bluuebunny/crossref_metadata_2025 huggingface dataset:
Assessment of the air purifier effectiveness under model conditions
Authors: Staszowska A
Published: February 2021

The aim of this study was to evaluate the operation of a stationary air purifier under the model conditions of a non-occupied test chamber with dimensions similar to a typical living room. The purifier was equipped with a system for neutralization of volatile organic compounds, disinfection (neutralizing chamber with a system of UVA lamps, plates made of TiO2, UVC lamp settings) and HEPA filters at the air outlet of the device. The conducted research focused on the effectiveness of removing bacterial bioaerosols (M. luteus and B. subtilis) as well as formaldehyde and the sum of volatile organic compounds. The assessment was made for two ranges of fan flow, 100 and 300 m3 / h (Standard and Turbo). The unit shows high efficiency in removing the tested bacterial strains, i.e. 100% after 60 and 90 minutes, respectively. Higher efficiency occurred for lower fan output. However, its effectiveness in removing TVOCs did not exceed 58%. Additionally, the formation of formaldehyde was noted during the operation of the purifier.
Modelling AOB-NOB competition in shortcut nitrification compared with conventional nitrification-denitrification process
Authors: Drewnowski J , Shourjeh M S , Kowal P , Cel W
Published: February 2021

In particular, mainstream deammonification and/or shortened nitrification-denitrification via nitrite (so-called “nitrite shunt”) is a promising new treatment concept that has the potential to revolutionise how nitrogen removal is achieved at WWTPs. Understanding the role of the AOB/NOB competition in the nitrogen cycle in wastewater treatment systems will change operational strategies of the novel nitrogen removal processes. The key role in this process is inhibition of NOB activity undesirably affects AOB activity and leads to inefficient partial nitrification process and when used as pre-treatment for Anammox it can limit nitrite supply to Anammox bacteria. Successful NOB repression requires a combination of such factors as a low DO concentration, a rapid transition from aerobic to anoxic conditions, and tight control of Temperature and/or pH. The major driving force behind the successful NOB washout is the inhibition of those bacteria based on the difference in the growth rate between AOB and NOB. The obtained results from this study show the mechanisms and operating conditions (e.g. DO concentration, Temp.) leading to complete domination of AOB over NOB under aerobic conditions. This paper presents the perspectives on modelling AOB-NOB competition in shortcut nitrification. The combined deammonification, shortened nitrification-denitrification and/or nitritation-anammox process was compared with conventional nitrification-denitrification based on own experiments and literature data. Its successful application as shortcut nitrification technology and new control system will represent a paradigm shift for the wastewater industry, offering the opportunity for sustainable wastewater treatment, energy-neutral or even energy-positive facilities, and substantial reductions in treatment costs.
Obtaining the 3D geometry of the blade in a training aircraft
Authors: Bąbel R , Sawicki K , Gąsiorowski M
Published: February 2021

The blade whose task is to generate together with the hub engine thrust is one of the most important construction elements of a propulsion unit in the PZL 130 Orlik trainer The design of appropriate profiles of the blade determines its efficiency and thus is one of the most important construction tasks due to complex blade shapes. After designing and manufacturing the blade, it is advisable to tests any possible geometric deviations in the model blade. It is also essential to carry out tests to specify changes in its geometry after a specified number of flying hours to inspect the risk of damage to the blade during its operation. Moreover, a number of studies are conducted on icing which occurs on the airframe and the blade itself. The aim of this paper is to present a technique of 3D scanning applied to the training aircraft blade so as to copy its precise geometry after a specified period of operation. Scanning enables the use of a created geometry for numerical analyses, in particular of icing during aircraft operation. The Nikon Maker MMDx scanner and the GeoMagic Design X Software were used to create the 3D model and scan the blade of the PZL 130 Orlik training aircraft.
Determining aircraft aerodynamic characteristics of regular and non-linear airframes and evaluating the efficiency of the applied methods
Authors: Uliczka M , Smykla I
Published: February 2021

This paper discusses three methods of determining aerodynamic characteristics and compares the research results. The research cases are two planes selected by the authors, i.e. EM-10 Bielik and YOKOSUKA MXY7 OHKA and investigated as an airframe with the so-called non-linear aerodynamic flow and a classical design. Aerodynamic characteristics was determined by the following methods: aerospace engineering formulas, CAD simulation of the airflow around the object and examining the prototype in a wind tunnel. The last section of the paper compares the obtained results and evaluates the efficiency of all methods to examine both types of the aircraft. The compared parameters are lift and drag versus angles of attack and aircraft polars.
Comparative study of demineralized coals by IR spectroscopy
Authors: Fedorova N I , Malysheva V Yu , Mikhaylova E S , Ismagilov Z R
Published: February 2021

The article presents the results of a study of the influence of ash content of coal on the qualitative characteristics of their IR spectra. Comparative analysis of the IR spectra of the initial and demineralized bituminous coals showed that the mineral components present in their composition in the form of silicates, clay minerals, and carbonates limit the resolution of the method in the range <970 cm-1, since their characteristic peaks are superimposed on the lines from organic matter of coal. Treatment of coals with mineral acids leads to a decrease in their ash content by 5-8 times, which results in an increase in the content of conventional organic matter in demineralized samples. This, in turn, leads to an increase in the optical density of absorption bands in the entire range of the study and, therefore, allows them to be identified more reliably.
Basic technologies of direct catalytic oxidation of H2S to sulfur
Authors: Khairulin S.R. , Kerzhentsev M.A. , Salnikov A.V. , Ismagilov Z.R.
Published: February 2021

A brief analysis of the existing technical solutions for the purification of gases from hydrogen sulfide is carried out. The huge volume of such emissions and the lack of ready-made solutions for mini-gas processing plants and mini-refineries determine the relevance of the development of environmentally reliable, efficient and compact technologies to solve this problem. The main results of tests of technologies and installations developed at the Institute of Catalysis of the Siberian Branch of the Russian Academy of Sciences (Novosibirsk) based on the direct catalytic oxidation of hydrogen sulfide are presented.
Pilot tests of low-temperature catalytic reduction of sulfur dioxide in realistic conditions of sulfur recovery unit at copper plant of Polar Division of PSC “Norilsk Nickel”
Authors: Khairulin S.R. , Yashnik S.A. , Salnikov A.V. , Ismagilov Z.R.
Published: February 2021

Pilot tests of low-temperature catalytic reduction of sulfur dioxide in realistic conditions (technological gases of Vanyukov furnace) of sulfur recovery unit at Copper Plant of Polar Division of JSC “Norilsk Nickel” have been carried out. It has been demonstrated that the developed CuCr catalyst provides sulfur recovery not less than 90% at GHSV-2000 h−1 in a temperature range 200-260°C.
Study of bitumoids extracted from O-alkylated brown coal
Authors: Shpakodraev K. M. , Zherebtsov S.I. , Malyshenko N.V. , Ismagilov Z. R.
Published: February 2021

The component composition of bitumen obtained from brown coal of grade 1B of the Tyulganskoye deposit of the South Ural basin was investigated using destructive O-alkylation with n-butanol. The positive effect of alkylating treatment on the bitumen yield is shown. A number of individual compounds were identified by gas chromatography-mass spectrometry in the composition of the studied bitumoids: n-Tetracosanol-1, Docosanoic acid, Tricosanoic acid, Podocarpa-5,8,11,13-tetraen-7-one, 13-hydroxy-14-isopropyl, etc. Among the identified substances, biologically active substances are present in significant concentrations: β-Sitosterol, gamma-Tocopherol, Sugiol, Behenic alcohol, etc.
A model to predict the elastic field radiated by a magnetostrictive patch transducer into an omnidirectional waveguide
Authors: Cousin G , Lhémery A , Grondel S
Published: February 2021

Magnetostrictive patch transducers (MPT) can be used as sources or sensors of elastic guided waves in non-destructive testing and structural health monitoring methods. A tool for simulating them is under development to help designing optimal MPT for a given application. It requires the prior accurate modelling of transduction phenomena involved in such patches and of the GW fields they generate. A MPT is made of a thin magnetostrictive strip under a static magnetic field, glued to the waveguide under examination and excited by an alternative current circulating in a coil. In the strip where they take place, transduction phenomena are similar to those generated by an electro-magnetic acoustic transducer (EMAT) in a ferromagnetic medium. They involve magnetostrictive strain, magnetization force and surface traction and Lorentz force (Clausse et al. 2017 J. Phys.: Conf. Ser.
797 102004), which can be transformed into equivalent surface stresses at the outer surface of the strip. A matrix model is developed to propagate the equivalent stresses from this outer surface to that of the waveguide. Once equivalent stress distributions are computed at this latter surface, a model (Barras et al. 2020 Ultrasonics
103 1060782) is used to predict the MPT radiation into the waveguide. Overall, the chaining of these models constitutes a semi-analytical multi-physics model for GW radiation by MPT of high computing efficiency.
Evidence of the formation of the shock scattering induced violent cavitation cluster during boiling histotripsy insonation: A numerical case study
Authors: Pahk K J
Published: February 2021

Boiling histotripsy is a promising noninvasive ultrasonic technique that can be used to mechanically destroy solid tumours. In boiling histotripsy, the formations and dynamics of a boiling vapour bubble and cavitation clouds contribute towards mechanical tissue fractionation. Whilst a number of numerical and experimental studies have been performed to examine and understand the evolution of a boiling bubble at the HIFU focus in a viscoelastic medium, little is known about the subsequent generation of cavitation clouds that form in between the boiling bubble and the HIFU transducer during boiling histotripsy insonation. Previous experimental observations suggest that the shock scattering by a boiling bubble may play a significant role in producing cavitation clouds. The main objective of the present study is, therefore, to investigate the relationship between the shock scattering phenomenon and the occurrence of cavitation clouds through (a) performing a numerical simulation of nonlinear wave propagation with the presence of a bubble at the HIFU focus and (b) comparing with the previous high speed camera observations of a cavitation cluster formation. The size of a bubble (i.e., 95.7, 128.1 and 258 μm in diameter) as well as the HIFU exposure conditions (i.e., a driving frequency of 1.1 MHz, peak positive and negative pressures of 68.4 MPa and −13.9 MPa) used in the simulations were obtained from the previous boiling histotripsy experiments conducted with a tissue gel phantom. The numerical results presented in this study clearly demonstrate that the shock scattering is the main cause of the creation of a cavitation cluster in boiling histotripsy.
Machine learning algorithms for the prediction of the mechanical properties of railways’ rail pads
Authors: Ferreño D , Sainz-Aja J A , Carrascal I A , Cuartas M , Pombo J , Casado J A , Diego S
Published: February 2021

Train operations generate high impact and fatigue loads that degrade the rail infrastructure and vehicle components. Rail pads are installed between the rails and the sleepers to damp the transmission of vibrations and noise and to provide flexibility to the track. These components play a crucial role to maximize the durability of railway assets and to minimize the maintenance costs. The non-linear mechanical response of this type of materials make it extremely difficult to estimate their mechanical properties, such as the dynamic stiffness. In this work, several machine learning algorithms were used to determine the dynamic stiffness of pads depending on their in-service conditions (temperature, frequency, axle-load and toe-load). 720 experimental tests were performed under different realistic operating conditions; this information was used for the training, validation and testing of the algorithms. It was observed that the optimal algorithm was gradient boosting for EPDM (R2 of 0.995 and mean absolute percentage error of 5.08% in test dataset), TPE (0.994 and 2.32%) and EVA (0.968 and 4.91%) pads. This algorithm was implemented in an application, developed on Microsoft. Net platform, that provides the dynamic stiffness of the pads characterized in this study as function of material, temperature, frequency, axle-load and toe-load.
Development of recycled polypropylene-based sustainable composites with recycled carbon fibre/Kenaf fibre hybrid reinforcements
Authors: Cong X Y , Pierce R , Liu X L
Published: February 2021

Recycled carbon fibre (RCF) and Kenaf fibre (KF) have been used as reinforcement materials in combination with recycled polypropylene (RPP) matrix to manufacture a sustainable composite. Maleic anhydride grafted polypropylene (MAPP) has also been used as a compatibilizer to modify the interface between fibres and matrix composites, resulting in improved composite strength and thermal resistance. After modified with MAPP, the recycled carbon fibre was combined with KF fiber to improve the KF/RPP composite properties such as mechanical and thermal stability. The results were indicated that the mechanical properties of RCF/RPP composite was improved with increasing of MAPP when MAPP added 8 Wt. %, these reached a Maximum of 77.6 MPa and 271.4 MPa, respectively. When the RCF combined with the KF hybrid composite, the mechanical strength of the hybrid composite was improved with the amount of RCF. The DSC results showed that the MAPP could reduce the Tc of RPP and increase the crystallization degree. The hybrid composite presented that the crystallization degree was increased with the increment of RCF content. The DMA results showed that the RCF can influence the β translation of RPP.
The growth mechanism of zinc oxide micro-rods via vapor-phase method
Authors: Pan J M , Yu Y , Liu J T , Wang L N
Published: February 2021

Two different ZnO micro-structures were deposited by a Chemical Vapour Deposited method in a small quartz tube. The micro-rods and micro-wires were found on the edge of the tube respectivly. The morphology and structural properties were texted by scanning electronic microscopy technique and X-ray diffraction. The results shows that the micro-rods have typical hexagonal wurtzite structure without any defect and the micro-wires have two types, the single ZnO crystal and the double-like one. The X-ray diffraction gives some information through the intense 002 peak which means the samples have a great wurtzite structure and grown up along the c-axis. The mechanism of the two samples also discussed, it is in relation to the substrate temperature and the concentration of the mixed gas.
Research on the influence of humid heat environment on the mechanical properties of multilayer composite structure
Authors: Wang W C , Yang H W , Li N , Kang Y S
Published: February 2021

For resin-based composite materials, the hot and humid environment has a very obvious impact on its performance. Moisture can penetrate into the composite material through diffusion and capillary action, which causes the resin matrix with plasticization, swelling and hydrolysis, and swelling and infiltration of liquid will lead to micro-stress inside the material. Thus, the polymer macromolecular chain will stretche or even break, and it can lead to the weakening of the interface properties of the resin and the fiber, which in turn leads to fluctuations in the mechanical properties of the composite material. In this paper, we carried out damp and heat tests on multilayer composite structures to study the effects of different temperature and humidity environments on the physical and chemical properties and mechanical properties of composite materials. The law of moisture absorption characteristics of composite materials is clarified, and the moisture absorption in the initial stage of moisture absorption is proportional to the moisture absorption time t1/2. With time increasing, the moisture absorption gradually tends to balance, and the higher are the damp and heat conditions, the greater the moisture absorption of the composite material will be. The moisture absorption is between 0.13% and 0.78% with different damp and heat environments. The chemical structure of the composite material itself has not changed significantly, and the damp-heat effect will induce the destruction of the fiber-matrix interface and the expansion of cracks along the pores, which weakens the bonding strength of the interface. As a result, the moisture makes the transverse performance and shear performance of the composite material greatly reducing, but has little effect on the longitudinal performance.
Mechanical properties, permeability and freeze-thaw durability of low sand rate pervious concrete
Authors: Liu H B , Zhou S , Wei H B , Li W J , Xiu R , Zhu B
Published: February 2021

To improve the mechanical properties, permeability and freeze-thaw resistance of pervious concrete (PC), make the gradation more reasonable, a kind of low sand rate pervious concrete (SPC) was prepared in this study. The sand was used to replace coarse aggregate with equal volume method. The effects of sand replacement rate (0%, 5%, 10% and 15%) on the compressive strength, flexural strength, effective porosity, permeability coefficient and compressive strength loss (under the freeze-thaw cycle) of SPC were studied. The results showed that the compressive strength and flexural strength increased first and then decreased with the increase of sand replacement rate, while the effective porosity and permeability coefficient showed the opposite trend. Moreover, the compressive strength of SPC with different sand replacement rate gradually decreased as the freeze-thaw cycles test continued. After 100 freeze-thaw cycles, the compressive strength loss rate of SPC with 5% sand content is the lowest and is 6.79% lower than that control group (0% content), which indicated that the addition of sand could significantly enhance the freeze-thaw durability of SPC. Based on the experimental results, the recommended sand replacement rate is 5%.
Thermal analysis of cylindrical molds using thermoplastic composite during robotic fiber placement
Authors: Liu X L , Han Z Y , Zhao Z Y , Sun S Z
Published: February 2021

Thermoplastic composites have gradually become a hotspot due to its low manufacturing cost and good weld ability. In this study, to realize the placement of the thermoplastic composite material carbon fiber/polyether ether ketone (CF/PEEK), the consolidation roller of the existing thermoplastic composite placement head is optimized. The process simulation analysis of the thermoplastic composite material is carried out. A two-dimensional heat transfer model of the thermoplastic prepreg laying process is established in ANSYS. Transient thermal analysis is carried out using the life and death unit technology. The optimum machining parameters are obtained through analyzing the influence of mold temperature, laying speed, and heating temperature on the temperature field of the first layer in curved surface laying.
The mode II delamination toughness of arc unidirectional fiber-reinforced composites with ENF test
Authors: Kang Y S , Zhang X Z , Wang L M , Jiang C
Published: February 2021

To obtain the mode II delamination toughness (the energy release rate GIIC) of arc unidirectional fiber-reinforced composites, the end notched flexure (ENF) test with arc specimen was used to study. In terms of theory, the formulas of compliance and GIIC for Arc-ENF specimen were derived by using energy method and Irwin-Kies formula, and the crack length correction and friction coefficient were respectively introduced to correct these formulas, with the verification by the numerical simulation. As the ENF test, the compliance curve of the Arc-ENF specimen was recorded under the condition of the constant loading speed, and the crack tip position was determined by the strain diagram of the specimen in 1-3 plane with the optical strain gauge. Finally, the friction coefficient and the GIIC of the Arc-ENF specimen in the ENF test were determined using the corrected formulas, the numerical simulation method and the ENF test data.
Preparation and characterization of 6-O-caffeic acid chitosan
Authors: Chen W P , Huang D J , Hu Z , Zhuang Y L , Lu S T
Published: February 2021

The modified chitosan retains the excellent properties of chitosan and can broaden its application. In this paper, an approach of protection-deprotection was used to synthesize 6-O-caffeic acid chitosan with chitosan as the raw material. Firstly, the free amino group on the 2-position carbon of chitosan was protected by phthaloylation, and then the -OH of 6-position carbon of chitosan reacted with caffeic acid by ester condensation. Finally, in the presence of hydrazine hydrate, the amino group was deprotected to form 6-O-caffeic acid chitosan. Fourier transform infrared (FTIR) spectroscopy and X-ray diffraction (XRD) characterized the structures of the intermediates and products. The results showed that 6-O-caffeic acid chitosan was successfully obtained. Thermogravimetric analysis indicated that 6-O-caffeic acid chitosan had better thermo-stability than chitosan in nitrogen. This will expand the application of chitosan in vaious fields.
Influence Analysis of Large-area PHC Pipe Pile Construction on the Surrounding Environment in Deep Silt Site
Authors: Zheng Zhongliang , Ding Jihui , Li Xiaoqing , Su Shuyu , Zhang Cong
Published: February 2021

There are a large number of deep and thick soft soil foundations along the river and coastal areas. PHC pipe piles have become one of the foundation treatment methods widely used in soft soil foundations. Taking the construction of a pile foundation project in Wenzhou as an example, the thickness of the dredger fill and silt at the site is 27.20∼33.60m, and the impact of large-area pile group construction on the surrounding environment is discussed. The results show that: (1) The load imposed on the pile top and the pile sinking depth during the construction of the foundation pile increase according to an exponential function. (2) The direction of horizontal soil squeezing deformation around the field is related to the position of the measuring point. The corner range is small and the middle range is larger, but the direction of maximum displacement is basically along the shortest line between the pile position and the measuring point. (3) The vertical direction of the measuring point varies greatly with the construction time and pile position, and the uplift and settlement appear repeatedly. The monitoring results can provide a reference for the construction of similar projects.
The test effect evaluation of distributed optical fiber sensing technology applied to stress test of bored pile
Authors: Zhang Long , Liu Zhenghong , Yu Yongtang , Zheng Jianguo , Huang Xiaowei , Chen Xiaosan
Published: February 2021

The application of distributed optical fiber sensing technology to stress test of bored pile is a kind of line measurement method developed in recent years. It has the advantages of more measuring points and stronger anti-interference, but its test effect is rarely compared with other methods in practical engineering. In order to evaluate the test effect of distributed optical fiber sensing technology, the optical fiber and sliding micrometer tube were embedded at the same time during the construction of test pile, and then the static load test of pile was carried out to compare the test results of the two. The test results show that the strain distribution of the pile obtained by the distributed optical fiber sensing technology and the sliding micrometer method are the same, and the maximum strain difference between them is about 100 με. The distributed optical fiber sensing technology can better reflect the detailed deformation of the pile.
Analysis and research on the bearing capacity of geocell reinforced cushion subgrade in liyu expressway
Authors: Wang Xiaoming , Zhou Yongxing , Feng Jiaqing , Pradhan Rupesh , Liu Guofeng
Published: February 2021

This paper takes the filling roadbed of the Lipu-Yulin Expressway (Liyu Expressway) project in the Guangxi Zhuang Autonomous Region as the backup project. Numerical simulation research is conducted by employing the general finite-element analysis software ABAQUS. The three-dimensional numerical models of the unreinforced soil embankment and reinforced embankment are formulated and the subgrade’s ultimate bearing capacity is calculated and solved by the elastoplastic finite element method. Effects of planar and three-dimensional reinforcement, i.e., geotextile and geocell, on the ultimate bearing capacity of the foundation are calculated and analysed. Simultaneously, the strength and deformation characteristics of geocells and geotextiles under embankment loads are studied. Research results show that the enhanced bearing capacity of geocell-reinforced foundation in this paper is increased by about 30%, which is greater than that of the planar reinforced material. This research results in this paper provide reference and theoretical basis for designing and analysing geocell-reinforced embankment in actual engineering practices.
Research on the influence of the intercalated rock stress by the approach of three tunnels
Authors: Wu Jinlin , Gong Lun , Zhou Shangjin , Gou Mingzhong , Huang Jianhua
Published: February 2021

The article relies on the Guang-Xing section of the southern section of the third phase of Chengdu Metro Line 1 to cross the Cheng-Hua Railway. The change of the stress with the approaching is analyzed. Study the stress change law of the intercalated rock under the change of the distance and angle: when the distance decreases, the maximum principal stress increases more obviously, which shows that the smaller distance, the easier the damage of intercalated rock. The stress state of the rock at different angles is that it is safer to overpassing and undercrossing, the horizontal approach is the most dangerous, and the other angles tend to be between the two. Through three-dimensional numerical simulation, the influence of the excavation process and construction method is analyzed, and it is found that the change of the secondary stress on the sandwiched rock by the mining method is relatively larger than that of the shield method. This makes the surrounding rock disturbance relatively large, resulting in the weakening of the sandwiched rock, which is directly manifested as the increase of the subgrade displacement.
Constitutive model of confined concrete with stirrups by acid rain erosion
Authors: Yue ZHENG , Shansuo ZHENG , Xiaohang LIU
Published: February 2021

In order to study the influence of stirrup corrosion level on the peak stress, peak strain, ultimate strain and shape of stress-strain curve of the confined concrete, 15 reinforced concrete prism specimens were subjected to acid rain erosion by artificial climate simulation technique followed by axial pressure tests. Based on Mander’s model and the existing research results, the calculation formulas of the peak stress f’
cco, peak strain £cco, ultimate strain ε
cco, ultimate strain ε
cu0 and shape factor r of the uncorroded specimens are determined. The factor calculation formulas for peak stress, peak strain, ultimate strain and shape factor of corroded specimens is developed by regression analysis of test data, respectively, and then the constitutive model of confined concrete by acid rain erosion is established. By comparing the simulation results with the experimental data, it can be found that all the peak stress, peak strain, ultimate strain and stress-strain curves shape of the specimens obtained by the proposed method are in good agreement with the experimental data. Thus the constitutive mode for confined concrete established in this paper can accurately reflect the mechanical performance of RC prism specimen by acid rain erosion, indicating its adaptiveness for estimating the residual bearing capacity and the seismic performance of RC structure under the acid rain environment.
Numerical analysis of reasonable distance between tunnel faces for twin tunnel
Authors: Li Changgui , Zhao Junbo , Hu Juan , Ju Xiuying , Tian Xiaoxu
Published: February 2021

Based on the MIDAS-GTS numerical analysis platform, the construction characteristics of the left and right holes of the newly-built twin tunnel with a large section and a small distance were systematically analyzed, and the evolution laws of the displacement changes of the tunnel and the mid-rock pillar under the left and right full-section tunnel method were studied. The results show that: (1) with the increase of the lag distance, the surface settlement decreases gradually. When the lag distance is greater than 2.0D, increasing the lag distance has little effect on the maximum settlement value. (2) The maximum value of the surface settlement trough occurs between the left and right tunnels, which is the superposition area affected by the two tunnels. (3) The increase of lag distance has little effect on the final horizontal displacement of arch waist and mid-rock pillar. Considering that the influence range of face excavation on the surrounding rock of the tunnel is within 15m, the lag distance should not be too large and should not be less than 15m. (4) With the decrease of the lag distance, the superposition effect of the twin tunnel becomes more and more obvious. With the increase of lag distance, this phenomenon begins to weaken obviously, and obvious separation phenomenon appears.
Particle flow analysis of basalt fiber gabion slope under conditions of rapid drawdown of water level
Authors: Fan ZHU , Zhenxue ZHU , Chao SU , Jianjian DAI , Heng ZHANG , Yujun MA
Published: February 2021

As a new green material, basalt fiber has the advantages of high strength and corrosion resistance, and is an ideal material for ecological protection technology. The rapid change of the hydraulic gradient within the slope caused by the sudden drop of river water level is an important factor inducing bank slope instability. Studying the stability of gabion slope protection under this condition is the key to evaluating the effect of gabion support. Taking a basalt fiber gabion slope protection project as an example, this paper carried out the stability study of the gabion slope protection under the condition of sudden drop in water level and compared it with the original slope. The stability was analyzed from the perspectives of deformation and stress, and revealed The deformation mechanism and the beneficial effects of the gabion structure during the instability failure process of the original slope. The results show that under the condition of a sudden drop in river water level, the use of gabion support from the left side of the slope to the slope surface can improve the stability of the slope, and there will be no continuous sliding surface in the slope, and the failure of gabion appears as partial dislocation and separation phenomenon. The research results provide important reference value for river gabion slope protection design and stability evaluation.
Simulation analysis of mechanical properties of shear connectors of steel-concrete composite beams
Authors: Fan Xin , Wu Jiong
Published: February 2021

In order to further study the mechanical properties and development distribution of shear connectors of steel-composite beam under the influence of concrete shrinkage and creep. In this paper, on the basis of the existing experimental research, ABAQUS software is used to establish the steel-composite beam model. The structural forms of the model include simply supported beam and continuous beam, and the shear connectors of steel-composite beam include three types: stud connectors, PBL connectors and composite connectors. The time development and spatial distribution of vertical displacement, connector shear force and slip at interface of each composite beam with concrete creep are calculated by finite element software, and some calculated results are in good agreement with the existing test results. By comprehensively comparing the calculation results of the key sections of each composite beam at some time points, the mechanical properties and their respective applications of the shear connectors of the steel-composite beam are analyzed and summarized, and the research results can guide the design and engineering application of the shear connectors of the steel-composite beam.
Comparative study on compressive and uplift load tests of PHC pipe pile
Authors: Ding Jihui , Zhang Cong , Gan Yu , Zhang Jinlei
Published: February 2021

There are 5∼8 m thick non self weight collapsible loess in the project site of a power plant. In order to study the bearing relationship between compressive and uplift piles in loess site, static load tests were carried out on PHC pipe piles with diameter of 400 mm and 500 mm and pile length of 12 m. Under the same pile top load, the displacement of uplift pile top is greater than that of compression pile top. Based on the measured load displacement curve, the uplift bearing capacity of PHC pipe pile with pile diameter of 500 mm is 32.5% higher than that of pile diameter of 400 mm. When the pile diameter is 400 mm and 500 mm respectively, the ultimate bearing capacity of PHC uplift pile is 26.24% and 27.70% of compression pile respectively. GM (1,1) model of grey system can fit and predict the load displacement curve of PHC pipe pile under compression and pull-out. Compared with the measured results,the relative error of GM (1,1) model of grey system is larger in the previous stages of load, and decreases gradually with the increase of load.
Layered soil exploration based on the time domain spectral induced polarization method
Authors: Li Xin , Chao Manni , Ju Lei , Wang Junlong , Zhang Kai , Wang Jiancheng
Published: February 2021

Soil stratification is the basic problem of soil development and utilization in the farmland, which can be used as a reference for later development and planting. Traditional soil stratification method is inefficient and needs to introduce new methods and techniques. In this paper, time domain spectral induced polarization method was introduced to carry out electric sounding exploration for the certain soil, and the observed data were processed and interpreted by using half-life time and deviation degree. The results show that the application of time domain spectral induced polarization method in soil stratification is feasible, and the half-life time and deviation degree are effective as interpretation parameters. The measured results and conclusions of this work can provide a basis for related research and the reference for relevant work.
Study on effect of mechanical sand on mechanical properties and fractal characteristics of mortar pore structure
Authors: Chen Can , Yang Haicheng , Yu Fang
Published: February 2021

The influence of stone powder content, fly ash and other factors on mechanical properties, pore structure and fractal dimension of machine-made sand mortar were studied, and the relationship between fractal dimension and mechanical properties of mortar was explored. The research shows that with the increase of the content of stone powder, the mechanical properties of mortar and the fractal dimension of pore structure of different sizes increase; the porosity and average pore size of the mortar decrease, and the ternary of cement-fly ash-stone powder The micro-particle system can effectively optimize the pore structure distribution of the mortar; the fractal dimension of the mortar using ordinary river sand is significantly smaller than that of machine-made sand under the same conditions; with the increase of the fractal dimension of the pore structure, the compressive strength and flexural strength of the mortar continue to increase Large, the fractal dimension and the macroscopic mechanical properties of the mortar show a good correlation.
Study on the Reinforcement Mechanism of the Deep Replacement Caverns for the Giant Slope Block Combined by Structural Planes
Authors: Lai Daoping , Xu Jianrong , Wu Guanye , Chen Yuan
Published: February 2021

The left bank of the cushion pond of Baihetan hydropower station is a slant and dip slope. The gently inclined intra-layer fault zones, the steep-dip faults and the unloading fissures cutting the slope to form several potentially unstable blocks. The computational results show that the stabilities of the blocks are controlled by inclined intra-layer fault zones. A method of treatment applying deep replacement caverns and load-reduction excavation was proposed to reinforce the unstable blocks. In order to study the reinforcement mechanism of the deep replacement caverns for the giant slope blocks controlled by inclined intra-layer fault zones, the 3D simulation analysis of the slope treatment construction was carried out by use of FLAC3D software, and a 3D geo-mechanical model was developed to carry out experimental research. The results of the calculation and experiment show that the deep concrete replacement caverns effectively control the shear and sliding deformation of the bottom slide surface and improve the stability of the blocks combined by structural surfaces. In the process of slope strength reduction and overloading, the slope deformation and cracking are gradually extended from the surface to the inner part, and shear stresses of the front deep replacement cavern are the largest of all the caverns. Therefore, it is more beneficial to control the deformation of the slope and improve the stability of the giant blocks by increasing the size of the front deep replacement cavern. The research results have important guiding significance for the reinforcement treatment of the giant blocks in the left bank of Baihetan cushion pond and similar projects.
Analysis on the Mechanical Characteristics of Onshore Wind Power Generation Foundation Structure
Authors: Zhou Heng , Li Xiaomin , Liu Jing , Di Shengjie
Published: February 2021

Based on the 3D finite element method, considering the plastic damage model of concrete, the uncoordinated deformation relationship between steel foundation ring and concrete, and the coordinated displacement relationship between steel bars and concrete, this paper conducts a simulation analysis on onshore wind power generation foundation, and studies the stress characteristics of the foundation under ultimate load condition. The results show that the lower part of the steel foundation embedded plate is a weak part, which not only needs to pay attention to the tensile failure, but also needs to prevent the compression failure. Perforated steel bars arranged on the top of steel plates have a obvious stress effect, which obviously strengthens the connection between steel plates and concrete. With the weakening of the connection between steel foundation and concrete, the top displacement and relative displacement of the contact surface between steel plate and concrete gradually increase. With the increase of friction coefficient between steel foundation and concrete, the stress of perforated steel bars and the displacement of foundation ring top surface also decrease. The research results of this paper can provide an important reference for the design and reinforcement of infrastructure.
Automatic detection method of bridge cracks based on residual network
Authors: Yan Wang , Junjie Ying , Junteng Mao , Yong Chen , Kai Wu
Published: February 2021

At present, the level of bridge crack detection is not high. In order to solve the problems of weak robustness of traditional image processing methods and time-consuming and laborious manual detection, a pixel level detection algorithm of bridge cracks based on adding residual block is proposed, which provides more intuitive and accurate detection results for bridge health assessment. Firstly, the concrete beam slab crack data set with a certain amount of data is built to train and test the model. After comparing and analyzing the four learning rates, 2×10−4 is chosen as the initial learning rate. Finally, in the aspect of fracture segmentation, the model proposed in this paper has good performance and good crack identification effect. It can accurately and efficiently locate, classify and identify fractures, which has certain practical application value.
Carbonation and Mechanical property of the Concrete Core Samples from a concrete dam after long-term operation
Authors: Zhiguo NIU , Yuan LI , Ri YOU
Published: February 2021

To investigate the ageing characteristics of dam concrete, concrete core samples were obtained from an existing dam. The compressive strength and carbonation depth were determined. The relationship between compressive strength, carbonation depth and operation time were analyzed. The results show that the compressive strength of dam concrete increases with operational time, the increasing rate of compressive strength was gradually decreased, and the compressive strength gradually increases with depth carbonation growth. There was a certain correlation between compressive strength, operational time and depth carbonation. The research results will provide a reference for the safety evaluation of hydraulic concrete structures in service.
Study on Mechanical Characteristics of Support Structure in Tunnel Entance Section under Mechanized Construction
Authors: Guo Hongyan , Tang Dengzhi , Yao Chengrui , Zhang Xiaolong
Published: February 2021

In view of the mechanical characteristics of the support structure under the mechanized construction conditions of the shallow buried section of the tunnel entrance, numerical simulation methods are used to compare and analyze the different cycle footage and the different tunnel face depth before and after the tunnel face reinforcement been carried out when the shallow buried section of the tunnel entrance is constructed by the micro-step method. The results of the study show that the primary support and pipe shed force increases with the increase in the depth of the tunnel face (buried depth), and decreases with the increase of the cyclic footage; When the fiberglass bolt is used to reinforce the face, the axial tensile stress of the fiberglass bolt can reach 18kN; Without reinforcement of the tunnel face, the primary support of the arch at the entrance of the tunnel is vulnerable to cause tensile damage; After the tunnel face is reinforced, the tensile stress of the primary support is significantly reduced.
Study on The Evaluation of Surrounding Rock Stability and Limit Displacement of High-Pressure Stratum Tunnel
Authors: Zhang Xiaolong , Guo Hongyan , Ye Lianchao , Tang Dengzhi
Published: February 2021

Aiming at the problem of the value of the stability and limit displacement of the surrounding rock of highway tunnel with high pressure, the method of numerical limit analysis is adopted, and one of the working conditions is analyzed in detail. Firstly, this paper adopts the formation structure method to calculate and establish a plane model for calculation and analysis with the help of FLAC3D software, so as to study the influence of reduction coefficient on surrounding rock deformation and its law. Secondly, by holding other variables unchanged, two different working conditions with and without high water pressure are compared and analyzed, and it is obtained that the ultimate safety factor of the integrity instability of surrounding rock of the formation tunnel with high water pressure is 1.30, and that of the integrity instability of surrounding rock of the formation tunnel without high water pressure is 1.80. Finally, the results are compared and analyzed and it is found that the stability of tunnel surrounding rocks with high pressure is lower than that without high pressure, and the limit displacement is greater than that without high pressure.
Study on the length of cable-free zone of wide cantilever cable stayed bridge with low pylon
Authors: Li Shuqin , Fan Keyu , Gan Tianyu
Published: February 2021

Low pylon cable-stayed bridge is a new type of composite bridge between girder bridge and traditional cable-stayed bridge. Because of its good mechanical properties, economic benefits and beautiful shape, low pylon cable-stayed bridge is widely used in highway and urban landscape bridges. In this paper, a wide and low pylon cable-stayed bridge under construction is taken as the research background, and the numerical simulation model is established by using the finite element analysis software MIDAS CIVIL. The influence of the length of the cable-free zone is studied. By changing the length of cable-free zone at the tower root and the length of cable-free zone in the middle of span, the influence of the length of non-cable zone on the deformation, bending moment, internal force and cable force of low pylon cable-stayed bridge at the completion stage is studied. The reasonable value range of non-cable zone length is obtained. The research results will provide theoretical guidance for the design and construction of similar projects.
Research on construction quality control of prefabricated concrete bridge based on BIM technology
Authors: Chao Song , Haoli Zhang , Guogang Ying , Shuangshuang Wang , Yidong Xu
Published: February 2021

In recent years, China has made great efforts to promote prefabricated concrete bridge technology. However, due to the construction quality problems, the application of prefabricated concrete bridge technology is limited. BIM technology can be applied to the whole life cycle of a construction project, which is a new way to solve the problem. This paper uses questionnaires to investigate the quality problems of prefabricated concrete structures, the necessity of BIM application at various stages and the application effects are analyzed. The results show that the application of BIM Technology in each stage of the project can improve some quality problems.
Research on neural network in consolidation effect of soft foundation
Authors: Wang Guang lu
Published: February 2021

The method and application situation of neural network is universal application. Datum of project and monitoring from a project of soft foundation by vacuum preloading was filtrated and summarized. After analysis and comparison, establishment of optimization neural network model was used to evaluate the consolidation effect. By the sensitivity of impact factors, it was analyzed that the main parameter of soft foundation consolidation process.