Effect of Particle-Size Gradation on Coarse Sand-Geotextile Interface Response in Cyclic and Postcyclic Direct Shear Test

Jun Wang,Hong-Tao Fu,Jing Shi,Jun-Feng Ni,Meng-Jie Ying,Fei-Yu Liu

doi:10.1155/2020/1323296

Abstract

In order to investigate the influence of sand particle-size gradation on cyclic and postcyclic shear strength behaviour on sand-geotextile interfaces, a series of monotonic direct shear (MDS), cyclic direct shear (CDS), and postcyclic direct shear (PCDS) tests were performed using a large-scale direct shear apparatus. The influence of cyclic shear history on the direct shear behaviour of the interface was studied. The results indicated that cyclic shear stress degradation occurred at the sand-geotextile interface. Shear volumetric contraction induced by the cyclic direct shear increased with the increase in cycle number. The lowest final contraction value was observed in discontinuously graded sand. In the MDS tests, there were great differences in interface shear strength due to the different particle-size gradations, whereas the differences between shear volumes were negligible. In the PCDS tests, the shear stress-displacement curves exhibited postpeak stress hardening behaviour for different particle-size gradations, and differences in shear volumes were detected. The well-graded sand-geotextile interface had a higher value of shear stiffness and a higher damping ratio relative to the other interfaces. Postcyclic shear stress degradation was observed for the discontinuously graded sand-geotextile interface.

Highlights

Soil reinforcement techniques were firstly put forward by Vidal [1] and have been widely applied in geotechnical engineering. e geotextile-reinforced soil structures, including reinforced retaining wall, slope, and embankment, play a vital role in the construction of infrastructure such as highway, railway, port, and airport
Both monotonic direct shear (MDS) and cyclic direct shear (CDS) tests were performed under different normal stresses. e interface shear properties, including shear stiffness, damping ratios, and shear strength envelope, were examined in detail
Testing Apparatus. e direct shear testing device used in this study is the ShearTrac-III Large-Scale Direct Shear Apparatus designed and constructed by Geocomp. e device consists of an upper box with dimensions of 305 mm × 305 mm in length and width and 100 mm in height and a lower box of 305 mm × 405 mm in length and width and 100 mm in height. e maximum horizontal displacement is 100 mm. e lower box is larger than the upper box, which ensures a constant contact area throughout the shearing process. e device can apply static shear as well as cyclic shear, and these effects can be either load-controlled or displacement-controlled

Summary

Introduction

Soil reinforcement techniques were firstly put forward by Vidal [1] and have been widely applied in geotechnical engineering. e geotextile-reinforced soil structures, including reinforced retaining wall, slope, and embankment, play a vital role in the construction of infrastructure such as highway, railway, port, and airport. Various experimental studies have been made to investigate the interface mechanism by direct shear tests, pull-out tests, inclined plane tests, and torsional ring shear tests [8,9,10,11] Among these testing methods, the direct shear method is one of the most commonly used methods in determining the frictional behaviour of geosynthetic-soil interface. E primary objective of this study is to investigate the effect of sand particle-size gradation on shear behaviours of the sand-geotextile interface via laboratory large-scale direct shear test. Both monotonic direct shear (MDS) and cyclic direct shear (CDS) tests were performed under different normal stresses. e interface shear properties, including shear stiffness, damping ratios, and shear strength envelope, were examined in detail

Materials and Methods

Influence of Cyclic Shear History on Interface Shear Behaviour

Findings

Discussion