쇄석다짐말뚝이 적용된 점토지반의 거동 분석을 위한 3차원 유한요소해석

Abstract

There are several methods for improving soft ground depending on the purpose of improvement. In South Korea, an increasing number of granular compaction pile constructions that press sand and granular into soft soil with constant density and create constant-diameter stakes have been conducted. Observing installments employed by granular compaction pile, the quantitative granular compaction pile technique does not present a quantitative design and depends on experiential design. Furthermore, there are a couple of problems such as uncertainty on construction, internal fracture, clogging, bulging failure, and shear fracture. A clear understanding of causes and preventive measures on these problems are insufficient. Errors are likely to occur due to huge differences from actual values such as stress concentration ratio and settlement as foreign design methods are directly adopted despite distinct characteristics of Korean instruments and materials. Therefore, this study aims to analyze stress concentration ratio and settlement according to shear strength of ground through earlier studies and finite element analysis and further the correlation of design influential factors. By using a finite element analysis program, it modelled the upgraded composite ground by using granular compaction pile, analyzed behaviors of composite ground on replacement ratio(10∼40%) and shear strength(25∼75kPa), and interpreted correlations of design factors. The result of finite element analysis displayed that the effect of replacement ratio on settlement of composite ground was smaller than ground strength. It was also found that the settlement reduction ratio of composite ground fell by over 60% at a replacement ratio of 30% or above, the maximum lateral displacement of granular compaction pile was made at a depth of 1.5 to 3 times bigger than pile diameter, and the difference in lateral displacement was a little slight at a replacement ratio of 40% or above. It is supposed that applying a replacement ratio of over 30% to an area, predicted to have excessive consolidation settlement and a replacement ratio of over 40% to an area, predicted to have bulging failure could prevent this problem.