Effect of the Surface Roughness on the Shear Strength of Granular Materials in Ring Shear Tests

Sueng-Won Jeong,Sung-Sik Park

doi:10.3390/app9152977

Abstract

Surface roughness plays an important role in estimating the shear strength of granular materials. A series of ring shear tests with different surface roughnesses (i.e., smooth and rough surfaces) were performed. A large-sized ring shear device, which is applicable for fine- and coarse-grained sediments, was developed to examine the shear strength of large particle sizes (i.e., commercial gravels with a mean grain size of 6 mm). In terms of surface roughness, the drainage- and shear-velocity-dependent shear strengths of the granular materials were examined. In this study, different shear velocities of 0.1, 0.5, and 1 mm/s were applied under drained and undrained conditions. The test results clearly show that shear stress is affected by drainage, shear velocity, and surface roughness. In particular, a typical strain-hardening behavior is exhibited regardless of the drainage and shear velocity condition. The measured shear strength obtained from both drained and undrained conditions increased with increasing shear velocity. All tests showed a large fragmentation using rough surfaces compared to the smooth surfaces of the device. The grain crushing was significant during shearing, even when normal stress was not applied. For a given shear velocity, surface roughness is an important feature in determining the shear strength of granular materials.

Highlights

The shear strength of granular materials is a very important parameter in engineering practice when examining the frictional and viscous characteristics of geomaterials [1,2]
The objective of this study was to examine the effect of surface roughness on the shear strength of gravels, as a granular matter, in the ring shear test
The test results indicated the shear characteristics of gravels, the minimization of the wall slip due to the rough surfaces in the inner and outer hollow cylinder box, the measured shear stress as a function of the shear velocity, and the grain crushing effect with respect to surface roughness at different drainage conditions and shear velocities

Summary

Introduction

The shear strength of granular materials is a very important parameter in engineering practice when examining the frictional and viscous characteristics of geomaterials [1,2]. A previous study found that granular materials have much more complex elastoplastic and viscous behaviors than materials with finer particles [5]. For this reason, surface roughness has often been taken into account in examining soil-structure interactions in geotechnical engineering practices for piles, foundations, retaining walls, tunnels, embankment, and earth reinforcement [6,7,8,9,10], because the soil-structure interaction is significantly influenced by the material’s properties, shape, roughness, and loading conditions (i.e., monotonic and cyclic loading). According to Hu and Pu [8], for a sandy size particle (0.075–2 mm), elastic perfect-plastic behavior is dominant for a smooth interface, while strain localization is dominant for a rough interface

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Conclusion