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第43期 |
加勁土壤 |
可選購電子書 |
李咸亨 |
1993/09/01 |
90 |
無庫存
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| AN INVESTIGATION OF CONTAMINATION OF BALLAST AND PERFORMANCE OF GEOTEXTILE IN A RAILROAD SYSTEM |
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| 許澤善 |
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| 本文中作者先行研究鐵路道碴一地工織物一路基土壤系統之滲透性、及土壤污染值隨時間和動力載重次數之增加而變化的情形，之後並提出了一詳實的路基土壤污染道碴及地工織物的程序，以便於了解地工織物在整個系統中之運作情形。 |
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| This paper presents some test results including the change in permeability and soil contamination value with the increase in the number of cycle of repeated load for a simulated ballast-geotextile-subgrade system. Reasons for the pumping action are discussed, and the sequence of the processes for clogging for the simulated railroad system is proposed. |
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| RESILIENT DESIGN METHOD OF REINFORCED RETAINING WALL |
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| 李咸亨、謝宗榮 |
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| 加勁擋土牆動態反應分析方式，可分類為有限元素分析法以及擬靜態極限平衡分析法。本文介紹之四種設計方法中，Richardson法及Yogendrakumar法以試驗資料配合有限元素分析為其研究基礎，而Bonaparte法及Vrymoed法則完全以極限平衡分析法為分析工具。文中加以比較說明其設計內涵，並援引其他影響動態行為因素加以印證。比較各種不同設計方法可知Richardson建議的方法明顯高估了設計加速度值，而加勁擋土牆之設計最好以拉出破壞模式作為安全因素之控制參數，以免發生整體瞬間崩解現象。一般設計時，對於土壤內摩擦角大都保守地採用殘餘摩擦角作為依據。 |
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| For the analysis of the dynamic response of the reinforced retaining wall, there are two techniques. One is finite element method and the other is pseudo-static limit equilibrium method. In this paper, four design methods were discussed. The Richardson's and Yogendrakumar's methods are based on finite element method, and the Bonaparte's and Vrymoed's methods are pseudo-static limit equilibrium method. Some influence factors were considered in this article as well. Comparing to other methods, the Richardson's method obviously overestimated the design accelerations. The factor of safety controlled by the break failure mode is considered to be larger than the pull-out failure mode in order to prevent the wall from collapse. Usually, the residual friction angle is used as the design parameter although it is considered conservative. |
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| PREPARE A REASONABLE GEOSYNTHETICS TEST AND CHOOSING STANDARD FOR TAIWAN USER |
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| 林 琛 |
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| 地工合成物一直在工程應用上扮演著非常重要的角色。不但有效的縮短工期，也大幅降低施工成本。可惜的是國內卻往往因為選材規範之混淆或檢驗標準之釐定困難而將之視同毒藥，棄而不用。因此儘速建立一套合理之地工合成物選材及檢驗標準，實乃當務之急。 |
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| Geosynthetics has been the most efficient construction material of civil engineering for more than twenty years, which really can reduce the cost and increase the project safety. Unfortunately some users in Taiwan are still confused by several important test and choosing standards, for the self-protection reason, the designer prefer stay with conventional method to use Geosynthetics. If we really wanted to improve our knowledge about Geosynthefics, the first thing is to prepare a reasonable standard of it. |
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| EVALUATION OF THE STATE-OF-THE-ART DESIGN AND ANALYTICAL APPROACHES FOR GEOSYNTHETIC-REIN-FORCED SOIL WALLS（GRSW） |
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| 周南山 |
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| 加勁式擋土牆之發展，可謂近廿年來土木工程中進展最為迅速的部份之一。不但學理上已漸趨成熟，實際應用上更是一日千里，加勁材料幾乎每月皆有新產品問世，尤以地工合成物加勁材料為最繽紛眩目、五光十色，令人目不接暇。台灣近年來由於建設多朝向山坡地發展，擋土牆日益增高，使得傳統式鋼筋混凝土牆甚難與地工合成物加勁擋土牆抗衡。
地工合成物加勁牆（Geosynthetic Reinforced Soil Walls，簡稱GRSW）一般可分為地工織布與不織布（Geotextile）及地工格網（Geogrid）牆二類。又加勁陡坡（Steep Reinforced Slopes）與加勁擋土牆極為類似，只是牆面非垂直而已。本文所謂加勁牆，乃取其較廣義之解釋，將「加勁陡坡」亦涵蓋在內。本文首先介紹地工合成物加勁擋土牆與傳統RC牆之比較，俾設計者在規劃階段可針對需要做一抉擇。其次，將介紹最新分析理論（State-of-the-art Analysis），並就各種極限平衡設計方法之原理與優缺點做一評估。最後，並探討有限元素法於加勁擋土牆之應用。 |
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| The analytical and design approaches for GRSW can be classified into two categories, namely, the limit equilibrium and the finite element methods. The limit equilibrium methods are typically based on relatively simple assumptions than on supporting empiricism, which result in diverse solutions among the various methods. The more prominent differences are probably due to significant disparity in defining allowable reinforcement strength and safety factors. The FEM methods, although too complicated for routine design, have demonstrated the ability in studying the behavior of GRSW. The results of FEM analyses, using DACSAR, to investigate the various factors affecting the performance of GRSW are presented. A design approach based on allowable deformation and tensile strain in the reinforcement is also developed. |
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| COMPARISON OF DIFFERENT DESIGN METHODS OF GEOTEXTILE-REINFORCED EARTH WALLS |
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| 陳景文、吳宗欣、Claybourn A.F |
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| 在土壤中加入張力構件以達到加勁目的之所謂加勁土壤（Reinforced Earth）的觀念與重力式擋土牆之設計觀念在數百年以前已有。但將兩個觀念合併用以建造加勁擋土牆之觀念則相當新近。法國之Vidal（1970）首先以鍍鋅鋼片為加勁材料，分層加入土壤中，並於牆前設置混凝土面版，用以抵抗土壓力。
近年來化工合成技術推陳出新，加勁土壤內所採用之加勁材料乃由已往之金屬材料逐漸被化工合成材料，即所謂的地工合成材料（Geosynthetics）所替代。在眾多種類之地工合成材料中，又以地工織物（Geotextiles）起源最早，使用最多，亦為最早被引進國內之地工加勁材料。在國內已廣泛的運用於各種大地工程上。其中又以地工織物為加勁材料之擋土牆最為普遍應用。分析其原因，主要為地工織物擋土牆在實際施工優於傳統式擋土牆者有下列諸端：（1）較具柔性，因而能承受甚大之沈陷量。（2）具較高之阻尼，適合建於地震較頻繁地區。（3）施工快速、開挖少毋庸依賴重機械施工。（4）無排水不佳之間題。
目前已有不少地工織物擋土牆的設計方法被發展出來，其中部份且已應用於工程實務設計。在國內這方面相關的文獻不少。如賴榮森和陳做季（民國76年）說明加勁土壤擋土結構之一般設計觀念及施工程序。李咸亨（民國79年）與張達德等人（民國79年）分別對地工織物加勁擋土牆之應力分佈與設計理念加以解說。然而，由於設計方法假設的條件及所根據的理論不同，導致設計所得結果相分歧。陳榮河（民國78年）曾以實例對數種加勁擋土牆之設計方法比較加勁材料之強度，各方法分析所得結果相當歧異。
本文則選擇六種已公開使用之設計方法。說明其設計假設之條件，並以兩種不同高度之牆體，比較不同設計方法分析所得之加勁材用量。所得結果可供工程界設計地工織物擋土牆選擇設計方法時之參考。 |
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| Six published design methods of geotextile-reinforced earth wall are reviewed and compared. Comparison were made of the results of designs for various wall heights and geometries for each of the methods by strictly following the design procedures. The results of tests conducted on two geotextile-reinforced test walls which were loaded to failure were then used to evaluate each of the analytical models by using the design methods without any safety margins. The design methods and the concepts on which they are based are described and their differences summarized. The results of the comparisons are presented along with conclusions based on the results.
To some extent, the differences in results obtained by the methods result from obvious differences in the analytical models used. However, the more prominent differences are due to significant disparity in defining allowable reinforcement strength and safety factors. For the most part, the demonstrated success of these structures to date is probably more attributable to the conservatism inherent in the design methods than to the accuracy of the analytical models. |
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| INTRODUCTION OF WELDED WIRE RETAINING WALL |
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| 林三賢 |
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| 加勁土壤材料，一般說來，不外是以各種地工合成材料製成的非金屬加勁材及版條或鋼片狀之金屬加勁材。本文主要目的在介紹另一種焊接鋼網加勁土壤擋土牆。設計之考慮及範例亦在文中討論。 |
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| In General, earth reinforcement meterials include all kinds of non-metallic geo-fabric or geotextile materials and mteal strips or steel bars. The purpose of this paper was introducing a special welded wire earth reinforcement retaining wall. The design method and design example was also discussed in the paper. |
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| STABILITY ANALYSIS OF REINFORCED SLOPES-DEVELOPMENT OF PC PROGRAM AND COMPARATIVE STUDIES |
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| 黃景川 |
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| 以極限平衡法（Limit equilibrium method）設計加勁土壤邊坡時，依其對象邊坡型式之不同，可分為兩大類；第一類為具鉛直或近鉛直之單坡度坡面擋土牆，其側向土壓力係數可依土壓係數公式求得者，此法在平地之結構物，如路堤護岸等應用較多；第二類為由多段坡度及退縮小平臺組合而成之邊坡，其坡面整體之側向土壓力係數無法由簡單之土壓公式求得者，此法在山坡整地或水土保持工程中應用較多。由於臺灣山坡地有效開發利用之必然趨勢，又加上土壤加勁技術漸受到普遍之採用，今後第二類分析法之使用必然更加頻繁。在大地工程中，分析不均質且邊界條件複雜之邊坡穩定問題時廣為工程界採用的方法為切片法（Bishop，1955，Spencer，1967，Janbu，1973）。因此，改良慣用之切片法使適用於加勁邊坡，可成為加勁邊坡穩定分析之有力工具。 |
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| A personal-computer-based program for analyzing the stability of reinforced slopes, RSLOPE1, is developed. In this program, the Felleniusand Bishop's simplified methods are modified according to various mechanisms of soil reinforcing. The results and limitations of this program are compared with some existing ones, namely, STABL6 and STABGM. It is found that the safety factor generated by RSLOPE1 is well comparable with those from other existing program. It is also demonstrated that the program RSLOPE1 calculates five types of factor safety to render a more sophisticated judgement on the stability of the reinforced slopes. |
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| ERROR ANALYSIS IN GEOTECHNICAL ENGINEERING DESIGN |
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| 趙國祥、秦中天 |
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| 大地工程師於進行分析設計時都會遇到若干隱含之不確定因素（Uncertainty），這些因素包括材料性質、荷重作用於土層之狀況以及運用之預測模式等。在傳統設計中，都是運用判斷與以往經驗選擇設計參數，並決定一個讓人接受之安全係數以進行保守的設計。可是，採用固定安全係數（Fixed Safety Factor）之方式從事分析設計卻有以下之缺點（Baecher，1985）：（1）由於並無直接處理這些不確定因素之變異量，而使每個設計用的估計量（Estimate）偏於保守，以致無法明確瞭解整個設計真正的〝安全係數〞；（2）由於土壤性質、荷重等估計量趨向保守及主觀，無法使預測行為具反復性（Repeatability），從品質保證的觀點來講，是一種不佳的品質保證；（3）因資料數量、品質之差異及使用設施之不同等因素，不確定因素之變異程度遂因位置之不同而變化，因此會造成不同程度之不利行為。
在基礎工程方面，對設計參數之決定通常是取其平均值作為設計依據，然因實際之土壤參數並非一個固定的常數，而是隨著地點、時間及空間分佈在改變。一般而言，任何土壤參數之真值（True Value）是無法準確地經由試驗或理論公式得到，僅能應用包含許多伴隨誤差的量測值進行概略地估計。
基於上述理由，本文介紹在大地工程分析設計中可能之不確定因素，並予以定量化，再藉由一些簡單之統計方法，俾能對處理離散資料及考慮不確定因素時有所助益。文內並引用可靠性指（Reliability Index）之觀念及與破壞機率之關係，以期在大地分析設計中之經濟及安全考量下尋
求合理之平衡。 |
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| Soil properties used in geotechnical engineering design always involve many implicit uncertainties. Today most of the geotechnical engineers make design using a fixed safety factor without taking the uncertainties into account. Therefore these designs may be unsafe or too conservative. The purpose of this paper is to identify the sources of uncertainty involved in soil parameters. An example showing various sources of field vane data uncertainties is given. Based on statistics and probability methods, the errors caused by these uncertainties can be quantified. Furthermore the uncertainty of the predicted byhavior can be estimated through simplified method dealing with the error propagation of soil properties. This paper also introduces the relationship between failure probability and reliability index in order to aid designer to choice a safety factor of which a balance between economy and safety concerns can be achieved. |
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