bluuebunny/crossref_metadata_2025 huggingface dataset:
An acceleration of microwave-assisted transesterification of palm oil-based methyl ester into trimethylolpropane ester
Authors: Aziz Nur Atiqah Mohamad , Yunus Robiah , Hamid Hamidah Abd , Ghassan Alsultan Abdul Kareem , Omar Rozita , Rashid Umer , Abbas Zulkifly
Published: November 2020

Microwave-assisted synthesis is known to accelerate the transesterification process and address the issues associated with the conventional thermal process, such as the processing time and the energy input requirement. Herein, the effect of microwave irradiation on the transesterification of palm oil methyl ester (PME) with trimethylolpropane (TMP) was evaluated. The reaction system was investigated through five process parameters, which were reaction temperature, catalyst, time, molar ratio of TMP to PME and vacuum pressure. The yield of TMP triester at 66.9 wt.% and undesirable fatty soap at 17.4% were obtained at 130 °C, 10 mbar, sodium methoxide solution at 0.6 wt.%, 10 min reaction time and molar ratio of TMP to PME at 1:4. The transesterification of palm oil-based methyl ester to trimethylolpropane ester was 3.1 folds faster in the presence of microwave irradiation. The total energy requirement was markedly reduced as compared to the conventional heating method. The findings indicate that microwave-assisted transesterification could probably be an answer to the quest for a cheaper biodegradable biolubricant.
Robust quantum point contact via trench gate modulation
Authors: Park Dongsung T. , Lee Seokyeong , Kim Uhjin , Choi Hyoungsoon , Choi Hyung Kook
Published: November 2020

Quantum point contacts (QPC) are a primary component in mesoscopic physics and have come to serve various purposes in modern quantum devices. However, fabricating a QPC that operates robustly under extreme conditions, such as high bias or magnetic fields, still remains an important challenge. As a solution, we have analyzed the trench-gated QPC (t-QPC) that has a central gate in addition to the split-gate structure used in conventional QPCs (c-QPC). From simulation and modelling, we predicted that the t-QPC has larger and more even subband spacings over a wider range of transmission when compared to the c-QPC. After an experimental verification, the two QPCs were investigated in the quantum Hall regimes as well. At high fields, the maximally available conductance was achievable in the t-QPC due to the local carrier density modulation by the trench gate. Furthermore, the t-QPC presented less anomalies in its DC bias dependence, indicating a possible suppression of impurity effects.
Dyschloremia is associated with failure to restore renal function in survivors with acute kidney injury: an observation retrospective study
Authors: Kee Youn Kyung , Jeon Hee Jung , Oh Jieun , Shin Dong Ho
Published: November 2020

Dyschloremia is common in critically ill patients. However, little is known about the effects of dyschloremia on renal function in patients with acute kidney injury (AKI) requiring continuous renal replacement therapy (CRRT). A total of 483 patients who received CRRT for AKI were selected and divided into three groups according to their serum chloride concentrations at the time of CRRT initiation. At 90 days after initiating CRRT, renal outcome, i.e., non-complete renal recovery, or renal failure, was assessed in the three groups. The hypochloremia group (serum chloride concentrations < 96 mEq/L, n = 60), the normochloremia group (serum chloride concentrations, 96–111 mEq/L, n = 345), and the hyperchloremia group (serum chloride concentrations > 111 mEq/L, n = 78) were classified. The simplified acute physiology score III was higher in the hyperchloremia and hypochloremia groups than in the normochloremia group. Multivariate logistic regression analyses showed that hypochloremia (odds ratio, 5.12; 95% confidence interval [CI], 2.56–10.23; P < 0.001) and hyperchloremia (odds ratio, 2.53; 95% CI, 1.25–5.13; P = 0.01) were significantly associated with non-complete renal recovery. Similar trends were observed for renal failure. This study showed that dyschloremia was independently associated with failure in restoring renal function following AKI.
Quantitative analysis of renal arterial variations affecting the eligibility of catheter-based renal denervation using multi-detector computed tomography angiography
Authors: Song Won Hoon , Baik Jinhwan , Choi Eue-Keun , Lee Hae-Young , Kim Hyeon Hoe , Park Sung-Min , Jeong Chang Wook
Published: November 2020

Catheter-based renal denervation (RDN) was introduced to treat resistant hypertension. However, the reduction in blood pressure after the RDN was modest. Catheter-based RDN was performed only at main renal arteries, except for accessory and branch arteries due to the diameter being too small for the catheter to approach. Here, we retrospectively analyzed the anatomy of diverse renal arteries via 64-channel multi-detector computed tomography angiograms of 314 consecutive donors who underwent living donor nephrectomy from January 2012 to July 2017. Occurrence rates of one or more accessory renal arteries in donors were 25.3% and 19.4% on the left and right sides, respectively. Early branching rates before 25 mm from the aorta to the right and left renal arteries were 13.7% and 10.5%, respectively. Overall, 63.1% and 78.3% of donors had no accessory artery bilaterally and no branched renal artery, respectively. As a result, 47.1% had only main renal arteries without an accessory artery and early-branching artery. Approximately half of the donors had multiple small renal arteries bilaterally, for which catheter-based denervation may not be suitable. Thus, preoperative computed tomography angiography requires careful attention to patient selection, and there is a need for improved methods for denervation at various renal arteries.
Evolution of ferritin levels in hepatitis C patients treated with antivirals
Authors: Chang Ming-Ling , Hu Jing-Hong , Yen Ching-Hao , Chen Kuan-Hsing , Kuo Chia-Jung , Lin Ming-Shyan , Lee Cheng-Han , Chen Shiang-Chi , Chien Rong-Nan
Published: November 2020

The evolution of ferritin levels in hepatitis C virus (HCV)-infected patients with sustained virological responses (SVRs) following various therapy regimens remains elusive. An 8-year prospective cohort study of 1194 HCV-infected patients [interferon-based therapy (n = 620), direct-acting antiviral agent (DAA) therapy (n = 355)] was conducted. At baseline, sex, alanine aminotransferase (ALT), triglycerides, homeostatic model assessment of insulin resistance (HOMA-IR), estimated glomerular filtration rate (eGFR), hemoglobin, iron/total iron-binding capacity (Fe/TIBC) and IFNL3-rs12979860 genotypes were associated with ferritin levels. At 24 weeks posttherapy, ALT, triglycerides, total cholesterol, eGFR, Fe/TIBC and the therapy regimen were associated with ferritin levels in SVR patients. Among interferon-treated patients, ferritin levels increased at 24 weeks posttherapy, regardless of SVR, and 24-week posttherapy ferritin levels were higher in non-SVR patients (n = 111) than in SVR patients (n = 509); ferritin levels began decreasing at 3 years posttherapy and were lower than pretherapy levels since 4 years posttherapy in SVR patients. Among DAA-treated SVR patients (n = 350), ferritin levels decreased and remained stable since 24 weeks posttherapy. ALT, triglycerides, eGFR, and Fe/TIBC were HCV-unrelated factors associated with ferritin levels; sex, HOMA-IR, total cholesterol, hemoglobin and IFNL3-rs12979860 genotype were HCV-related factors associated with ferritin levels. In interferon-treated SVR patients, the increased trend of posttherapy ferritin levels was not reversed until 4 years posttherapy. In DAA-treated SVR patients, ferritin levels decreased since 24 weeks posttherapy.
Coassembly of nucleus-targeting gold nanoclusters with CRISPR/Cas9 for simultaneous bioimaging and therapeutic genome editing
Authors: Tao Yu , Yi Ke , Hu Hanze , Shao Dan , Li Mingqiang
Published: November 2020

Protamine–gold nanoclusters were developed as nanocarriers for CRISPR/Cas9 delivery to achieve efficient genome editing and bioimaging.
Bioactive 3D porous cobalt-doped alginate/waterborne polyurethane scaffolds with a coral reef-like rough surface for nerve tissue engineering application
Authors: Chen Yue , Long Xirui , Lin Weiwei , Du Bohong , Yin Hang , Lan Wanling , Zhao Daiguo , Li Zhen , Li Jiehua , Luo Feng , Tan Hong
Published: November 2020

Bioactive 3D porous cobalt-doped alginate/waterborne polyurethane scaffolds with a coral reef-like rough surface were prepared for nerve tissue engineering application.
Most super-Earths formed by dry pebble accretion are less massive than 5 Earth masses
Authors: Venturini Julia , Guilera Octavio Miguel , Ronco María Paula , Mordasini Christoph
Published: November 2020

Aims. The goal of this work is to study the formation of rocky planets by dry pebble accretion from self-consistent dust-growth models. In particular, we aim to compute the maximum core mass of a rocky planet that can sustain a thin H-He atmosphere to account for the second peak of the Kepler size distribution.

Methods. We simulate planetary growth by pebble accretion inside the ice line. The pebble flux is computed self-consistently from dust growth by solving the advection–diffusion equation for a representative dust size. Dust coagulation, drift, fragmentation, and sublimation at the water ice line are included. The disc evolution is computed solving the vertical and radial structure for standard α-discs with photoevaporation from the central star. The planets grow from a moon-mass embryo by silicate pebble accretion and gas accretion. We perform a parameter study to analyse the effect of a different initial disc mass, α-viscosity, disc metallicity, and embryo location. We also test the effect of considering migration versus an in situ scenario. Finally, we compute atmospheric mass loss due to evaporation over 5 Gyr of evolution.

Results. We find that inside the ice line, the fragmentation barrier determines the size of pebbles, which leads to different planetary growth patterns for different disc viscosities. We also find that in this inner disc region, the pebble isolation mass typically decays to values below 5 M⊕ within the first million years of disc evolution, limiting the core masses to that value. After computing atmospheric mass loss, we find that planets with cores below ~4 M⊕ become completely stripped of their atmospheres, and a few 4–5 M⊕ cores retain a thin atmosphere that places them in the “gap” or second peak of the Kepler size distribution. In addition, a few rare objects that form in extremely low-viscosity discs accrete a core of 7 M⊕ and equal envelope mass, which is reduced to 3–5 M⊕ after evaporation. These objects end up with radii of ~6–7 R⊕.

Conclusions. Overall, we find that rocky planets form only in low-viscosity discs (α ≲ 10−4). When α ≥ 10−3, rocky objects do not grow beyond 1 Mars mass. For the successful low-viscosity cases, the most typical outcome of dry pebble accretion is terrestrial planets with masses spanning from that of Mars to ~4 M⊕.
A quantitative reverse Faber-Krahn inequality for the first Robin eigenvalue with negative boundary parameter
Authors: Cito Simone , La Manna Domenico Angelo
Published: November 2020

The aim of this paper is to prove a quantitative form of a reverse Faber-Krahn type inequality for the first Robin Laplacian eigenvalueλβwith negative boundary parameter among convex sets of prescribed perimeter. In that framework, the ball is the only maximizer forλβand the distance from the optimal set is considered in terms of Hausdorff distance. The key point of our stategy is to prove a quantitative reverse Faber-Krahn inequality for the first eigenvalue of a Steklov-type problem related to the original Robin problem.
Error estimation of the Besse Relaxation Scheme for a semilinear heat equation
Authors: Zouraris Georgios E.
Published: November 2020

The solution to the initial and Dirichlet boundary value problem for a semilinear, one dimensional heat equation is approximated by a numerical method that combines the Besse Relaxation Scheme in time [C. R. Acad. Sci. Paris Sér. I 326 (1998)] with a central finite difference method in space. A new, composite stability argument is developed, leading to an optimal, second-order error estimate in the discrete Lt∞(Hx2)-norm at the time-nodes and in the discrete Lt∞(Hx1)-norm at the intermediate time-nodes. It is the first time in the literature where the Besse Relaxation Scheme is applied and analysed in the context of parabolic equations.
Behavioral effects of a four-wing attractor with circuit realization: a cryptographic perspective on immersion
Authors: Khan Najeeb Alam , Qureshi Muhammad Ali , Hameed Tooba , Akbar Saeed , Ullah Saif
Published: November 2020

In this paper, we propose an innovative chaotic system, combining fractional derivative and sine-hyperbolic nonlinearity with circuit execution. The study of this system is conducted via an analog circuit simulator, using two anti-parallel semiconductor diodes to provide hyperbolic sine nonlinearity, and to function as operational amplifiers. The multi-stability of the system is also enhanced with the help of multi-equilibrium points for distinct real orders of system. The system explores the generation of a four-wing attractor in different phases, both numerically and electronically. By changing the input parameters of the system, different graphs are generated for current flow in state, phase, and space, to confirm the precision of the fractional order derivatives. A reasonable simulation shows that the deliberate circuit provides effective chaos in terms of speed and accuracy, which is comensurate with the numerical simulation. This nonlinear chaotic behavior is utilized to encrypt sound (.wav), images (.jpg), and animated (.gif) data which are a major requirement for the security of communication systems. The proposed circuit performs chaos and cryptographic tasks with high-effective analog computation, and constitutes a novel approach to this area of research.
Stacking of predictors for the automatic classification of disruption types to optimize the control logic
Authors: Murari A. , Rossi R. , Lungaroni M. , Baruzzo M. , Gelfusa M.
Published: November 2020

Nowadays, disruption predictors, based on machine learning techniques, can perform well but they typically do not provide any information about the type of disruption and cannot predict the time remaining before the current quench. On the other hand, the automatic identification of the disruption type is a crucial aspect required to optimize the remedial actions and a prerequisite to forecasting the time left for intervening. In this work, a stack of machine learning tools is applied to the task of automatic classification of the disruption types. The strategy is implemented from scratch and completely adaptive; the predictors start operating after the first disruption and update their own models, following the evolution of the experimental program, without any human intervention. Moreover, they are designed to implement a form of transfer learning, in the sense that they identify autonomously the most important disruption classes, generating new ones when necessary. The results obtained are very encouraging in terms of both prediction performance and classification accuracy. On the other hand, regarding the narrowing of the warning times, some progress has been achieved, but new techniques will have to be devised to obtain fully satisfactory properties.
Editorial
Authors: Colbeck Roger , Loveridge Leon , Weigert Stefan
Published: November 2020

In June 2018, our friend and colleague Paul Busch [1–3] passed away unexpectedly. Paul’s death put an abrupt end to a particularly productive period during which many of his ideas–after a long incubation period–came to fruition. There would have been more to come.

To remember Paul and to celebrate his achievements a memorial event was held in York a year after his untimely death. On the 18th and 19th June 2019, the workshop “Mathematical Foundations of Quantum Mechanics–in memoriam Paul Busch” took place at King’s Manor, a historic building dating back to the 15th century. Around 35 people attended the event: colleagues old and new, current and former students, collaborators, friends, admirers and family members. The meeting was kindly supported by the Department of Mathematics at the University of York, Paul’s academic home since 2005, and by the Institute of Physics, of which Paul was an Elected Fellow.
Time-energy uncertainty does not create particles
Authors: Roberts Bryan W , Butterfield Jeremy
Published: November 2020

In this contribution in honour of Paul Busch, we criticise the claims of many expositions that the time-energy uncertainty principle allows both a violation of energy conservation and particle creation, provided that this happens for a sufficiently short time. But we agree that there are grains of truth in these claims: which we make precise and justify using perturbation theory.
Effect of the hydraulic fracturing-induced slippage of regional natural fracture on casing deformation in horizontal shale gas wells: A case study on the Weiyuan block
Authors: Zeng Y J , Liu K , Ding S D , Zhou S M , Tao Q , Du J L , Du X Y
Published: November 2020

Casing deformation problems are widespread in the shale gas field, and the dominant natural fracture reactivation and slippage are treated as the main reasons for these casing deformations. This study establishes a mechanical model and uses the field data of Weiyuan to study the fracture slippage and the casing deformation. According to rock mechanics, the dominant natural fracture can be reactivated by the fluid injected into the fracture. A higher fluid pressure in the fracture can induce a larger slippage and a higher shear stress on the casing. The fracture slippage is not uniform along the fracture. Moreover, the maximum slippage is located at the center of the reactivation zone. The in-situ stress, friction coefficient, and angle between the fracture and the maximum in-situ stress can affect the slippage. Case studies on the casing deformation of two wells in Weiyuan have shown that the calculated slippage according to the analytical model herein is in accordance with the detected data in the field. In summary, this study provides a reliable and quick method for determining the slippage of the dominant fracture reactivation based on the distance from the fracture center.
Application of Inverted Vertical Line Method in Landslide Monitoring
Authors: Yang Zhongmin , Zhang Yufang , Li Jian
Published: November 2020

The inverted vertical line method is generally used in dam monitoring. It relies on the relative displacement between the vertical wire and vertical coordinate instrument installed in the dam wall to monitor the deformation of the dam at different heights. In this study, the inverted vertical line method is applied to a landslide monitoring process. Firstly, a geological exploration well is excavated during geological supplementary exploration. A fixed point is embedded in the exploration well basement as a vertical reference. Secondly, a buoy is erected at the wellhead. Thirdly, vertical coordinate instruments are installed at the upper and lower sides of the predicted sliding surface to monitor the displacement of the rock mass. Finally, the sliding direction and displacement of the sliding body are determined by analyzing the monitoring data. Hence, real-time monitoring of the landslide deformation is possible through the field application of the aforementioned method. Furthermore, the reliability of the inverted vertical line method in landslide monitoring was verified by comparing the monitoring results obtained with that from an inclinometer.
Numerical Analyses on the Rockbolt Behaviour in Rock Wedges Reinforcement Using 2D-DDA
Authors: Wang Wenqi , Nie Wen , Li Xu , Liu Shuang
Published: November 2020

One major concern in the design and construction of caverns in jointed rock mass is the potential failure of rock wedges falling from the roof or sliding out from the sidewalls. The rockbolts are commonly used to improve the stability and to prevent failure in the caverns. In this paper, the two-dimensional discontinuous deformation analysis (2D-DDA) method was used to analyse the stability of the rock wedge supported by rockbolts on the cavern roof. The joint relaxation method was adopted to represent a deformable rock joint under stresses. Parametric studies were conducted to investigate the effects of the confining pressure, the spacing and the angle between rockbolt and direction of wedge falling on the stability of the rock wedge. The numerical simulation results indicate that the wedge is self-supporting after stress redistribution if the confining pressure is larger than the critical confining pressure and the semi-apical angle of the wedge is less than the friction angle of rock joint. The force in rockbolt slightly decreases with reduced rockbolts spacing but increase when the rockbolt is not along the falling direction of rock wedge.
Shale Brazilian split test and numerical simulation of the discrete element method
Authors: Wang Jiong , Wang Yang , Gong Weili , Wang Zhaoxuan
Published: November 2020

This study performs a shale Brazilian split test by setting the loading and bedding directions at different angles to study the effect of anisotropy caused by the bedding structure and heterogeneity caused by different particles on the mechanical properties of shale. The results indicate that the cracks of the specimens splitting and breaking at 0° and 90° all extend vertically through the disk. A combination of Neper and 3DEC software is applied to the numerical simulation study of the shale splitting process through the discrete element method. The shale splitting failure modes are divided into three categories. At 0° and 90°, the cracks extend linearly through the loading ends, and the models show bedding and particle tensile failures, respectively. At 15°, the cracks run diagonally through the rock sample from the end of the upper loading section, parallel to the bedding direction. At 30° to 75°, the cracks propagate from the loading end along the parallel bedding direction. The experiments and numerical simulations verify that bedding influences the shale splitting failure mode and the mechanical behavior. Therefore, the investigation of the mechanical problems caused by the destruction of shale gas mining has a far-reaching significance.
Preliminary numerical analysis of the influence of pit-in-pit excavation on the stability of the foundation pit supported by diaphragm wall
Authors: Shao Yong , Chen Congxin , Zheng Yun , Zhang Yapeng
Published: November 2020

Pit-in-pit is common in foundation pit-engineering practice. Pit-in-pit excavation disturbs the stress field in the passive zone of the foundation pit, which induces the loss of soil resistance in the passive zone and adversely affects the safety of the foundation pit. Based on a real foundation pit supported by diaphragm wall in Hohhot, this study used the finite difference software FLAC3D to establish a finite difference model of the foundation pit. At different construction steps and excavation parameters, the horizontal displacements of the diaphragm wall, the vertical displacement of the soil around the foundation pit, and the plastic zone of the model were analyzed. It was found that the excavation of the inner pit intuitively impacted the deformation of the diaphragm wall, and the asymmetry of the position of the inner pit led to the whole pit’s deformation in a certain direction. Furthermore, we reported that the increase in excavation parameters h and l increased the subsidence of the soil closer to the inner pit. Moreover, excavation parameters, including L, h, and l, are proportional to the volume of the plastic area. This study provides reference value for designing foundation pits containing pit-in-pit.
Design of composite foundation for high-rise buildings in complex red bed karst site
Authors: Wei ping PENG , Zhong yi WEN , Xi PENG , Wei LIU , Qinghua ZHANG
Published: November 2020

Ground collapse occurs frequently in deep foundation construction in the shallow overlying rock-karst area, constituting a major hidden danger to personal safety and engineering quality. This study reveals the structural characteristics of honeycomb heterogeneous anisotropic rock mass through the geological radar scanning and the foundation optimization design of a high-rise building (35 floors) in the red layer karst site. Meanwhile, the giant karst cave pipeline is filled and reinforced by karst grouting, and an artificial dam is constructed to block the groundwater transport channel. Based on the analysis results of the stability against the punching and cutting of the karst cave roof, the composite foundation of the plain concrete rigid pile with low-bearing capacity and high replacement rate is proposed. Regarding the extremely thin karst cave roof area, the steel pipe pile is used for underpinning and reinforcement, effectively avoiding the risk of local instability and construction collapse caused by the effective length of the pile and large stress at the pile end. After completing the building, it runs well. Meanwhile, the monitoring shows that the maximum settlement deformation of the high-rise building is only 9.63 mm.
Study on hysteretic deformation characteristics and energy dissipation of granite under cyclic loading
Authors: Han Chao , Li Dejian , Rao Yuanhao , Wang Jiwei
Published: November 2020

The cyclic load test of granite under different paths is conducted using the strain control method. The nonlinear hysteretic deformation behavior is analyzed, and the energy evolution law in the process is described in detail. Three specific discoveries were made. (1) The skeleton curve shape in the cyclic test is less affected by the increase in the upper load limit and shows good loading memory characteristics. (2) The hysteretic characteristics of the stress-strain curve characterize the energy dissipation process. Dissipated energy is divided into plastic hysteresis and damping energy consumption. Damping energy consumption accounts for a considerable proportion of the total energy consumption at all levels, and the changing trend of the two is positively correlated. The upper limit of the cyclic load can significantly change the plastic hysteretic energy. (3) The loading-unloading process is more prone to large hysteresis deformation, and the unloading-reloading process has an unloading threshold. When the unloading amount is less than the threshold, the unloading-reloading curve linearly coincides, and the energy is dissipated during the process. When the unloading amount is greater than the threshold, damping energy will be generated to increase energy dissipation, and the hysteresis characteristic will appear.
Study on the mechanism of dynamic slip-weakening for a rock material interface based on a vibration experiment
Authors: Zhang K , Liu Y R , Yang Q
Published: November 2020

Slip-friction of faults and joint fractures is of great significance in the study of rock mass structural engineering stability and earthquake generation mechanism. Laboratory friction experiment is a great method to determine the frictional strength of rock interfaces. A large number of low-velocity experiments has been conducted to explain the friction mechanism in the regime of direct shear mode. However, the friction mechanism in the regime of vibration mode has rarely been studied. To study the slip-friction mechanism of rock interface under the vibration mode, a dynamic friction experiment with two blocks on a vibrating platform was performed. The experiments were conducted with hard granite samples at a vibration frequency of 1–10Hz, vibration amplitude 0.5–5mm, and normal stress of 0.5–4.5MPa. The results demonstrate that slip- and frequency-weakening phenomena were noticed and the general quantitative relationship of the three characteristic friction parameters is μ
3 > μ
1 > μ
2. Moreover, the normal stress has a significant effect on the weakening degree of the friction coefficient, and the change in the surface roughness may correlate with the change in the weakening degree.
A proposed method for mathematical quantitative description of fractures from borehole wall images
Authors: Han Zengqiang , Wang Chuanying , Jiao Yuyong , Wang Chao , Wang Jinchao
Published: November 2020

Fractures from borehole wall images are different from those from surface outcrop in trace pattern, distribution pattern, parameters description and so on. Focus on the geometric parameters of fractures from borehole images, a method for mathematical quantitative description of these fractures is proposed. The fracture from borehole images is described into a point in spatial coordinate system, and this point is defined Fracture Feature Point. The key parameters including dip direction, dip angle and position depth of fractures from borehole wall images are converted into coordinates of fractures feature points. The related calculation equations are deduced in local coordinate system and spatial coordinate system. Furtherly, the space distribution regularities of the fractures based on the distribution characteristics of fracture feature points are summarized. Typical application in multiple boreholes of this description method is studied and an analysis method for any two fractures’ connectivity is established based on Fracture Feature Point. The results of an engineering example research show that the method is effective in fractures connectivity analysis. The mathematical quantitative description method of fractures from borehole wall images will provide new ideas of the research on deep rock mass structure.
Strain Response of Tunnel Anchor Using Rayleigh Scattering-based Optical Fiber Sensing Technology in the Field Test
Authors: Shuai Wang , Yihu Zhang , Wei Hu
Published: November 2020

Tunnel anchor is a relatively new type of anchor for suspension bridges. Loading tests on a scale model in site are generally considered to be the most direct way to evaluate the bearing capacity of the tunnel anchor system. The response of the anchor body has received minimal attention and involves only a few or no measuring points, because the anchor plug does not undergo elastoplastic failure in a model test. This article intends to explore the relationship between the strain response of the anchor and the state of the surrounding rock. Optical fiber strain sensing technology based on adjustable wavelength optical time domain reflectometry (i.e., TW–COTDR) was applied to the scale model test of Baotaping Bridge tunnel anchor. The strain distribution and evolution of the entire anchor body were determined by optical measurements during overload. In the elastic and plastic stages of the anchor system, the strain around the anchor body linearly decreased from back to front, except for the top arch and the bottom plate at the end. The anchor strain–load curve was nonlinear, similar to the displacement–load curve, but unrelated to concrete damage, which signaled that plasticity began to appear in the anchor system. Therefore, the strain response of the anchor body can be used as an alternative to determine bearing capacity of the anchor system, especially when the displacement is too small to observe.
Deformation response and anchorage control of excavation unloading of high and steep rock slope
Authors: Dong Zhihong , Ding Xiuli , Huang Shuling , Wu Yongjin , Wu Aiqing
Published: November 2020

The stability and anchorage control of high and steep slopes in Southwest China are challenging problems in engineering construction. Considering the unloading stability of high and steep rock slopes, field monitoring and numerical analysis methods are used for feedback analysis to study the deformation, stress response, anchorage support scheme, and anchorage stress characteristics during the unloading process of slope excavation. The research shows that the displacement of rock mass of the high slope gradually increases and the local deformation exceeds 200 mm. The unloading relaxation area resulting from slope excavation is 25 m deep. The safety of the slope can be guaranteed after the joint reinforcement of deep anchor cable.
In-situ stress measurement technology and field application based on micro-optical imaging measurement method
Authors: Wang Yiteng , Wang Chuanying , Han Zengqiang , Wang Chao , Hao Haiyang
Published: November 2020

In-situ stress is natural stress existing in rock masses. As an important basic parameter, accurate in-situ stress is highly beneficial to the theoretical research and engineering application of rock mechanics. In-situ tests in boreholes are the most direct and effective way to obtain in-situ stress. However, the high temperature and high water pressure testing environment in boreholes limits the application scope of measurement sensors. In this study, a micro-optical imaging measurement method is proposed. On the basis of this method, an aperture measurement device is developed, and a complete set of in-situ stress measurement technology is formed. Laboratory and field application tests are carried out. The results of the temperature and pressure test in a laboratory show that the in-situ stress test technology improves service temperature and pressure and offers an extensive application range. The field test on a shallow borehole in an iron mine roadway and a deep borehole in a shale gas exploration well reveals the deformation of the test boreholes in the process of stress relief. This result proves the feasibility of the in-situ stress measurement technology. On the basis of the theory of elasticity, in-situ stress is calculated with reference to the in-situ diameter deformation of the boreholes and the mechanical parameters of the rock core. A number of in-situ stress tests are carried out under different borehole depths, and the testing times are recorded. Results show that the application of wireline coring drilling technology speeds up the test process. Hence, it can boost the operability of the in-situ stress test. In sum, the in-situ stress measurement technology based on the micro-optical imaging measurement method is feasible and operable and may thus improve the application depth of the in-situ stress measurement method based on the stress relief method.
Disaster characteristics and cause analysis of railroad slope in complicated and dangerous mountainous areas
Authors: Liu Hongyu , Ma Xianjie , Li Jian , Li Jiaming , Li Wei , Hou Lijie
Published: November 2020

With the vigorous development of China’s railroad industry, increased railroad construction has extended to complex and dangerous mountainous areas. During the construction and operation of railroads in this area, various geological disasters are inevitable, bringing significant difficulties to railroad construction and significant threats to personal safety. This study focuses on the typical railroad passing through dense and dangerous mountainous areas as the research object. Through on-site investigations, the characteristics of slope disasters along the railroad were analyzed following the laws of disaster distribution and characteristics of disaster development. The study analyzes the causes of slope disasters by investigating internal and external factors. The research results show that the geological disasters along the railroad can be divided into landslides and collapses, of which there are 8 landslide disasters and 15 collapse catastrophes. Landslides are characterized as creeping and fretting stages according to their development characteristics. Collapses can be divided into four types of dangerous rock masses according to the scale of disaster distribution. Many factors influence the development of landslide geological disasters, and the development of geological disasters is the result of the combined action of multiple influencing factors. By analyzing the slope disaster along the railroad, this study provides an effective reference basis for constructing complex mountain railroads in the future.
DFOS-based association rules analysis on the multi-fields information of Majiagou landslide
Authors: Zhang Lei , Shi Bin , Zheng Xing , Sun Yi-Jie
Published: November 2020

The multi-fields information of landslide can be obtained using distributed optical fiber sensing (DFOS) technology. Nevertheless, it is still a quite complicated work to analyze massive amounts of multi-fields information, and to evaluate the slope stability under multifields coupling effect. This paper introduced a data mining method named association rules analysis, and designed a DFOS-based monitoring system to record the multi-field information, including strain field, deformation field, seepage field, temperature field and environmental parameters, respectively. Taking Majiagou landslide as an example, the association rules analysis of the multi-field monitoring information revealed the reservoir water level is the domain factor that influences the deformation of Majiagou landslide. The correlation analysis method can explore the internal relationship among different fields of a landslide and provide scientific basis for slope stability evaluation and landslide early-warning.
Borehole parameter optimization for supercritical carbon dioxide phase-transition fracturing
Authors: Cheng W J
Published: November 2020

In recent years, supercritical carbon dioxide phase-transition fracturing (SCDPTF) has extensively been used in rock engineering as an environmentally friendly rock breaking technology. It is important to improve the energy efficiency and rock breaking effect by examining the SCDPTF borehole parameters. In this study, SCDPTF was first analyzed by numerical simulations. Based on the numerical simulation results, field tests were subsequently performed to determine the optimal borehole parameters. The results indicate that the rock mass around the borehole under the carbon dioxide phase-transition fracturing load can be divided into a crushing zone, a cracking zone, and a vibration zone. The radius of the crushing zone was ~0.297 m and that of the cracking zone was ~1.399 m, respectively. The optimal minimum burden line was 1.8 m, and the optimal borehole spacing was 2.5 m, respectively. The abovementioned results could provide effective guidance for the parameter design of SCDPTF.
Study on dynamic response of rock foundation pit blasting excavation to adjacent buildings
Authors: Jiang Teng-fei , Jiang An-nan , Li Xing-sheng
Published: November 2020

Focusing on safety problems of the blasting excavation of foundation pits near existing buildings, this study takes the Jinggangshan Road Station of Qingdao Metro Line 1 as the engineering background and establishes a three-dimensional numerical model of a foundation pit blasting excavation based on the dynamic response characteristics of buildings using the FLAC3D finite difference software. Moreover, the present study examines the dynamic response law of foundation pit blasting excavations under blasting vibrations and analyzes blasting vibration velocities at different measuring points near buildings. Results show that the blasting vibration velocity of key measuring points is consistent with the numerical simulation results. This finding demonstrates that the numerical model is reasonable; the influence of blasting vibrations on buildings presents different trends with varying heights, mainly concentrated in the lower part of the blasting side; the vibration velocity of the measuring points of buildings varies with different horizontal distances; and the impact of the monitoring points near the blasting side is far greater than that of the measuring points far from the blasting side. Velocity decreases as the distance between the detonation centers increases. The results have certain reference value and guiding significance in the selection of reasonable blasting parameters and the effective improvement of the safety threshold of foundation pit blasting vibrations.
Experimental Research on In-situ Monitoring of Coalbed Methane Extraction Pipes in a Coal Mine Working Face
Authors: Sang Haomin , Wang Zhiqiang
Published: November 2020

To study the stress and deformation characteristics of the coalbed methane (CBM) extraction pipe and to overcome the obstruction of the CBM extraction channel, an in-situ monitoring test of the extraction pipe was performed based on a coal mine working face in the Huainan mining area. According to the data of CBM overrun and field situation, the in-situ stress and deformation test of the CBM extraction pipes was designed and implemented, and the actual stress variation and deformation of the extraction pipe in the borehole was measured, which revealed the mechanical properties of the CBM extraction pipe as the working face advanced. The results show that the stress value of each measuring point increased as the working face advanced, and there was obvious stress concentration at the depth of 50 m. When the working face was ~35 m away from the test hole, there was a major increase in the stress growth rate. This work has guiding significance for the reasonable selection of CBM extraction pipes and optimization of extraction schemes in deep coal mines.
Factors affecting the deformation of the surrounding rock of tunnel based on rough set theory
Authors: Hou Shoujiang
Published: November 2020

The deformation of surrounding rock is a common hazard in tunnel engineering, and it can negatively affect the quality and safety of a project. Therefore, the analysis of factors affecting the deformation of tunnels surrounding rock has essential engineering significance. This work selected two subjective factors affecting the deformation of the surrounding rock of a tunnel, namely, the excavation method and the excavation footage, and four objective factors (i.e., the tunnel burial depth, the degree of weathering, the groundwater conditions, and the uniaxial compressive strength of rocks) as the factors affecting the deformation of tunnel surrounding rock. Data on the factors influencing deformation of 25 typical deformation sections of the Tianqiao Mountain Tunnel under construction were collected to establish the condition attributes in the decision table. The actual deformation level was used as the decision attribute in the decision table. Rough set theory was used to perform a completely objective analysis of these six factors. Results of the analysis show that the groundwater conditions are the most influential factor in surrounding rock deformation with a weight of 0.3333, and the degree of weathering is a redundant factor. This study can be used as a guide for reducing or avoiding the deformation of the surrounding rock of a tunnel.
Case study: Analysis of the correlation between casing deformation and fracture zone in Changning Block, Sichuan
Authors: Zhaowei Chen , Hu Cao , Xiaojin Zhou , Qiyong Gou , Haozhe Zhang
Published: November 2020

Casing deformation is an engineering problem that restricts the efficient development of shale gas in the Sichuan Basin. This paper analyzed the correlation between 67 casing deformation points and 256 fracture zones in the N201 wellfield, and conducted a statistical analysis of the distribution of the orientation of fracture zones, which may have/have not caused casing deformation. The Mohr–Coulomb criterion was used to analyze the stress state and the slip risk of these fracture zones. The results show indicate the following. (1) Fracture zone is the main factor leading to casing deformation. (2) Fracture zones with 60°–90° and 110°–120° orientations are likely to cause casing deformation, whereas fracture zones with 50°–70° orientation are relatively less likely to cause casing deformation. (3) The analysis of stress state shows that the orientations of high-risk fractures range from 74°–100° and 130°–160°, the orientations of medium-risk fractures range from 64°–74°, 100°–130°, and 160°–170 °, and the orientations of low-risk fractures are in the range of 0°–64° and 170°–180°. The theoretical results are basically consistent with the field statistical results. These results provide an explanation for the field statistical results in theory. This work not only demonstrates that a fracture zone is the major geological factor that causes casing deformation, but also provides a feasible method for us to predict the casing deformation in the future.
Landslide Susceptibility Prediction Based on the Information Value-Logistic Regression Model and Geographic Information System
Authors: Huang Faming , Ye Zhou , Zhou Chuangbing , Yao Chi , Hu Qichao , Jiang Shui-Hua
Published: November 2020

The landslide susceptibility prediction (LSP) is generally implemented using certain types of single models; however, certain drawbacks exist in the single models; e.g., it is difficult to clearly reflect the weights of landslide-related environmental factors if only the information value (IV) model is adopted. To overcome these limitations, this study proposes an IV-logistic regression (IV-LR) model for LSP. The landslides that occurred in the southern part of Chongyi County, China, are used as study cases. Nine environmental factors—elevation, slope, plane curvature, profile curvature, relief amplitude, distance to river, lithology, normalized difference vegetable index, and normalized difference built-up index—are adopted based on remote sensing and geographic information system. Certain landslide grid units and the same number of non-landslide grid units are used as the output variables of these models. The IV, LR, and IV-LR models are used to implement the LSP in the southern part of Chongyi County. The predicted landslides susceptibility in Chongyi County mostly occurred in areas with low elevations, close distance to rivers, carbonate lithology, low vegetation coverage rate, and densely populated areas. The results show that the prediction rate of the IV-LR model (80.4%) is higher than that of the LR model (76.8%), followed by the IV model (72.8%); they further demonstrate that the IV-LR model has its unique superiority and rationality compared with the IV and LR models.
Regional-scale detection of unrecorded landslides in mountainous terrains by using interferometric stacking technique
Authors: Chen Lichuan , Liu Pengfei , Liao Weiming , Zhang Kui , He Fei , Zeng Liang
Published: November 2020

Landslide hazard investigation by using a standard geological survey in a mountainous terrain can result in low accuracy and poor update rate. These deficiencies could lead to unrecorded landslides, which could be catastrophic. Synthetic aperture radar interferometry (InSAR), which can detect subtle ground surface movements in large areas, is considered as a promising solution for detecting unrecorded landslides in mountainous terrains. To evaluate its feasibility, this study conducted analysis work and associated field survey in Fengjie County. The county is characterized by a mountainous terrain and is located in a notoriously landslide-prone area in the Three Gorges reservoir in China. A total of 30 SAR images captured by the Sentinel-1A satellite in 2018 were processed to obtain the ground surface movements of the county. InSAR results identified 276 anomalous regions that were not recorded in the local inventory map. Of these regions, 18 were verified as unrecorded landslides on the basis of the field survey. The observable deformation of the landslides recorded in the local inventory map was also detected by InSAR. This work, which is not supposed to diminish the importance of standard geological surveys, could improve the accuracy and update rate of local inventory maps.