scholarly journals Study on Dynamic Mechanical Properties and Failure Mechanism of Sandstones under Real-Time High Temperature

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-19
Author(s):  
JiaZhi Zhang ◽  
Ming Li ◽  
Gang Lin ◽  
Lianying Zhang ◽  
Hao Yu ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Compressive Strength ◽  
Elastic Modulus ◽  
High Temperature ◽  
Strain Rate ◽  
Real Time ◽  
Dynamic Mechanical Properties ◽  
Peak Strain ◽  
Dynamic Mechanical ◽  
Dynamic Compressive Strength

The research on dynamic mechanical properties of rocks under high temperature is the basis for safe and efficient implementation of deep coal mining and underground coal gasification engineering. In this paper, the split Hopkinson bar (SHPB) with real-time high-temperature function was adopted to systematically study dynamic mechanical properties of sandstones. The research showed that under the condition of a fixed temperature, with the increase of strain rate, the dynamic compressive strength and dynamic peak strain of sandstone increased gradually, and the variation of dynamic elastic modulus with strain rate was not obvious. With the increase of temperature, the dynamic compressive strength of sandstone increased first and then decreased, the dynamic peak strain increased gradually, and the dynamic elastic modulus decreased overall. The variation law of macroscopic failure mode and energy dissipation density with temperature was revealed, and the change mechanism was explained considering the influence of high temperature on the internal structure of sandstone. Based on the principle of component combination and the theory of micro-element strength distribution, the dynamic statistical damage constitutive model was established, and its parameters had certain physical significance. Compared with the experimental results, the established model can well describe the dynamic stress-strain relationship of sandstone under real-time high temperature.

scholarly journals Dynamic Mechanical Properties and Damage Mechanism of Freeze-Thaw Sandstone under Acid Corrosion

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-15
Author(s):  
Xiaoxiao Cao ◽  
Meimei Feng ◽  
Kangsheng Yuan
Keyword(s):  
Mechanical Properties ◽  
Compressive Strength ◽  
Elastic Modulus ◽  
Strain Rate ◽  
Coupling Effect ◽  
Acid Corrosion ◽  
Dynamic Mechanical Properties ◽  
Peak Strain ◽  
Freeze Thaw ◽  
Dynamic Compressive Strength

During the construction of geotechnical engineering in cold regions, the stability of rock is inevitably affected by freeze-thaw cycles and hydrochemical corrosion. In order to study the effect of hydrochemical corrosion on dynamic mechanical properties of freeze-thaw rocks, dynamic compression tests were carried out on sandstone samples corroded by four different concentrations of HCl solutions with the same number of freeze-thaw cycles using split-Hopkinson pressure bar (SHPB) test system. The coupling effects of freeze-thaw cycles with different concentrations of HCl solutions and strain rate on mechanical properties of sandstones were explored. The results showed that strain rate could enhance the dynamic compressive strength and peak strain but had no significant effect on the elastic modulus. The coupling effect of freeze-thaw cycles and acid corrosion weakened the dynamic compressive strength, and elastic modulus but enhanced the peak strain. In addition, X-ray diffractometer (XRD) and scanning electron microscope (SEM) were used to analyze the changes of mineral composition and microstructure damage of sandstone samples under the coupling effect of acid corrosion and freeze-thaw cycles. The analysis results were basically consistent with the damage characteristics of macro mechanical properties. The research results can provide reference for open pit coal mining in cold regions.

scholarly journals Experimental Study on Dynamic Mechanical Properties and Energy Evolution Characteristics of Limestone Specimens Subjected to High Temperature

2020 ◽  
Vol 2020 ◽  
pp. 1-12 ◽  
Author(s):  
Qi Ping ◽  
Chuanliang Zhang ◽  
Haipeng Su ◽  
Hao Zhang
Keyword(s):  
Mechanical Properties ◽  
Compressive Strength ◽  
Elastic Modulus ◽  
High Temperature ◽  
Incident Energy ◽  
Dynamic Mechanical Properties ◽  
Energy Evolution ◽  
Strain And Strain Rate ◽  
Evolution Characteristics ◽  
Dynamic Compressive Strength

To study the effect of high temperature on the dynamic mechanical properties and energy evolution characteristic of limestone specimens, the basic physical parameters of limestone specimens that cool naturally after experiencing high temperatures of room temperature (25°C), 200°C, 400°C, and 600°C were tested. In addition, compression tests with 6 impact loading conditions were conducted using SHPB device. The changes of basic physical properties of limestone before and after temperature were analyzed, and the relationship among dynamic characteristic parameters, energy evolution characteristics, and temperature was discussed. Test results indicated that, with the increase of temperature, the surface color of specimen changed from gray-black to gray-white, and its volume increased, while the mass, density, and P-wave velocity of specimen decreased. The dynamic compressive stress-strain curve of limestone specimens after different high-temperature effects could be divided into three stages: elasticity stage, yield stage, and failure stage. Failure mode of specimen was in the form of spalling axial splitting, and the degree of fragmentation increased with the increase of the temperature and incident energy. With the increase of the temperature, the reflection energy, the absorption energy, the dynamic compressive strength, and dynamic elastic modulus of rock decreased, while its transmission energy, the dynamic peak strain, and strain rate increased. The dynamic compressive strength, dynamic elastic modulus, dynamic strain, and strain rate of limestone specimens all increased with the increase of incident energy, showing a quadratic function relationship.

scholarly journals SHPB Testing and Analysis of Bedded Shale under Active Confining Pressure

2020 ◽  
Vol 2020 ◽  
pp. 1-8
Author(s):  
Guoliang Yang ◽  
Jingjiu Bi ◽  
Xuguang Li ◽  
Jie Liu ◽  
Yanjie Feng
Keyword(s):  
Mechanical Properties ◽  
Elastic Modulus ◽  
Strain Rate ◽  
Peak Stress ◽  
Confining Pressure ◽  
Dynamic Mechanical Properties ◽  
Dynamic Elastic Modulus ◽  
Peak Strain ◽  
Dynamic Mechanical ◽  
Bedding Angle

Shale gas is the most important new energy source in the field of energy, and its exploitation is very important. The research on the dynamic mechanical properties of shale is the premise of exploitation. To study the dynamic mechanical properties of shale from the Changning-Weiyuan area of Sichuan Province, China, under confining pressure, we used a split Hopkinson pressure bar (SHPB) test system with an active containment device to carry out dynamic compression tests on shale with different bedding angles. (1) With active confining pressure, the shale experiences a high strain rate, and its stress-strain curve exhibits obvious plastic deformation. (2) For the same impact pressure, the peak stress of shale describes a U-shaped curve with an increasing bedding angle; besides, the peak stress of shale with different bedding angles increases linearly with rising confining pressure. The strain rate shows a significant confining pressure enhancement effect. With active confining pressure, the peak strain gradually decreases as the bedding angle increases. (3) As a result of the influence of different bedding angles, the dynamic elastic modulus of shale has obvious anisotropic characteristics. Shale with different bedding angles exhibits different rates of increase in the dynamic elastic modulus with rising confining pressure, which may be related to differences in the development of planes of weakness in the shale. The results of this study improve our understanding of the behavior of bedded shale under stress.

scholarly journals Study on Long-Term Dynamic Mechanical Properties and Degradation Law of Sandstone under Freeze-Thaw Cycle

2020 ◽  
Vol 2020 ◽  
pp. 1-10
Author(s):  
Qingsong Pu ◽  
Junhong Huang ◽  
Fuling Zeng ◽  
Yi Luo ◽  
Xinping Li ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Compressive Strength ◽  
Elastic Modulus ◽  
Strain Rate ◽  
Air Pressure ◽  
Freeze Thaw ◽  
Dynamic Mechanical ◽  
Thaw Cycle ◽  
Freeze Thaw Cycle ◽  
Dynamic Compressive Strength

This study is based on the tunnel-face slope engineering of Dongfeng tunnel in Shanxi section of China’s Shuozhou-Huanghua Railway. The sandstone specimens in the perennial freeze-thaw zone of the slope were collected to carry out freeze-thaw cycle static physical mechanics test and split Hopkinson pressure bar (SHPB) dynamic mechanical test. Thus, the damage process of sandstone under freeze-thaw cycle and impact load is studied. Also, the dynamic compressive strength and dynamic elastic modulus of sandstone are analysed under different loading strain rates and freeze-thaw cycle based on LS-DYNA, a dynamic finite element program. The results showed that the dynamic compressive strength of sandstone subjected to multiple freeze-thaw cycles under 0.04 MPa air pressure has a greater damage ratio than that under 0.055 MPa and 0.07 MPa air pressure, which was more likely to cause damage to slope sandstone than in actual engineering; the dynamic compressive strength and elastic modulus of sandstone decrease greatly within a certain range of freeze-thaw cycles and loading strain rate, leading to significant deterioration. When the freeze-thaw cycle exceeded 200 times and the strain rate was greater than 200 s−1, the physical and mechanical properties of sandstone gradually tended to be stable.

scholarly journals Research on the Dynamic Mechanical Properties and Energy Dissipation of Expansive Soil Stabilized by Fly Ash and Lime

2019 ◽  
Vol 2019 ◽  
pp. 1-13 ◽  
Author(s):  
Sheng-quan Zhou ◽  
Da-wei Zhou ◽  
Yong-fei Zhang ◽  
Wei-jian Wang ◽  
Dongwei Li
Keyword(s):  
Mechanical Properties ◽  
Compressive Strength ◽  
Fly Ash ◽  
Expansive Soil ◽  
Dynamic Mechanical Properties ◽  
Test Results ◽  
Absorbed Energy ◽  
Dynamic Mechanical ◽  
Stabilized Soil ◽  
Dynamic Compressive Strength

To probe into the dynamic mechanical properties of expansive soil stabilized by fly ash and lime under impact load, the split-Hopkinson pressure bar (SHPB) test was carried out in this study. An analysis was made on the dynamic mechanical property and final fracture morphology of stabilized soil, and the failure mechanism was also explored from the perspective of energy dissipation. According to the test results, under the impact pressure of 0.2 MPa, plain soil and pure fly ash-stabilized soil exhibit strong plasticity. After the addition of lime, the stabilized soil shows obvious brittle failure. The dynamic compressive strength and absorbed energy of stabilized soil first increase and then decrease with the change of mix proportions. Both the dynamic compressive strength and the absorbed energy reach the peak value at the content of 20% fly ash and 5% lime (20% F + 5% L). In the process of the test, most of the incident energy is reflected back to the incident bar. The absorbed energy of stabilized soil increases linearly with the rise of dynamic compressive strength, while the absorbed energy is negatively correlated with the fractal dimension. The fractal dimension of pore morphology of the plain soil is lower than that of the fly ash-lime combined stabilized soil when it comes to the two different magnification ratios. The test results indicate that the modifier content of 20% F + 5% L can significantly improve the dynamic mechanical properties of the expansive soil.

Experimental and Numerical Analysis of Qinling Mountain Engineered Rocks during Pulse-Shaped SHPB Test

2015 ◽  
Vol 16 (3-4) ◽  
pp. 165-171
Author(s):  
Shi Liu ◽  
Jinyu Xu
Keyword(s):  
Compressive Strength ◽  
Elastic Modulus ◽  
Strain Rate ◽  
Energy Absorption ◽  
Absorption Rate ◽  
Failure Modes ◽  
Dynamic Compression ◽  
Peak Strain ◽  
Compression Stress ◽  
Dynamic Compressive Strength

AbstractIn order to study the dynamic compression mechanical properties of engineering rock under high strain rate （100~102 S−1）loads, dynamic compression tests of three common engineering rocks (marble, sandstone and granite) taken from the Qinling Mountain are studied subjected to five different kinds of shock air pressure using Φ 100 mm split Hopkinson pressure bar test system improved with purple copper waveform shaper. The dynamic compression stress-strain curves, dynamic compressive strength, peak strain, energy absorption rate and elastic modulus of three rocks variation with strain rate are researched. The dynamic compression failure modes under different strain rates are analyzed. Then the three-dimensional numerical simulations of waveform shaper shaping effects and stress wave propagation in the SHPB tests are carried out to reproduce the test results. The research results show that the dynamic compression stress-strain curves show certain discreteness, and there is an obvious rebound phenomenon after the peak. With the increase in strain rate, the dynamic compressive strength, peak strain and energy absorption rate are all in a certain degree of increase, but the elastic modulus have no obvious change trend. Under the same strain rate, the dynamic compressive strength of granite is greatest while of sandstone is least. With the increase in strain rate, the margin of increase in peak strain and energy absorption rate of granite is greatest while of sandstone is least. The failure modes of the sample experience a developing process from outside to inside with the increase of strain rate.

scholarly journals Study on Dynamic Mechanical Properties and Damage Evolution Model of Siltstone

2019 ◽  
Vol 2019 ◽  
pp. 1-10
Author(s):  
Guoliang Zhang ◽  
Haipeng Jia ◽  
Shuaifeng Wu
Keyword(s):  
Mechanical Properties ◽  
Strain Rate ◽  
Stress Wave ◽  
Damage Evolution ◽  
Dynamic Mechanical Properties ◽  
Cumulative Damage ◽  
Peak Strain ◽  
Rapid Rise ◽  
Dynamic Mechanical ◽  
Stable Development

This paper is focused on exploring the dynamic mechanical properties and damage process of siltstone. For this purpose, different stress wave wavelengths (0.5 m∼2.0 m) and different strain rates (25 s−1∼120 s−1) were applied to siltstone specimens in the SHPB dynamic impact test. The experimental results show that the dynamic compressive strength of siltstone is linearly positively correlated with the strain rate, and the dynamic increase factor is linearly positively correlated with the natural logarithm of strain rate; the peak strain is linearly positively correlated with the strain rate, and the increase in wavelength causes the peak strain to increase. Through multiple impact tests, it is concluded that the cumulative damage to siltstone increases with the number of impacts. The cumulative damage curve exhibits an initial rapid rise, followed by a stable development, followed by another rapid rise. With increasing wavelength of the stress wave, the stable development of the curve gradually decreases, the cumulative damage to the siltstone is intensified, and the number of repeated impacts is reduced. Meanwhile, a model for damage evolution is established based on the inverse of the Gompertz function, and the physical meanings of the model parameters are determined. The model can reflect the influence of both stress wave parameters and impact times. Verification of the model demonstrates the rationality of the model and the correctness of the physical meaning of the parameters. The model could be applied in future studies of damage to sedimentary rocks.

scholarly journals Uniaxial Dynamic Mechanical Properties Of Tunnel Lining Concrete Under Moderate-Low Strain Rate After High Temperature

2015 ◽  
Vol 61 (2) ◽  
pp. 35-52 ◽  
Author(s):  
L. X. Xiong
Keyword(s):  
Mechanical Properties ◽  
Compressive Strength ◽  
Elastic Modulus ◽  
Strain Rate ◽  
High Temperatures ◽  
Concrete Specimen ◽  
Tunnel Lining ◽  
Strain Rates ◽  
Peak Strain ◽  
Increasing Temperature

AbstractTo investigate the mechanical properties of tunnel lining concrete under different moderate-low strain rates after high temperatures, uniaxial compression tests in association with ultrasonic tests were performed. Test results show that the ultrasonic wave velocity and mass loss of concrete specimen begin to sharply drop after high temperatures of 600 °C and 400 °C, respectively, at the strain rates of 10-5s-1 to 10-2s-1. The compressive strength and elastic modulus of specimen increase with increasing strain rate after the same temperature, but it is difficult to obtain an evident change law of peak strain with increasing strain rate. The compressive strength of concrete specimen decreases first, and then increases, but decreases again in the temperatures ranging from room temperature to 800 °C at the strain rates of 10-5s-1 to 10-2s-1. It can be observed that the strain-rate sensitivity of compressive strength of specimen increases with increasing temperature. In addition, the peak strain also increases but the elastic modulus decreases substantially with increasing temperature under the same strain rate.

scholarly journals Dynamic Behaviors of Mortar Reinforced with NiTi SMA Fibers under Impact Compressive Loading

Materials ◽  
2021 ◽  
Vol 14 (17) ◽  
pp. 4933
Author(s):  
Eusoo Choi ◽  
Ha-Vinh Ho ◽  
Junwon Seo
Keyword(s):  
Mechanical Properties ◽  
Compressive Strength ◽  
Strain Rate ◽  
Specific Energy ◽  
Peak Strain ◽  
Recovery Stress ◽  
Specific Energy Absorption ◽  
Dog Bone ◽  
Dynamic Compressive Strength ◽  
Mortar Matrix

In this study, a compressive impact test was conducted using the split Hopkinson pressure bar (SHPB) method to investigate SMA fiber-reinforced mortar’s impact behavior. A 1.5% fiber volume of crimped fibers and dog-bone-shaped fibers was used, and half of the specimens were heated to induce recovery stress. The results showed that the appearance of SMA fibers, recovery stress, and composite capacity can increase strain rate. For mechanical properties, the SMA fibers reduced dynamic compressive strength and increased the peak strain. The specific energy absorption of the reinforced specimens slightly increased due to the addition of SMA fibers and the recovery stress; however, the effect was not significant. The composite behavior between SMA fibers and the mortar matrix, however, significantly influenced the dynamic compressive properties. The higher composite capacity of the SMA fibers produced lower dynamic compressive strength, higher peak strain, and higher specific energy absorption. The composite behavior of the dog-bone-shaped fiber was less than that of the crimped fiber and was reduced due to heating, while that of the crimped fiber was not. The mechanical properties of the impacted specimen followed a linear function of strain rate ranging from 10 to 17 s−1; at the higher strain rates of about 49–67 s−1, the linear functions disappeared. The elastic modulus of the specimen was independent of the strain rate, but it was dependent on the correlation between the elastic moduli of the SMA fibers and the mortar matrix.

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