scholarly journals Investigation for Influences of Seepage on Mechanical Properties of Rocks Using Acoustic Emission Technique

Geofluids ◽  
2020 ◽  
Vol 2020 ◽  
pp. 1-10
Author(s):  
Saisai Wu ◽  
Xiaohan Zhang ◽  
Junping Li ◽  
Zhao Wang
Keyword(s):  
Mechanical Properties ◽  
Acoustic Emission ◽  
Rock Mass ◽  
Shear Failure ◽  
Great Influence ◽  
Average Energy ◽  
Acoustic Emission Technique ◽  
Failure Patterns ◽  
Initial Rupture ◽  
Emission System

The behavior of rock mass is governed by the properties of both the rock material and discontinuities in the rock mass. Surrounding environments including the existence of water also have a great influence on the behavior and mechanical properties of rocks. In this study, a novel-designed compression and seepage testing system, associated with an acoustic emission system, was designed and constructed. The changes in the specimens resulting from the uniaxial compression were monitored by an acoustic emission technique. The characteristics of the acoustic emission parameters at different stages including compaction and crack initiation, crack propagation, and catastrophic failure were analyzed. The existence of seepage had direct influences on the mechanical properties and failure patterns of the specimens. The specimens tested in pure compression conditions demonstrated strong burst proneness and ruptured into separate pieces, while for the specimens with seepage, no burst proneness was observed and the specimens tended to fail along a macroscopic shear failure plane. The highest average energy of the acoustic signal occurred at the stage of initial rupture of rock specimens, rather than at the stage of widespread rupture. The studies explored the possibilities of using the acoustic emission technique to investigate the problems associated with the seepage in geotechnical and rock engineering and provided meaningful results for further research in this field.

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 Mechanical Properties of Sandstones under Initial Unloading Damage

2021 ◽  
Vol 2021 ◽  
pp. 1-12
Author(s):  
Hengbin Zhang ◽  
Lehua Wang ◽  
Jianlin Li ◽  
Huafeng Deng ◽  
Xiaoliang Xu
Keyword(s):  
Mechanical Properties ◽  
Rock Mass ◽  
Shear Failure ◽  
Rock Sample ◽  
Triaxial Compression ◽  
Deformation Modulus ◽  
Peak Strength ◽  
Repeated Loading ◽  
Adjustment Process ◽  
Loading Test

To study the influence of initial unloading damage on the mechanical properties of sandstone, the repeated loading test of unloading damaged sandstone was carried out considering 8 initial unloading quantities of 100%, 93.33%, 86.67%, 80%, 73.33%, 66.67%, 40%, and 0%. The results were compared with those of the triaxial compression test of intact samples. The results show that the peak strength of intact samples is higher than that of unloading damaged samples, and the difference is more obvious when the unloading quantity is more than 80%. During the unloading process, the strain increasing rate of rock samples is obvious, and the lateral dilatation is significant, and the deformation modulus and compressive strength of the rock sample deteriorate obviously. From the energy point of view, the greater the unloading damage, the smaller the stored elastic strain energy, which leads to the decrease of peak strength. At present, the unloading fracture inside the rock sample has developed, and the failure mode of the sample gradually changes from compression shear failure to tensile shear failure. In the process of engineering rock mass excavation, the unloading area and unloading damage amount of the rock mass is a dynamic adjustment process. To ensure the safety of the engineering rock mass, it is suggested to determine reasonable reinforcement time, reinforcement area, and reinforcement measures.

scholarly journals Experimental Investigation on Failure Modes and Mechanical Properties of Rock-Like Specimens with a Grout-Infilled Flaw under Triaxial Compression

2019 ◽  
Vol 2019 ◽  
pp. 1-14
Author(s):  
Huilin Le ◽  
Shaorui Sun ◽  
Feng Zhu ◽  
Haotian Fan
Keyword(s):  
Mechanical Properties ◽  
Rock Mass ◽  
Epoxy Resin ◽  
Failure Modes ◽  
Shear Failure ◽  
Fractured Rock ◽  
Triaxial Compression ◽  
Friction Angle ◽  
Confining Pressure ◽  
Compression Tests

Flaws existing in rock mass are one of the main factors resulting in the instability of rock mass. Epoxy resin is often used to reinforce fractured rock mass. However, few researches focused on mechanical properties of the specimens with a resin-infilled flaw under triaxial compression. Therefore, in this research, epoxy resin was selected as the grouting material, and triaxial compression tests were conducted on the rock-like specimens with a grout-infilled flaw having different geometries. This study draws some new conclusions. The high confining pressure suppresses the generation of tensile cracks, and the failure mode changes from tensile-shear failure to shear failure as the confining pressure increases. Grouting with epoxy resin leads to the improvement of peak strengths of the specimens under triaxial compression. The reinforcement effect of epoxy resin is better for the specimens having a large flaw length and those under a relatively low confining pressure. Grouting with epoxy resin reduces the internal friction angle of the samples but improves their cohesion. This research may provide some useful insights for understanding the mechanical behaviors of grouted rock masses.

scholarly journals Exploring the Effect of Asperity Order on Mechanical Character of Joint Specimen from the Perspective of Damage

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-17
Author(s):  
Zhouhao Yuan ◽  
Yicheng Ye ◽  
Binyu Luo
Keyword(s):  
Mechanical Properties ◽  
Acoustic Emission ◽  
Normal Stress ◽  
Failure Mode ◽  
Shear Failure ◽  
Joint Surface ◽  
Normal Stresses ◽  
Joint Specimen ◽  
Waviness And Unevenness ◽  
Softening Stage

The joint morphology is multiscale. The effect of each asperity order on the mechanical properties of joints is different. The shear mechanical properties of joint specimens are related to its surface damage characteristics. At present, there are still few studies on the effect of roughness on the shearing mechanical properties of joint from the perspective of damage of each asperity order. In this paper, the standard roughness profile was chosen as initial morphology. The standard roughness profile was decomposed into waviness and unevenness by the method combine the ensemble empirical mode decomposition (EEMD) and the cut-off criterion. Then, the joint specimen which contains waviness and unevenness and the specimen which only contains waviness were prepared by the 3D engraving technology. The 40 sets of joint specimens with different asperity order were subjected to direct shear tests under different normal stresses. Based on the 3D scanning technology and ICP iterative method, the damaged area and the damage volume were calculated. Based on the damage volume data and the acoustic emission (AE) data, the effect of asperity order to the joint mechanical behaviour was studied. The results indicate that (1) under low normal stress, the unevenness plays a control role in the failure mode of the joint specimen. Under low normal stress, the joint surface containing only waviness exhibits slip failure, and the joint surface with unevenness exhibits shear failure. With the increase of the normal stress, the failure mode of the specimen containing only waviness changes from slip failure to shear failure; (2) the unevenness controls the damage degree of the joint specimen. The damaged area, damage volume, AE energy rate, and accumulative AE energy of the joint specimen with unevenness are larger than those of the specimen with only waviness, and this difference increases with the normal stress increase; (3) the difference between the joint specimen with unevenness and specimen with only waviness mainly exists in the prepeak nonlinear stage and the postpeak softening stage. The characteristic parameters of acoustic emission generated in the postpeak softening stage of the joint specimen with unevenness are greater than those of the specimen with only waviness. This phenomenon can be used to explain the stress drop difference at the postpeak softening stage; (4) the AE b value can be used to evaluate the damage of joint specimens. Analysing the damage difference of each asperity order under different normal stresses is of great significance to the analysis of the influence of the morphology of the joint surface on the mechanical properties of the joint.

Research Status and Prospect of Rock Mass Acoustic Emission Instrument

2013 ◽  
Vol 671-674 ◽  
pp. 280-283
Author(s):  
Qing Zhang ◽  
Lei Wang
Keyword(s):  
Acoustic Emission ◽  
Rock Mass ◽  
Elastic Wave ◽  
Internal Force ◽  
Target Component ◽  
Destructive Testing ◽  
Engineering Research ◽  
Research Status ◽  
Emission System ◽  
Rock Mass Deformation

Acoustic emission technique based on sampling and disposing of the elastic wave caused by rock mass deformation, can comprehend the internal force, damaged degree of target component or material. Acoustic emission system as a dynamic non-destructive testing program, has now been widely used in various fields of engineering. Research on rock mass acoustic emission technology is to identify the stable status of the rock mass by using acoustic emission instrument to receive the elastic wave. Rock mass acoustic emission instrument requires high precision and high sampling frequency. The research status of the acoustic emission instrument and the problems appears in developing the device introduced in this article could be the reference for the future study.

scholarly journals Some important aspects of rock mechanics and geomechanics

2019 ◽  
Vol 109 ◽  
pp. 00114 ◽  
Author(s):  
Oleksii Voloshyn ◽  
Oleh Riabtsev
Keyword(s):  
Mechanical Properties ◽  
Rock Mass ◽  
Coal Mining ◽  
Rock Mechanics ◽  
Elastic Limit ◽  
Great Influence

This work considers the analysis of important aspects of rock mechanics, such as the variability of the mechanical properties of rocks under the samples testing, the continuity of the rock mass and the deformation beyond the elastic limit, which have a great influence on the accuracy and reliability when conducting geomechanical studies of the rock mass during coal mining. The main methods for solving geomechanical problems are shown.

Sign in / Sign up

Export Citation Format

Share Document