摘要
本文針對台北國際金融中心(Taipei International Financial Center, TIFC)大樓深開挖計畫進行三維數值分析並探討微型樁於深開挖期間對鄰房的保護效果。首先進行台北國際金融中心塔樓區之深開挖模擬，所有輸入參數先依據實驗室及現地試驗結果推求後再依照真實施工過程進行數值分析，分析中並納入地下水的穩態滲流計算以模擬開挖中地下水的洩降現象。最後，再依連續壁側向變形、地表沉陷及孔隙水壓消散之數值分析結果與現場量測數據來作比較，以確認模擬過程的正確性及輸入參數的準確性。

依照上述確認之三維深開挖模擬程序，建立一個典型的台北深開挖數值模式，並於模式中加入微型樁防護，藉由改變微型樁打設參數如角度、樁長和樁距，來探討微型樁不同打設參數對連續壁檔土開挖的防護效果。採用連續壁最大位移和地表沉陷的減小量，來評估微型樁的最佳打設角度、樁長和樁距。根據本研究分析結果顯示，微型樁打設參數以角度15度、樁長30公尺、樁距40公分對於典型台北都會區深開挖(20公尺深)之地表沉陷有最佳的防護效果。另外，打設微型樁所減少的地表沉陷量較之於連續壁最大側向變形量有較明顯的表現。

ABSTRACT
An elasto-plastic, Undrained, seepage, three-dimensional (3-D) Finite Difference Method (FDM) is adopted to investigate the effects of micropile protection on lateral wall movement and ground settlement around multi-strutted deep excavations in Taipei. The technique as well as the numerical procedures for modeling the excavation processes was proposed using FDM program, FLAC3D, to assess the significance of micropile protection in typical-sized excavation. In the study, a 3-D finite difference analysis incorporated with groundwater seepage flow analysis of a full-scale bottom-up deep excavation in TIFC (Taipei International Financial Center) project was initially conducted to verify the numerical procedures and a series of parametric studies of micropile protection with various inclination, spacing and length are discussed on reducing of the maximum lateral wall movement and ground surface settlement for a standard deep excavation in Taipei subsoil. Importantly, the soil parameters used in the analysis is determined by direct back-analysis procedure of TIFC field instrumentation data which was considered as one of the well-organized instrumentation project in Taipei Metropolitan.

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