地中壁圍束直接基礎橋墩之抗液化受震行為：離心模型試驗

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Title:	地中壁圍束直接基礎橋墩之抗液化受震行為：離心模型試驗
Authors:	林鼎曜;Lin, Ding-Yao
Contributors:	土木工程學系
Keywords:	土壤液化;橋墩基礎;直接基礎;地中壁;圍束;沉陷;傾斜
Date:	2025-01-06
Issue Date:	2025-04-09 15:55:09 (UTC+8)
Publisher:	國立中央大學
Abstract:	台灣位屬於地震頻繁的歐亞板塊交界處，土壤液化現象常會伴隨著大地震發生，使橋樑基礎產生嚴重沉陷與傾斜的損壞，導致橋梁喪失交通功能甚至倒塌。這種類型的液化損害以座落在有液化潛能基礎土壤，且採用直接基礎支橋墩最可能發生。台灣過去許多橋墩採用直接基礎，且座落在有液化潛能基礎土壤，但設計時並未考慮土壤液化的影響，現因規範設計地震力大幅提升，須重新檢討其耐震能力時，發現土壤液化的影響無法忽略，因此顧問公司為提升此類橋墩基礎的抗液化耐震能力，有採用於直接基礎周邊設置地中壁圍束基礎土壤，避免土壤流失的抗液化對策。此類抗液化對策是否有效，目前尚有許多爭議，且相關模型試驗之研究成果並不多見。為此，本研究規劃一系列的離心模型試驗，驗證地中壁圍束直接基礎橋墩之抗液化受震行為，以沒有設置地中壁之直接基礎橋墩液化試驗為標準參考組，以地中壁長度與地中壁是否與基礎版結合為變因，分析地中壁之改良成效。試驗結果顯示地中壁可以有效抑制土壤液化時之橋墩基礎的損害的沉陷與傾斜，並影響超額孔隙水壓的激發與消散過程，改善了橋墩基礎的穩定性。其中地中壁的貫入長度越深，與基礎版的剛性結合對液化基礎的穩定性有更明顯的改善。;Taiwan is located at the earthquake-prone boundary of the Eurasian Plate, where soil liquefaction commonly occurs during large earthquakes. This phenomenon can cause severe settlement and tilting damage to bridge foundations, compromising bridge functionality or even leading to collapse. Such liquefaction-induced damage is most likely to occur in bridge piers with shallow foundations seated on liquefaction-prone soils. In Taiwan, many bridge piers were constructed with shallow foundations on liquefiable soils without considering the effects of liquefaction during design. As seismic design codes have significantly increased the required design forces, reassessment of these structures′ seismic resilience has revealed that the impact of soil liquefaction cannot be overlooked. Consequently, consulting firms have implemented an anti-liquefaction measure to enhance the seismic performance of these bridge foundations by installing diaphragm walls around shallow foundations to prevent soil loss. However, the effectiveness of this anti-liquefaction strategy remains debated, and few experimental studies have addressed this issue. To this end, this study plans a series of centrifuge model tests to verify the anti-liquefaction seismic behavior of bridge piers with shallow foundations surrounded by diaphragm walls. A bridge pier with a shallow foundation without diaphragm walls will be used as a standard reference. The study will assess the effectiveness of the underground wall by varying the wall’s penetration depth and examining whether it is rigidly connected to the foundation slab. The test results indicate that diaphragm walls can effectively mitigate settlement and tilting damage to bridge foundations during soil liquefaction. Additionally, the walls influence the generation and dissipation of excess pore water pressure, thereby enhancing the stability of bridge foundations. Greater improvement in stability is observed with deeper wall penetration and rigid connection to the foundation slab.
Appears in Collections:	[Graduate Institute of Civil Engineering] Electronic Thesis & Dissertation

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