Rock and Soil Mechanics ›› 2022, Vol. 43 ›› Issue (10): 2689-2697.doi: 10.16285/j.rsm.2022.5637

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Modification of linear regression method for rock shear strength parameters under triaxial condition

LI Bin1, WANG Da-guo2, HE Zhi-liang1, WANG Peng1   

  1. 1. School of Environment and Resource, Southwest University of Science and Technology, Mianyang, Sichuan 621010, China 2. School of Civil Engineering and Geomatics, Southwest Petroleum University, Chengdu, Sichuan 610500, China
  • Online:2022-10-28 Published:2022-11-25
  • Contact: WANG Da-guo, male, born in 1975, PhD, Professor, PhD supervisor, research interests:computational mechanics. E-mail: E-mail:
  • About author:LI Bin, male, born in 1988, PhD, Reader, research interests: reliability of geotechnical engineering and mining rock mechanics and engineering.
  • Supported by:
    the National Natural Science Foundation of China (51904248, 42171108).

Abstract: The triaxial strength envelope of rocks is usually nonlinear, and the shear strength parameters obtained by the linear regression method (LRM) are highly sensitive to confining pressure. In order to enable LRM to consider the influence of confining pressure on the estimation of shear strength parameters, the confining pressure effect coefficient of triaxial strength of rocks is defined. An exponential function is constructed to express the relationship between the coefficient and confining pressure, which is also introduced into the correction of LRM. A linear regression method considering confining pressure effects (CCPE-LRM) is proposed. At the same time, a rationality test method is proposed, and a distance coefficient is defined as an index to characterize the difference between the estimated and actual values of shear strength parameters. Through the verification and analysis of the triaxial strength data of various types of rocks in the published literature, the results show that the distance coefficients of various rocks are small, and the shear strength envelopes obtained by CCPE-LRM are all close to the Mohr circles in an approximately tangent state. It indicates that the shear strength envelope obtained by CCPE-LRM can replace the ideal shear strength envelope to a certain extent, and the shear strength parameters estimated by this method are in good agreement with the theoretical shear strength parameters. These prove that CCPE-LRM LRM has a good applicability.

Key words: rock shear strength parameters, linear regression method, confining pressure effect, triaxial strength of rocks, shear strength envelope