Effect of Morphology Parameter Determination on Contact Behavior of Rock Joints under Compressive Loading

Feng Tian Tang,Zhi Cheng Tang,Hassan Nasir

doi:10.1155/2021/6669422

Abstract

The closure behavior of rock joints is of critical importance to the study of hydromechanical behaviors and geophysical properties of jointed rock masses. Theoretical contact models, used to predict the relations of normal stress versus closure deformation, rely on morphology parameters of rock joint as the input parameters. The relevance of the contact models depends on the inherent assumptions and the accuracy with which the input parameters are determined. In the present study, morphology parameters of three rock joints are determined by the spectral moment approach and peak identification method, respectively. The differences are found to vary significantly depending on the selected method. The phenomenon would be related to the definition of an asperity peak on joint profile. The spectral method only considers the so-called asperity peaks, while the deterministic approach further accounts for the asperity shoulders. Finally, the morphology parameters determined by the two methods are treated as the input parameters of a validated theoretical model. The comparisons between the theoretical curves and the experimental results indicate that parameters determined by the deterministic method would be more reliable.

Highlights

Rock joints affect the mechanical properties of rocks, so do the morphology parameters of joints [1, 2]
Compared to 5PP and 7PP criteria, 3PP criterion would be more reliable to identify the peaks on a rock joint profile, which was widely used [21, 22, 24,25,26,27]. e peak density and standard deviation of peak height can be directly calculated as all the peaks are identified. e radius of curvature for each peak is accurately and uniquely determined by its circumcircle. en, the arithmetic average value of all the asperity peak radii is treated as the overall curvature of the profile
As the average asperity heights increase, the peak density determined by the spectral moment approach increases from 0.39 to 0.46, with an increase of about 17.9%, while the one determined by the peak identification method decreases from 0.28 to 0.15, with a reduction of about 46.4%. e peak density is reported to decrease with the increase of roughness, as is the case for the peak identification method which is in line with many theoretical and experimental observations for rough surfaces [28, 29]

Summary

Introduction

Rock joints affect the mechanical properties of rocks, so do the morphology parameters of joints [1, 2]. The application of available morphology parameters can fall broadly into three categories: (1) describing the geometrical features, such as Tse and Cruden [3], International Society for Rock Mechanics [4], Xie et al [5], Belem et al [6], Zhang et al [7], and Li and Zhang [8]; (2) establishing the peak shear strength criteria, such as Barton and Choubey [9], Tatone and Grasselli [10], and Rasouli and Harrison [11]; and (3) serving as input parameters for theoretical contact models, such as Greenwood and Williamson [12], Brown and Scholz [13], Misra [14], Lanaro and Stephansson [15], and Xia et al [16]. The relevance of the theoretical models is dependent on their inherent assumptions and the accuracy with which the input parameters are determined

Objectives

Methods

Findings

Conclusion