TIAN G H, ZHANG L Y, ZHANG Q Z,et al.Creep characteristics and nonlinear constitutive modeling of coal rock containing pressure relief boreholes[J].Journal of Henan Polytechnic University(Natural Science) ,2026,45(2):213-220.

doi:10.16186/j.cnki.1673-9787.2024010047

Received:2025/01/17

Revised  :2025/04/30

Published:2026/01/28

Creep characteristics and nonlinear constitutive modeling of coal rock containing pressure relief boreholes

Tian Guanghui1, Zhang Liyi1, Zhang Qingzhao2,3, Liu Weijian1, Zhang Zhizeng4

1.School of Intelligent Construction and Civil Engineering， Zhongyuan University of Technology， Zhengzhou  450007， Henan， China；2.Department of Geotechnical Engineering，Tongji University， Shanghai  200092， China；3.Key Laboratory of Geotechnical and Underground Engineering of the Ministry of Education， Tongji University， Shanghai  200092， China；4.College of Geosciences and Engineering， North China University of Water Resources and Electric Power， Zhengzhou  450045， Henan， China

Abstract: Objectives The influence of pressure relief borehole diameter on the long-term stability of pressure relief roadways is investigated through graded loading creep tests on coal rock specimens with different borehole diameters.  Methods First， creep characteristics and long-term stability of coal rock are comparatively analyzed for different pressure relief borehole diameters. Second， Najar damage theory is introduced to analyze damage characteristics of coal rock during creep stages from an energy perspective. Third， considering the hardening effect of viscosity coefficient as a time-dependent non-stationary parameter， a parameter nonlinear constitutive equation is proposed. Finally， the steady-state creep rate inflection point method is employed to determine the long-term strength of coal rock with different borehole diameters. Results The results indicate that the pressure relief borehole diameter significantly influences creep characteristics， creep damage and long-term strength of coal rock. During creep， the pressure relief borehole diameter exhibits a distinct size effect on both creep strain and initial creep rate， with larger boreholes resulting in greater creep strain and higher initial creep rate. Throughout the creep process， damage gradually increases while damage rate decreases and eventually stabilizes， with damage showing a positive correlation with borehole diameter. The derived parameter-nonlinear Maxwell creep equation， incorporating with the viscosity coefficient， accurately describes the creep process. Long-term strength demonstrates a negative correlation with borehole diameter.  Conclusions The findings contribute to maintaining long-term stability of pressure relief roadways and provide theoretical insights for rockburst prediction and mine safety.

Key words: coal rock; pressure relief borehole; creep; damage; constitutive model; long-term strength