scholarly journals Energy Dissipation and Damage Evolution Characteristics of Salt Rock under Uniaxial Cyclic Loading and Unloading Tension

2021 ◽  
Vol 2021 ◽  
pp. 1-9
Author(s):  
Anqi Zhu ◽  
Jianfeng Liu ◽  
Zhide Wu ◽  
Lu Wang ◽  
Hejuan Liu ◽  
...  
Keyword(s):  
Energy Dissipation ◽  
Damage Evolution ◽  
Damage Variable ◽  
Plastic Deformation Zone ◽  
Salt Rock ◽  
Cyclic Loading And Unloading ◽  
Cyclic Tension ◽  
Evolution Characteristics ◽  
Fracture Crack ◽  
Strength And Deformation

Salt rock has been regarded as the optimal surrounding rock for underground gas storage (UGS), and it is occasionally subjected to cyclic tension because of the gas injection and production of salt cavern, which leads to the change in mechanical properties of salt rock. In this paper, a laboratory study is conducted to investigate the energy dissipation and damage evolution characteristics of salt rock under uniaxial cyclic tension monitored by acoustic emission (AE) machine. Compared to monotonic tension, both tensile strength and deformation capacity of salt rock are enhanced under cyclic tension. The fracture crack is approximately a single linear crack with large elliptical plastic deformation zone, which is consistent with the spatial distribution of AE events. In yield stage, the proportion of dissipative energy increases first but decreases subsequently. The relationship between AE energy-based damage variable and displacement is established. It is concluded that the damage variable is a piecewise power correlation with displacement while the growth rate of damage variable increases in the pre-peak stage but decreases in post-peak stage.

scholarly journals Damage and fractal evolution trends of sandstones under constant-amplitude and tiered cyclic loading and unloading based on acoustic emission

2019 ◽  
Vol 15 (7) ◽  
pp. 155014771986102
Author(s):  
Dongxu Liang ◽  
Nong Zhang ◽  
Lixiang Xie ◽  
Guangming Zhao ◽  
Deyu Qian
Keyword(s):  
Acoustic Emission ◽  
Cyclic Loading ◽  
Damage Evolution ◽  
Damage Accumulation ◽  
Fractal Dimensions ◽  
Damage Variable ◽  
Constant Amplitude ◽  
Kaiser Effect ◽  
Cyclic Loading And Unloading ◽  
Loading And Unloading

It is of significance to study the damage and destruction of rock under cyclic loading in geotechnical engineering. We determined the trends in damage evolution of sandstone under constant-amplitude and tiered cyclic loading and unloading under uniaxial compression. The results of the study show that (1) the variation of acoustic-emission events was consistent with the stress curves and 89% of all acoustic-emission events occurred during the cycling stages. The observed Kaiser effect was more notable in tiered cycling. (2) The damage variable increased sharply in the cycling stages and its increment was 0.07 higher for tiered cycling than constant-amplitude cycling. Sandstone exhibited greater damage under tiered cyclic loading and unloading. (3) Equations for the evolution of the damage variable under the two cycle modes were obtained by fitting of experimental data. (4) The fractal dimensions of the constant-amplitude cycle were larger than those of the tiered cycle. The process of damage and destruction presents a trend of reducing fractal dimension. The damage accumulation of sandstone under tiered cycling was faster than under constant-amplitude cycling. These results provide references for damage and early warning of rock under both constant-amplitude and tiered cyclic loading and unloading.

scholarly journals Analysis of Damage Evolution of Sandstone under Uniaxial Loading and Unloading Conditions Based on Resistivity Characteristics

2019 ◽  
Vol 2019 ◽  
pp. 1-12 ◽  
Author(s):  
Guoyin Wu ◽  
Kui Wang ◽  
Mingjie Zhao ◽  
Zhichao Nie ◽  
Zhen Huang
Keyword(s):  
Stress State ◽  
Damage Evolution ◽  
Damage Model ◽  
Damage Variable ◽  
Uniaxial Loading ◽  
Experimental Comparison ◽  
Variable Expression ◽  
Cyclic Loading And Unloading ◽  
Sandstone Rock ◽  
Loading And Unloading

In complex rock engineering, understanding the stress state and determining stability and damage evolution are necessary. To more accurately provide a theoretical basis for judging the stress state of bedrock in engineering, this study experimentally addressed the damage evolution of sandstone under loading and unloading conditions. A theoretical relationship between rock resistivity and porosity was obtained according to the Archie formula, which allowed the derivation of the sandstone damage variable expression. Then, sandstone rock samples were used for experimental evaluation, and the feasibility of the theoretically determined damage variable was verified. Finally, through theoretical and experimental comparison analysis, we developed a correlative damage model for sandstone under uniaxial loading and unloading. The results show that the damage variable varies linearly with strain. The proposed correlative equation describes this behavior accurately for loading and unloading conditions. Based on the results of this study, the correlative damage model of sandstone under cyclic loading and unloading conditions can be further improved to be a complete constitutive damage model.

Study on mechanical properties and damage evolution of carbonaceous shale under triaxial compression with acoustic emission

2021 ◽  
pp. 105678952199119
Author(s):  
Kai Yang ◽  
Qixiang Yan ◽  
Chuan Zhang ◽  
Wang Wu ◽  
Fei Wan
Keyword(s):  
Mechanical Properties ◽  
Acoustic Emission ◽  
Water Content ◽  
Damage Evolution ◽  
Damage Assessment ◽  
Triaxial Compression ◽  
Confining Pressure ◽  
Damage Variable ◽  
Natural State ◽  
Carbonaceous Shale

To explore the mechanical properties and damage evolution characteristics of carbonaceous shale with different confining pressures and water-bearing conditions, triaxial compression tests accompanied by simultaneous acoustic emission (AE) monitoring were conducted on carbonaceous shale rock specimens. The AE characteristics of carbonaceous shale were investigated, a damage assessment method based on Shannon entropy of AE was further proposed. The results suggest that the mechanical properties of carbonaceous shale intensify with increasing confining pressure and degrade with increasing water content. Moisture in rocks does not only weaken the cohesion but also reduce the internal friction angle of carbonaceous shale. It is observed that AE activities mainly occur in the post-peak stage and the strong AE activities of saturated carbonaceous shale specimens appear at a lower normalized stress level than that of natural-state specimens. The maximum AE counts and AE energy increase with water content while decrease with confining pressure. Both confining pressure and water content induce changes in the proportions of AE dominant frequency bands, but the changes caused by confining pressure are more significant than those caused by water content. The results also indicate that AE entropy can serve as an applicable index for rock damage assessment. The damage evolution process of carbonaceous shale can be divided into two main stages, including the stable damage development stage and the damage acceleration stage. The damage variable increases slowly accompanied by a few AE activities at the first stage, which is followed by a rapid growth along with intense acoustic emission activities at the damage acceleration stage. Moreover, there is a sharp rise in the damage evolution curve for the natural-state specimen at the damage acceleration stage, while the damage variable develops slowly for the saturated-state specimen.

Experimental Study on Damage Evolution Characteristics of Rock-Like Material

2019 ◽  
Vol 44 (10) ◽  
pp. 8503-8513
Author(s):  
Zhang Jinhao ◽  
Chen Hongkai ◽  
Wang He ◽  
Zhou Zheng
Keyword(s):  
Experimental Study ◽  
Damage Evolution ◽  
Evolution Characteristics

scholarly journals Damage Evolution Characteristics of Rock Salt under Different Stress Conditions

2019 ◽  
Vol 2019 ◽  
pp. 1-12 ◽  
Author(s):  
Chunping Wang ◽  
Jianfeng Liu ◽  
Lu Wang
Keyword(s):  
Tensile Test ◽  
Rock Salt ◽  
Compression Test ◽  
Damage Evolution ◽  
Confining Pressure ◽  
High Energy ◽  
Brazilian Test ◽  
Evolution Characteristics ◽  
Direct Tensile ◽  
Direct Tensile Test

Understanding the damage evolution characteristics of rock material is essential to the long-term stability and safety analysis of the underground facility. In this study, a series of cyclic loading tests under tensile or compressive stresses are conducted to investigate the damage evolution, deformation, peak strength, and failure pattern of rock salt. A special attention is paid on the microcracking process by using a 3D acoustic emission (AE) test system. The laboratory tests show that the damage degree of rock salt under compression is the highest, followed by the damage in the direct tensile test. The lowest value of damage is determined by using the Brazilian test. The damage degrees where the damage rate starts to decrease are about 0.83 in the direct tensile test, about 0.75 in the Brazilian test, and about 0.91 in the compression test. The failure mode of rock salt changes from the tensile mode in the uniaxial compression test to the compression-shear mode in the confined compression test at low confinement. But from the confining pressure of 15 MPa, the rock salt displays great plastic dilatant distortion and without appreciable macroscopic fractures. Accordingly, with increasing confining pressure, the positions where the rapid increase in cumulative AE counts occurs and where the AE event with high energy appears are changed, from the beginning of the test at low confinement to the postpeak stage of the test at high confinement.

scholarly journals Study on Damage Evolution and Resistivity Variation Regularities of Coal Mass Under Multi-Stage Loading

2019 ◽  
Vol 9 (19) ◽  
pp. 4124 ◽  
Author(s):  
Xiangchun Li ◽  
Qi Zhang
Keyword(s):  
Damage Evolution ◽  
Damage Mechanics ◽  
Sudden Change ◽  
Coal Mass ◽  
Damage Variable ◽  
Evolution Process ◽  
Good Correspondence ◽  
Multi Stage ◽  
Resistivity Variation ◽  
The Relationship

In order to describe resistivity variation regularities during the process of damage evolution of loading coal mass more comprehensively and accurately, electrical resistivity and acoustic emission (AE) characteristics of coal mass were tested by 3532-50 LCR tester and AMSY-6 AE data acquisition system under the condition of multi-stage loading, and resistivity variation characteristics were analyzed with stress changing. The damage evolution process of coal mass was studied by the measurement of the AE parameters, and the resistivity curve was obtained in the damage conditions based on the relationship between the AE damage variable and the resistivity. The results show that resistivity and stress curves of coal mass have a good correspondence during the multi-stage loading, and the resistivity shows a trend of fluctuating downward with the increasing of stress. The resistivity increases sharply to the maximum value when the load increases to the ultimate compressive strength of specimens. AE information can reveal effectively damage evolution process of microcracks formation, expansion and fracture in coal mass under external force, and during multi-stage loading, the cumulative AE ringing counts curve of coal mass have three different types of growth trends: stable stage, sudden change stage, gradual increasing stage. Meanwhile, the relationship between resistivity and AE damage variable is established based on the formula of damage variable under uniaxial compression and combined with continuous damage mechanics, and its rationality is verified.

Study On the Damage Evolution Equation of Rockburst

2008 ◽  
Vol 33-37 ◽  
pp. 663-668
Author(s):  
Quan Sheng Liu ◽  
Bin Liu ◽  
Wei Gao
Keyword(s):  
Energy Dissipation ◽  
Evolution Equation ◽  
Damage Evolution ◽  
Minimum Energy ◽  
Strength Criterion ◽  
Internal Variable ◽  
Total Strength ◽  
Damage Evolution Equation ◽  
Traditional Research ◽  
Minimum Energy Dissipation

This paper introduces the principle of minimum energy dissipation and its general procedures to establish development equation of internal variable. With the accepted viewpoint that the damage is only mechanics of energy dissipation during the rockburst and utilizing the total strength criterion based on released strain energy, the general damage evolution equation is deduced. Compared with the traditional research method of damage evolution equation, this method has universal and objective characteristics.

Two-Way Coupled Multiscale Model for Predicting Mechanical Behavior of Bone Subjected to Viscoelastic Deformation and Fracture Damage

2017 ◽  
Vol 139 (2) ◽  
Author(s):  
Taesun You ◽  
Yong-Rak Kim ◽  
Taehyo Park
Keyword(s):  
Mechanical Behavior ◽  
Material Properties ◽  
Damage Evolution ◽  
Multiscale Model ◽  
Local Scale ◽  
Viscoelastic Deformation ◽  
Rate Dependent ◽  
Deformation And Fracture ◽  
Evolution Characteristics ◽  
Fracture Damage

This paper presents a two-way linked computational multiscale model and its application to predict the mechanical behavior of bone subjected to viscoelastic deformation and fracture damage. The model is based on continuum thermos-mechanics and is implemented through the finite element method (FEM). Two physical length scales (the global scale of bone and local scale of compact bone) were two-way coupled in the framework by linking a homogenized global object to heterogeneous local-scale representative volume elements (RVEs). Multiscaling accounts for microstructure heterogeneity, viscoelastic deformation, and rate-dependent fracture damage at the local scale in order to predict the overall behavior of bone by using a viscoelastic cohesive zone model incorporated with a rate-dependent damage evolution law. In particular, age-related changes in material properties and geometries in bone were considered to investigate the effect of aging, loading rate, and damage evolution characteristics on the mechanical behavior of bone. The model successfully demonstrated its capability to predict the viscoelastic response and fracture damage due to different levels of aging, loading conditions (such as rates), and microscale damage evolution characteristics with only material properties of each constituent in the RVEs.

Sign in / Sign up

Export Citation Format

Share Document