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| DEVELOPMENT OF THE SMALL STRAIN TRIAXIAL TEST ON SOILS AND ITS APPLICATION |
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| 龔東慶、歐章煜 |
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| 小應變、三軸試驗、勁度、局部應變 |
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| 早期由於三軸儀器功能之限制，一般傳統三軸試驗量測土壤應變量大約只能達到0.1～0.05%，造成土壤模式的發展和相關參數的選取都侷限於此應變範圍之試驗結果。然而越來越多的現地監測資料顯示，現地土壤因施工引致之應變量，除了靠近施工位置應力集中區域外，大都小於0.05%，因此近二十年來，國際大地工程界致力於發展土壤小應變試驗，包括三軸試驗儀器的改良以及小應變量測儀器的開發，土壤小應變之行為才逐漸為人所瞭解，也深深地影響後來更高階土壤模式的發展。本文詳細介紹進行小應變三軸試驗之發展，以及試驗結果在發展土壤模式和分析工程變形行為之應用。 |
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| The strain of soils measured by the conventional triaxial apparatus can at best reach the value as small as 0.1～0.05%, beyond which is out of the functional limitation in the triaxial apparatus. The fact also limits the development of soil models and the selection of soil parameters. More and more field observation data, however, showed that soil strains induced by construction were mostly less than 0.05% except those within the stress concentration zone near the construction site. Accordingly, over the last twenty years, international geotechnical engineering circles have been devoted to developing small strain tests, including the improvement of the triaxial apparatus and the development of small strain instruments. Researchers thus gradually recognize the importance of the small strain behavior of soils, which deeply influences the development of later advanced soil models. This paper introduces the development of small strain triaxial tests in detail and its application to developing the soil models and the analysis of engineering behavior. |
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| Strain controlled cyclic triaxial tests under small to medium strains |
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| 林靜怡、何輔仁、黃安斌 |
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| 動態三軸試驗、剪力波速、模數遞減、阻尼係數 |
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| 土壤模數（剪力或楊氏）與阻尼係數為大地工程動態行為分析中重要之參數，試驗結果通常以割線模數或阻尼係數與應變之關係來展示，這些關係可以統稱為土壤非線性動力性質。為了分析的需求，非線性動力性質試驗所必須涵蓋之應變範圍通常在10-4%至1.0%之間。早期因受限於試驗儀器之功能，應變10-2%以下之動態土壤行為以共振柱試驗來量測，當應變大於10-2%時則使用另一試體進行動態扭剪、單剪或三軸試驗。由於應力路徑或/和試體間之差異，此一程序不但需要許多昂貴之試驗設備而且其模數和阻尼係數與應變之關係曲線常在試驗方法更換之處發生不連續的現像。因此使用單一試體在所需之應變範圍下以同樣之受剪模式來進行土壤非線性動力性質試驗，可以避免前述之問題並可改進試驗之品質。作者採用高精密度、高扭力輸出之步進馬達作為載重單元輸出及控制，配合非接觸式趨近儀作為微小位移之量測以求得局部應變量，並加入bender element剪力波速量測元件另外單獨求得最大剪力模數，進而建立在中小應變範圍下之連續非線性動力性質。本文敘述作者所發展之試驗儀器與使用方法並展示其結果。 |
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| Soil modulus (shear or Young’s modulus) and damping ratio are important parameters in geotechnical dynamic analyses. Test results are typically presented as relationships between secant modulus or damping ratio and strain, these relationships are referred to as the non-linear dynamic soil properties. In order to provide the necessary parameters for analyses, the non-linear dynamic soil properties must include the soil behavior under a range of strain from 10-4% to 1.0%. Because of the limitation in the experimental capabilities, when the strain was less than 10-2%, the dynamic soil parameters were usually determined by resonant column tests. When the strain exceeded 10-2%, a separate specimen tested under a torsional, simple shear or triaxial shearing mode would be required to establish the dynamic properties. Due to discrepancies in stress path and/or those between soil specimens, this procedure requires the expenses to set up a multiple-unit experimental system and a discontinuity often occurs in the modulus or damping ratio – strain curves where the test method changes. Thus, using a single specimen to perform the dynamic testing under the required strain strange can avoid some of these experimental problems and improve the quality of test data. Using a high torque stepper motor as the driving system, coupled with a high resolution non-contact proximiters and bender element shear wave velocity measurement devices, the authors developed a triaxial test apparatus capable of performing strain controlled cyclic triaxial tests under small to medium strain range. This paper describes the development of this apparatus and presents a series of results to demonstrate its capabilities. |
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| MEASUREMENT OF MATRIC SUCTION IN UNSATURATED SOIL SLOPE AND ITS APPLICATION IN THE ANALYSIS OF SLOPE STABILITY |
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| 拱祥生、林宏達、吳宏偉 |
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| 基質吸力、張力計、暫態分析、不飽和滲流、邊坡穩定 |
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| 不飽和土壤邊坡存在的基質吸力對於邊坡的穩定性具有相當重要的影響。國際間對於如何正確量測土壤基質吸力仍然處於研究試驗階段，本文主要目的為介紹現地邊坡基質吸力量測的關鍵技術，並利用假設案例闡述基質吸力對邊坡穩定的影響。本文首先簡介目前較成熟的現地邊坡基質吸力量測原理、方法及儀器設備，接著應用現地邊坡基質吸力的監測案例來說明實際量測的結果與邊坡工程行為的關係。現地邊坡存在的基質吸力可利用不飽和土壤滲流原理加以分析驗證，並將結果提供後續邊坡穩定分析使用，本文配合氣候條件及坡面植生狀態的改變，利用不飽和滲流有限元素程式進行暫態分析，並將結果輸入邊坡穩定分析程式，以探討降雨對不飽和土壤邊坡工程行為的影響。 |
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| The matric suction that exists in the unsaturated soil slopes will significantly affect the stability of soil slopes. How to measure matric suction accurately and reliably is still being under extensive research worldwide. This paper introduces some major techniques for measuring matric suction in the field and illustrates the influence of matric suction to the stability of soil slopes. Firstly, this paper describes the principle, measuring method and major equipment such as tensiometers and thermal conductivity sensors. Subsequently, case histories of measuring matric suction in the field are described and the effects of matric suction on the behavior of unsaturated soil slopes are reported and discussed. In addition, a series of finite element transient seepage analyses have been conducted to investigate the climate and vegetation conditions of slope surface on slopes. The results of the transient seepage analysis are input to slope stability analyses to study the influence of rainfall to slope stability of unsaturated soil slope. |
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| LARGE BIAXIAL SHEAR BOX TESTS ON SHAKING TABLE |
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| 翁作新、陳家漢 |
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| 振動台，地震，砂土，地盤反應，土壤液化 |
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| 為模擬實際地震波作用下砂土的受震反應行為，因而發展出大型二維多層剪力試驗盒，並使用國家地震中心之振動台進行大尺寸物理模型二維振動試驗。本試驗之試體尺寸為1.88 m×1.88 m×1.52 m，試驗盒以十五層鋁合金框架堆疊而成，每層框架能各自以兩組相互垂直之線性滑軌於水平面上進行平面二維無扭轉運動，並發展一大型砂土霣落器採用水中沉降法進行試體準備，再利用微貫入錐試驗及壓力波量測來檢測土壤試體之均勻度、密度與飽和度。振動台剪力盒試驗分別進行一維及二維兩種振動模式，根據初步結果可知此雙軸向剪力試驗盒之性能合乎要求，能夠將一維及二維之地震力傳遞至砂土試體，將來可用以進行地震作用下土壤液化、地盤受震反應與土壤結構互制之探討。 |
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| For the study of the soil behavior under earthquake shaking, a physical model test using a large-scale shear box on the shaking table at the National Center for Research on Earthquake Engineering (NCREE) is developed. A laminar shear box movable in 2 axes, with a specimen size of 1.88m×1.88m in plan and 1.52m in height, is designed and manufactured in cooperation with Mechanical Industry Research Laboratories at Industrial Technology Research Institute. The shear box is composed of 15 layers of aluminum alloy frames. Each layer consists of an inner frame and an outer frame, which are allowed to move freely without torsion on the horizontal plane subjecting to the two-dimensional shear wave action induced by the shaking table. The sand specimen inside the shear box is prepared by the wet sedimentation method from a specially made pluviation device. The uniformity, density and saturation of the sand were checked by mini-cone penetration tests and P-wave velocity measurements. Pore pressures within the soil, displacements, accelerations and velocities of various depths of the frames were measured during tests under both one- and two-dimensional shakings. The preliminary test results show that the performance of the biaxial shear box is satisfactory. This shear box on shaking table will be used to study the problems of soil liquefaction, ground motions, and soil-structure-interaction during earthquakes. |
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| LARGE PENETRATION TEST OF GRAVELLY GROUND SOUNDING |
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| 蔡錦松、劉衍志、黃安斌 |
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| 大型貫入試驗、卵礫地層、能量檢測 |
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| 卵礫地層一般認定為堅實地層，地質鑽探常用之標準貫入試驗(SPT)與圓錐貫入試驗(CPT)不易在此類地層發揮，因此較少進行強度評估。然而集集地震造成台灣中部卵礫地層液化案例，加上台灣中部地區卵礫地層遍佈，於液化評估面及工程需求面，皆有必要發展可適切表現該類地層特性之現地試驗法。本文提出大型貫入試驗(Large Penetration Test, LPT)，於台中縣大里溪左岸福田橋西側高灘地進行國內首次試驗。文中參考北美地區貝克貫入試驗(Becker Penetration Test, BPT)相關研究做為試驗規畫依據，詳述器材設計、施作細節與試驗結果計算流程，並提出改進與發展建議，做為後續評估卵礫地層強度之本土經驗。 |
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| It is a thought that gravelly ground is so hard that commonly seen sounding methods, such as SPT and CPT, are not applicable. As a consequence, evaluation of such ground condition is very rare in real practices. In Taiwan, gravelly ground covers most central area, and liquefaction occurred in the Ji-Ji earthquake reveals that gravelly ground is liquefiable once subjected to strong seismic motion. A suitable sounding method for the relevant evaluation of liquefaction potential is thus desired. This paper describes a Large Penetration Test (LPT), which was proposed and adopted in an in situ test project performed at a site by Darli river side near Futen bridge. Becker Penetration Test (BPT) is described herein as a comparison for the development of devices and the associated technical details. Testing results are shown and discussions with recommendations are stated for further development and improvement of LPT in local practices. |
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| EVALUATION AND RECOMMENDATION ON TOUGHNESS INDICES FOR STEEL FIBER REINFORCED SHOTCRETE |
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| 袁士哲、鄭富書、林銘郎、傅子仁 |
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| 韌性、鋼纖維噴凝土、三點抗彎試驗 |
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| 撓曲韌性是鋼纖維噴凝土作為隧道開挖支撐構件相當重要的力學特性。它能對隧道提供有效而即時的支撐，可承受相當的變形與現地應力，適用於開挖後需快速支撐的岩盤。目前世界各國依其使用鋼纖維噴凝土的經驗及對韌性的認知，發展出各種不同的評量方法，作為現場施工品質控制的指標。本文針對鋼纖維噴凝土的韌性行為，於國內隧道進行實作研究，系統性地分析控制鋼纖維噴凝土三點抗彎試驗韌性的變數，對各類韌性指標的適用性進行評比。研究結果顯示：針對三點抗彎試驗而言，計算至較大變形量且不考慮累積能量的指標較能適切地反映出合理的韌性趨勢。綜合分析國內外相關的國家規範與技術建議後，本文依據實作研究的成果，對鋼纖維噴凝土提出韌性分級，提供國內未來訂立相關技術規範的參考與依據。 |
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| Flexural toughness is one of the pivotal mechanical characteristics of Steel Fiber Reinforced Shotcrete (SFRS) when it serves as part of tunnel support system. It enables effective and timely support for tunnels under excavation, being capable of tolerating relatively large deformation and in-situ stress, and thus is applicable to soft or squeezing rock conditions in Taiwan. Nowadays, a variety of concepts and technologies toward the toughness indices of SFRS has been developed. Serving as checkpoints for quality control of on-site operation, a precise toughness index is essentially important to justify the actual performance of SFRS. This article presents the toughness behavior of SFRS through a series of systematically designed experiments conducted on-site in a railway tunnel project. It aims at identifying the controlling factors and associated influence to the performance of SFRS, which is frequently measured from third-point tests. Accordingly, evaluation is implemented to highlight which indices are actually indicative of the toughness of SFRS made from various premixed formula. The results demonstrate that indices involving greater deflection, instead of accumulated absorbed energy, tend to have better elucidation of the actual trend. To contribute to national standard establishment in the near future, suitable indices and associated rough classifications are recommended based on aforementioned experimental results. |
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| THE CHIUFENERSHAN LANDSLIDE, NANTOU HSIEN |
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| 黃鑑水、陳勉銘、許銘義 |
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| 山崩、九份二山、順向坡 |
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| 九二一集集大地震在南投縣國姓鄉南港村的九份二山地區引發了大規模的順向坡滑動，崩塌及堆積總面積約200公頃，崩滑土石方三千萬立方公尺以上，並堵塞溪谷形成堰塞湖，有廿餘人喪命。本文根據地質背景特性及搜集各種崩塌現象資料，綜合分析發生山崩原因及加以分類，供各界參考。 |
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| A large-scale dip-slope landslide, the Chiufenershan landslide, was triggered by the 921 Chi-Chi earthquake on Sept. 21, 1999. On the landslide, over thirty million cubic meters volume of rock masses slid down, covering a area about 200 hectares, blocking streams to form two dammed lakes, and causing people deaths in excess of 20. Based on geological investigations and various field landslide features collected , the classification and factors causing landslide were elucidated. |
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