SUN G H, QI Y Z, LIU Z Y,et al.Study of damage precursors under cyclic loading and unloading in red sandstone based on K-means clustering［J］.Journal of Henan Polytechnic University（Natural Science），doi: 10.16186/j.cnki.1673-9787.2024070082

doi:10.16186/j.cnki.1673-9787.2024070082

Received：2024-07-24

Revised：2024-09-20

Online：2024-11-01

Study of damage precursors under cyclic loading and 

unloading in red sandstone based on K-means clustering

SUN Guanghua^1,2,3, QI Yuzhu^1,2, LIU Zhiyi^1,2,3, HAN Kaiming^1,2, GUO Jiang^1,2,

WU Bingwei^1,2

(1.School of Mining Engineering, North China University of Science and Technology, Tangshan 063210, China；2. School of Mining Engineering, Tangshan City Key Laboratory of Mining Development and Security Technology, Tangshan 063210, China；3. School of Mining Engineering, Hebei Provincial Mining Development and Safety Technology Laboratory, Tangshan 063210, China)

Abstract: [Objective] In engineering practice, rocks are often in the state of cyclic loading and unloading, and in order to explore the problem of failure precursors of red sandstone under cyclic loading and unloading, [Methods] The acoustic emission mechanical monitoring test of red sandstone under cyclic loading and unloading was carried out, and the cluster analysis of acoustic emission characteristic parameters was carried out by using the k-means clustering algorithm to study the rock damage and fracture mode. [Results] The results show that the AE events mainly occur during cyclic loading, and the AE events in the unloading stage occur very rarely and enter the "intermittent period", and the number of AE events increases suddenly and enters the "active phase" with the accumulation of the number of cycles. The B value of AE is the largest in the initial stage of cyclic loading and unloading, and with the increase of the number of cycles, the B value of AE decreases step by step and stabilizes in the range of 0.75~1.25, and the B value of AE decreases sharply before the rock enters the rupture stage. According to the k-means clustering, the acoustic emission signals during rock damage and rupture were divided into three categories, namely cluster 1, cluster 2 and cluster 3, and each cluster corresponded to different damage stages. At the end of the cyclic loading and unloading stage, the energy of the cluster 3 acoustic emission event increased sharply, reflecting the obvious increase of the fracture scale of the sandstone at the end of loading until the failure, which can be used as a precursor to the failure of the rock. [Conclusion] The analysis shows that the acoustic emission signals of cluster 3 appear sporadically in the elastic deformation stage of rocks, and with the accumulation of cycles, the acoustic emission signals continue to appear intensively before the complete failure stage of rocks.

Key words: cyclic loading and unloading; acoustic emission; b-value analysis; cluster analysis; precursors of rock destruction

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