scholarly journals Influence of Two Cooling Methods on Dynamic Mechanical Properties of High Temperature Sandstone

2021 ◽  
Vol 2021 ◽  
pp. 1-12
Author(s):  
Qi Ping ◽  
Qi Diao ◽  
Dezhi Qi ◽  
Chen Wang ◽  
Chuanliang Zhang
Keyword(s):  
Compressive Strength ◽  
High Temperature ◽  
Reduction Rate ◽  
Quadratic Function ◽  
Dynamic Mechanical Properties ◽  
Dynamic Strain ◽  
Physical Parameters ◽  
Water Cooling ◽  
Dynamic Compressive Strength ◽  
Cooling Methods

To study the influence of different cooling methods on dynamic mechanical properties of high temperature rock, both natural cooling and water cooling were used to cool high temperature (100°C∼1000°C) coal mine sandstone to room temperature (20°C). Basic physical parameters of sandstone were measured, and impact compression tests were carried out by using the SHPB test device. Comparative analysis shows that the volume expansion rate, mass loss rate, density reduction rate, and P-wave velocity reduction rate of sandstone specimens are positively correlated with the temperature in a quadratic function. The deteriorate rate of physical parameters of water cooling sandstone specimens is slightly larger than that of natural cooling. The variation of dynamic stress-strain curves is basically consistent. Compaction stage of water cooling is slightly larger than that of natural cooling. With the increase in temperature, dynamic compressive strength of sandstone specimens first increases, then decreases, and reaches maximum at 300°C. Subsequently, dynamic compressive strength decreases in a quadratic function with the temperature, and dynamic compressive strength of water cooling sandstone specimens is significantly lower than that of natural cooling. The dynamic elastic modulus also first increases and then decreases with the temperature and reaches maximum at 300°C. The dynamic elastic modulus of water cooling sandstone specimens is lower than that of natural cooling, but they are roughly the same at 1000°C. Dynamic strain increases in a quadratic function with the temperature, and dynamic strain of water cooling sandstone specimens is greater than that of natural cooling. The impact failure of sandstone specimens is intensified with the temperature, and the failure degree of water cooling is greater than that of natural cooling.

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 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 Experimental Research on the Influence of Temperature on the Static Properties of Skarn

2021 ◽  
Vol 2021 ◽  
pp. 1-13
Author(s):  
Lei Liu ◽  
Xiang Meng ◽  
Hao Qin ◽  
Zhaozhao Chang
Keyword(s):  
Mechanical Properties ◽  
High Temperature ◽  
Testing Machine ◽  
Strain Curve ◽  
Physical Parameters ◽  
Peak Strain ◽  
Static Properties ◽  
Static Tests ◽  
High Temperature Mechanical Properties ◽  
Cooling Methods

Studying the high-temperature mechanical properties of rocks is of great significance to engineering disasters caused by deep rock mining and underground protection projects. In view of insufficient research on the high-temperature mechanical properties of deep rocks in southwestern China, we used high-temperature heating devices and statics equipment to conduct static tests on Skarn. XW7L-12 box-type resistance furnace was adopted to heat Skarn (25°C, 200°C, 400°C, 600°C, and 800°C), and the temperature effect of its basic physical parameters (density and wave velocity) was measured and analyzed. Uniaxial compression experiments were performed on two cooling methods of Skarn (natural cooling and water cooling) by a constant stress pressure testing machine to obtain a stress-strain curve and analyze its statics index (peak strength, tensile strength, elastic modulus, and peak strain) and the change rule of failure mode with temperature rise and different cooling methods. With the temperature increasing, various static mechanical indexes of Skarn will be greatly affected. Meanwhile, the different cooling methods are not related to the change trend of the mechanical properties of Skarn under high temperature.

Comparative experimental study on physical and mechanical properties of quartz sandstone after water-cooling and natural-cooling under high temperature

2021 ◽  
pp. qjegh2020-181
Author(s):  
Haopeng Jiang ◽  
Annan Jiang ◽  
Fengrui Zhang
Keyword(s):  
Mechanical Properties ◽  
Compressive Strength ◽  
Elastic Modulus ◽  
Uniaxial Compressive Strength ◽  
Heating Temperature ◽  
Physical And Mechanical Properties ◽  
P Wave ◽  
Water Cooling ◽  
Average Value ◽  
Cooling Methods

Experimental tests were conducted to study the influence of natural cooling and water cooling on the physical and mechanical properties of quartz sandstone. This study aims to understand the effect of different cooling methods on the physical and mechanical properties of quartz sandstone (such as mass, volume, density, P-wave velocity, elastic modulus, uniaxial compressive strength, etc.). The results show that the uniaxial compressive strength (UCS) and elastic modulus(E) of the specimens cooled by natural-cooling and water-cooling decrease with heating temperature. At 800℃, after natural cooling and water cooling, the average value of UCS decreased by 34.65% and 57.90%, and the average value of E decreased by 87.66% and 89.05%, respectively. Meanwhile, scanning electron microscope (SEM) images were used to capture the development of microcracks and pores within the specimens after natural-cooling and water-cooling, and it was found that at the same temperature, water cooling treatment was more likely to cause microcracks and pores, which can cause more serious damage to the quartz sandstone. These results confirm that different cooling methods have different effects on the physical and mechanical properties of quartz sandstone, and provide a basis for the stability prediction of rock mass engineering such as tunnel suffering from fire.

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.

scholarly journals Effect of Heating Rate on the Dynamic Compressive Properties of Granite

Geofluids ◽  
2019 ◽  
Vol 2019 ◽  
pp. 1-12 ◽  
Author(s):  
Ronghua Shu ◽  
Tubing Yin ◽  
Xibing Li
Keyword(s):  
Compressive Strength ◽  
Elastic Modulus ◽  
Heating Rate ◽  
High Speed ◽  
Split Hopkinson Pressure Bar ◽  
Quadratic Function ◽  
Peak Strain ◽  
Hopkinson Pressure Bar ◽  
Compressive Properties ◽  
Dynamic Compressive Strength

Variation in the heating rate due to different geothermal gradients is a cause of much concern in underground rock engineering such as deep sea and underground tunnels, nuclear waste disposal, and deep mining. By using a split Hopkinson pressure bar (SHPB) and variable-speed heating furnace, the dynamic compressive properties of granite were obtained after treatments at different heating rates and temperatures; these properties mainly included the dynamic compressive strength, peak strain, and dynamic elastic modulus. The mechanism of heating rate action on the granite was simultaneously analyzed, and the macroscopic physical properties were discussed. The microscopic morphological features were obtained by scanning electron microscopy (SEM), and the crack propagation was determined by high-speed video camera. The experimental results show that the dynamic compressive strength and elastic modulus both show an obvious trend of a decrease with the increasing heating rate and temperature; the opposite phenomenon is observed for the peak strain. The relationships among the dynamic compressive properties and temperature could be described by the quadratic function. The ductility of granite is enhanced, and the number and size of cracks increase gradually when the heating rate and temperature increase. The microstructure of rock is weakened by the increased thermal stress, which finally affects the dynamic compressive properties of rock.

scholarly journals Mechanical test of granite with multiple water–thermal cycles

2021 ◽  
Vol 9 (1) ◽  
Author(s):  
Li Yu ◽  
Hai-Wang Peng ◽  
Yu Zhang ◽  
Guo-wei Li
Keyword(s):  
Tensile Strength ◽  
Compressive Strength ◽  
High Temperature ◽  
Thermal Shock ◽  
Mechanical Test ◽  
Tensile Modulus ◽  
Physical And Mechanical Properties ◽  
P Wave ◽  
Water Cooling ◽  
Thermal Shocks

AbstractTo study the influence of thermal shock caused by water-cooling on the physical and mechanical properties of high-temperature granite, granite was subjected to an increasing number of high-temperature (300 °C) water-cooling and thermal shock treatment cycles, and static mechanical experiments were carried out on the treated granite. The results support the following conclusions: (1) thermal shock causes an increase in the number and size of the pores and cracks within the granite; thus, its volume expands, density decreases, water absorption rate increases, and P-wave velocity decreases. (2) With an increase in the number of thermal shocks, both the compressive strength and tensile strength of the granite decrease, and there is a linear relationship between the compressive strength and tensile strength. (3) With an increase in the number of thermal shocks, the plasticity of the granite increases and its resistance to deformation weakens, which is manifested as a decrease in both the compressive modulus and tensile modulus of the granite. After 15 cycles of thermal shock, the compressive elastic modulus and tensile modulus of the granite decreased by 25.18% and 46.76%, respectively. (4) The m and s values of the damaged granite were calculated based on the Hoek–Brown empirical criterion, and it was found that both of these parameters decrease with the increase in the number of thermal shocks. The calculation results can provide a reference for engineering rock mass failure.

scholarly journals Physics and Dynamics Characteristics and Energy Analysis of Freeze-Thaw Limestone

2020 ◽  
Vol 2020 ◽  
pp. 1-12 ◽  
Author(s):  
Qi Ping ◽  
Hongjian Sun ◽  
Chuanliang Zhang ◽  
Xin Zhou
Keyword(s):  
Compressive Strength ◽  
Loading Rate ◽  
Dynamic Compression ◽  
Quadratic Function ◽  
Longitudinal Wave Velocity ◽  
Energy Increase ◽  
Absorbed Energy ◽  
Freeze Thaw ◽  
Shpb Test ◽  
Dynamic Compressive Strength

In order to study the physical and dynamic properties of rock after damage, an open-type saturated water freeze-thaw test at ±20°C was carried out on the limestone specimen, the size, quality, and longitudinal wave velocity with measured after freeze-thaw cycles for 0, 10, 20, 30, 40, 50, 60, 70, 80, 90, and 100 times, and the SHPB test device was used to carry out the impact compression test with eight kinds of loading rate. This text analyzes the damage evolution characteristics on the physical properties of limestone of cycle times of freeze-thaw and discusses the dynamic compression mechanical characteristics and energy dissipation law of limestone specimens after freeze-thaw cycles. The test results show that the mass and longitudinal wave velocity of the specimen decreased and the volume and density increased. The damage factors have the quadratic function positive correlation with the cycle time of freeze-thaw. Moreover, the dynamic compression stress-strain curves of the specimens under different loading rates are similar in shape, and the curve shows an upward trend with increasing loading speed. In addition, with the loading rate increasing, the dynamic compressive strength and dynamic elastic modulus of the specimen increased and the dynamic strain decreased. In the SHPB test, the reflected energy, transmitted energy, and absorbed energy all increased linearly with incident energy. The dynamic compressive strength and absorbed energy increase as a power function, and the strain rate and absorbed energy increase as a quadratic function.

scholarly journals Experimental Research on Mechanical Properties of High-Temperature Sandstone with Different Cooling Methods

2020 ◽  
Vol 2020 ◽  
pp. 1-9
Author(s):  
Minglei Zhang ◽  
Runde Qiu ◽  
Lei Yang ◽  
Yuting Su
Keyword(s):  
Mechanical Properties ◽  
Carbon Dioxide ◽  
Acoustic Emission ◽  
High Temperature ◽  
Water Cooling ◽  
Longitudinal Wave Velocity ◽  
Liquid Carbon ◽  
Liquid Carbon Dioxide ◽  
Attenuation Rate ◽  
Cooling Methods

Various tests including the longitudinal wave velocity tests and uniaxial compression tests have been conducted to evaluate the impact of cooling methods (including natural cooling, water cooling, and cooling by liquid carbon dioxide) on mechanical properties of sandstone under the natural status and high temperature. The acoustic emission signals were also monitored during the tests. According to the tests conducted, the sandstone sample density attenuation rate and the longitudinal wave velocity attenuation rate are higher than those of the specimen under natural status while the uniaxial compressive strength and Young’s modulus are lower. Comparing with the sandstone under the natural status, the compression sections of the stress-strain curves of the high-temperature sandstone samples treated by three cooling methods are longer with lower strain peak values. The order of the acoustic emission is revealed as follows: the sample cooled by liquid carbon dioxide < the sample cooled by water < sample cooled naturally < the sample under natural status, which suggests that the rapid cooling (cooled by liquid carbon dioxide) produces the severest damage on the sample, followed by the water cooling and natural cooling methods. In addition, the relationship between the sample strength weakening coefficient and the cooling rate is defined based on the statistical data of the cooling time of the high-temperature specimen under the three cooling methods.

scholarly journals An Experimental Study on the Mechanical Properties of High-Temperature Granite under Natural Cooling and Water Cooling

2021 ◽  
Vol 2021 ◽  
pp. 1-11
Author(s):  
Yanan Gao ◽  
Yunlong Wang ◽  
Taiping Lu ◽  
Liuzhou Li ◽  
Jinwen Wu ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Elastic Modulus ◽  
High Temperature ◽  
Poisson’S Ratio ◽  
Heating Temperature ◽  
Axial Strain ◽  
Peak Stress ◽  
Poisson's Ratio ◽  
Water Cooling ◽  
Cooling Methods

With the further development of deep rock mechanics engineering, such as the exploitation and utilization of geothermal resources, the exploitation of deep mineral resources, and the safe disposal of nuclear waste, the study of mechanical properties of deep high-temperature rock is gaining the attention of the researchers. However, not only the high temperature but also the cooling condition/method that will be used in the construction such as drilling cooling will also greatly affect the mechanical properties of the rock. In this paper, the mechanical behaviour and the evolution of the mechanical properties of the high-temperature (600°C–1,000°C) granite under different cooling methods are studied. The following conclusions can be obtained: (1) The peak stress of the granite decreases with the heating temperature. Compared with natural cooling, water cooling has a more significant effect on strength degradation. (2) The increase of the heating temperature increases the maximum axial strain of the granite. The water cooling method more greatly induces the maximum axial strain of granite than the natural cooling. The maximum axial strain of the specimen under the water cooling reaches 117.3% of that under natural cooling (800°C). (3) The elastic modulus of the granite decreases with the heating temperature. Water cooling will have a stronger effect on the reduction of the elastic modulus than natural cooling. The maximum difference value (2.02 GPa) of the elastic modulus under the different cooling methods occurs at the temperature of 800°C. (4) Poisson’s ratio of the granite increases with heating temperature, and the cooling method does not have an evident effect on it. The relationship between Poisson’s ratio and the heating temperature under different cooling methods can be described using the linear model. (5) According to the influence of the temperature on the peak stress, the elastic modulus, and Poisson’s ratio, the heating temperature domain can be divided into the unapparent zone, the significant zone, and the mitigation zone. (6) The thermal stress due to the nonuniform temperature field and the different thermal expansion coefficients is incompatible. Such incompatibility stresses the essences of the degradation of the mechanical properties of the granite.

Sign in / Sign up

Export Citation Format

Share Document