{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,7,1]],"date-time":"2026-07-01T06:11:52Z","timestamp":1782886312278,"version":"3.54.5"},"reference-count":32,"publisher":"MDPI AG","issue":"1","license":[{"start":{"date-parts":[[2025,12,26]],"date-time":"2025-12-26T00:00:00Z","timestamp":1766707200000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"State Key Research Development Program of China","award":["2024YFC2909500"],"award-info":[{"award-number":["2024YFC2909500"]}]},{"name":"State Key Research Development Program of China","award":["2024YFC2909504"],"award-info":[{"award-number":["2024YFC2909504"]}]},{"name":"Youth Science and Technology Innovation Fund of BGRIMM Technology Group","award":["04-2368"],"award-info":[{"award-number":["04-2368"]}]},{"DOI":"10.13039\/501100001809","name":"National Natural Science Foundation of China","doi-asserted-by":"publisher","award":["52504086"],"award-info":[{"award-number":["52504086"]}],"id":[{"id":"10.13039\/501100001809","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100001809","name":"National Natural Science Foundation of China","doi-asserted-by":"publisher","award":["52174221"],"award-info":[{"award-number":["52174221"]}],"id":[{"id":"10.13039\/501100001809","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100001809","name":"National Natural Science Foundation of China","doi-asserted-by":"publisher","award":["52474269"],"award-info":[{"award-number":["52474269"]}],"id":[{"id":"10.13039\/501100001809","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>Microseismic\/acoustic emission (AE) monitoring enables real-time, non-destructive observation of deformation and failure processes in rock during loading and unloading. Accordingly, this study designed two experimental schemes\u2014sandstone loading and unloading\u2014to comparatively investigate the spatiotemporal evolution characteristics of AE during sandstone failure under these distinct stress paths. Based on AE waveform time-frequency parameters and AE source location results obtained during testing, the failure evolution patterns of rock under both loading paths were analyzed. The results demonstrate that: (1) In both loading and load-unloading experiments, rock failure exhibited a distinct four-stage characteristic. Under pure loading conditions, failure concentrated near the point of catastrophic rupture, whereas unloading triggered premature rock fracturing, with a more pronounced AE response observed during the unloading phase. (2) For both loading paths, the dominant frequencies of AE waveforms were concentrated within the 0\u2013200 kHz range. A distinct low-frequency (0\u2013100 kHz), high-amplitude zone emerged prominently during Stage 4 in both cases. (3) AE source locations under load-unloading conditions revealed that during Stage 3\u2014characterized by vertical loading combined with lateral unloading in the minimum principal stress direction\u2014tensile failure cracks nucleated within the rock. Subsequently, during Stage 4 of the loading phase, these cracks propagated and coalesced, ultimately forming a macroscopic fracture surface on the sandstone specimen. (4) The AE source location results under pure loading failure conditions indicate that under uniaxial vertical loading, compression-shear failure fractures begin to develop within the rock mass during Stage 3. With continued loading in Stage 4, these shear fractures propagate through to the specimen surface, forming a through-going shear fracture plane.<\/jats:p>","DOI":"10.3390\/s26010167","type":"journal-article","created":{"date-parts":[[2025,12,29]],"date-time":"2025-12-29T00:50:42Z","timestamp":1766969442000},"page":"167","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":1,"title":["Comparative Analysis of the Spatiotemporal Evolution Patterns of Acoustic Emission Source Localization Under True Triaxial Loading and Loading-Unloading Conditions in Sandstone"],"prefix":"10.3390","volume":"26","author":[{"given":"Peng","family":"Chen","sequence":"first","affiliation":[{"name":"China-South Africa Joint Research Center for Development and Utilization on Mineral Resources, BGRIMM Technology Group, Beijing 100160, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Shibo","family":"Yu","sequence":"additional","affiliation":[{"name":"China-South Africa Joint Research Center for Development and Utilization on Mineral Resources, BGRIMM Technology Group, Beijing 100160, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Hui","family":"Wang","sequence":"additional","affiliation":[{"name":"China-South Africa Joint Research Center for Development and Utilization on Mineral Resources, BGRIMM Technology Group, Beijing 100160, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Zhixiu","family":"Wang","sequence":"additional","affiliation":[{"name":"China-South Africa Joint Research Center for Development and Utilization on Mineral Resources, BGRIMM Technology Group, Beijing 100160, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-2028-4138","authenticated-orcid":false,"given":"Nan","family":"Li","sequence":"additional","affiliation":[{"name":"School of Mines, China University of Mining and Technology, Xuzhou 221116, China"},{"name":"State Key Laboratory for Fine Exploration and Intelligent Development of Coal Resources, China University of Mining and Technology, Xuzhou 221116, China"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2025,12,26]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"322","DOI":"10.1016\/j.jmrt.2020.12.010","article-title":"Mechanical properties of rock\u2013coal bi-material samples with different lithologies under uniaxial loading","volume":"10","author":"Yin","year":"2020","journal-title":"J. Mater. Res. Technol."},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"8883537","DOI":"10.1155\/2020\/8883537","article-title":"Study on Impact Tendency of Coal and Rock Mass Based on Different Stress Paths","volume":"2020","author":"Zhang","year":"2020","journal-title":"Adv. Civ. Eng."},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"104439","DOI":"10.1016\/j.ijrmms.2020.104439","article-title":"True triaxial strength and failure characteristics of cubic coal and sandstone under different loading paths","volume":"135","author":"Lu","year":"2020","journal-title":"Int. J. Rock Mech. Min. Sci."},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"107028","DOI":"10.1016\/j.measurement.2019.107028","article-title":"Real-time measuring and warning of surrounding rock dynamic deformation and failure in deep roadway based on machine vision method","volume":"149","author":"Xu","year":"2020","journal-title":"Measurement"},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"104074","DOI":"10.1016\/j.tust.2021.104074","article-title":"Analysis of the interaction between tunnel support and surrounding rock considering pre-reinforcement","volume":"115","author":"Sun","year":"2021","journal-title":"Tunn. Undergr. Space Technol."},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"437","DOI":"10.1016\/j.ijmst.2022.11.008","article-title":"In-situ observations of damage-fracture evolution in surrounding rock upon unloading in 2400-m-deep tunnels","volume":"33","author":"Guo","year":"2023","journal-title":"Int. J. Min. Sci. Technol."},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"170","DOI":"10.5004\/dwt.2023.29419","article-title":"Stability of surrounding rock in broken zone of the tunnel in rich water and mountains","volume":"290","author":"Xu","year":"2023","journal-title":"Desalination Water Treat."},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"116844","DOI":"10.1016\/j.measurement.2025.116844","article-title":"Precursory characteristics of coal-rock failure using acoustic emission and computed tomography under uniaxial monotonic and cyclic compression","volume":"247","author":"Lu","year":"2025","journal-title":"Measurement"},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"1043","DOI":"10.1007\/s00603-022-03104-2","article-title":"Acoustic Emission Characteristics of Coal Failure Under Triaxial Loading and Unloading Disturbance","volume":"56","author":"Zhou","year":"2022","journal-title":"Rock Mech. Rock Eng."},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"5531","DOI":"10.1007\/s00603-025-04423-w","article-title":"Real-Time Identification of Rock Failure Stages Using Deep Learning: A Case Study of Acoustic Emission Analysis in Rock Engineering","volume":"58","author":"Pu","year":"2025","journal-title":"Rock Mech. Rock Eng."},{"key":"ref_11","first-page":"4210","article-title":"Microseismicity of an Unstable Rock Mass: From Field Monitoring to Laboratory Testing","volume":"15","author":"Colombero","year":"2018","journal-title":"J. Geophys. Res. Solid Earth"},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"104096","DOI":"10.1016\/j.ijrmms.2019.104096","article-title":"Microseismic Investigation of Mining-Induced Brittle Fault Activation in a Chinese Coal Mine","volume":"123","author":"Cheng","year":"2019","journal-title":"Int. J. Rock Mech. Min. Sci."},{"key":"ref_13","first-page":"2990","article-title":"Acoustic Emission Monitoring Technology for Coal and Gas Outburst","volume":"15","author":"Li","year":"2019","journal-title":"Energy Sci. Eng."},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"1065","DOI":"10.1016\/j.ijmst.2023.07.006","article-title":"Rock Dynamics in Deep Mining","volume":"33","author":"He","year":"2023","journal-title":"Int. J. Min. Sci. Technol."},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"109226","DOI":"10.1016\/j.engfracmech.2023.109266","article-title":"Stress-Induced AE Varying Characteristics in Distinct Lithologies Subjected to Uniaxial Compression","volume":"286","author":"Wang","year":"2023","journal-title":"Eng. Fract. Mech."},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"286","DOI":"10.1016\/j.ijrmms.2009.09.003","article-title":"Rock Burst Process of Limestone and its Acoustic Emission Characteristics under True-Triaxial Unloading Conditions","volume":"47","author":"He","year":"2010","journal-title":"Int. J. Rock Mech. Min. Sci."},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"106097","DOI":"10.1016\/j.ijrmms.2025.106097","article-title":"Rockburst probability early warning method based on integrated infrared temperature and acoustic emission parameters","volume":"189","author":"Ren","year":"2025","journal-title":"Int. J. Rock Mech. Min. Sci."},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"105519","DOI":"10.1016\/j.ijrmms.2023.105519","article-title":"Comprehensive Early Warning Method of Microseismic, Acoustic Emission and Electromagnetic Radiation Signals of Rock Burst Based on Deep Learning","volume":"170","author":"Di","year":"2023","journal-title":"Int. J. Rock Mech. Min. Sci."},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"333","DOI":"10.1007\/s12517-021-09423-y","article-title":"Rock Burst Initiation and Precursors in a Model Specimen Based on Acoustic Emission and Infrared Monitoring","volume":"15","author":"Lin","year":"2022","journal-title":"Arab. J. Geosci."},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"106060","DOI":"10.1016\/j.tust.2024.106060","article-title":"Rockburst Early-Warning Method Based on Time Series Prediction of Multiple Acoustic Emission Parameters","volume":"153","author":"Ma","year":"2024","journal-title":"Tunn. Undergr. Space Technol."},{"key":"ref_21","doi-asserted-by":"crossref","unstructured":"Dong, L., Zhang, Y., and Ma, J. (2020). Micro-Crack Mechanism in the Fracture Evolution of Saturated Granite and Enlightenment to the Precursors of Instability. Sensors, 20.","DOI":"10.3390\/s20164595"},{"key":"ref_22","doi-asserted-by":"crossref","unstructured":"Choi, Y.-C., Chung, B., and Jung, D. (2024). A Proposed Algorithm Based on Variance to Effectively Estimate Crack Source Localization in Solids. Sensors, 24.","DOI":"10.20944\/preprints202409.0708.v1"},{"key":"ref_23","doi-asserted-by":"crossref","unstructured":"Liu, C., Zhao, C., Huang, Y., and Lyu, G. (2025). Ground Pressure Control Measures and Microseismic Verification During the Recovery Process of Residual Ore Bodies. Appl. Sci., 15.","DOI":"10.3390\/app152111467"},{"key":"ref_24","doi-asserted-by":"crossref","unstructured":"Hou, C., Li, X., Chen, Y., Li, W., Liu, K., Dong, L., and Sun, D. (2024). Optimization and Numerical Verification of Microseismic Monitoring Sensor Network in Underground Mining: A Case Study. Mathematics, 12.","DOI":"10.3390\/math12223500"},{"key":"ref_25","doi-asserted-by":"crossref","unstructured":"Li, N., Fang, L., Huang, B., Chen, P., Cai, C., Zhang, Y., Liu, X., Li, Z., Wen, Y., and Qin, Y. (2022). Characteristics of Acoustic Emission Waveforms Induced by Hydraulic Fracturing of Coal under True Triaxial Stress in a Laboratory-Scale Experiment. Minerals, 12.","DOI":"10.3390\/min12010104"},{"key":"ref_26","doi-asserted-by":"crossref","first-page":"177","DOI":"10.1016\/j.ijrmms.2018.07.016","article-title":"Rockburst Mechanism and Prediction Based on Microseismic Monitoring","volume":"110","author":"Ma","year":"2018","journal-title":"Int. J. Rock Mech. Min. Sci."},{"key":"ref_27","doi-asserted-by":"crossref","first-page":"903","DOI":"10.1098\/rspa.1998.0193","article-title":"The empirical mode decomposition and the Hilbert spectrum for nonlinear and non-stationary time series analysis","volume":"454","author":"Huang","year":"1998","journal-title":"Proc. R. Soc. Lond. Ser. A Math. Phys. Eng. Sci."},{"key":"ref_28","doi-asserted-by":"crossref","unstructured":"Torres, M.E., Colominas, M.A., Schlotthauer, G., and Flandrin, P. (2011, January 22\u201327). A complete ensemble empirical mode decomposition with adaptive noise. Proceedings of the IEEE International Conference on Acoustics, Speech and Signal Processing (ICASSP), Prague, Czech Republic.","DOI":"10.1109\/ICASSP.2011.5947265"},{"key":"ref_29","doi-asserted-by":"crossref","first-page":"2297","DOI":"10.1007\/s11053-021-09821-9","article-title":"Acoustic Emission Source Location Monitoring of Laboratory-Scale Hydraulic Fracturing of Coal Under True Triaxial Stress","volume":"30","author":"Li","year":"2021","journal-title":"Nat. Resour. Res."},{"key":"ref_30","first-page":"2","article-title":"Fourier analysis and spectral estimation","volume":"89","author":"Antoni","year":"2017","journal-title":"Mech. Syst. Signal Process."},{"key":"ref_31","doi-asserted-by":"crossref","first-page":"58869","DOI":"10.1109\/ACCESS.2022.3179517","article-title":"A Review of Wavelet Analysis and Its Applications: Challenges and Opportunities","volume":"10","author":"Guo","year":"2022","journal-title":"IEEE Access."},{"key":"ref_32","unstructured":"(2021). Standard Test Method for Primary Calibration of Acoustic Emission Sensor (Standard No. E1106-12R21)."}],"container-title":["Sensors"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/1424-8220\/26\/1\/167\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,12,29]],"date-time":"2025-12-29T00:53:58Z","timestamp":1766969638000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/1424-8220\/26\/1\/167"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2025,12,26]]},"references-count":32,"journal-issue":{"issue":"1","published-online":{"date-parts":[[2026,1]]}},"alternative-id":["s26010167"],"URL":"https:\/\/doi.org\/10.3390\/s26010167","relation":{},"ISSN":["1424-8220"],"issn-type":[{"value":"1424-8220","type":"electronic"}],"subject":[],"published":{"date-parts":[[2025,12,26]]}}}