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力学与实践 ›› 2020, Vol. 42 ›› Issue (1): 35-41.doi: 10.6052/1000-0879-19-300

• 应用研究 • 上一篇    下一篇

基于多尺度页岩巴西劈裂试验的岩石强度尺度效应根源研究1)

李帅*, 2), 陈军斌*, 王汉青, 聂向荣*, 赵文景*, 姚欢迎*   

  1. * 西安石油大学陕西省油气井及储层渗流与岩石力学重点实验室,西安 710065;
    † 中国石油大学(北京)油气资源与探测国家重点实验室,北京 102249
  • 收稿日期:2019-08-13 发布日期:2020-03-13
  • 通讯作者: 2) 李帅,硕士研究生,主要研究方向为岩石力学与油气田特种增产技术。E-mail: lishuai_xsy@163.com
  • 基金资助:
    1) 国家自然科学基金资助项目(51674197,51874239)

A STUDY ON THE ORIGIN OF SCALE EFFECT OF ROCK STRENGTH BASED ON MULTI-SCALE SHALE BRAZILIAN SPLITTING TEST1)

LI Shuai*, 2), CHEN Junbin*, WANG Hanqing, NIE Xiangrong*, ZHAO Wenjing*, YAO Huanying*   

  1. * Shaanxi Key Laboratory of Well Stability and Fluid & Rock Mechanics in Oil and Gas Reservoirs, Xi'an Shiyou University, Xi'an 710065, China;
    † State Key Laboratory of Petroleum Resources and Exploration, China University of Petroleum (Beijing),Beijing 102249, China
  • Received:2019-08-13 Published:2020-03-13

摘要: 为探究页岩抗拉强度尺度效应规律及岩石强度尺度效应根源,采集鄂尔多斯盆地延长组长7 段陆相页岩野外露头,制作成直径为50 mm,高度分别为15.32 mm,20.39 mm,25.46 mm 和30.28 mm四种尺度的岩样并进行巴西劈裂试验,在分析岩样抗拉强度尺度效应规律的基础上,对岩石强度尺度效应根源提出了新的认识。结果表明:页岩最大载荷和破裂面条数随岩样尺度增大而增大,抗拉强度随岩样尺度增大而减小,破裂时间与岩样尺度相关性较差;非均质性和端部摩擦效应是目前解释岩石强度尺度效应根源的主要观点,页岩巴西劈裂试验结果中抗拉强度存在良好的尺度效应现象,这表明岩石强度尺度效应并不是完全根源于试件与压头之间的端部摩擦作用;岩石强度尺度效应由岩石非均质性和端部摩擦效应共同作用而成,对于小尺度岩样,端部摩擦效应占据主导地位,对于大尺度岩样,非均质性占据主导地位,不同类型的岩石,其岩样尺度的" 小"与"大"不同。对岩石强度尺度效应规律和根源的研究有助于提高岩体强度预测的准确性,并为揭示岩石破坏机理提供一定借鉴。

关键词: 巴西劈裂试验, 强度尺度效应, 端部摩擦效应, 非均质性, 主导地位

Abstract: In order to explore the scale effect of the shale tensile strength and the origin of the scale effect of the rock strength in general, the outcrop of the continental shale of Chang 7 of Yanchang Formation in Ordos Basin is collected to make rock samples of 50 mm in diameter and 15.32 mm, 20.39 mm, 25.46 mm and 30.28 mm in length for the Brazilian splitting test. On the basis of analyzing the rock tensile strength, a new understanding of the origin of the scale effect is proposed. It is shown that the maximum load on the shale and the number of rupture surfaces increase with the increase of the sample size, while the tensile strength decreases with the increase of the sample size, and the correlation between the fracture time and the sample size is poor. The heterogeneity and the end friction effect are the main causes of the scale effect of the rock strength. The obvious scale effect of the tensile strength in the Brazilian shale splitting test results indicates that the scale effect of the rock strength is not entirely rooted in the end friction between the specimen and the indenter. The scale effect of the rock strength is formed by the interaction of the heterogeneity and the end friction effect. For small scale rock samples, the end friction effect plays the dominant role, and for large scale rock samples, the heterogeneity plays the dominant role. For various types of rocks, the size of rock samples may be neither "small" nor "large". The study of the scale effect and its origin for the rock strength is helpful to improve the accuracy of the rock strength prediction and for revealing the rock failure mechanism.

Key words: Brazilian splitting test, strength scale effect, end friction effect, heterogeneity, leading role

中图分类号: 

  • TE31