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| A PERMANENT GROUT AND THE DYNAMIC BEHAVIOR OF ITS GROUTED SAND |
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| 米倉亮三、廖洪鈞、林英堂 |
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| 恒久性灌漿材料、灌漿砂土、抗液化能力 |
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| 為克服水泥系列灌漿材料難以滲入砂質土壤孔隙，以及水玻璃系灌漿材料耐久性不佳的問題，目前日本已有兼具水泥系材料的恒久性和溶液型材料的高滲透性之恒久性灌漿材料被開發出來。由於土壤灌漿是最適合用來提升既有建築物基礎下方土壤抗液化能力的方法，因此本文將針對此種恒久性灌漿材料和其灌漿砂土之抗液化能力加以探討，內容包括灌漿砂土之恆久性、長期強度和透水性變化、以及在軸向反覆加載下之動態行為。整體而言，雖然恒久性灌漿材料之膠體強度不高，但是經恒久性灌漿材料灌漿後之砂土，卻能具備長期抵抗地震引致之液化問題所需的穩定性和動態行為反應。 |
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| To deal with the penetrability problem of cement grout in sandy soil and the durability problem of sodium silicate grout, a new permanent type grout has been developed in Japan during the past years. It has the durability of cement grout and the penetrability of solution grout. So this new permanent type grout can be used to improve the liquefaction resistance of in-situ sandy soil under existing buildings. This paper will present some of the strength and permeability properties of this new grout and its grouted sand. They include the chemical and physical stability of grout and the long-term permeability of grouted sand. The dynamic response of the grouted sand under triaxial cyclic test was studied as well. The test results have shown that this grout can provide the strength needed to increase the liquefaction resistance of sandy soil underlying the existing buildings. |
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| DEVELOPMENT OF SUPER FINE CEMENT AND ITS APPLICATIONS IN SOIL IMPROVEMENT |
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| 黃亦敏、李維峰、林平全、張東源 |
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| 地質改良材料、優良級配、地盤改良、爐石 |
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| 地質改良通常用來處理軟弱土壤或敏感地質，以解決基礎開挖可能會遭遇的穩定性問題。針對上述問題，國內研發一項具有優良級配且經濟性的專業地質改良材料－高細度地質改良材料，高細度地質改良材料主要是以回收再利用煉鋼過程中產出之水淬高爐爐石與其他添加助劑進行調配，一方面利用爐石耐磨的特性磨製高細度粉末以調整材料成品之顆粒特性，製成粒徑均佈之地質改良專用材料，一方面也藉爐石的再利用以降低材料生產成本，並可呼應環保減廢再生的觀念。本文內容即針對高細度地質改良材料之研發成果加以詳述，包括高細度地質改良材料的組成與實驗室基本性質試驗，以及實際工程案例的追蹤分析。 |
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In an effort to develop soil improvement agent that is more cost effective and has better performance, the blast furnace slag was recently used to develop new super fine cement (SFC) for soil improvement purpose. Advantages of the super fine cement include better water-resistant and improved soil strength resulted from a well-graded grain size distribution. Moreover, because the SFC is recycled from the manufacture process of iron, not only the price of the SFC cement is very compatible with other Portland cement but also recycling slag is a typical case of waste reduction.
In this paper, the authors will first present the material properties of the developed SFC cement. A case history will then be presented to describe the applications of this new cement in deep soil mixing pile wall construction. Finally, performance of the SFC cement would be summarized as conclusions of this paper.
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| UNDRAINED SHEAR STRENGTH OF GROUT PILES IMPROVED CLAY FOR BRACED EXCAVATION |
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| 廖洪鈞、杜明昇、蘇世豐 |
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| 開挖工程、軟弱黏土、攪拌樁、不排水剪力強度、模型試驗 |
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| 為增加黏土層開挖底部之穩定性，常使用攪拌樁改良方式來增加底部土壤之強度。可是目前工程界對攪拌樁改良後土壤之等值剪力強度決定，仍是停留在經驗公式之層級。有鑑於此，本文透過模型試驗的方式，模擬攪拌樁改良後之開挖行為，並評估攪拌樁改良土之等值剪力強度。為減少因縮小模型尺寸所產生之尺寸效應問題，本模型試驗將保持原型與模型之穩定數(gH/Su)相等。因此在模型試驗過程中，黏土強度將依現場尺寸和模型試體尺寸之縮小比值而減少。攪拌樁改良土等值剪力強度之求取，是藉由比較攪拌樁改良和全面改良後之開挖底部隆起量來決定。試驗結果顯示，在增加黏土層開挖底部穩定性方面，攪拌樁體強度對攪拌樁改良土剪力強度發揮的貢獻度，只有攪拌樁體強度之一小部份而已，而且其貢獻值要小於慣用經驗公式所採用之數值。 |
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| To increase the base stability of braced excavations in soft clay, grout piles are frequently used to improve the base soil. Although the strength of base soil has crucial effect on the base stability of excavation, it is mostly determined by means of empirical equations so far. To rationalize the empirical equation commonly used, this paper will evaluate the apparent shear strength of grout piles improved clay based on the results of a model test simulating deep excavation in soft clay. The size effect of the model test was minimized by keeping the base stability numbers (= gH/Su) of the model test and the field excavation being equal. The undrained shear strength Su of soil used in the model test was reduced according to the size reduced from the prototype. The composite undrained shear strength of grout piles improved clay is evaluated by comparing the basal heave behavior of soil with grout piles improvement and that of soil with 100% ground improvement. Test results indicate that the contribution of grout piles to the undrained shear strength of the base soil underlying a deep excavation is only a small fraction of the grout pile strength. The contributed grout pile strength is smaller than the value which is usually adopted in the empirical equation for the undrained shear strength of grout piles improved clay. |
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| OUTWARD DEFORMATION OF DIAPHRAGM WALL INDUCED BY JET GROUTING |
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| 謝旭昇、王崑瑞、楊易璋 |
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| 高壓灌漿、壁體變位 |
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| 高壓灌漿工法常用於軟弱粘土之深開挖工程，其目的在於提高開挖區內土壤之強度，藉以提高開挖之穩定性及抑制壁體變位量。但高壓灌漿施作過程中常發現連續壁有外擠現象，其位移量可能高達十數公分，嚴重時甚至導致壁體破裂。基本上壁體外擠之主要原因並非灌漿所使用之壓力過大，而是因灌漿過程中無法順利迴漿排土，基地內土壤之體積因水泥漿之注入而持續增加，造成壁體受力向外推擠。本文以一實際施工案例說明高壓灌漿對連續壁之影響，文中除陳述現場觀測結果外，並以理論說明壁體外移之機制。 |
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| Jet grouting is often used in deep excavation projects to improve the strength of soft ground. It not only increases the stability of excavation, but also limits the lateral displacement of retaining walls. However, it is often found that jet grouting may induce lateral outward displacement of diaphragm walls. The amount of displacement may exceed 10cm, leading to crack of diaphragm wall in extreme cases. Contrary to general belief, the outward movement of diaphragm wall is not induced by the seemingly high grouting pressure infact, difficulties in expelling waste disposal from the grout hole that leads to expansion of the soil mass is perhaps the governing mechanism. This paper presents to case of history a deep excavation. Both the construction characteristics of jet grouting as well as displacement patterns of diaphragm wall are addressed. The mechanism that leads to the outward movements of diaphragm wall is also delineated via a theoretical approach. |
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| USE OF FINITE ELEMENT ANALYSIS IN BERMED EXCAVATION AND its associated PROBLEMS |
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| 謝百鉤 |
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| 土戧，開挖，有限元素法，壁體側向位移 |
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| 本研究以二個土戧擋土開挖工程為例，探討有限元素法預測土戧擋土開挖的結果及問題。研究結果顯示：有限元素法可合理的預測土戧開挖之短期土壤位移行為，但由於未能考量土戧漸進破壞的影響以及用以地盤改良之攪拌樁和粘土間互制行為，因此無法模擬開挖後擋土壁持續產生之側向位移，致使預測所得之壁體側向位移和現地最後觀測結果比較起來會有低估的現象。 |
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| The finite element method is used in this study to investigate behavior of two bermed excavations. The results show that the finite element method can reasonably predict the short-term behavior of ground movement induced by bermed excavation. But the longer-term lateral deflection of retaining wall after excavation can not be reasonably simulated without considering the progressive failure behavior of berm and the interaction behavior between grout piles and clay. |
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| GROUND IMPROVEMENT OF COASTAL INDUSTRIAL PARKS IN TAIWAN |
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| 張吉佐、曾文德、許建裕 |
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| 擠壓砂樁、動力壓密、礫石樁、深層液化夯實 |
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| 台灣濱海工業區主要為水力回填造成的新生地。因原沖積土層與回填地層大多屬於飽和且疏鬆的沉泥質細砂，且地下水位高，在地震規模大，震央距離近等相關條件下，土壤液化的機會必定相當高。本文主要針對常用於台灣濱海工業區的幾種地盤改良工法：擠壓砂樁工法、動力壓密工法、礫石樁工法、及深層液化夯實工法等；對其改良機制、適用範圍、改良成效及施工案例等於文中概述，作為日後辦理上述地盤改良時的設計施工參考。 |
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| Most coastal industrial parks in Taiwan were mainly completed through hydraulic fill reclamation. Most sites were reclaimed by dredging. Their subsoil conditions are mainly composed of grey silty sand locally laminated with grey silty clay and/or sandy silt. The liquefaction potential of saturated silty sand at various depths underlying each site is high due to high ground water table and potentially large earthquake ground shaking. The main purpose of this paper is to briefly illustrate the mechanism, arrangement, efficiency, and practical experience of various ground improvement method, such as sand compaction pile method, dynamic consolidation method, stone column method, and deep liquefaction compaction method. The objective for the whole article also intends to provide useful references for design and construction of similar projects in the future. |
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| EVALUATION OF CONSTRUCTION CHARACTERISTICS AND IMPROVEMENT EFFICIENCY OF STONE COLUMNS |
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| 呂彥龍、蘇百加 |
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| 礫石樁，CPT，平鈑載重試驗，施工序列，外凸破壞 |
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近年來，考量抗液化需求及為提供上部儲槽構造物足夠之承載力，兼具前述兩項功能之礫石樁施工法，已被廣泛地採用在國內大型海埔新生地開發案。礫石樁於現地施工時是一種藝術，因為現地施工過程所遭遇之困難地盤狀況，並無法於設計階段進行合理假設，而需於現場即時加以解決。因此,本文蒐集一礫石樁工區施工案例，來說明礫石樁於困難地盤之施工特性；此案例顯示礫石樁於軟弱地盤施作成果，其擠壓力與施工序列之安排有相當重要關係。
此外，本文並蒐集五組國內包括有CPT及平鈑載重試驗成果之礫石樁試驗區，該試驗成果顯示礫石樁變形模數約在1400～3700tf/m2左右，礫石樁與樁體間土層應力分擔比則在1.8附近。
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| To deal with liquefaction of reclaimed land and to provide the oil tank foundation with enough bearing capacity, stone columns were widely adopted in the large reclaimed land development projects recently. The construction of stone columns is a state of the art practice due to the unforeseen ground conditions which are unknown on the design stage, but must be resolved during construction immediately. A case history of stone column construction on the difficult ground is selected to illustrate this phenomenon. This case shows that the results of stone column compaction pressure are significantly influenced by the arrangement of construction sequence. Five sets of CPT results and plate load test results from different pilot test field on a reclaimed land base are presented in this paper also. Test results indicate that the strain modulus of stone column ranges from 1400 tf/m2 to 3700 tf/m2. The stress concentration factor n of 1.8 between stone columns and the surrounding soil was obtained from this pilot test. |
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| CASE STUDY OF GROUND IMPROVEMENT WORK ON AIRSIDE PAVEMENTS OF SECOND BANGKOK INTERNATIONAL AIRPORT |
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| 林本騏、莫若楫 |
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| 國際機場、地盤改良、垂直排水帶、預壓土堤、監測系統、壓密沉陷 |
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| 建造曼谷第二國際機場以取代日漸飽和的現有曼谷國際機場的構想始自六十年代，在歷經超過三十個的政府輪替後，終於在1991年拍板定案並定於2004年底完成第一期工程後開始營運。新機場預計每年將可處理超過三千萬人次的客運量及一百四十六萬噸的貨運量。由於機場工址地表下有約十至十二米厚、俗稱“曼谷軟土”的高塑性、高含水量、低強度的軟弱黏土，因此以垂直排水帶及土堤預壓方式來進行地盤改良以減少機場完工後所產生的壓密沉陷已成為機場建設的先期必要工程。本文主旨在介紹日前剛完工的機場空側包括跑道、滑行道、停機坪等的地盤改良工程的設計理論及施工方法，並經由儀器監測結果和土壤性質於地盤改良前後的變化來評估地盤改良的成效。 |
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| The construction of Second Bangkok International Airport has been planned since 1960 to accommodate the rapid growth of air traffic in this region. The 41 years project, which has passed more than 30 governments, was finally approved for the construction in 1991 and is scheduled to open in December 2004 with capacity to deal with 30 million passengers and 1.46 million tons of cargo per year. Due to the underlying high compressibility and low strength soft marine clay, ground improvement by Prefabricated Vertical Drains with preloading embankment is selected to reduce the post-construction settlement prior to the permanent airport facilities construction. This paper discusses the design concept and construction method of the on-going ground improvement project at Airside Pavements for the new airport construction. The ground improvement performance is evaluated through the monitoring data and the change of soil properties. |
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