준설토와 Bottom ash 재활용을 위한 무보강 및 섬유 보강 복합지반재료의 역학적 특성 비교

Abstract

Lightweight soil is a cement-treated soil with a light unit weight and a high shear strength. A composite geo-material (CGM) was developed to recycle both dredged soil and bottom ash. CGM consists of dredged clayey soil, cement, air-foam and bottom ash. Reinforcement such as waste fishing net or monofilament were added into CGM in order to increase shear strength and improve mechanical characteristics of lightweight soil. The objective of this study is to investigate engineering properties, strength characteristics, stress-strain behaviors and shear wave velocities of both unreinforced and reinforced CGMs. Test specimens were fabricated by various mixing conditions including cement content, initial water content, air-foam content, bottom ash content and content of fibers (waste fishing net, monofilament) and then several series of unconfined compression test, direct shear test and elastic wave test were performed on the test specimens. The experimental results of CGMs indicated that the stress-strain behaviour was strongly influenced by mixing conditions such as cement content, initial water content, air-foam content, bottom ash content and content of fibers. Unconfined compressive strength of CGM increased with increases in cement content and bottom ash content, but decreased with increases in water content and air-foam content. It was shown from unconfined compression test that unconfined compressive strength of reinforced CGM generally increased by adding waste fishing net or monofilament, but amount of increase in compressive strength was not proportional to content of fibers. These similar results were also shown in direct shear tests. In CGMs, secant modulus (E50) was increased as its compressive strength increased due to the inclusion of bottom ash. Elastic soil moduli of unreinforced and reinforced CGMs were also evaluated from shear wave velocity.