scholarly journals Study on Dynamic Behavior and Energy Dissipation of Rock considering Initial Damage Effect

2021 ◽  
Vol 2021 ◽  
pp. 1-10
Author(s):  
Aihong Lu ◽  
Jinhai Xu ◽  
Yu Xia ◽  
Lei Sun
Keyword(s):  
Rock Mass ◽  
Test System ◽  
Energy Ratio ◽  
Dissipated Energy ◽  
Peak Strain ◽  
Impact Compression ◽  
Damage Degree ◽  
Initial Damage ◽  
Transmitted Energy ◽  
Rock Specimens

To explore the influence of initial damage on the dynamic characteristics of rock mass, the Φ 50 mm split Hopkinson pressure bar (SHPB) test system was used, and the uniaxial impact compression tests on yellow sandstone specimens with different damage degrees were conducted, and then the variation law of mechanical properties of rock specimens with the initial damage was determined. The test results show that the dynamic stress-strain curve of rock specimens with initial damage can be roughly divided into compaction stage, elastic deformation stage, crack evolution stage, and strain-softening stage; the higher the initial damage degree of rock mass, the more significant the compaction stage. With the increase of the initial damage degree, the dynamic elastic modulus and peak stress of rock mass decrease gradually in a power number, while the peak strain of rock mass increases exponentially. With the increase of the initial damage degree, both the reflected energy ratio and the dissipated energy ratio decrease linearly, while the transmitted energy ratio increases linearly; the increasing rate of the transmitted energy ratio is greater than the decreasing rate of the reflected energy ratio.

scholarly journals Experimental Study on Stress Uniformity and Deformation Behavior of Coals with Different Length-to-Diameter Ratios under Dynamic Compression

2021 ◽  
Vol 2021 ◽  
pp. 1-12
Author(s):  
Qiupeng Yuan ◽  
Guangxiang Xie ◽  
Lei Wang ◽  
Zhenhua Jiao ◽  
Peng Zou ◽  
...  
Keyword(s):  
Deformation Behavior ◽  
Dynamic Compression ◽  
Test System ◽  
Peak Strain ◽  
Test Protocol ◽  
Impact Compression ◽  
Stress Equilibrium ◽  
Shpb Test ◽  
Stress Uniformity ◽  
Elastic Stage

In this study, a uniaxial impact compression test was performed on coal samples with length-to-diameter L / D ratios of 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, and 1 using a Φ 50 mm split Hopkinson pressure bar (SHPB) test system. This study researched the stress uniformity and deformation behavior of coal samples with different L / D ratios during dynamic compression, defined the stress equilibrium coefficient ξ , proposed a new method for determining whether a sample meets the stress uniformity hypothesis, and obtained the critical L / D ratio of 0.6 and the optimal L / D ratio of 0.3 or 0.4 for coal samples to obtain the stress equilibrium. The experimental results showed that the dynamic stress-strain curve of coal had an elastic stage, a plastic stage, and a failure stage. As the L / D ratio increased, the proportion of the elastic stage to the prepeak curve of the samples declined progressively; with an increase in the L / D ratio, the peak part of the curve also changed from “sharp” to “stagnated,” while an increase in the plasticity led to strain softening. As the L / D ratio of the samples increased, the average strain rate decreased approximately as a power function, and the decreasing trend was gradually reduced from 296.49 s−1 ( L / D =0.3) to 102.85 s−1 ( L / D =1), with a reduction of approximately 65.31%. With an increase in the L / D ratio, the peak strain gradually decreased exponentially. This study concluded that the SHPB test protocol design is of a certain reference value for low-density, low-strength, heterogeneous brittle materials, such as coal.

scholarly journals Analysis of Energy Dissipation Characteristics of Damaged Sandstone under Impact Load

2021 ◽  
Vol 2021 ◽  
pp. 1-10
Author(s):  
Feng Wang ◽  
Haibo Wang ◽  
Ying Xu ◽  
Bing Cheng ◽  
Qianqian Wang
Keyword(s):  
Rock Mass ◽  
Energy Dissipation ◽  
Cyclic Loading ◽  
Dynamic Load ◽  
Impact Load ◽  
Peak Strain ◽  
Dissipation Energy ◽  
Cyclic Loading And Unloading ◽  
Damage Degree ◽  
Loading And Unloading

Before rock burst, coal, and gas outburst dynamic load, rock mass in geotechnical engineering has been an indifferent degree of damage. The dissipation energy of rock mass under dynamic load reflects the difficulty of rock breaking. In view of the energy dissipation of damaged rock mass under dynamic load, the cyclic loading and unloading test is carried out to make sandstone in different damage states, and the damage degree of sandstone is characterized by the change of longitudinal wave velocity before and after cyclic loading and unloading. Then, the rock with different damage degrees is tested by adopting the split Hopkinson pressure bar (SHPB). Finally, the energy dissipation characteristics of damaged rock under impact load are analyzed. The results show that the damage factor of sandstone increases with the increase of the upper limit of stress after cyclic static loading. The dynamic strength and peak strain of damaged sandstone increase with the increase of impact pressure and decrease with the increase of damage degree. With the increase of damage degree of sandstone, the reflection energy and dissipation energy of sandstone increase, while the transmission energy decreases.

scholarly journals Damage Ratio Based on Statistical Damage Constitutive Model for Rock

2019 ◽  
Vol 2019 ◽  
pp. 1-12 ◽  
Author(s):  
Ying Chen ◽  
Lin Zhang ◽  
Hui Xie ◽  
Jianfeng Liu ◽  
Hong Liu ◽  
...  
Keyword(s):  
Rock Mass ◽  
Constitutive Model ◽  
Damage Mechanics ◽  
Damage Index ◽  
Confining Pressure ◽  
Peak Strain ◽  
Rock Damage ◽  
Damage Degree ◽  
Damage Constitutive Model ◽  
Critical Damage

The study of damage characteristics of rock mass is of great significance to the analysis of rock mass structure. According to the characteristics of the microscopic unit strength of rock with random distribution, the Weibull distribution is widely used as the statistical functions of the strength of the microunit of rock to establish the damage constitutive model. The concepts of damage ratio De and damage index Cc are proposed. Damage ratio is mainly used to describe the law of damage evolution in rock. Damage index can be used to evaluate the damage degree of rock. The influence of confining pressure on distribution parameters and damage ratio is analyzed through uniaxial and triaxial compression tests of sandstone. The results show that damage ratio is an index of structural characteristics of rock damage, which can reflect the evolution characteristics of microcracks in rock under spatial stress. Critical damage ratio refers to the damage ratio corresponding to the peak stress of rock and can be used as a parameter to characterize the strength of rock for corresponding to the peak strain one to one. The critical damage ratio is linearly related to the logarithmic function of confining pressure. Its relationship is as follows: Der=Ccln⁡σ3+b. With the increase of σ3, the increasing trend of Der slows down and gradually tends to a certain value. The larger the damage index is, the more serious the damage of rock is. The smaller the damage index is, the less serious the damage of rock is. Therefore, the damage index can be used to evaluate the damage degree of rock. It will be an important direction of rock damage mechanics research to distinguish the severity of rock damage by using damage index as the limit value.

scholarly journals Effect of Joint Density on Rockburst Proneness of the Elastic-Brittle-Plastic Rock Mass

2021 ◽  
Vol 2021 ◽  
pp. 1-9
Author(s):  
Jiliang Pan ◽  
Fenhua Ren ◽  
Meifeng Cai
Keyword(s):  
Rock Mass ◽  
Elastic Strain ◽  
Strain Energy ◽  
Elastic Strain Energy ◽  
Jointed Rock ◽  
Jointed Rock Mass ◽  
Joint Density ◽  
Dissipated Energy ◽  
Uniaxial Compression Test ◽  
Plastic Rock

The prediction of rockburst proneness is the basis of preventing and controlling rockburst disasters in rock engineering. Based on energy theory and damage mechanics, the quantitative functional relationship between joint density and energy density was derived. Then, the theoretical results were verified by numerical simulation and uniaxial compression test, and the effect of joint density on rockburst proneness of the elastic-brittle-plastic rock mass was discussed. The results show that the relationship between the joint density and the dissipated energy index of the jointed rock mass is a logarithmic function. With the same total input energy, the higher the joint density, the more the damage dissipation energy. Even in the case of high joint density, the rock mass still has limited resistance to external failure. Under the same joint density, the strength of parallel jointed rock mass is better than that of the cross-jointed rock mass, and the parallel jointed rock mass can accumulate more elastic strain energy and has higher rockburst proneness. The joint density is closely related to the ability of the rock mass to store high strain energy. The higher the joint density is, the weaker the ability to accumulate the elastic strain energy of rock mass is and the lower the rockburst proneness is. It is helpful to predict rockburst proneness by investigating and studying the properties of geological discontinuities. The research results have some theoretical and engineering guiding significance for the prediction of rockburst proneness of the jointed rock mass.

The Application of Hydraulic Fracturing in Storage Projects of Liquefied Petroleum Gas

2006 ◽  
Vol 306-308 ◽  
pp. 1509-1514 ◽  
Author(s):  
Jing Feng ◽  
Qian Sheng ◽  
Chao Wen Luo ◽  
Jing Zeng
Keyword(s):  
Rock Mass ◽  
Hydraulic Fracturing ◽  
Stress Measurement ◽  
Test Procedure ◽  
In Situ Stress ◽  
Test System ◽  
Petroleum Engineering ◽  
Liquefied Petroleum Gas

It is very important to study the pristine stress field in Civil, Mining, Petroleum engineering as well as in Geology, Geophysics, and Seismology. There are various methods of determination of in-situ stress in rock mass. However, hydraulic fracturing techniques is the most convenient method to determine and interpret the test results. Based on an hydraulic fracturing stress measurement campaign at an underground liquefied petroleum gas storage project which locates in ZhuHai, China, this paper briefly describes the various uses of stress measurement, details of hydraulic fracturing test system, test procedure adopted and the concept of hydraulic fracturing in arriving at the in-situ stresses of the rock mass.

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.

Experimental Study and Numerical Simulation of Rock Mass Seepage Characteristics of Tunnel Engineering

2011 ◽  
Vol 243-249 ◽  
pp. 3538-3545
Author(s):  
Yong Dong Jiang ◽  
Ling Xiong ◽  
Xing Yang Yang ◽  
Quan Zhen ◽  
Zong Ling Yan
Keyword(s):  
Numerical Simulation ◽  
Rock Mass ◽  
Pore Pressure ◽  
Confining Pressure ◽  
Test System ◽  
Surrounding Rock ◽  
Simultaneous Action ◽  
Seepage Field ◽  
Variation Characteristics ◽  
Seepage Characteristics

In this research, the MTS815 rock mechanics test system , produced by American MTS co., has been conducted with transient method to study the seepage characteristics of rock under different confining pressure. Experiments have obtained the following results: with the confining pressure increased, penetration ability of water in rock decreased, but the start-up pressure gradient increased; permeability of rock decreased with the increase of effective confining pressure, which had negative exponent functional relationship between them. Based on previous researches, the study has established filtration equation which couples with stress field, temperature field and seepage field. Combined with the practical tunnel project, numerical simulated the variation characteristics of deformation of tunnel surrounding rock, pore pressure and seepage field under three fields non-coupling and coupling, numerical simulation obtained: the difference among deformation of surrounding rock, pore pressure and seepage field distribution under the coupling and non-coupling is remarkable, so it must consider the simultaneous action of fluid - solid - heat when we need to research the working of seepage law of groundwater in tunnel rock mass, and the research results enjoy important theoretical significance and practical application value.

Characterization and Constitutive Modeling of a Plasticized Poly(vinyl Chloride) for a Broad Range of Strain Rates

2001 ◽  
Vol 74 (4) ◽  
pp. 560-573 ◽  
Author(s):  
Yan Wang ◽  
Ellen M. Arruda ◽  
Phillip A. Przybylo
Keyword(s):  
Vinyl Chloride ◽  
Constitutive Modeling ◽  
Split Hopkinson Pressure Bar ◽  
Test System ◽  
Strain Rates ◽  
Impact Compression ◽  
Plasticized Pvc ◽  
Rate Dependent ◽  
Poly Vinyl Chloride ◽  
Compression Data

Abstract The mechanical behavior, morphological characterization and constitutive modeling of plasticized poly(vinyl chloride) (or PVC) are studied in this paper. The plasticized PVC is tested to large strains over a broad range of strain rates. Uniaxial and plane strain compression data at various constant strain rates ranging from −0.001 to −10 s−1 are collected on a conventional servohydraulic test system. Additional uniaxial impact compression data at approximately constant strain rates ranging from −1160 to −5560 s−1 are obtained using an aluminum split Hopkinson pressure bar apparatus. The large strain load/unload response of the plasticized PVC is nonlinear, it contains hysteresis and plastic deformation, and the initial response is highly rate dependent when the strain rate spans the transition zone between quasi-static and impact strain rates at room temperature. The morphology of plasticized PVC is analyzed via differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA), and described as a physically entangled network. A three-dimensional rate dependent constitutive model for plasticized PVC is developed and shown to successfully predict its stress—strain behavior over a broad range of strain rates.

scholarly journals Study of Acoustic Emission and Mechanical Characteristics of Coal Samples under Different Loading Rates

2015 ◽  
Vol 2015 ◽  
pp. 1-11 ◽  
Author(s):  
Huamin Li ◽  
Huigui Li ◽  
Baobin Gao ◽  
Dongjie Jiang ◽  
Junfa Feng
Keyword(s):  
Acoustic Emission ◽  
Elasticity Modulus ◽  
Loading Rate ◽  
Peak Stress ◽  
Test System ◽  
Strong Impact ◽  
Peak Strain ◽  
Compression Tests ◽  
Loading Rates ◽  
The Relationship

To study the effect of loading rate on mechanical properties and acoustic emission characteristics of coal samples, collected from Sanjiaohe Colliery, the uniaxial compression tests are carried out under various levels of loading rates, including 0.001 mm/s, 0.002 mm/s, and 0.005 mm/s, respectively, using AE-win E1.86 acoustic emission instrument and RMT-150C rock mechanics test system. The results indicate that the loading rate has a strong impact on peak stress and peak strain of coal samples, but the effect of loading rate on elasticity modulus of coal samples is relatively small. When the loading rate increases from 0.001 mm/s to 0.002 mm/s, the peak stress increases from 22.67 MPa to 24.99 MPa, the incremental percentage is 10.23%, and under the same condition the peak strain increases from 0.006191 to 0.007411 and the incremental percentage is 19.71%. Similarly, when the loading rate increases from 0.002 mm/s to 0.005 mm/s, the peak stress increases from 24.99 MPa to 28.01 MPa, the incremental percentage is 12.08%, the peak strain increases from 0.007411 to 0.008203, and the incremental percentage is 10.69%. The relationship between acoustic emission and loading rate presents a positive correlation, and the negative correlation relation has been determined between acoustic emission cumulative counts and loading rate during the rupture process of coal samples.

Sign in / Sign up

Export Citation Format

Share Document