深開挖中扶壁及地中壁之效率分析

Efficiency of Buttress Walls and Cross Walls in Deep Excavation

葉家佑(Chia-Yu Yeh)

指導教授 ： 陳水龍

國立臺北科技大學/工程學院/土木與防災研究所/碩士(2012年)

https://doi.org/10.6841/NTUT.2012.00260

摘要

台灣過去之深開挖工程案例，常以地質改良之方式提升基地內土壤勁度及強度，進而達到減少擋土壁體之側向變形量，但近年來扶壁及地中壁逐漸取代地質改良之方式。由於目前尚未有扶壁及地中壁之標準設計規範，只能依靠大地工程師之經驗及數值分析之結果進行設計。本研究採用「有限元素法」所撰寫之三向度數值軟體「Plaxis 3D Foundation」，先利用實際案例驗證軟體模擬扶壁及地中壁之分析和比對，再針對扶壁及地中壁數量與連續壁變形量之變位折減率探討，藉以提升分析之精確性和瞭解扶壁及地中壁之行為。
分析結果顯示，扶壁及地中壁皆可有效抑制連續壁側向變形，地中壁抑制連續壁側向變形之效果最好，其次是扶壁。本案例西側採用五道扶壁之變位折減率DRR可達到約49.66%，而南北側採用五道地中壁，在距離地中壁約6m內之連續壁側向位移均在2cm以下，地中壁間距SCW與基址長度L之比值為0.21以下，其變位折減率DRR均可達到約77.42%以上。

關鍵字

扶壁 ； 地中壁 ； 連續壁 ； 數值分析 ； 深開挖

並列摘要

Geotechnical improvement was often introduced in deep excavations in Taiwan as a means to improve the soil stiffness and strength at the excavation site, thus leading to reduced lateral displacement in retaining structures. However, a trend emerged in recent year that internal buttresses and cross walls are used in place of geotechnical improvement. As there is still lack of standard design code for internal buttresses and cross walls, the design can only rely on the experience of individual geotechnical engineers and the result of numeric analysis. The 3D numeric analysis program, Plaxis 3D Foundation, developed using “finite element method” was introduced in this study. First a real-life case was selected for analysis and comparison for the program-simulated buttresses and cross walls, and then the number of internal buttresses and cross walls and the displacement reduction rate found on the displacements in diaphragm walls were investigated to improve the accuracy of analysis and better understanding of the behaviors of buttresses and cross walls.
The analysis result shows that internal buttresses and cross walls were effective in suppressing lateral displacement in diaphragm walls. The suppression of lateral displacement in diaphragm walls was better with cross walls than with internal buttresses. The west side of the selected case which was installed with 5 buttresses displayed a displacement reduction rate (DRR) up to 49.66%. The south and north sides were each installed with 5 cross walls. The lateral displacement in the diaphragm wall within approximately 6m of the cross walls were limited to 2cm or less. The ratio between cross wall interval, SCW, and site length, L, was less than 0.21. The DRR reached up to 77.42%.

並列關鍵字

Buttresses ； Diaphragm wall ； Numerical analysis ； Deep excavation

參考文獻

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