Ground surface settlement of Double-O-tube shield tunnel for Airport Access MRT in Taipei Basin

• Main Authors: Wan-yi Ka, 柯婉伊
• Other Authors: 陳水龍
• Format: Others
• Language: zh-TW
• Published: 2011
• Online Access: http://ndltd.ncl.edu.tw/handle/3jxzaa

碩士 === 國立臺北科技大學 === 土木與防災研究所 === 99 === This study evaluated the ground surface settlement caused by double-o-tube shield tunnel construction, using Taoyuan International Airport MRT Line Taipei-Sanchung Section CA450A as an example. PLAXIS 2D software of the infinite element method was used to conduct numerical analysis on the single bore tunnels at various depths of earth covering according to the geologic conditions of the sections in actual cases, in order to compare the parameter relationship between the two numerical analysis methods of percentage of area reduction of the tunnel and soil released stress based on the same maximum ground surface settlement. In the case of DOT shield tunnel, PLAXIS numerical analysis was carried out on the ground surface settlement of 7 monitored sections. Through intercomparison among the ground surface curve by the numerical analysis, settlement observation data by in-situ monitoring and empirical formula calculation in terms of the ground surface settlement trough, the applicability of PLAXIS on analyzing the Double-o-tube shield tunnel has been verified, which could help to understand possible influences in the process of Double-o-tube shield tunnel excavation and influence range to adjacent structures, and provide reference for future Double-o-tube shield tunnel project application. The maximum ground surface settlement relationship of the percentage of area reduction of the tunnel and soil released stress by the numerical analysis of the parallel-tube shield tunnel presented a non-linear relationship at 20m of the central depth of the tunnel, and presented a linear relationship when it reached 24m and 27m of the central depth of the tunnel. In the case of Double-o-tube shield tunnel of Taipei-Sanchung Section, the ground surface settlement troughs of the Double-o-tube shield tunnel calculated by way of empirical formula superposition method and the equal-area method were similar according to the comparison of results by the three methods of numerical analysis, empirical formula and in-situ monitoring. However, in the comparison of results of empirical formula calculation and in-situ monitoring, the settlement troughs were identical in shape and trending but the maximum ground surface settlement values at the tunnel center presented certain difference. In the comparison of the results of numerical analysis simulation and in-situ monitoring, the maximum ground surface settlement values at the tunnel center and the shape and trending of ground surface settlement troughs were identical. The soil released stress value obtained by the numerical analysis presented a direct proportional linear relationship with the maximum ground surface settlement and the in-situ loss rate, which can be used in numerical analysis of the soil released stress of Double-o-tube shield tunnel in the future so as to predict the upper and lower limits of possible ground surface settlement.