小型基地於軟弱黏土層開挖行為之簡化分析

A Simplified Approach to Analyze the Excavation Behavior of Small Sites in Soft Clay

周昭如(Chao-Ju Chou)

指導教授 ： 葛宇甯

國立臺灣大學/工學院/土木工程學研究所/碩士(2016年)

https://doi.org/10.6342/NTU201603716

摘要

本研究主要探討小型基地於軟弱黏土層連續壁之開挖行為。在工程實務上，目前不論基地的大小，連續壁之分析設計一般皆考慮為平面應變之狀況。但對小型基地而言，三向度效應之影響時常導致連續壁之實際變位量遠小於考量平面應變所得之設計值，也就是說，設計過度保守且連續壁之配筋量超過實際所需。近年來，也越來越多研究透過三維軟體去做開挖行為之模擬分析，但計算量時常過大且耗時，實務上較不適用。因此，本研究為了簡化計算量，以一維軟體做分析，並且將三向度效應考量在一維軟體中作為修正因子。此修正因子為考量側壁為扶壁的方式，考慮扶壁兩側之側向摩擦力，進而提高土壤之被動土壓力，使得整體之土壤勁度增加。此外，也透過一些學者提出之平面應變比之預估方法以及預估式納入在此簡化分析方法中，作為應取等值扶壁長度之建議值。本文以六個小型開挖案例為對象，探討如何將三向度效應納入設計考量。基本上是以延伸扶壁之設計概念，將垂直於主體連續壁之側壁考量為扶壁，而扶壁之長度則可透過一些圖表查得。分析結果再與監測結果比較，顯示本文所建議之方式可合理模擬小型基地連續壁之開挖行為。

關鍵字

小型開挖基地 ； 三向度效應 ； 軟弱黏土 ； 平面應變比 ； 扶壁

並列摘要

For a relatively small excavation site in soft clay, the observed wall displacement is much smaller than the result predicted by a one-dimensional (1D) or two-dimensional (2D) numerical analysis, disregarding its significant three-dimensional (3D) effect. Much work has been done on several 3D numerical programs to simulate deep excavation, while little has been focused on the small site behaviors. Moreover, using 3D numerical programs to do such analysis is time consuming, which is an inappropriate way for engineers to do the routine work. The approach described herein uses a 1D simplified approach increasing in system stiffness to capture 3D behavior in the small site, incorporating different plane strain ratios (PSR) from previous studies. To justify the accuracy, several case histories have been studied to verify this approach. The results indicate that the new approach is valid to capture the small site behavior in excavation.

並列關鍵字

small excavation site ； three-dimensional effect ； soft clay ； plane strain ratio ； buttress wall

參考文獻

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