폐어망과 토목섬유를 이용한 보강 경량토의 역학적 특성 연구

Abstract

A lightweight soil is a cement-treated soil that consists of dredged clayey soil, cementing material and air-foam. Lightweight soil is characterized as a material with light unit weight as well as high shear strength. Reinforced lightweight soil is a lightweight soil reinforced with waste fishing net or geogrid in order to increase its compressive strength. This paper investigates engineering properties, strength characteristics, stress-strain behaviors, consolidation characteristics and shear wave velocities of both unreinforced and reinforced lightweight soils. Test specimens were fabricated by various mixing conditions including cement content, initial water content, air content and content of fiber (waste fishing net, geogrid) and then several series of unconfined compression test, direct shear test, standard one-dimensional consolidation test and elastic wave test were performed. The experimental results of lightweight soils indicated that unconfined compressive strength increased with increase in cement content, but decreased with increases in water content and air-foam content. It was also shown that compressive strength of reinforced lightweight soil generally increased by adding waste fishing net or geogrid, but amount of increase in compressive strength was not proportional to content of waste fishing net. This result was also shown in that of direct shear test. In reinforced lightweight soil, secant modulus (E50) was increased as the strength increased due to the inclusion of fiber. However, consolidation characteristics of lightweight soil such as yielding stress, compression index, coefficient of consolidation and coefficient of permeability were almost same, irrespective of adding waste fishing net or geogrid. Elastic soil moduli of unreinforced and reinforced lightweight soils were also evaluated from shear wave velocity.