A Study on Friction Anisotropy between Sand and Surface Asperities of Plate Using Modified Direct Shear Test

Seung-Hun Lee; Song-Hun Chong

doi:10.7843/kgs.2022.38.2.29

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2022 Vol.38, Issue 2 Preview Page

Research Article

A Study on Friction Anisotropy between Sand and Surface Asperities of Plate Using Modified Direct Shear Test 수정된 직접 전단 시험기를 이용한 모래와 표면 돌출부를 갖는 플레이트 사이의 마찰 이방성에 대한 연구

28 February 2022. pp. 29-38

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Abstract

The friction anisotropy of shear resistance can be selectively used in geo-structures. For example, larger axially loaded deep foundation, soil nails, and tiebacks increase load carrying capacity due to induced large shear resistance while pile penetration and soil sampling produce minimal shear resistance. Previous studies confirmed direction-dependent shear resistance induced by interface between soil and surface asperity of plate inspired by geometrical shape of snake scale. The aim of this paper is to quantitatively evaluate interface friction angle with different surface asperities. Using the modified direct shear test, a total of 51 cases, which sand are prepared at the relative density of 40%, are conduced including 9 plates, two shear direction (shearing direction against the height of surface asperity is increased or decreased during shearing test), and three initial vertical stress (100 kPa, 200 kPa, 300 kPa). Experimental results show that shear stress is increased with higher height of surface asperity, shorter length of surface asperity, and the shearing direction that the height of surface asperity increases. Also, interface friction angle is decreased with larger surface asperity ratio, and shearing direction with increasing height of surface asperity produces larger interface friction angle regardless of the surface asperity ratio.

Keywords

Friction anisotropy

Interface friction angle

Modified direct shear test

Shearing direction

Surface asperity

마찰 방향에 따른 전단 저항의 이방성을 지반 구조물에서 선택적으로 이용할 수가 있다. 예를 들어서, 축방향으로 하중을 가하는 깊은 기초, 소일 네일링, 타이백 등은 큰 전단 저항이 유발되므로 하중 전달 능력을 증가시키지만, 이와 반대로 말뚝 관입과 흙 시료 채취 등은 최소화된 전단 저항만 유발된다. 기존 연구는 뱀 비늘의 기하학적 형상과 유사한 표면 돌출부를 갖는 플레이트와 흙 경계면에서 유발되는 전단 저항 변화를 확인하였다. 본 논문에서는 표면 돌출부의 형상에 따른 경계면 마찰각의 변화를 정량적으로 평가하였다. 수정된 직접 전단 시험기를 이용하여 상대 밀도가 40%로 조성된 모래 시료에 대해 9개의 플레이트, 2개의 전단 방향(전단 시 돌출부 높이가 증가와 감소하는 방향), 그리고 3개의 초기 수직 응력(100kPa, 200kPa, 300kPa) 조건으로 총 51가지 경우를 실험 하였다. 실험 결과, 전단 응력은 돌출부 높이가 높을수록, 돌출부 길이가 짧을수록, 돌출부 높이가 증가하는 전단 방향에서 크게 나타났다. 또한, 표면 돌출부 비가 증가할수록 경계면 마찰각은 감소하였고, 표면 돌출부 비와 상관없이 모든 경우에서 전단 시 돌출부 높이가 증가하는 방향에서 더 큰 경계면 마찰각을 보였다.

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Information

Publisher :The Korean Geotechnical Society
Publisher(Ko) :한국지반공학회
Journal Title :Journal of the Korean Geotechnical Society
Journal Title(Ko) :한국지반공학회 논문집
Volume : 38
No :2
Pages :29-38
Received Date : 2022-01-25
Revised Date : 2022-02-09
Accepted Date : 2022-02-15
DOI :https://doi.org/10.7843/kgs.2022.38.2.29

Journal of the Korean Geotechnical Society ISSN:1229-2427(Print) 2288-646X(Online) 한국지반공학회 논문집

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