쇄석다짐말뚝으로 보강된 연약지반의 동적 거동특성 분석

Abstract

Analysis of Dynamic Behavior Characteristics of Soft Ground by Reinforcement of Granular Compaction Pile Kwon, Yi Hyuk Advisor : Prof. Kim, Daehyeon, Ph. D. Department of Civil Engineering Graduate School of Chosun University Recently, the demand for the development of social infrastructure and living land has been increasing due to the continuous development in Korea, but the ground that meets the conditions is limited. Accordingly, it is necessary to develop soft ground for efficient use of the land. Various methods are applied to the improvement of soft ground depending on economic feasibility and construction, which can be mainly classified into a substitution method, a dehydration method, a vibration hardening method, and a mixed treatment method. Among them, the Granular Compaction Pile is known as an efficient and economical method for reinforcing soft ground to support the load of the appropriate size of the upper structure among various soft ground treatment methods. The Granular Compaction Pile method is a method of improving soft ground by replacing approximately 10-40% of the existing soil with materials such as sand and crushed stone, creating a stake through a constant press-fitting process. The Granular Compaction Pile method cannot establish measures to prevent destruction because the type and cause of destruction are not clearly presented during construction on the clay ground, and if destroyed after construction, it is not clear to identify the cause of destruction. Therefore, in this study, an laboratory model experiment was conducted through a 1g vibration zone test to confirm the dynamic behavior characteristics of the soft ground to which the Granular Compaction Pile method was applied. After the accelerometer was laid on the model ground of the lower weathered soil ground and the upper viscous soil ground, the dynamic behavior characteristics of the ground according to each input seismic wave were confirmed, and the reliability of the laboratory model ground was verified by nonlinear time history analysis. As a result of the acceleration amplification rate analysis, seismic waves were amplified by an average of 1.68 times for unreinforced ground. On the other hand, the reduction effect on the acceleration amplification rate was clearly shown at the point reinforced by the Granular Compaction Pile. A comparative analysis of the acceleration amplification rate according to the location of the reinforced point shows an average of 1.65 times on the left side of the reinforced point, an average of 1.49 times on the center point, and an average of 1.53 times on the right side, which is considered effective in controlling seismic wave amplification considering the incompatibility of the Granular Compaction Pile ground. In particular, the lowest amplification rate at the central point is judged to be the point where the reinforcement of the Granular Compaction Pile can most effectively reduce the propagation of seismic energy. As a result of numerical analysis, PGA's tendency graph showed uniform regularity of upward movement, which is different from some bending phenomena in laboratory experiments. It is judged that acceleration amplification is constant due to the uniform distribution of ground properties to the modeling ground during numerical analysis, and in the case of laboratory experiments, some ground resolutions are not evenly distributed depending on the experimental conditions and the method of creating the ground model.