A method to model the effect of pre-existing cracks on P-wave velocity in rocks

Crack closure is one of the reasons inducing changes of P-wave velocity of rocks under compression. In this context, a method is proposed to investigate the relationships among P-wave velocity, pre-existing cracks, and confining pressure based on the discrete element method (DEM). Pre-existing open...

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Main Authors: Haimeng Shen, Xiaying Li, Qi Li, Haibin Wang
Format: Article
Language:English
Published: Elsevier 2020-06-01
Series:Journal of Rock Mechanics and Geotechnical Engineering
Subjects:
Online Access:http://www.sciencedirect.com/science/article/pii/S1674775519307255
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author Haimeng Shen
Xiaying Li
Qi Li
Haibin Wang
author_facet Haimeng Shen
Xiaying Li
Qi Li
Haibin Wang
author_sort Haimeng Shen
collection DOAJ
description Crack closure is one of the reasons inducing changes of P-wave velocity of rocks under compression. In this context, a method is proposed to investigate the relationships among P-wave velocity, pre-existing cracks, and confining pressure based on the discrete element method (DEM). Pre-existing open cracks inside the rocks are generated by the initial gap of the flat-joint model. The validity of the method is evaluated by comparing the P-wave velocity tested on a sandstone specimen with numerical result. As the crack size is determined by the diameter of particles, the effects of three factors, i.e. number, aspect ratio, and orientation of cracks on the P-wave velocity are discussed. The results show that P-wave velocity is controlled by the (i.e. number) of open micro-cracks, while the closure pressure is determined by the aspect ratio of crack. The reason accounting for the anisotropy of P-wave velocity is the difference in crack number in measurement paths. Both of the number and aspect ratio of cracks can affect the responses of P-wave velocity to the applied confining pressure. Under confining pressure, the number of open cracks inside rocks will dominate the lowest P-wave velocity, and the P-wave velocity of the rock containing narrower cracks is more sensitive to the confining pressure. In this sense, crack density is difficult to be back-calculated merely by P-wave velocity. The proposed method offers a means to analyze the effect of pre-existing cracks on P-wave velocity.
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spelling doaj.art-e0e34eff73bc4adda805f0cfe2e65a152022-12-22T01:27:46ZengElsevierJournal of Rock Mechanics and Geotechnical Engineering1674-77552020-06-01123493506A method to model the effect of pre-existing cracks on P-wave velocity in rocksHaimeng Shen0Xiaying Li1Qi Li2Haibin Wang3State Key Laboratory of Geomechanics and Geotechnical Engineering, Institute of Rock and Soil Mechanics, Chinese Academy of Sciences, Wuhan, 430071, China; University of Chinese Academy of Sciences, Beijing, 100049, ChinaState Key Laboratory of Geomechanics and Geotechnical Engineering, Institute of Rock and Soil Mechanics, Chinese Academy of Sciences, Wuhan, 430071, China; University of Chinese Academy of Sciences, Beijing, 100049, ChinaState Key Laboratory of Geomechanics and Geotechnical Engineering, Institute of Rock and Soil Mechanics, Chinese Academy of Sciences, Wuhan, 430071, China; University of Chinese Academy of Sciences, Beijing, 100049, China; Corresponding author.State Key Laboratory of Geomechanics and Geotechnical Engineering, Institute of Rock and Soil Mechanics, Chinese Academy of Sciences, Wuhan, 430071, China; University of Chinese Academy of Sciences, Beijing, 100049, ChinaCrack closure is one of the reasons inducing changes of P-wave velocity of rocks under compression. In this context, a method is proposed to investigate the relationships among P-wave velocity, pre-existing cracks, and confining pressure based on the discrete element method (DEM). Pre-existing open cracks inside the rocks are generated by the initial gap of the flat-joint model. The validity of the method is evaluated by comparing the P-wave velocity tested on a sandstone specimen with numerical result. As the crack size is determined by the diameter of particles, the effects of three factors, i.e. number, aspect ratio, and orientation of cracks on the P-wave velocity are discussed. The results show that P-wave velocity is controlled by the (i.e. number) of open micro-cracks, while the closure pressure is determined by the aspect ratio of crack. The reason accounting for the anisotropy of P-wave velocity is the difference in crack number in measurement paths. Both of the number and aspect ratio of cracks can affect the responses of P-wave velocity to the applied confining pressure. Under confining pressure, the number of open cracks inside rocks will dominate the lowest P-wave velocity, and the P-wave velocity of the rock containing narrower cracks is more sensitive to the confining pressure. In this sense, crack density is difficult to be back-calculated merely by P-wave velocity. The proposed method offers a means to analyze the effect of pre-existing cracks on P-wave velocity.http://www.sciencedirect.com/science/article/pii/S1674775519307255Pre-existing cracksP-wave velocityDiscrete element method (DEM)Anisotropic rock
spellingShingle Haimeng Shen
Xiaying Li
Qi Li
Haibin Wang
A method to model the effect of pre-existing cracks on P-wave velocity in rocks
Journal of Rock Mechanics and Geotechnical Engineering
Pre-existing cracks
P-wave velocity
Discrete element method (DEM)
Anisotropic rock
title A method to model the effect of pre-existing cracks on P-wave velocity in rocks
title_full A method to model the effect of pre-existing cracks on P-wave velocity in rocks
title_fullStr A method to model the effect of pre-existing cracks on P-wave velocity in rocks
title_full_unstemmed A method to model the effect of pre-existing cracks on P-wave velocity in rocks
title_short A method to model the effect of pre-existing cracks on P-wave velocity in rocks
title_sort method to model the effect of pre existing cracks on p wave velocity in rocks
topic Pre-existing cracks
P-wave velocity
Discrete element method (DEM)
Anisotropic rock
url http://www.sciencedirect.com/science/article/pii/S1674775519307255
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