scholarly journals Investigation of the Effects of Freeze-Thaw Cycles on Geomechanical and Acoustic Characteristics of Tuff Specimens under Different Stress Paths

2020 ◽  
Vol 2020 ◽  
pp. 1-20
Author(s):  
Yong-gang Xiao ◽  
Chang-hong Li ◽  
Jie Cao ◽  
Yu Wang ◽  
Zhi-qiang Hou ◽  
...  
Keyword(s):  
Frequency Band ◽  
Physical And Mechanical Properties ◽  
Peak Stress ◽  
Open Pit ◽  
Natural State ◽  
Uniaxial Compression Test ◽  
Peak Strain ◽  
Loading Test ◽  
Freeze Thaw ◽  
Rock Samples

In the process of development and construction of open-pit mine slope in the high altitude and cold area, freeze-thaw (F-T) cycles have an important impact on rock engineering structure. F-T cycles lead to the decrease in physical and mechanical properties of rock, which is closely related to the stability of open-pit slope. In this paper, the influence of F-T cycles on geomechanical and acoustic emission (AE) characteristics of tuff specimens under different stress paths was studied by using F-T cycle treatment, in situ AE monitoring, and uniaxial loading test. The results indicated that under the same stress path, the cumulative AE count/energy of rock samples subjected to F-T cycles was less than that of rock samples not subjected to F-T cycles. The peak frequency distribution of AE signal during the loading process of rock specimen presented the phenomenon of frequency bands. The width of the low-frequency band of the rock samples subjected to F-T cycles was larger than that of the rock samples under the natural state. The frequency and width of the high-frequency band of the rock samples subjected to F-T cycles were larger than those of the rock samples under the natural state. The rock samples subjected to F-T cycles had higher plastic strain than those without F-T cycles. According to the uniaxial compression test results of F-T rock samples under different stress paths, the peak stress and peak strain have little change, but the AE characteristics were obviously different.

scholarly journals Geomechanical and Acoustic Properties of Intact Granite Subjected to Freeze–Thaw Cycles during Water-Ice Phase Transformation in Beizhan’s Open Pit Mine Slope, Xinjiang, China

Water ◽  
2019 ◽  
Vol 11 (11) ◽  
pp. 2309 ◽  
Author(s):  
Yu Wang ◽  
Wenkai Feng ◽  
Huajian Wang ◽  
Jianqiang Han ◽  
Changhong Li
Keyword(s):  
Energy Balance ◽  
Fatigue Damage ◽  
Frequency Band ◽  
Open Pit Mine ◽  
Acoustic Properties ◽  
Open Pit ◽  
Cold Regions ◽  
Detection Techniques ◽  
Freeze Thaw ◽  
Energy Balance Approach

The deterioration of rock geomechanical behaviors subjected to freeze–thaw (F–T) action is a determining factor for rock engineering and rock structures in cold regions. In this work, taking six groups of granite obtained from an open pit mine as the research object, F–T cycle treatment, in-situ AE (acoustic emission) monitoring and ultrasonic detection techniques were performed to experimentally reveal the effects of F–T fatigue damage on the mechanical and acoustic properties of granite. The results indicate that the F–T action impacts the rock’s mesoscopic structure, deformation, strength, P and S-wave velocities, AE pattern and energy release. The accumulated AE counts and accumulated AE energy show a decreasing trend as the F–T cycle increases. The frequency spectrum revealed that the width of the low frequency band decreases and the high frequency band increases with increasing F–T cycles, indicating that there is an increase in large-scale cracks for a sample with high F–T treatment. In addition, energy balance analysis further illustrates the energy dissipation and release mechanism. The energy proportion used to drive the crack propagation is relatively small with high F–T treatment, and the final released energy becomes the minimum. The energy evolution characteristics analyzed by the energy balance approach is in good agreement with AE results. It is suggested that the F–T fatigue damage influences the rock energy storage and release characteristics and the instability of rock in the cold regions.

scholarly journals Dynamic Characteristics of Sandstone under Coupled Static-Dynamic Loads after Freeze-Thaw Cycles

2020 ◽  
Vol 10 (10) ◽  
pp. 3351
Author(s):  
Bo Ke ◽  
Jian Zhang ◽  
Hongwei Deng ◽  
Xiangru Yang
Keyword(s):  
Energy Absorption ◽  
Dynamic Characteristics ◽  
Shear Failure ◽  
Strain Curve ◽  
Peak Stress ◽  
Peak Strain ◽  
Compression Stress ◽  
Stress Strain Curve ◽  
Stress Strain ◽  
Freeze Thaw

The effect of temperature fluctuation on rocks needs to be considered in many civil engineering applications. Up to date the dynamic characteristics of rock under freeze-thaw cycles are still not quite clearly understood. In this study, the dynamic mechanical properties of sandstone under pre-compression stress and freeze-thaw cycles were investigated. At the same number of freeze-thaw cycles, with increasing axial pre-compression stress, the dynamic Young’s modulus and peak stress first increase and then decrease, whereas the dynamic peak strain first decreases and then increases. At the same pre-compression stress, with increasing number of freeze-thaw cycles, the peak stress decreases while the peak strain increases, and the peak strain and peak stress show an inverse correlation before or after the pre-compression stress reaches the densification load of the static stress–strain curve. The peak stress and strain both increase under the static load near the yielding stage threshold of the static stress–strain curve. The failure mode is mainly shear failure, and with increasing axial pre-compression stress, the degree of shear failure increases, the energy absorption rate of the specimen increases first and then decreases. With increasing number of freeze-thaw cycles, the number of fragments increases and the size diminishes, and the energy absorption rates of the sandstone increase.

Experimental Research on Acoustic Emission of Granite under Uniaxial Compression and Splitting Tensile

2012 ◽  
Vol 232 ◽  
pp. 24-27
Author(s):  
Zong Zhan Li ◽  
Jun Lin Tao ◽  
Yi Li
Keyword(s):  
Compressive Strength ◽  
Acoustic Emission ◽  
Uniaxial Compression ◽  
Uniaxial Compressive Strength ◽  
Loading Rate ◽  
Testing Machine ◽  
Peak Stress ◽  
Uniaxial Compression Test ◽  
Peak Strain ◽  
Ae Energy

This paper makes the acoustic emission of granite under uniaxial compression and splitting tensile test by electro-hydraulic testing machine and AE .We studied the relationship of uniaxial compressive strength and splitting tensile strength with the loading rate and AE characteristics of granite .The results show that uniaxial compressive strength and peak strain raise with loading rate, the AE energy gradually increases and get maximum in the 30% of the peak stress in the process of uniaxial compression test, and in the splitting tensile AE energy generates in the initial loading and gets maximum when the granite brittle fracture.

scholarly journals On the Fracture Evolution and Instability of Pyrite-Filled Marble Exposed to Freeze-Thaw-Compression Loads

Lithosphere ◽  
2021 ◽  
Vol 2021 (Special 4) ◽  
Author(s):  
Yu Wang ◽  
Haonan Yang ◽  
Chun Zhu ◽  
Shaohua Gao
Keyword(s):  
Progressive Failure ◽  
Failure Process ◽  
Peak Stress ◽  
Image Correlation ◽  
Natural Fracture ◽  
Open Pit ◽  
Full Field ◽  
Strain Concentration ◽  
Freeze Thaw ◽  
Stimulation Of

Abstract The preexistence of the geological discontinuities in cold regions is susceptible to freeze-thaw weathering and rock instability, and even the occurrence of geological hazards is strongly impacted by the discontinuities. Knowledge of how natural fracture affects the rock field deformation is crucial to rock stability prediction. This work is aimed at revealing the influences of freeze-thaw on failure process for pyrite-filled marble obtained from an open pit slope. All the tested marbles were selected to roughly have the same initial pyrite band; the full-field displacement and the progressive failure behaviors under uniaxial compression were qualitatively and quantitatively analyzed using 3D digital image correlation (3D DIC) technique. The testing results show that the previous freeze-thaw action weakens the cementation between the rock matrix and pyrite band; the peak stress and strain are obviously impacted by the freeze-thaw treatment. In addition, the stimulation of pyrite bands influences the displacement development and high strain concentration pattern. The stimulation of pyrite band results in the formation of strain concentration zone, and shear sliding occurs until rock failure. Moreover, it is found that the stimulation of pyrite band and its localized strain takes place progressively and develops fast for marble exposed to higher freeze-thaw treatment. It is suggested that the field deformation development depends on the stimulation of the pyrite bands.

Influence of Replacement Rate on Triaxial Mechanical Performance of Recycled Concrete

2014 ◽  
Vol 584-586 ◽  
pp. 1531-1535 ◽  
Author(s):  
Yi Sheng Su ◽  
Er Cong Meng ◽  
Zong Ping Chen ◽  
Jun Yu Wu
Keyword(s):  
Mechanical Performance ◽  
Great Influence ◽  
Peak Stress ◽  
Confining Pressure ◽  
Recycled Concrete ◽  
Recycled Aggregate ◽  
Peak Strain ◽  
Replacement Rate ◽  
Loading Test ◽  
The Impact

Replacement rate is an important factor that affects the mechanical properties of recycled concrete. In order to study the influence of replacement rate on triaxial mechanical performance of recycled concrete, 20 recycled concrete cylinder specimens for conventional triaxial loading test with recycled aggregate replacement rate as changing parameters were designed. The results show that replacement rate has a great influence on peak stress of recycled concrete specimens under uniaxial stress, but the effects of replacement rate gradually decreased with the increase of lateral confining pressure. The influence of replacement rate on peak strain is larger than peak stress, the impact of replacement rate on peak strain gradually decreased with the increase of lateral confining pressure. The elastic modulus of recycled concrete specimens changes with different replacement rate, and the fluctuations is in the range of 20%. The results will provide reference for further theoretical study of recycled concrete.

scholarly journals Compressive Behavior, Microstructural Properties, and Freeze–Thaw Behavior of Tailing Recycled Aggregate Concrete with Waste Polypropylene Fiber Addition

Materials ◽  
2021 ◽  
Vol 14 (21) ◽  
pp. 6712
Author(s):  
Fan Xu ◽  
Tao Li ◽  
Chenghua Li ◽  
Zhijun Li ◽  
Sheliang Wang ◽  
...  
Keyword(s):  
Polypropylene Fiber ◽  
Strain Curve ◽  
Peak Stress ◽  
Recycled Aggregate Concrete ◽  
Recycled Aggregate ◽  
Cement Matrix ◽  
Peak Strain ◽  
Aggregate Concrete ◽  
Freeze Thaw ◽  
Thaw Cycle

To improve the high brittleness of recycled aggregate concrete containing iron ore tailings (TRAC), the feasibility of adding polypropylene fiber (PPF) to TRAC was studied by performing a compression stress–strain curve test, scanning electron microscope characterization, and a freeze–thaw cycle test. The results indicated that PPF had a beneficial impact on reducing the brittleness of TRAC. With the increase in PPF content, the peak strain increased, the elastic modulus decreased, and the peak stress and energy absorption capacity increased at first and then decreased. Furthermore, the microstructure investigation revealed that the interface friction between the PPF, aggregate, and cement matrix was the main source of energy dissipation. When the load acted on the concrete, the stress was dispersed to the fiber monofilaments, thus effectively enhancing the peak stress and peak strain of concrete and suppressing the generation and development of cracks in the concrete. In terms of freeze–thaw resistance, adding a small amount of PPF could reduce the negative effects of the freeze–thaw process on the cement matrix. On the premise of ensuring strength, the waste utilization should be as high as possible. Therefore, it was suggested that the content of PPF in fiber-reinforced tailings recycled aggregate concrete (TRAC-PP) should be 0.6%.

scholarly journals Experimental Investigation of Porous and Mechanical Characteristics of Single-Crack Rock-like Material under Freeze-Thaw Weathering

Minerals ◽  
2021 ◽  
Vol 11 (12) ◽  
pp. 1318
Author(s):  
Songtao Yu ◽  
Yuxian Ke ◽  
Hongwei Deng ◽  
Guanglin Tian ◽  
Junren Deng
Keyword(s):  
Mechanical Properties ◽  
Elastic Modulus ◽  
Pore Structure ◽  
Strain Energy ◽  
Peak Stress ◽  
Rock Material ◽  
Peak Strain ◽  
Freeze Thaw ◽  
Spectrum Area ◽  
Crack Angle

Freeze-thaw weathering changes the pore structure, permeability, and groundwater transportation of rock material. Meanwhile, the change in rock material structure deduced by frost heaving deteriorates mechanical properties of rock material, leading to instability and insecurity of mine slopes in cold regions. In this paper, rock-like specimens containing prefabricated cracks at different angles and having undergone various freeze-thaw cycles are used as the object. Their pore structure, compressive mechanical properties, strain energies, failure characteristics, and the connection between pore structure and mechanical properties are analyzed. Results show that the porosity, spectrum area of mesopores, and spectrum area of macropores increase with the increase in freeze-thaw cycles, while crack angle shows no obvious influence on pore structure. Peak stress and elastic modulus drop with the increase in freeze-thaw cycles, while peak strain shows an increasing trend. Peak stress and elastic modulus decrease in the beginning, and then increase with the increase in crack angle, while peak strain shows a reverse trend. Elastic strain energy and pre-peak strain energy drop with the increase in freeze-thaw cycles. Elastic strain energy decreases first, and then increases with the increase in crack angle. The correlation between the spectrum area of macropores and elastic modulus is the strongest among different pores. Elastic modulus and peak stress decrease with the increase in macropore spectrum area, and peak strain increases with the increase in macropore spectrum area.

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.

scholarly journals Experimental Study on the Effect of Freeze-Thaw Cycles on Axial Tension and Compression Performance of Concrete after Complete Carbonization

2021 ◽  
Vol 2021 ◽  
pp. 1-16
Author(s):  
Dafu Cao ◽  
Jiaqi Liu ◽  
Yanling Zhou ◽  
Wenjie Ge ◽  
Xin Zhang
Keyword(s):  
Compressive Stress ◽  
Axial Compression ◽  
Compressive Strain ◽  
Strain Curve ◽  
Peak Stress ◽  
Experimental Result ◽  
Peak Strain ◽  
Freeze Thaw ◽  
Axial Tension ◽  
Thaw Cycle

The effect of freeze-thaw cycles on the axial tension and axial compression properties of completely carbonized concrete are investigated in this study. Three grade concrete specimens (C30, C40, and C45) were fabricated. The freeze-thaw cycle test was carried out on the completely carbonized specimens, followed by axial tension and axial compression tests. The results show that completed carbonization increases the axial tensile peak stress of C30, C40, and C45 concrete specimens by 8.7%, 9.7%, and, 12.1%, respectively. The peak axial tension strain increased by 1.9%, 7.2%, and 9.6%, respectively. The peak axial compressive stress increased by 10.5%, 19.1%, and 24.1%, respectively. The peak axial compressive strain decreased by 13.7%, 14.1%, and 14.3%, respectively. With the increase of freeze-thaw cycles, the peak stress of tensile stress, peak strain, and compressive stress of concrete decrease continuously. The peak strain of compressive strain increases. The lower the strength grade of concrete, the faster the decline rate of stress and strain. According to the data changes of peak stress and peak strain at different times of freeze thaw after carbonization, the stress-strain curve fitting formula for concrete under freeze-thaw cycles after complete carbonization is put forward, which has a good coincidence with the experimental result.

scholarly journals Mechanical Properties of Tonalite Subjected to Combined Effects of Chemical Corrosion and Freeze-Thaw Cycles

2019 ◽  
Vol 9 (18) ◽  
pp. 3890 ◽  
Author(s):  
Chao Xu ◽  
Youliang Chen ◽  
Suran Wang ◽  
Akbar Javadi ◽  
Xi Du ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Electron Microscope ◽  
Scanning Electron Microscope ◽  
Physical And Mechanical Properties ◽  
Bending Test ◽  
Uniaxial Compression Test ◽  
Combined Effects ◽  
Chemical Corrosion ◽  
Freeze Thaw ◽  
Scanning Electron

This paper presents an investigation into the coupled effects of chemical corrosion (by Nitric acid solution) and freeze-thaw cycles on the physical and mechanical properties and damage deterioration of tonalite specimens. The experiments included the uniaxial compression test, three-point bending test, the Young’s modulus test, the X-ray diffraction test and the scanning electron microscope test. The damage condition of tonalite specimens was analyzed using scanning electron microscope (SEM). The experimental results reveal that chemical erosion has a significant influence on the propagation of micro cracks and accelerates the development of damage in the tonalite samples under monotonic loading. Due to cementation, no noticeable difference in uniaxial compressive strength was observed between the specimens subjected to combined effects of chemical corrosion and freeze-thaw cycles and those subjected to freeze-thaw cycles only. The amount of cementing materials in the chemically treated samples was found using SEM, which shows that chemical reactions promoted mechanical properties to some extent.

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