soil profiles with different vegetation conditions had similar characteristics in variations of SOM δ13C and δ15N and increased with depth, respectively. However, the patterns of δ13C in our sites were less pronounced than the patterns of δ15N primarily because the discrimination against 13C during organic matter decomposition is weaker than the discrimination against 15N. Except for the shrub profiles, significant correlations were found between the two stable isotopes, 15N and 13C. Combined with information on SOM contents, the variations of the isotopic values of SOM showed a mixing process of litter inputs between different soil profiles. Two controls of soil isotopic compositions were established: new litter inputs and overall isotopic fractionation during decomposition. In conclusion, the overall isotopic fractionation during decomposition left residual soil N and C enriched in 15N and 13C, explaining the high δ15N and δ13C values observed in deeper soil.
Investigation on labile organic carbons in soils developed from limestone and sandstone in karst areas of southwest China
Authors: Li Long-Bo , Wang Xiao-Dan , Zhang Ping , Zhu Yao-Qiang , Ren Ming-Qiang , Cai Da-Wei
Published: November 2020

Although labile soil organic carbons (LSOC) represent only a small part of soil organic carbon (SOC), they are an important source of energy for the belowground portion of the ecosystem and play a crucial role regarding changes in the quality of soil organic matter (SOM). This study measured and compared the content of LSOC and SOC in limestone soil (developed from limestone) and sandstone soil (developed from sandstone) in the karstic area of southwest China to better understand the impacts of different soil types on LSOC (water-extractable and readily oxidizable organic carbon) and evaluate the existence of a possible relationship between LSOC and SOC in the soil. The results demonstrated that the amounts of SOC, soil readily oxidizable carbon (SROC), and soil water-extractable organic carbon (WEOC) (hot-water extractable organic carbon (hot-WEOC) and cold-water extractable organic carbon (cold-WEOC)) were the highest in the surface soil and decreased with increasing depth in both types of soil profiles. In addition, the content of SOC and LSOC were significantly higher in the limestone soil profiles than those in the sandstone soil profiles. This may be as a result of the occurrence of higher pH values and higher content of calcium, magnesium, and clay minerals in the limestone soil than in the sandstone soil. The proportions of WEOC in total SOC extracted at 25°C and 70°C in the sandstone soil profiles displayed higher average values of 0.040% and 0.527%, respectively, whereas the limestone soil profiles displayed lower average values of 0.015% and 0.255% for the WEOC extracted at 25°C and 70°C, respectively. Regarding the SROC content, both soil profiles showed higher values than WEOC content, ranging from 39.4%–55.2%. The results also showed that for the two types of soils significant correlations were found between samples of SROC, WEOC, and SOC (P < 0.01). Among the LSOC, the hot-WEOC showed clear differences between different soil types, and significant relationships were observed for not only SOC but also SROC. The correlation coefficients between hot-WEOC and SOC or SROC were higher than those between cold-WEOC and SOC or SROC. This study, therefore, suggests that hot-WEOC could be a useful indicator of changes in the quality of SOM in different soil types.
Bottom Hole Pressure Calculation of Fractured Carbonate Formation
Authors: Zhang Yichi , Yang Jin , Liu Wei , Li Mu , Zhang Zhenxiang , Zhao Xin
Published: November 2020

Carbonate formation is widely distributed in China, mainly showing the sensitivity of the target formation and the development of fracture and cavity types and narrow pressure window. Drilling complicated conditions such as formation leakage or bottom hole pressure less than formation pressure due to gas entering wellbore occur from time to time. To solve these problems, calculating the bottom hole pressure accurately and conducting managed pressure drilling (MPD) for fractured carbonate formation are necessary. In this study, the single-phase hydraulic model based on H-B rheological model is calculated. According to the characteristics of fractured carbonate formation, the drilling fluid leakage model is obtained. By coupling the leakage model with the single-phase wellbore hydraulic model, the bottom hole pressure calculation method is suitable for fractured carbonate formation, which can provide reference for managed pressure control drilling technology. Such a technology is verified by Bozhong X well through the above calculation method of bottom hole pressure. The model is used to simulate the leakage behavior of transverse and longitudinal fractures. Moreover, the variation characteristics of the leakage rate and cumulative leakage amount of the drilling fluid in the fracture are investigated. By comparing the loss control with conventional drilling and MPD, the advantages of controlled pressure drilling operation in the loss control are described.
Numerical Simulation of Explosion of Late-excavated Tunnel Parts of Double-arch Tunnel without Middle Drift
Authors: Xu J F , Xie X Y , Zhou Y X , Qian Z F , Jin G L , Liu Z Y , Ruan X C
Published: November 2020

Compared with the construction method of a tunnel with a middle drift, the construction method of a tunnel without a middle drift is a more advanced, novel, efficient, and energy efficient. Moreover, the blasting excavation of late-excavated tunnel parts exerts a vibration impact on the lining structure of early excavated tunnel parts. To analyze and predict the influence of late-excavated tunnel blasting on an early excavated tunnel and surrounding rocks in a triangular area, this study uses the Ansys LS-DYNA software to build a three-dimensional tunnel model simulating multihole blasting and the fluid–solid interaction method to assess the interaction of different materials. In addition, the different working conditions of surrounding rock levels and explosive equivalents are simulated. The distribution law of peak particle vibration velocity and maximum principal stress peak value of surrounding rocks and the lining along the transverse and longitudinal directions of the early excavated tunnel are generalized based on the numerical simulation results. The influence of the blasting of a late-excavated tunnel on the initial lining, secondary lining, and the middle triangular area of a double-arch tunnel is analyzed. The relationship between the surrounding rock level, explosive equivalent, and vibration velocity peak value is concluded. The field experiment-measured vibration velocities from the double-arch tunnel without a middle drift in the Chenjiachong tunnel of the Chuyao expressway in Yunnan Province, China, are in satisfactory agreement with the numerical simulation results. The results of this study are verified by the field blasting vibration data of the Chenjiachong and Changba tunnels and can provide reference and guidance for the blasting engineering practices of late-excavated double-arch tunnels without a middle drift.
Simulation of CO2 Injection into Fractured Coal Samples
Authors: Li Li , Liang Weiguo , Yang Jianfeng , Dusseault Maurice B.
Published: November 2020

Coal bed formation is widely considered a potential reservoir for CO2 geological storage. The injection of CO2 into coalbed formations is beneficial for reducing the CO2 concentration in the atmosphere and enhancing the recovery of coalbed methane, which is a clean fuel. Natural coal mass is a complex system comprising fractures and matrixes. However, fluid transportation in this system is complicated, and its study is challenging. In this study, a dual-permeability model is established to investigate gas transportation and storage in the coal mass during CO2 injection. Furthermore, the fluid transportation in the fracture and the matrix are studied, along with the mass transfer between them. The fully-coupled multiphysics model is solved using the finite element method. Besides, experiments on CO2 injection and storage in the large fractured coal sample are performed using a special apparatus designed by the Taiyuan University of Technology (TUT). Furthermore, the results of the laboratory experiments and those of the numerical simulation are compared, and the model is confirmed to have high reliability. The simulation results demonstrate that the gas transportation in the fracture is much faster than that in the matrix. The pressure difference and the mass transfer between the fracture and the matrix are the primary causes of pressure increase in the matrix. However, there is a time delay between the change in pressure difference and the mass transfer. During the gas injection process, the evolution of permeability is obvious because of a decrease in effective stress. Furthermore, various cases are simulated to explore the influence of matrix permeability on the results. The results show that higher matrix permeability triggers more mass transfer and that it takes less time to complete CO2 storage. The enhancement of coal matrix permeability can promote CO2 flow rate in the coalbed mass and improve CO2 injection efficiency.
Study on the characterization of rock heterogeneity and simulation of fracture process based on the mesoscopic structure
Authors: Yanbo ZHANG , Enyuan ZHANG , Xulong YAO , Peng LIANG , Baozhu TIAN , Lin SUN , Xiangxin LIU , Shuai WANG
Published: November 2020

This study aims to explore the effect of rock heterogeneity caused by meso-structure differences on the macro-mechanical properties and fracture evolution process. With the help of computed tomography, the meso-structure characteristics of coarse-grained red sandstone are obtained, starting from the meso-structure level. The digital characterization of heterogeneous rocks is completed with the use of image-processing methods, and a rock equivalent crystalline model is constructed. A numerical simulation study is performed with the particle flow PFC3D 5.0 program. The results show that (1) the main form of rock heterogeneity is a meso-structure difference, and this determines the rock’s macro-mechanical properties and failure characteristics. The meso-structure difference mainly plays a role in the post-peak damage weakening stage of rock, and the slight difference leads to damage in different development modes. (2) The crack initiation starts at the cemented and crystalline grid surfaces, which is randomly distributed. The crack evolution process is selective and affected by the types and distribution of the surrounding mineral particles. The development of cracks is dominated by secondary cracks, distributed in strips, in the area of mineral particles with strong mechanical properties. In contrast, cracks are densely developed and spread around in a cluster in the area of mineral particles with weak mechanical properties.
The Influence of the Variable Thickness of Prestressed Linings with Annular Anchors on its Mechanical Properties
Authors: Wang Yujie , Cao Ruilang , Shen Qiang , Zhao Yufei , Qi Wenbiao
Published: November 2020

By embedding annular anchors, prestressed linings with annular anchors provide active prestress, which can effectively resist the high internal water pressure in large-diameter hydraulic tunnels. The variable thickness of concrete liners along the circumference can significantly influence the mechanical properties of the lining. On the basis of the prestressed lining of a 6.8-m-diameter pressure tunnel in the Yinsong Diversion Project, we adopted a 3D numerical modeling method to study the influence of the average and local thicknesses of the lining on its mechanical properties. The results show that the prestress of the lining used in resisting the internal water pressure is ultimately derived from tensioning the annular anchors. The average thickness of the lining has little effect on its load-bearing capacity. In elliptical lining, an annulus of a slight tensile stress area appeared on the inner side of the lining, whereas the crown and invert sections will form the weak area because of structural bending moments.
Long-term stability of gravity anchorage with notched sill for suspension bridge on soft rock ground
Authors: Wu C J , Lai Y J , Cao X J , Yu J
Published: November 2020

The biaxial shear creep test was carried out to investigate the shear rheological characteristics and long-term shear strength on the cemented interface between concrete and bedrock and study the long-term stability of gravity anchorage with notched sill situated on soft rock. The shear rheological model was proposed and its corresponding parameters were identified. A numerical simulation of the shear test with thin-layer element was adopted to simulate the shear rheological behavior of the cemented interface, which was verified reasonably by test results. Further numerical simulation using the 3D viscoelastic–plastic model was implemented to study the long-term stability of gravity anchorage with notched sill. The shear creep test results showed that the Burges rheological constitutive model can fully reflect the shear rheological characteristics of the cemented interface; the long-term shear strength decreased markedly with time, especially cohesion. In addition, time-dependent numerical simulation on the stability of gravity anchorage with notched sill indicated that the displacement of the anchorage foundation of Ganjiang Bridge experienced a transient stage of creep decay and then quickly entered into stable state under the tension of the main cable. The anti-sliding effect of notched sill showed distinct time-dependent property. As the creep displacement increased, the resistance at the normal face of the notched sill functioned well and remained constant when the creep displacement was stable.
DEM simulation of internal erosion around a submerged defective pipe
Authors: Wu Binzhong , Yan Qiong , Wang Li , Chen Quansheng , Wang Tuo , Zhang Fengshou
Published: November 2020

Internal erosion caused by broken sewer pipes often leads to ground subsidence in urban area, which is a major risk to public safety and has caused substantial socioeconomic loss. In order to ensure the ground stabilization and the safety of buried pipelines, it is necessary to understand the process of internal erosion around a submerged defective pipe. In this paper, the Dynamic Fluid Mesh (DFM) is coupled with the three-dimensional discrete element method (DEM) to simulate internal erosion in gap-graded soils above a defective pipe. In this fluid-solid coupling scheme, the fluid mesh can be generated according to the soil skeleton formed by coarse particles and updated at regular intervals. Seepage forces are calculated and applied on solid particles in the DEM model. The approach accounts for permeability and porosity changes due to soil skeleton deformation and internal erosion. In this study, some gap-graded soils samples with different size ratio are established. A defective pipe is placed below the sample. After that, different hydraulic gradients are applied to the sample. Fine particles are washed away from the hole in the pipe. The results indicate that the erosion process can be divided into three stages according to changes in the erosion rate. In the initial stage, numerous fine particles are washed away, and the flow rate increases with the increase of eroded particles. Subsequently, the erosion rate decreases and the flow rate tends to reach a steady state. Finally, only a small proportion of particles fall down from the outlets and the erosion rate levels off to zero gradually. Parametric studies show that the increase of hydraulic gradient increase the eroded particle mass. The number of erosion particles from the bottom layer is much larger than those from the upper layers as more fine particles in the upper layers are locked.
Research on the Design of Landslide Anti-sliding Engineering Based on Inverse Parameter Calculation and the GEO-Slope Limit Equilibrium Method
Authors: Ma Xianjie , Liu Hongyu , Li Jian , Li Jiaming , Li Wei , Hou Lijie
Published: November 2020

Landslide is one of the most widely distributed and most severe geological hazards among the types of slope damage. China is among the countries most seriously affected by landslide disasters in the world. The unreasonable landslide anti-slide design will not only miss the best time for landslide treatment but also cause unnecessary engineering waste. Some may even worsen slope deformation and damage. Thus, reasonable slope protection and reinforcement and landslide anti-slide engineering design have become the current research fascination. This paper uses the Chengdu–Lanzhou Railway as the research object. This railway exhibits the typical characteristics of “four poles and three heights” in engineering geology. The main geological hazards and typical geological conditions of the Chengdu–Lanzhou Railway are systematically explained. The reasons for the determination of the principal axis section of the most unfavorable landslide and the basis for the determination of the sliding surface are summarized. Moreover, in this paper, a reasonable anti-slide engineering design is proposed. Finally, the friction coefficient of the main sliding section is calculated using the method of the coefficient of stability of the block, and the landslide thrust is calculated. Then, the stability coefficient of the landslide is verified using the GEO-Slope limit equilibrium method to determine whether the anti-slide engineering design is reasonable. This article provides a more scientific anti-skid engineering design idea and a scientific analysis method for the rationality of anti-skid engineering design.
Thermally induced failure process of brittle rocks based on a thermo-mechanical coupling model
Authors: Zhao H J , Ma F S , Guo J
Published: November 2020

The thermal expansion and the extraction characteristics of a rock are observed in a common phenomenon caused by the rock’s exposure to significant temperature differences. A thermally induced rock damage is a complex process full of uncertain physical and mechanical processes. Hence, investigating the mechanism of brittle materials is significant for both scientific and engineering applications. This study proposes a thermo-mechanical coupling model based on a continuous–discontinuous element method to simulate the thermal cracking processes in brittle rocks. In this micro-mechanical model, the rock matrix is simulated as an assembly of blocks bonded to each other. A spring model is employed to model the contacts in the blocks to simulate the mechanical deformation properties, while a thermal model is applied between their bonds to simulate heat conduction. The model validity is verified herein. Furthermore, the cracking process of brittle materials under the thermal stresses caused by the temperature gradient is studied using a thick-wall cylinder model. Consequently, the simulation results show that the microscopic crack initiation and propagation processes can be reasonably simulated at the cooling stage using the thermo-mechanical coupling model. Different geological and operation conditions are also further studied to reveal their effects on the patterns of induced fractures. This study provides a possible method for analyzing the thermal damage process and mechanism of brittle materials.
Slope failure mechanism affected by mining subsidence: a case study of highway slopes in Yangquan, Shanxi Province, China
Authors: Chao Zhang , Tiefeng Li , Xudong Han
Published: November 2020

This paper presents details of highway slopes affected by a mining subsidence event that occurred in the Yangquan coal mining area of China in 2016. To ascertain the developmental characteristics of surface deformation, a few methods were applied for investigation and monitoring, such as multiple field investigations, unmanned aerial vehicle measurements, and time-series interferometric synthetic-aperture radar techniques. An accurate numerical simulation was conducted on two slopes for stability analysis and mining subsidence prediction. Results show that the mining subsidence developed from south to north, which was consistent with the mining direction; two subsidence centers were distributed on the ground, and the north one was located in the southeast slope foot of the highway. The influence of the mining subsidence whose subsidence magnitude reached 4 m is obviously different on both sides of the highway. Although the rock and soil structure were damaged seriously, the northwest slope was completely unstable, whereas the southeast slope remained standing. The differences were studied to illuminate that slope instability is not only due to the mechanical properties of rock mass decrease dramatically but also relates to the direction of horizontal traction force, the spatial distribution of the working face, and the effective free surface of the slope. This paper presents a case of mining landslide failure for researchers.
Creep and swelling of bentonite for the safety of disposal pit in high-level radioactive waste repository
Authors: Liu Y M , Cao S F , Tong Q
Published: November 2020

Displacement of the canisters with high-level radioactive waste (HLW) could be induced by creep and swelling of buffer material bentonite in the disposal pit of HLW geological repository. The displacement of the canisters could lead to the safety of HLW repository decrease. Several large scale experiments with bentonite and heater which was only regarded as components that would simulate the reference canister with respect to dimensions, weight and thermal emission were conducted in situ and laboratory respectively. The evolution of displacement of the heater, RH and stress in the bentonite indicate that the displacements of the heater are controlled by consolidation and volumetric/deviatoric creep of the bentonite under the heater induced by weight of heater, thermal expansion of heater and bentonite with heating, as well as swelling process of bentonite with the hydration. The canisters could move upward slightly in disposal pit during the early phase of HLW disposal. With the saturation of bentonite and stress redistribution in bentonite, the canisters could remain steady and minor fluctuation. After the bentonite in the disposal pit saturated fully, the canisters might move downward due to the weight of canisters. The thickness of buffer material around HLW canister and long-term stability of HLW canister should be considered in the design of the HLW repository.The parameters and evaluation of THM processes taking place in the compacted bentonite-buffer during the early phase of HLW disposal can provide a reliable database for numerical modeling and further investigations of EBS, and the design of HLW repository.
Effect of stress condition on the creep behaviour of Beishan granite
Authors: Chunping Wang , Jianfeng Liu , Jian Liu
Published: November 2020

In China, a deep granite formation in Beishan area is currently considered as a potential host rock for high-level radioactive waste repositories. Creep tests were conducted by two modes, namely single step loading mode on several samples and multi-step loading mode on single sample. According to the experiment results, the granite specimens failed almost at the same axial strain and volumetric strain at a given confining pressure, despite of the differences in deviatoric stress, stress ratio or strain ratio. The increase in stress condition (deviatoric stress, stress ratio, or strain ratio) could accelerate the cracking process and creep strain rate, and consequently resulted in a shorter time to failure. The stress effect on the cracking process was also confirmed by the acoustic emission (AE) energy rate. Significant increases in AE energy rate and the percentage of AE events with high energy could be observed with the increase of deviatoric stress. It was indicated from the results that, the stress ratio and strain ratio were more reasonable when discussing the influence of stress condition, perhaps because they were defined by considering both the applied stress level and the mechanical properties of rock material.
Evolution of mechanical parameters of deep sandstone and its constitutive model under the condition of different stress paths
Authors: Zhang Junwen , Fan Wenbing , Song Zhixiang , Wang Shanyong
Published: November 2020

Using a multifunctional true triaxial fluid–solid coupling system, the mechanical properties of deep sandstone and its constitutive model were studied under the simulated depths 1000, 1500, and 2000 m and different stress paths. In stress path 1, σz
is increased while unloading along the x-axis (σx
decreased). Path 2 involves an increase in σz
with two-sided unloading. Path 3 involves an increase in σz
with one-sided unloading σx
and σy
true triaxial loading. In addition, the evolution law of the Poisson’s ratio μ and deformation modulus E of the deep sandstone under different stress paths and simulated depths were studied. The experimental results show that the following: (1) The μ–σz
curves of the sandstone at different simulated depths and the same stress path are similar. As σz
increases, the Poisson’s ratio first decreases and then increases to a maximum value, and subsequently, it abruptly decreases. On the other hand, the initial value of the deformation modulus E increases with an increase in the simulated depth. (2) Under the same simulated depth and different stress paths, the deformation trends of the E–σz
curves of the deep sandstone are quite different. Under the stress paths 1 and 2, the deformation modulus E of the deep sandstone first increases and then sharply decreases as σz
increases. On the other hand, it first decreases and then increases under the condition of stress path 3. (3) A constitutive model for the deep sandstone is proposed herein. The research results can provide some important references for deep rock mechanics.
Investigation on the evolution of shale mineral composition under the fluid–solid coupling
Authors: Cao Han , Chen Yu , Zhu Haolong , Zhao Yu
Published: November 2020

To understand the mechanism of the fluid–shale interaction that influences the physical properties of shale during fluid–solid coupling, in this study, we investigated the changes in the mineral composition of the shale and ion concentration of the fracturing fluid during the fluid–solid coupling at the Niutitang formation in Northwest Hunan, China. The results show that the shale contains more brittle minerals but fewer clay minerals and the mineral composition of the shale in weakly alkaline fracturing fluid changes obviously. Brittle minerals decrease initially and then increase afterward under the fluid–solid coupling, which is related to the pH value and ion concentration of the fracturing fluid. These new findings can provide technical support for the prediction of the physical parameters of shale after the fluid–solid coupling and for the design of a hydraulic fracturing scheme.
Damage Evolution Characteristics of Non-fractured Regions during the Rock Fracture Process of Cracked Chevron Notched Brazilian Disc Specimens with Different Water Contents
Authors: Zhao Kui , Yang Daoxue , Zeng Peng , Song Lin , Wang Jinjian
Published: November 2020

To investigate the influence of water content on crack evolution during the fracture process of the red sandstone rock material, the damage and mechanical properties of cracked chevron notched Brazilian disc red sandstone specimens, with different water contents, were experimentally investigated. Using a P-wave velocity meter, the damage information of red sandstone specimens with different water contents, in the non-fractured region, during the pure mode I and II fracture processes, was quantitatively analyzed. The experimental results show that the damage amount of the non-fractured region, during the pure mode I and II fracture processes, increases linearly with an increase in the internal water content of the red sandstone specimens. Thus, the results from this study can provide certain theoretical basis for studying the evolution mechanism of microcracks in the fracture process of CCNBD specimens with the disparate water contents.