| Summary: | 碩士 === 國立臺灣科技大學 === 營建工程系 === 104 === To increase the stability of the excavation, ground improvement techniques are commonly used. With the column type of the ground improvement, the soil was often mixed with the cement to make the soilcrete. The improved soil within the excavation zone thus forms a composite material. The engineering properties of the composite material are usually simulated by the equivalent parameters. However, with the complicated mechanism within the excavation zone, the performance of the equivalent parameters needed to be evaluated. In this study, the proposed equivalent parameters equations were investigated by using the finite element method (FEM) with the simulation of triaxial test. The axial compression (AC) test, the axial extension (AE) test, and the lateral compression (LC) test with the composite soil sample were modeled in the finite element analysis. The FEM results yielded close results with the proposed equivalent parameters equations. Furthermore, a hypothetical excavation case with ground improvement piles was adopted in the 3D and 2D finite element analysis. In the 3D analysis, the real allocation simulation of improvement piles was performed. Results showed that the strength of the improvement piles mostly depended on the tensile strength of the pile. In addition, an equation was derived to estimate the equivalent strength of the composite soil within the improvement zone. In the 2D analysis, the equivalent material simulation was performed. The soil and the improvement piles within the improvement zone was regard as an equivalent material which was calculated from the equivalent parameters equations. Results showed that the 2D analysis can yield as good as the 3D analysis on the wall displacement. The maximum wall displacement ratio can reach 0.99 and 1.01 for the closest results. Therefore, the 3D condition of the improvement piles can be analyzed with the 2D analysis.
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