scholarly journals Study on Characteristics of Energy Storage and Acoustic Emission of Rock under Different Moisture Content

2021 ◽  
Vol 13 (3) ◽  
pp. 1041
Author(s):  
Chuanming Li ◽  
Nan Liu ◽  
Wanrong Liu ◽  
Ruimin Feng
Keyword(s):  
Acoustic Emission ◽  
Energy Storage ◽  
Water Content ◽  
Elastic Limit ◽  
Test System ◽  
Natural State ◽  
Uniaxial Compression Test ◽  
Sound Emission ◽  
Underground Engineering ◽  
Rock Samples

In order to study the energy storage and sound emission characteristics of rocks under different water content, uniaxial compression test, cyclic loading, unloading test and sound emission test were carried out using RMT-150B rock mechanics test system and DS5 acoustic emission system. The results show that the total strain energy of saturated rock samples and the area of hysteresis loop are the largest in the same period number, which indicates that the presence of water can reduce the elastic limit of rock samples, making the rock very easy to deform and even damage. Acoustic emission tests show that the damage energy of water-bearing rocks is small. The higher the water content, the smaller the peak damage energy. The bending energy index WET of the rock sample under saturated and natural state is smaller than that under dry state, which further indicates that the presence of water can reduce the elastic limit of the rock and soften it. The results can provide a basis for the prediction of underground engineering construction and rock failure instability.

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.

scholarly journals Mechanical Properties and Acoustic Emission Characteristics of Karst Limestone under Uniaxial Compression

2018 ◽  
Vol 2018 ◽  
pp. 1-14 ◽  
Author(s):  
Jianxun Chen ◽  
Qingsong Wang ◽  
Jiaqi Guo ◽  
Yanbin Luo ◽  
Yao Li ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Acoustic Emission ◽  
Water Content ◽  
Uniaxial Compression ◽  
Wave Velocity ◽  
Brittle Failure ◽  
Shear Failure ◽  
Testing Machine ◽  
Natural State ◽  
Saturated State

Firstly, I-RPT ultrasonic detector was used to test the wave velocity of karst limestone with different initial microstructure and water content. Then, RMT-150B rock testing machine and DS2-16B acoustic emission system were used to test the acoustic emission (AE) under uniaxial compression. Mechanical properties and AE characteristics were obtained during rock failure. The detailed relationship between stress-strain and AE characteristics was studied in this paper. Research results indicated the following: (1) For samples with many primary fissures and defects, wave velocity in dry state was larger than that in its natural state. From natural state to saturated state, the wave velocity tended to increase. For samples with good integrity, wave velocity increased with increasing of water content. (2) In the dry state, the samples presented tension failure. In saturated state, the samples presented tension-shear failure. For samples with cracks and good integrity, samples showed brittle failure. For samples with many corrosion pores which showed ductile damage under natural and saturated state, the spalling phenomenon was enhanced under saturated state. (3) With increasing of water content, the peak stress and AE peak reduced dramatically. In brittle failure, AE peak could be considered a sign of failure. In ductile failure, AE activity decreased gradually with the decrease of stress. (4) The mechanical properties and AE characteristics corresponding to four main fracture propagation types were also discussed.

scholarly journals Experimental System of Hydrodynamic Action of Dunhuang Mogao Grottoes under Temperature-Humidity-Mechanical (THM) Coupling

Geofluids ◽  
2020 ◽  
Vol 2020 ◽  
pp. 1-23
Author(s):  
Zhigang Tao ◽  
Huixia Xu ◽  
Hongzhen Peng ◽  
Weixin Liu
Keyword(s):  
Water Absorption ◽  
Liquid Water ◽  
Water Adsorption ◽  
Test System ◽  
Surrounding Rock ◽  
Uniaxial Compression Test ◽  
Rock Samples ◽  
Mogao Grottoes ◽  
Logarithmic Curve ◽  
Sandstone Rock

In order to thoroughly investigate the weathering mechanism of the murals in Dunhuang Mogao Grottoes, based on the independently developed hydrodynamic test system of the surrounding rocks under the combined action of temperature, humidity, and stress, this study performed the liquid water adsorption test and gaseous water adsorption test of the surrounding rocks of the support body of Dunhuang Mogao Grottoes, as well as the softening test of the strength of liquid water adsorbed by the rock samples. The experimental results are as follows: (a) Q–t curve and lnw–lnt curve of the three types of black sandstone rock samples obtained by analyzing the nonpressure water absorption experiment data indicate that the Q–t curve of the rock samples showed a similar trend with time, with the initial curve being steep and rapid increase in the water absorption; the double logarithmic curve of water absorption is convex and tends to be saturated. (b) The absorbing water softening test analysis was carried out for four types of siltstone specimens with intensity of pressure; bibulous rate was found to vary with time, and sample parameters such as compressive strength and elastic modulus decreased linearly with increasing water absorption at different times of uniaxial compression test. (c) Through the summer and winter and cave surrounding rock within the sample, the gas adsorption of water simulation was combined with the adsorption curve analysis, indicating that the adsorption characteristics of the surrounding rock and the correlation of larger sample depend on season. These research results provide a reliable theoretical basis and technical support for the protection of the murals in the Mogao Grottoes of Dunhuang and the prevention and control by salt damage.

Experimental and numerical studies on fracture characteristics of notched granite beams under cyclic loading and unloading

2020 ◽  
Vol 56 (1) ◽  
pp. 3-17
Author(s):  
Xiaojing Li ◽  
Peijie He ◽  
Jianhui Tang ◽  
Xudong Chen
Keyword(s):  
Acoustic Emission ◽  
Cyclic Loading ◽  
Correlation Method ◽  
Average Frequency ◽  
Test System ◽  
Underground Engineering ◽  
Three Point Bending ◽  
Cyclic Loading And Unloading ◽  
Loading And Unloading ◽  
Felicity Ratio

In underground engineering, such as mining engineering and deep tunnel engineering, the rock is often loaded and unloaded repeatedly. The strength of rock under cyclic load is lower than that under static load. To obtain the fracture response of the rock, the three-point bending tests of notched granite beams under cyclic loading and unloading were carried out with Electro-hydraulic Servo Material Test System. The acoustic emission technology was adopted to monitor the acoustic emission events of sample in the process of fracture. It is revealed that the fracture toughness of granite under cyclic loading and unloading is lower than that under static loading. Based on the acoustic emission energy obtained from monitoring, the damage evolution during cyclic loading and unloading was analyzed. The fracture mode of granite samples is analyzed by the RA value-average frequency correlation method. And the Felicity ratio during the loading and unloading cycle was calculated to evaluate the severity of initial damage of the material. It is revealed that Kaiser effect appears only in the elastic deformation stage of cyclic loading unloading bending. The Holmquist–Johnson–Cook damage constitutive model and Weibull distribution were used to establish the heterogeneous granite model. And the three-point bending of the model under cyclic loading and unloading was simulated to disclose the crack growth mechanism of rock. The study may provide some references for rock instability control in geotechnical engineering construction.

scholarly journals Investigation of the Effects of Freeze-Thaw Cycles on Geomechanical and Acoustic Characteristics of Tuff Specimens under Different Stress Paths

2020 ◽  
Vol 2020 ◽  
pp. 1-20
Author(s):  
Yong-gang Xiao ◽  
Chang-hong Li ◽  
Jie Cao ◽  
Yu Wang ◽  
Zhi-qiang Hou ◽  
...  
Keyword(s):  
Frequency Band ◽  
Physical And Mechanical Properties ◽  
Peak Stress ◽  
Open Pit ◽  
Natural State ◽  
Uniaxial Compression Test ◽  
Peak Strain ◽  
Loading Test ◽  
Freeze Thaw ◽  
Rock Samples

In the process of development and construction of open-pit mine slope in the high altitude and cold area, freeze-thaw (F-T) cycles have an important impact on rock engineering structure. F-T cycles lead to the decrease in physical and mechanical properties of rock, which is closely related to the stability of open-pit slope. In this paper, the influence of F-T cycles on geomechanical and acoustic emission (AE) characteristics of tuff specimens under different stress paths was studied by using F-T cycle treatment, in situ AE monitoring, and uniaxial loading test. The results indicated that under the same stress path, the cumulative AE count/energy of rock samples subjected to F-T cycles was less than that of rock samples not subjected to F-T cycles. The peak frequency distribution of AE signal during the loading process of rock specimen presented the phenomenon of frequency bands. The width of the low-frequency band of the rock samples subjected to F-T cycles was larger than that of the rock samples under the natural state. The frequency and width of the high-frequency band of the rock samples subjected to F-T cycles were larger than those of the rock samples under the natural state. The rock samples subjected to F-T cycles had higher plastic strain than those without F-T cycles. According to the uniaxial compression test results of F-T rock samples under different stress paths, the peak stress and peak strain have little change, but the AE characteristics were obviously different.

scholarly journals Experiment and Mechanism Investigation on Freezing-Thawing of Sandstone with Different Water Contents

2021 ◽  
Vol 2021 ◽  
pp. 1-11
Author(s):  
Guilei Song ◽  
Longxiao Chen ◽  
Kesheng Li ◽  
Deng Zhang ◽  
Junhao Xu ◽  
...  
Keyword(s):  
Acoustic Emission ◽  
Water Content ◽  
Shear Failure ◽  
Freezing Temperature ◽  
Emission Characteristics ◽  
Underground Engineering ◽  
Empirical Formulas ◽  
Splitting Failure ◽  
Acoustic Emission Test ◽  
Water Contents

Freezing-thawing cycles seriously affect the safety of underground engineering in cold regions. At present, most research studies focus on the effect of number and freezing temperature on freezing-thawing cycles. As another important factor, the mechanism of rock mass water content affecting freezing-thawing is less studied. This paper studied the influence of the water content on mechanical property, microstructure, and acoustic emission characteristics of sandstone. The results indicated that the uniaxial compressive strength (UCS) and elastic modulus (E) of sandstone after 20 freezing-thawing cycles decreased as the water content increased. However, the decreasing rate of UCS gradually decreased, while the decreasing rate of E gradually increased. Furthermore, the empirical formulas of UCS and E about water content were obtained. The porosity and plasticity of sandstone after 20 freezing-thawing cycles increased as the water content increased. The empirical formulas of UCS and E about water content were obtained. The porosity and plasticity of sandstone after 20 freezing-thawing cycles increased as the water content increased. The decreasing trend of UCS with porosity was the same as that of UCS with water content. The failure form of sandstone gradually changed from splitting failure to shear failure. The results of the acoustic emission test showed that the stress-strain curves combined with acoustic emission ring counting could reveal the damage evolution process of sandstone during loading.

scholarly journals Acoustic Emission Location Experiment Research on Stope Roof Breakage Boundaries Time-Varying Process

2015 ◽  
Vol 9 (1) ◽  
pp. 797-805
Author(s):  
Liang Zhong-Yu ◽  
Chen Zhan-Qing ◽  
Gao Feng ◽  
Zhou Yu-xin
Keyword(s):  
Acoustic Emission ◽  
Test System ◽  
Small Error ◽  
Time Varying ◽  
Sound Emission ◽  
Rock Stratum ◽  
Emission Signal ◽  
Image Diagnosis ◽  
Orientation Method ◽  
Fracture Section

This paper utilizes self-designed time-varying boundary sound emission test system for rock stratum fracture to complete the sound emission orientation test upon the fracture of marble slab. A new method—image diagnosis and orientation method is proposed to locate fracture section. Sound emission signal Y Position and Events-X position distribution point diagram is utilized to determine the position of fracture surface; by analyzing the time-varying curve of Counts, Energy and Hits of acoustic emission signal in the same stage, the occurrence moment of rock stratum fracture section is confirmed and the development mechanism of fracture section is analyzed. Through study, it can be concluded that located fracture section position is close to actual fracture position, indicating that sound emission image diagnosis technique is characterized by high orientation precision, small error and good orientation effect; sound emission image diagnosis orientation method has very excellent maneuverability and practicability.

scholarly journals A Coordinated Control of Offshore Wind Power and BESS to Provide Power System Flexibility

Energies ◽  
2021 ◽  
Vol 14 (15) ◽  
pp. 4650
Author(s):  
Martha N. Acosta ◽  
Francisco Gonzalez-Longatt ◽  
Juan Manuel Roldan-Fernandez ◽  
Manuel Burgos-Payan
Keyword(s):  
Energy Storage ◽  
Power System ◽  
Wind Power ◽  
Single Layer ◽  
Coordinated Control ◽  
Test System ◽  
Power Converter ◽  
Control Logic ◽  
Battery Energy Storage ◽  
Battery Energy

The massive integration of variable renewable energy (VRE) in modern power systems is imposing several challenges; one of them is the increased need for balancing services. Coping with the high variability of the future generation mix with incredible high shares of VER, the power system requires developing and enabling sources of flexibility. This paper proposes and demonstrates a single layer control system for coordinating the steady-state operation of battery energy storage system (BESS) and wind power plants via multi-terminal high voltage direct current (HVDC). The proposed coordinated controller is a single layer controller on the top of the power converter-based technologies. Specifically, the coordinated controller uses the capabilities of the distributed battery energy storage systems (BESS) to store electricity when a logic function is fulfilled. The proposed approach has been implemented considering a control logic based on the power flow in the DC undersea cables and coordinated to charging distributed-BESS assets. The implemented coordinated controller has been tested using numerical simulations in a modified version of the classical IEEE 14-bus test system, including tree-HVDC converter stations. A 24-h (1-min resolution) quasi-dynamic simulation was used to demonstrate the suitability of the proposed coordinated control. The controller demonstrated the capacity of fulfilling the defined control logic. Finally, the instantaneous flexibility power was calculated, demonstrating the suitability of the proposed coordinated controller to provide flexibility and decreased requirements for balancing power.

scholarly journals Ensemble Learning Approach for the Prediction of Quantitative Rock Damage Using Various Acoustic Emission Parameters

2021 ◽  
Vol 11 (9) ◽  
pp. 4008
Author(s):  
Hang-Lo Lee ◽  
Jin-Seop Kim ◽  
Chang-Ho Hong ◽  
Dong-Keun Cho
Keyword(s):  
Acoustic Emission ◽  
Difficult Problem ◽  
Radioactive Waste Disposal ◽  
Parameter Analysis ◽  
Support Vector ◽  
Uniaxial Compression Test ◽  
Rock Damage ◽  
Initiation Frequency ◽  
Combined Features ◽  
Future Work

Monitoring rock damage subjected to cracks is an important stage in underground spaces such as radioactive waste disposal repository, civil tunnel, and mining industries. Acoustic emission (AE) technique is one of the methods for monitoring rock damage and has been used by many researchers. To increase the accuracy of the evaluation and prediction of rock damage, it is required to consider various AE parameters, but this work is a difficult problem due to the complexity of the relationship between several AE parameters and rock damage. The purpose of this study is to propose a machine learning (ML)-based prediction model of the quantitative rock damage taking into account of combined features between several AE parameters. To achieve the goal, 10 granite samples from KAERI (Korea Atomic Energy Research Institute) in Daejeon were prepared, and a uniaxial compression test was conducted. To construct a model, random forest (RF) was employed and compared with support vector regression (SVR). The result showed that the generalization performance of RF is higher than that of SVRRBF. The R2, RMSE, and MAPE of the RF for testing data are 0.989, 0.032, and 0.014, respectively, which are acceptable results for application in laboratory scale. As a complementary work, parameter analysis was conducted by means of the Shapley additive explanations (SHAP) for model interpretability. It was confirmed that the cumulative absolute energy and initiation frequency were selected as the main parameter in both high and low-level degrees of the damage. This study suggests the possibility of extension to in-situ application, as subsequent research. Additionally, it provides information that the RF algorithm is a suitable technique and which parameters should be considered for predicting the degree of damage. In future work, we will extend the research to the engineering scale and consider the attenuation characteristics of rocks for practical application.

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