A Novel Discontinuity Roughness Parameter and Its Correlation with Joint Roughness Coefficients

Huizhen Zhang,Chenlong Wang,Zejin Yang,Zhiqiang Li,Changsuo Zhang

doi:10.3390/en14227631

Abstract

Joint roughness determination is a fundamental issue in many areas of rock engineering, because joint roughness has significant influences on mechanical properties and deformation behavior of rock masses. Available models suggested in the literature neglected combined effects of shear direction, scale of rock discontinuities, inclination angle, and amplitude of asperities during the roughness calculations. The main goals of this paper are to establish a comprehensive parameter that considers the characteristics of the size effect, anisotropy, and point spacing effect of the discontinuity roughness, and to investigate the correlation between the proposed comprehensive parameter and joint roughness coefficients. In this work, the Barton ten standard profiles are digitally represented, then the morphological characteristics of the discontinuity profiles are extracted. A comprehensive parameter that considers the characteristics of the size effect, anisotropy, and point spacing effect of the discontinuity roughness is established, and its correlation with joint roughness coefficients (JRC) is investigated. The correlation between the proposed discontinuity roughness parameter and the joint roughness coefficients can predict the JRC value of the natural discontinuities with high accuracy, which provides tools for comprehensively characterizing the roughness characteristics of rock discontinuities. The roughness index Rvh[−30∘,0] reflects the gentle slope characteristics of the rock discontinuity profiles in the shear direction, which ignores the segments with steep slopes greater than 30° on the discontinuity profiles. The influence of steep slope segments greater than 30° should be considered for the roughness anisotropy parameter in the future.

Highlights

According to the measurement results of the rock discontinuity surface topography, the use of reasonable parameters to characterize roughness has always been a difficult problem in the fields of engineering geology and rock joint mechanics, because joint roughness has significant influences on mechanical properties and deformation behavior of rock masses
The main goal of this paper is to establish a comprehensive parameter that considers the characteristics of the size effect, anisotropy, and point spacing effect of the discontinuity roughness, and to investigate the correlation between the proposed comprehensive parameter and joint roughness coefficients
The results show that the joint roughness coefficients (JRC) evaluation Equatio2n0 o(1f 623) established by the roughness parameter Mhl has high prediction accuracy

Summary

Introduction

According to the measurement results of the rock discontinuity surface topography, the use of reasonable parameters to characterize roughness has always been a difficult problem in the fields of engineering geology and rock joint mechanics, because joint roughness has significant influences on mechanical properties and deformation behavior of rock masses. Roughness, which refers to the local departures from planarity, influences the friction angle, dilatancy, and peak shear strength. Researchers have made quantitative analyses based on discrete data points of joint surfaces obtained via various measurement methodologies over the past five decades. This subject originated in 1966 when Patton [1] used regular tooth undulation angles to express the rock discontinuity surface roughness and for the first time explained the importance of discontinuity surface roughness to its shear strength, namely:

Objectives

Methods

Conclusion