scholarly journals Blasting-Induced Permeability Enhancement of Ore Deposits Associated with Low-Permeability Weakly Weathered Granites Based on the Split Hopkinson Pressure Bar

Geofluids ◽  
2018 ◽  
Vol 2018 ◽  
pp. 1-14 ◽  
Author(s):  
Lei Yan ◽  
Wenhua Yi ◽  
Liansheng Liu ◽  
Jiangchao Liu ◽  
Shenghui Zhang
Keyword(s):  
Split Hopkinson Pressure Bar ◽  
Deformation Modulus ◽  
Constant Speed ◽  
Initial Porosity ◽  
Peak Strain ◽  
Variable Speed ◽  
Hopkinson Pressure Bar ◽  
Impact Compression ◽  
Split Hopkinson ◽  
Pressure Bar

By utilizing the improved split Hopkinson pressure bar (SHPB) test device, uniaxial, constant-speed cyclic, and variable-speed cyclic impact compression tests were conducted on weakly weathered granite samples. By combining nuclear magnetic resonance (NMR) and triaxial seepage tests, this study investigated the change laws in the mechanical properties, porosity evolution, and permeability coefficients of the samples under cyclic impacts. The results showed that in constant-speed cyclic impacts with increasing impact times, deformation modulus decreased, whilst porosity firstly decreased and then increased. Furthermore, dynamic peak strength firstly increased and then decreased whereas peak strain constantly increased before failure of the samples. In the variable-speed cyclic impacts, as impact times increased, deformation modulus firstly increased and then declined with damage occurring after four impact times. The compaction process weakened and even disappeared with increasing initial porosity. Three types of pores were found in the samples that changed in multiscale under cyclic loading. In general, small pores extended to medium- and large-sized pores. After three variable-speed cyclic impacts, the porosity of the samples was larger than the initial porosity and the permeability coefficient was greater than its initial value. The results demonstrate that the purpose of enhancing permeability and keeping the ore body stable can be achieved by conducting three variable-speed cyclic impacts on the samples.

A comparative study on dynamic mechanical performance of concrete and rock

2015 ◽  
Author(s):  
Xia Zhengbing ◽  
Zhang Kefeng ◽  
Deng Yanfeng ◽  
Ge Fuwen
Keyword(s):  
Mechanical Performance ◽  
Split Hopkinson Pressure Bar ◽  
Dynamic Compression ◽  
Peak Strain ◽  
Hopkinson Pressure Bar ◽  
Dynamic Mechanical ◽  
Strain And Strain Rate ◽  
Split Hopkinson ◽  
Pressure Bar ◽  
Relationship Of

Recently, engineering blasting is widely applied in projects such as rock mineral mining, construction of underground cavities and field-leveling excavation. Dynamic mechanical performance of rocks has been gradually attached importance both in China and abroad. Concrete and rock are two kinds of the most frequently used engineering materials and also frequently used as experimental objects currently. To compare dynamic mechanical performance of these two materials, this study performed dynamic compression test with five different strain rates on concrete and rock using Split Hopkinson Pressure Bar (SHPB) to obtain basic dynamic mechanical parameters of them and then summarized the relationship of dynamic compressive strength, peak strain and strain rate of two materials. Moreover, specific energy absorption is introduced to confirm dynamic damage mechanisms of concrete and rock materials. This work can not only help to improve working efficiency to the largest extent but also ensure the smooth development of engineering, providing rich theoretical guidance for development of related engineering in the future.

Effects of Temperature and Strain-Rate on the Compressive Strength of Concrete

2010 ◽  
Vol 168-170 ◽  
pp. 2619-2624
Author(s):  
Chuan Xiong Liu ◽  
Yu Long Li
Keyword(s):  
Compressive Strength ◽  
Strain Rate ◽  
Split Hopkinson Pressure Bar ◽  
Peak Strain ◽  
Hopkinson Pressure Bar ◽  
Split Hopkinson ◽  
Compressive Strength Of Concrete ◽  
Pressure Bar ◽  
Increasing Temperature ◽  
Compressive Tests

Dynamic compressive tests were carried out for concrete specimens after exposure to temperatures 23°C, 400°C, 600°C and 800°C by using Split Hopkinson Pressure Bar(SHPB) apparatus. Cylindrical specimens with 98mm in diameter and 49mm in length were used in tests. The strain rates achieved in tests ranged from 30s-1 to 220s-1. The results showed that the compressive strength increases with increasing strain-rate, but decreases with the increase of temperature. However, the effect of strain-rate on improving the compressive strength of concrete decreases with the increase of temperature. Moreover, the strain-rate has an improvement on the peak strain of concrete, and the accretion rate increases with increasing temperature.

scholarly journals Research On Water-Immersion Softening Mechanism of Coal Rock Mass Based on Split Hopkinson Pressure Bar Experiment

2021 ◽  
Author(s):  
Zhiyuan Liu ◽  
Gang Wang ◽  
Jinzhou Li ◽  
Huaixing Li ◽  
Haifeng Zhao ◽  
...  
Keyword(s):  
Moisture Content ◽  
Coal Sample ◽  
Split Hopkinson Pressure Bar ◽  
Water Immersion ◽  
Compression Tests ◽  
Hopkinson Pressure Bar ◽  
Impact Compression ◽  
Split Hopkinson ◽  
Pressure Bar ◽  
The Impact

Abstract The coal mining process is affected by multiple sources of water such as groundwater and coal seam water injection. Understanding the dynamic mechanical parameters of water-immersed coal is helpful to the safe production of coal mines. The impact compression tests were performed on coal with different moisture contents by using the ϕ50 mm Split Hopkinson Pressure Bar (SHPB) experimental system, and the dynamic characteristics and energy loss laws of water-immersed coal with different compositions and water contents were analyzed. Through analysis and discussion, it is found that: (1) When the moisture content of the coal sample is 0%, 30%, 60%, the stress, strain rate and energy first increase and then decrease with time; (2) When the moisture content of the coal sample increases from 30% to 60%, the stress "plateau" of the coal sample disappears, resulting in an increase in the interval of the compressive stress and a decrease in the interval of the expansion stress. (3) The increase of the moisture content of the coal sample will affect its impact deformation and failure mode. When the moisture content is 60%, the incident rod end and the transmission rod end of the coal sample will have obvious compression failure, and the middle part of the coal sample will also experience expansion and deformation. (4) The coal composition ratio suitable for the impact experiment of coal immersion softening is optimized.

Energy Absorption Mechanism of Thermoplastic Fiber-Reinforced Plastics under Impact Loading Using Split-Hopkinson Pressure-Bar Method

2020 ◽  
Vol 858 ◽  
pp. 47-52
Author(s):  
Ayuta Nambu ◽  
Shogo Adachi ◽  
Tomoya Yabu ◽  
Yuji Ishitsuka ◽  
Atushi Hosoi ◽  
...  
Keyword(s):  
Failure Mode ◽  
Split Hopkinson Pressure Bar ◽  
Progressive Failure ◽  
Mode Analysis ◽  
Fiber Reinforced ◽  
Hopkinson Pressure Bar ◽  
Impact Compression ◽  
Split Hopkinson ◽  
Energy Absorbing ◽  
Pressure Bar

The energy absorbing performance in the progressive failure of glass long-fiber-reinforced polyamide was evaluated by using the split Hopkinson pressure-bar method. An impact compression test of glass long-fiber-reinforced polyamide was performed from –30 °C to 90 °C, and the temperature-independent energy absorbing performance was confirmed only for the progressive failure mode. To clarify this phenomenon, compression tests, interlaminar compressive shear tests and mode-I fracture-toughness tests were conducted under static and impact conditions. The compression strength and the shear strength of all specimens decreased with an increase in temperature. The toughness improved with temperature. In addition to the mechanical tests, failure-mode analysis was performed by using a three-dimensional X-ray microscope to clarify the absorbing mechanism. From the above, it was concluded that the temperature-independent energy absorbing performance results from a balance of these mechanical properties against the temperature change.

Testing Techniques to Eliminate Frictional Effect and to Achieve Constant Strain-Rate in Split Hopkinson Pressure Bar Impact Compression System

2011 ◽  
Vol 673 ◽  
pp. 77-82
Author(s):  
Minoru Yamashita ◽  
Mitsuru Suganuma ◽  
Yasuhisa Sato
Keyword(s):  
Strain Rate ◽  
Split Hopkinson Pressure Bar ◽  
Constant Strain Rate ◽  
Intrinsic Stress ◽  
Hopkinson Pressure Bar ◽  
Impact Compression ◽  
Compression System ◽  
Frictional Effect ◽  
Split Hopkinson ◽  
Pressure Bar

In order to obtain the intrinsic stress – strain relationship by split Hopkinson pressure bar (SHPB) impact compression system, two testing techniques to eliminate the frictional effect and hold the prescribed constant strain-rate are demonstrated. The extrapolation method eliminating frictional effect at the tool – specimen interface was exhibited. Several specimens with different height were used for changing the initial diameter / height ratio in the method, where the circular plates were laminated. In order to maintain the constant strain-rate during compression, the incident pulse was adjusted to elevate in accordance with the compression force, where the tapered cylindrical striker bar was applied. Test material is a fully annealed pure aluminum. The intrinsic stress – strain relationship at strain-rate of 1000 /s was determined and the strain-rate sensitivity was also determined. The numerical simulation of the SHPB impact compression system was also performed using the dynamic explicit finite element method. The additional evidence for these experimental techniques to accomplish the elimination of friction and the constant strain-rate was shown.

Analysis of the Impact of the Frequency Range of the Tensometer Bridge and Projectile Geometry on the Results of Measurements by the Split Hopkinson Pressure Bar Method

2013 ◽  
Vol 20 (4) ◽  
pp. 555-564 ◽  
Author(s):  
Wojciech Moćko
Keyword(s):  
Test Bench ◽  
Split Hopkinson Pressure Bar ◽  
Dynamic Deformation ◽  
Spectral Width ◽  
Hopkinson Pressure Bar ◽  
Computing Environment ◽  
Split Hopkinson ◽  
Pressure Bar ◽  
The Impact ◽  
Bench Model

Abstract The paper presents the results of the analysis of the striker shape impact on the shape of the mechanical elastic wave generated in the Hopkinson bar. The influence of the tensometer amplifier bandwidth on the stress-strain characteristics obtained in this method was analyzed too. For the purposes of analyzing under the computing environment ABAQUS / Explicit the test bench model was created, and then the analysis of the process of dynamic deformation of the specimen with specific mechanical parameters was carried out. Based on those tests, it was found that the geometry of the end of the striker has an effect on the form of the loading wave and the spectral width of the signal of that wave. Reduction of the striker end diameter reduces unwanted oscillations, however, adversely affects the time of strain rate stabilization. It was determined for the assumed test bench configuration that a tensometric measurement system with a bandwidth equal to 50 kHz is sufficient

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