scholarly journals Mechanical Characteristics of Cement-Based Grouting Material in High-Geothermal Tunnel

Materials ◽  
2020 ◽  
Vol 13 (7) ◽  
pp. 1572 ◽  
Author(s):  
Mingnian Wang ◽  
Yunpeng Hu ◽  
Cheng Jiang ◽  
Yicheng Wang ◽  
Dagang Liu ◽  
...  
Keyword(s):  
High Temperature ◽  
Relative Humidity ◽  
Mechanical Characteristics ◽  
Coupling Effect ◽  
Peak Stress ◽  
Curing Temperature ◽  
Peak Strain ◽  
Humidity Effect ◽  
Grouting Material ◽  
Study Results

The cement-based grouting materials used for practical purposes in high-geothermal tunnels are inevitably affected by humidity and high temperature, leading to the deterioration of mechanical properties. Based on the characteristics of changing high temperatures and two typical conditions of hot-humid and hot-dry environments in high-geothermal tunnels, many mechanical strength tests were carried out on the grouting material cured under different environmental conditions. The study results indicated that high temperature and low relative humidity were unfavorable to the development of mechanical characteristics of grouting material, but the coupling effect of two factors could improve the strength at early ages and reduce the degradation of long-term strength. As the curing temperature exceeded 56.3 °C, the humidity effect on strength played a more important role in recovering the strength of grouting material damaged by high temperature. Temperature had more significant impact on the relative peak stress while the relative humidity had greater influence on the relative peak strain. A calculation compressive constitutive model was prospered, which considering both temperature and relative humidity. The study results may provide much valuable experimental data and theoretical supporting for the design of compression constitutive of cement-based grouting material in high-geothermal tunnel.

Comparison Analysis on the Mechanical Properties of HSC and NSC after the Action of High Temperatures

2014 ◽  
Vol 1014 ◽  
pp. 49-52
Author(s):  
Xiao Ping Su
Keyword(s):  
Mechanical Properties ◽  
High Temperature ◽  
High Temperatures ◽  
High Strength Concrete ◽  
Elasticity Modulus ◽  
Strain Curve ◽  
Peak Stress ◽  
High Strength ◽  
Peak Strain ◽  
Strength Concrete

With the wide application of high strength concrete in the building construction,the risk making concrete subject to high temperatures during a fire is increasing. Comparison tests on the mechanical properties of high strength concrete (HSC) and normal strength concrete (NSC) after the action of high temperature were made in this article, which were compared from the following aspects: the peak stress, the peak strain, elasticity modulus, and stress-strain curve after high temperature. Results show that the laws of the mechanical properties of HSC and NSC changing with the temperature are the same. With the increase of heating temperature, the peak stress and elasticity modulus decreases, while the peak strain grows rapidly. HSC shows greater brittleness and worse fire-resistant performance than NSC, and destroys suddenly. The research and evaluation on the fire-resistant performance of HSC should be strengthened during the structural design and construction on the HSC buildings.

scholarly journals Study on Mechanical Properties of Basalt Fiber Shotcrete in High Geothermal Environment

Materials ◽  
2021 ◽  
Vol 14 (24) ◽  
pp. 7816
Author(s):  
Yueping Tong ◽  
Yan Wang ◽  
Shaohui Zhang ◽  
Yahao Chen ◽  
Zhaoguang Li ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Compressive Strength ◽  
Constitutive Model ◽  
Basalt Fiber ◽  
Strain Curve ◽  
Peak Stress ◽  
Curing Temperature ◽  
Peak Strain ◽  
Transverse Cracks ◽  
Geothermal Environments

With the development of infrastructure, there are growing numbers of high geothermal environments, which, therefore, form a serious threat to tunnel structures. However, research on the changes in mechanical properties of shotcrete under high temperatures and humid environments are insufficient. In this paper, the combination of various temperatures (20 °C/40 °C/60 °C) and 55% relative humidity is used to simulate the effect of environment on the strength and stress–strain curve of basalt fiber reinforced shotcrete. Moreover, a constitutive model of shotcrete considering the effect of fiber content and temperature is established. The results show that the early mechanical properties of BFRS are improved with the increase in curing temperature, while the compressive strength at a later age decreases slightly. The 1-day and 7-day compressive strength of shotcrete at 40 °C and 60 °C increased by 10.5%, 41.1% and 24.1%, 66.8%, respectively. The addition of basalt fiber can reduce the loss of later strength, especially for flexural strength, with a increase rate of 11.9% to 39.5%. In addition, the brittleness of shotcrete increases during high temperature curing, so more transverse cracks are observed in the failure mode, and the peak stress and peak strain decrease. The addition of basalt fiber can improve the ductility and plasticity of shotcrete and increase the peak strain of shotcrete. The constitutive model is in good agreement with the experimental results.

Mechanical and Acoustic Emission Characteristics of Limestone after High Temperature

2012 ◽  
Vol 446-449 ◽  
pp. 23-28
Author(s):  
Gang Wu ◽  
De Yong Wang
Keyword(s):  
Mechanical Properties ◽  
Acoustic Emission ◽  
High Temperature ◽  
Strain Curve ◽  
Peak Stress ◽  
Mechanical Parameter ◽  
Emission Characteristic ◽  
Uniaxial Compression Test ◽  
Peak Strain ◽  
Different Temperatures

The mechanical properties and acoustic emission evolution process of limestone under the action of high temperature load were investigated by combining methods of uniaxial compression test and acoustic emission (AE) technique. The temperature varies in the range of 100, 200, 400, 600 and 800°C. By analysis of AE parameters and the mechanical parameter, the relations of stress-time (strain)-accumulative counts of AE, stress-time (strain)-AE rates under different temperatures are analyzed. The results show that the temperature does not obviously affect the mechanical properties of limestone at the temperature ranging from 100 to 400°C, the accumulative ring-down counts and accumulative energy increase with the rise of temperature. However, when the temperature is above 400°C, the mechanical properties of limestone deteriorate rapidly with the increase of temperature, and also the peak stress of limestone decrease in different extents. In the meantime, the accumulative ring-down counts decrease coupled with the change of mechanical parameter. The brittle fracture is main failure mode of limestone when the temperature is below 800°C and the change of peak strain of limestone is unobvious. The stress-strain curve conforms to the acoustic emission curve which shows that changes of minerals formation and microstructure due to high temperature result in the changes of mechanical and acoustic emission characteristic of limestone.

Effects of temperature gradient on the granite’s mechanical properties

2021 ◽  
pp. 1-10
Author(s):  
Jinyong Pei ◽  
Huagang He ◽  
Dongtao Hu ◽  
Shanke Lv ◽  
Jing Wang ◽  
...  
Keyword(s):  
High Temperature ◽  
Temperature Gradient ◽  
Strain Curve ◽  
Peak Stress ◽  
Tangent Modulus ◽  
Peak Strain ◽  
Compression Tests ◽  
Different Temperatures ◽  
Effects Of Temperature ◽  
Increasing Temperature

Temperature gradient significantly affects the production of surrounding rock stress in mining engineering. The mechanics and deformation characteristics of the rock will change under the temperature gradient, thereby increasing the probability of accidents in the roadway. This paper conducts uniaxial compression tests on granite at different temperatures from room temperature to 250∘C, and analyzes in detail the changes in the stress-strain curve, peak stress, peak strain and tangent modulus of granite under high temperature and different temperature gradient conditions. The results of this study are as follows: (1) Under high temperature conditions, the granite’s peak stress and tangent elastic modulus increased with temperature from 17 to 100∘C, then decreased from 100∘C to 250∘C, whereas the granite’s peak strain increased steadily with increasing temperature; (2) under temperature gradient, the granite’s peak stress and tangent modulus first decreased and then increased with increasing temperature gradient, while the granite’s peak strain first decreased and then increased at 100∘C, but first increased and then decreased from 150∘C to 250∘C.

INFLUENCE OF FORCED CONVECTION IN LIQUID INSIDE THE TIN ON DURATION OF STERILIZATION IN THE COURSE OF FISH PROCESSING

2017 ◽  
pp. 137-144
Author(s):  
Gennadiy Valentinovich Alexeev ◽  
Elena Igorevna Verboloz
Keyword(s):  
High Temperature ◽  
Liquid Phase ◽  
Forced Convection ◽  
Thermal Process ◽  
Processing Time ◽  
Fish Processing ◽  
Study Results ◽  
Equipment Modernization ◽  
Bottom To Top

The article focuses on the process of intensive mixing of liquid phase in the tin during high-temperature sterilization, i.e. sterilization when temperature of the heat carrier reaches 150-160°C. It has been stated that for intensification of the thermal process during sterilization of tinned fish with liquid filling it is preferable to turn a tin from bottom to top. This operation helps to increase the driving power of the process and to shorten warming time. Besides, high-temperature sterilization carried out according to experimental modes, where the number of tin turnovers is calculated, greatly shortens processing time and improves quality of the product. In this case there is no superheating, all tins are evenly heated. The study results will contribute to equipment modernization and to preserving valuable food qualities.

scholarly journals Axial Stress-Strain Performance of Recycled Aggregate Concrete Reinforced with Macro-Polypropylene Fibres

2021 ◽  
Vol 13 (10) ◽  
pp. 5741
Author(s):  
Muhammad Junaid Munir ◽  
Syed Minhaj Saleem Kazmi ◽  
Yu-Fei Wu ◽  
Xiaoshan Lin ◽  
Muhammad Riaz Ahmad
Keyword(s):  
Axial Stress ◽  
Peak Stress ◽  
Polypropylene Fibre ◽  
Recycled Aggregate Concrete ◽  
Recycled Aggregate ◽  
Recycled Aggregates ◽  
Peak Strain ◽  
Stress Strain ◽  
Polypropylene Fibres ◽  
Aggregate Concrete

The addition of macro-polypropylene fibres improves the stress-strain performance of natural aggregate concrete (NAC). However, limited studies focus on the stress-strain performance of macro-polypropylene fibre-reinforced recycled aggregate concrete (RAC). Considering the variability of coarse recycled aggregates (CRA), more studies are needed to investigate the stress-strain performance of macro-polypropylene fibre-reinforced RAC. In this study, a new type of 48 mm long BarChip macro-polypropylene fibre with a continuously embossed surface texture is used to produce BarChip fibre-reinforced NAC (BFNAC) and RAC (BFRAC). The stress-strain performance of BFNAC and BFRAC is studied for varying dosages of BarChip fibres. Results show that the increase in energy dissipation capacity (i.e., area under the curve), peak stress, and peak strain of samples is observed with an increase in fibre dosage, indicating the positive effect of fibre addition on the stress-strain performance of concrete. The strength enhancement due to the addition of fibres is higher for BFRAC samples than BFNAC samples. The reduction in peak stress, ultimate strain, toughness and specific toughness of concrete samples due to the utilisation of CRA also reduces with the addition of fibres. Hence, the negative effect of CRA on the properties of concrete samples can be minimised by adding BarChip macro-polypropylene fibres. The applicability of the stress-strain model previously developed for macro-synthetic and steel fibre-reinforced NAC and RAC to BFNAC and BFRAC is also examined.

scholarly journals Experimental Study on Biaxial Dynamic Compressive Properties of ECC

Materials ◽  
2021 ◽  
Vol 14 (5) ◽  
pp. 1257
Author(s):  
Shuling Gao ◽  
Guanhua Hu
Keyword(s):  
Strain Rate ◽  
Lateral Pressure ◽  
Deformation Modulus ◽  
Strain Curve ◽  
Peak Stress ◽  
Pressure Level ◽  
Strain Rates ◽  
Peak Strain ◽  
Stress Strain Curve ◽  
Toughness Index

An improved hydraulic servo structure testing machine has been used to conduct biaxial dynamic compression tests on eight types of engineered cementitious composites (ECC) with lateral pressure levels of 0, 0.125, 0.25, 0.5, 0.7, 0.8, 0.9, 1.0 (the ratio of the compressive strength applied laterally to the static compressive strength of the specimen), and three strain rates of 10−4, 10−3 and 10−2 s−1. The failure mode, peak stress, peak strain, deformation modulus, stress-strain curve, and compressive toughness index of ECC under biaxial dynamic compressive stress state are obtained. The test results show that the lateral pressure affects the direction of ECC cracking, while the strain rate has little effect on the failure morphology of ECC. The growth of lateral pressure level and strain rate upgrades the limit failure strength and peak strain of ECC, and the small improvement is achieved in elastic modulus. A two-stage ECC biaxial failure strength standard was established, and the influence of the lateral pressure level and peak strain was quantitatively evaluated through the fitting curve of the peak stress, peak strain, and deformation modulus of ECC under various strain rates and lateral pressure levels. ECC’s compressive stress-strain curve can be divided into four stages, and a normalized biaxial dynamic ECC constitutive relationship is established. The toughness index of ECC can be increased with the increase of lateral pressure level, while the increase of strain rate can reduce the toughness index of ECC. Under the effect of biaxial dynamic load, the ultimate strength of ECC is increased higher than that of plain concrete.

scholarly journals Cultivation of gerbera irrigated with treated domestic effluents

2010 ◽  
Vol 14 (6) ◽  
pp. 582-588 ◽  
Author(s):  
Lisânea M. O. Damasceno ◽  
Aderson S. de Andrade Júnior ◽  
Hans R. Gheyi
Keyword(s):  
High Temperature ◽  
Experimental Design ◽  
Relative Humidity ◽  
Plant Development ◽  
Leaf Growth ◽  
Treated Wastewater ◽  
Nutritional Requirements ◽  
Randomized Experimental Design ◽  
Growth Production ◽  
Domestic Effluents

This paper evaluates the nutritional impact on growth, production and quality variables of gerbera crop when fertigated with treated domestic effluents. An experiment was carried out in greenhouse at the Embrapa Meio-Norte in Teresina, in the State of Piauí, Brazil, from July to October 2007. A completely randomized experimental design with five treatments and five replications was adopted. The treatments investigated were T1 - 100% of water and nutritional requirements of crop were met with chemical fertigation (N e K2 O); T2 - 25% volume of water through fertigation and 75% treated wastewater effluents (TWE); T3: 50% volume of water through fertigation and 50% TWE; T4: 75% volume of water with fertigation and 25% TWE; and T5 - 100% volume of water supplied through TWE. Leaf growth and plant development were favored by the application of 50% fertigation and 50% TWE (T3). As for commercial requirements, the best results for number of flowers were obtained with T4. However, concerning quality, T2 produced flowers in July and August with longer stems, but in the months of September and October, no treatment achieved this standard due to high temperature and low relative humidity of the air in the region.

scholarly journals Research on the Mechanical Characteristics of H-section Steel Frame under the Action of Thermo Mechanical Coupling

2021 ◽  
Vol 233 ◽  
pp. 03022
Author(s):  
Yucheng LI ◽  
Wei WANG ◽  
Xing WANG
Keyword(s):  
High Temperature ◽  
Plastic Strain ◽  
Mechanical Characteristics ◽  
Simulation Software ◽  
Frame Structure ◽  
Concentrated Load ◽  
Composite Frame ◽  
Fire Environment ◽  
Full Cross Section ◽  
Composite Frame Structure

The research on the mechanical characteristics of concrete-filled steel tubular composite frame under high temperature fire environment is one of the research hotspots. In this paper, the finite element simulation software is used to analyze the concrete-filled steel tubular composite frame structure. The failure mode of the flexural deformation of the composite frame structure under high temperature fire environment is introduced. The simulation results of the deformation and displacement of the single-layer single span and two-layer two-span composite frame structure are deeply studied, including the different temperature field, structural field, structural field of each beam and column The results show that: with the temperature rising, the horizontal plastic strain, vertical displacement and local plastic region of beam and column are redistributed and changed in high temperature fire environment, and the flexural effect of two-story two-span concrete-filled steel tubular composite frame under different fire positions is analyzed. The results show that: with the temperature rising, the horizontal plastic strain at the concentrated load is not the results show that the deflection and deformation redistribution are obvious, and the deflection and deformation redistribution are obvious at the joint points of beams and columns. Finally, a mechanism is formed and destroyed. The flexure effect of mode 1 is larger than that of condition 2, which indicates that the flexural effect of two-story two span CFST composite frame under full cross-section fire is larger than that of condition 2 It should be better. The research results can provide reference value for the reinforcement and repair of CFST composite frame under high temperature fire.

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