›› 2018, Vol. 39 ›› Issue (10): 3727-3734.doi: 10.16285/j.rsm.2016.2312

• Geotechnical Engineering • Previous Articles     Next Articles

Correction of the problems of blockiness evaluation method for fractured rock mass

CHEN Qing-fa1, 2, NIU Wen-jing2, ZHENG Wen-shi1, 2, LIU Jun-guang1, YIN Ting-chang1, 2, FAN Qiu-yan1   

  1. 1. College of Resources, Environment and Materials, Guangxi University, Nanning, Guangxi 530004, China; 2. State Key Laboratory of Geomechanics and Geotechnical Engineering, Institute of Rock and Soil Mechanics, Chinese Academy of Sciences, Wuhan, Hubei 430071, China
  • Received:2016-10-08 Online:2018-10-11 Published:2018-11-04
  • Supported by:
    This work was supported by the Young Foundation of the National Natural Science Foundation of China (41402306), the Key Projects of Guangxi Province Natural Science Foundation (2014GXNSFDA118034), the Scientific Research & Technological Development Projects of Guangxi (1598017-5) and the Open Research Fund of State Key Laboratory of Geomechanics and Geotechnical Engineering (Z016015).

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Abstract: Blockiness is a new index to evaluate the integrity of rock mass, and it can represent the degree of rock mass fracture in three dimensions. However, current blockiness evaluation methods have not considered the cutting degree of rock mass, the size of the block, unrestricted basic application conditions and unreasonable ratings of blockiness levels. In this study, the causes of these limitations were analysed in-depth. Moreover, the concept of block volume percentage was defined referring to the calculation principles of the rock mass cutting degree, three-dimensional (3D) block modulus and volume RQD. A comprehensive percentage calculation method of block volume was proposed, in which the scale effect of rock blocks was considered. The ratings of blockiness levels and the values of the classification index were determined, and the improved blockiness evaluation method was developed. By comparing the rating results of the modified blockiness evaluation method and the Chinese codes for geotechnical engineering, the rationality of the modified blockiness evaluation method was analysed. Based on the Tongkeng Zn polymetallic orebody and Wudongde Hydropower Project, the case studies of the modified blockiness evaluation method were conducted. The results showed that the block volume percentages of No. 4 testing area at the 255 m level in the Tongkeng Zn polymetallic orebody, the PD49-1 adit and PD4 branch adit in Wudongde Hydropower Station were 11.18%, 12.847% and 10.168% by using the modified block evaluation method, respectively. In addition, they all belonged to slight-blockiness categories, and the rock mass was moderately integrated. Compared with the conventional blockiness evaluation method, the block volume percentage calculated by the modified blockiness evaluation method can more accurately represent the integrity of the rock mass from a 3D perspective. The findings in this study are significant for accurately characterising the 3D integrity of rock mass.

Key words: fractured rock mass, blockiness evaluation method, block volume percentage, defect correction, rock mass integrity

CLC Number: 

  • TU 457
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