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| LATERAL SPREADING TRIGGERED BY QUAY WALL MOVEMENTS USING CENTRIFUGE SHAKING TABLE TESTS |
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| 李崇正 吳秉儒 熊大綱 |
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| 側向擴展、液化、沉箱碼頭、離心模型的震動台試驗 |
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| 本文主要探討液化引致沉箱碼頭移出導致的地盤側向擴展現象。首先歸納阪神淡路大震中港島及六角島與集集大震後台中港的破壞災象及型態。然後利用裝置於離心機掛台上的震動台，進行沉箱碼頭的離心模型震動試驗，將模型試驗所呈現的破壞型態與現場的破壞案例比較，並討論碼頭側滑引起的地盤側向擴展的破壞機制。 |
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| The phenomena of liquefaction–induced lateral spreading of saturated cohesionless soils triggered by movements of caisson type quay walls are studied. First of all, the patterns of ground failure at the Taichung Habor in Taiwan, and Port Island and Rokko Island in Japan were investigated in detail. Then, a series of centrifuge shaking table tests were carried out to study both the deformation characteristics of backfills and the response of caisson type quay walls during liquefaction induced by strong earthquakes. A comparison of test results and observed field ground failure is made and the possible mechanisms of lateral spreading triggered by quay wall movements are discussed. |
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| USE OF BLASTING DENSIFICATION METHOD IN COMPACTING SANDY SOILS |
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| 鄭富書 余昌學 趙基盛 陳福勝 何泰源 |
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| 地盤改良、炸震夯實法、砂土 |
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軟弱土層之各種改良方法中，炸震夯實法係藉由引爆深埋土中之炸藥、造成大規模之土壤液化，隨後土壤顆粒由於自重而重新堆置，形成緊密之結構而達改良之目的。因此，對於深層、大範圍之砂性土壤改良作業而言，本法之施作速度快、毋需特殊器具，可供工程界作為夯實方法之新選擇。
本文就炸震夯實之發展歷史、基本原理與作用機制、夯實成效影響因素與工程設計實務作一系統性介紹。此外，室內模型試驗探討土壤變形組態與全尺度之現地試驗結果亦列於本文中。試驗結果發現，在乾燥土層中開炸後，炸源周圍土體形成之空洞陷落，造成地表沉陷；若於不飽和土體中開炸，炸後空洞維持不崩坍。現地試驗結果顯示，此法之成果顯著，造成地表達85公分之沉陷，且SPT及CPT貫入阻抗亦提昇；改良深度達全鑽孔深度，約20公尺左右。同時，實驗結果亦顯示開炸形態與炸藥引爆方式對炸後孔隙水壓分佈及是否引起大規模之土壤液化有關而影響夯實成效甚鉅。 |
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Among the methods for improving the strength of weak soils, Blasting Densification method (BDM) is characterized with fastness in constructional time and low-cost, compared to other methods. As BDM is conducted by detonating explosives in a borehole, this method enables efficient compaction of sandy soil in a great depth or any depths desired.
The historical development of BDM, the mechanism and the design concepts of BDM are presented with focus on elucidating the key factors influencing the effectiveness of compaction. Meanwhile, model tests conducted in laboratory and full-scaled in-situ tests have been conducted to further identify the deformation of the soil body after the blasting and to access the validity of adopting BDM in Taiwan. Model test results indicate that a cavity was formed at the moment of explosion, followed by collapsing of the cavity, provided sufficient overburden exists. Field test results reveal that the layout of the blasting sequence and detonation delay play an important role in inducing liquefaction of the loose stratum, which in turn results in a more compacted structure of particles and thus improves the strength of the soil. |
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| PROBABILISTIC ANALYSIS FOR EARTHQUAKE-INDUCED SOIL LIQUEFACTION |
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| 黃富國 陳正興 |
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| 土壤液化、蒙地卡羅模擬法、地震危害度分析、液化風險分析。 |
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| 工程上慣常使用之土壤液化(soil liquefaction)潛能評估法，係直接利用地震危害度分析所得之硬地盤最大地表加速度PGA值，及工址可能發生之最大地震規模Mu作分析，其結果往往過於保守，對於液化發生之機率未作評估。本研究利用蒙地卡羅模擬法(Monte Carlo simulation)產生與台灣地區地震危害度相符(hazard consistent)之地表運動參數，並據以評估地盤發生土壤液化損害之年超越機率，此法不僅能充分且合理地反映震區特性對工址可能產生的影響，更能直接評估土層液化之損害風險，其結果可提供大地工程規劃、設計及決策時風險管理之參考。 |
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| In engineering practices, the potential of soil liquefaction during earthquakes is evaluated based on the maximum ground acceleration and the largest magnitude of earthquake of the site. The results obtained are usually over-conservative due to the lack of probability basis. In this paper, a method based on the probabilities of earthquake occurrence and liquefaction occurrence is proposed. A large number of earthquake data, which are consistent with the hazard curve of Taiwan area, are generated by using the method of Monte Carlo simulation. Based on that, the risk of liquefaction damage of a typical soil profile is evaluated using several liquefaction-assessment models. The results thus obtained give the risk-based liquefaction potential which is consistent with the seismic hazard of the site |
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| MICROZONATION OF SOIL LIQUEFACTION POTENTIAL FOR KAOHSIUNG METROPOLITIAN AREA |
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| 陳景文 林宏翰 |
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| 液化潛能微分區、液化評估、高雄都會區 |
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| 為建立高雄都會區之土壤液化潛能微分區圖，本文採用交通部震區劃分圖建議值與加速度建議值，配合數種簡易經驗法進行土層液化潛能評估，評估各鑽孔各深度點位之安全係數，且為了瞭解對地表可造成之災害，另再以Iwasaki深度加權法評估，以建立高雄都會區液化潛能微分區圖。經評估結果顯示，任一種簡單經驗評估法所得結果為高雄都會區沿海地帶、市中心部分地區、左營蓮池潭附近及楠梓區北面液化潛能指數相對較高。 |
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| Several simplified empirical methods were used to evaluate the liquefaction potential of Kaohsiung area. Microzonation map of liquefaction potential is constructed base on the liquefaction potential index proposed by Iwasaki. The result obtained from any empirical methods shows that the liquefaction potential in nearshore district of Kaohsiung, certain areas in downtown and Lotus Pond in Tsoying district are higher than the other in-land districts. |
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| SEISMIC DESIGN OF PILE FOUNDATION IN A LIQUEFIED GROUND |
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| 黃俊鴻 |
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| 土壤液化、地盤流動、基樁、地盤變位 |
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| 本文簡要介紹液化地盤中樁基礎之耐震設計觀念，包括液化土模數與強度之折減、地盤流動變位對基樁之影響以及樁、液化土與結構物之互制行為。此外，也介紹了兩種考慮地盤流動對基樁影響的擬靜態分析模式，並建議一種能考慮樁、液化土與結構物互制行為之簡單一維有限元素分析模式，供各界參考 |
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| This paper gives a brief introduction to the concept of seismic design of pile foundation in a liquefied ground. The concept includes the considerations of modulus and strength reductions of liquefied soil, the effect of liquefaction-induced ground displacement on the pile, and the interactive behavior among pile, liquefied soil and superstructure. Two pseudo-static design methods are introduced to compute the kinematic force from liquefaction-induced ground displacement on the pile. A simple one dimensional finite element model is also proposed to model the interactions among pile, liquefied soil and superstructure |
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| ASSESSING PROBABILISTIC METHODS FOR LIQUEFACTION POTENTIAL EVALUATION |
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| 莊長賢 林三賢 (譯) |
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| 液化，或然率，邏輯回歸，貝氏映射函數 |
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| 本文旨在評價現有或然率方法用以評估液化之潛能。強調的重點為比較以四種不同方法得出之液化或然率。其中兩種方法為以SPT為根據，另外兩方法則為採CPT。SPT-或CPT-為依據之評估，邏輯回歸及貝氏方法則用於映射安全係數至液化或然率。此研究顯示貝氏方法比邏輯回歸法得到較保守的結果。以危害度為基準的液化潛在性評估方法則於文中討論。 |
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| This paper presents an assessment of existing probabilistic methods for liquefaction potential evaluation. Emphasis is placed on comparison of probabilities of liquefaction calculated with four different methods. Two of these methods are based on SPT, and the other two are based on CPT. In both SPT- and CPT-based evaluation, logistic regression and Bayesian techniques are applied to map factor of safety to probability of liquefaction. The present study shows that the Bayesian approach yields more conservative results than does the logistic regression approach, although results from the two approaches are quite comparable. Discussion of the procedure for risk-based liquefaction potential evaluation is also presented |
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