計劃成果自評可供推廣之研發成果資料表

本研究探討條形振動夯實造成砂土密度和土壓力的變化。本研究以氣乾之渥太華砂為回填

土，回填土高1.5 公尺。回填土初始相對密度為 34%。為了在實驗室模擬雙向平面應變的

情況，本研究採用塑膠膜潤滑層來降低砂土和填砂槽側牆間的摩擦力。根據實驗結果，本 研究獲得以下幾項結論：

1. 對於疏鬆砂土，土體內的垂直土壓力和水平土壓力可分別以

σ

_v = 和 Jaky 公式來進

γ z

行合理的估算。

2. 隨著夯實機夯實趟數的增加，條形夯實區之地表沉陷量隨之增大。地表沉陷量和夯實趟 數之間的關係可以用雙曲線的模式來模擬。

3. 砂土的相對密度變化等高線範圍，會隨著夯實趟數增加而擴大。

4. 垂直土壓力變化量的等高線近似於同心圓的形狀，而殘餘垂直土壓力

Δσ

v 會由圓心區

域向外逐漸減少。土體內最大

Δσ

v值會隨著夯實趟數增加而增大。

5. 在夯實機夯實 1 和 2 趟後，殘餘水平土壓力

Δσ

_h的等高線會形成兩個較高的應力區，

水平土壓力變化量會由中心區域逐漸減少。然而在夯實機夯實4 和 8 趟後，殘餘水平土

壓力的等高線則近似於一個同心圓的形狀。夯實影響的區域 (

Δσ

h = 0.2 kN/m² 應力等 高線) 深度會隨著夯實能量增加而增大。

6. 在夯實一趟後，土壤所受夯實影響的機制可以用基礎下方土壤之局部剪力破壞的情況來

解釋。然而，當夯實趟數增加到8 趟後，被夯實土壤之機制可用方形鋼樁以振動打樁機

貫入砂質地盤的情況來模擬。本研究內容與計劃書完全相符。

本研究獲得數項創新發現，具工程實用價值，上述該研究成果已於2009年10月於埃及 亞歷山卓市(Alexandria, Egypt)舉行的第17屆國際土壤力學及大地工程研討會(17^th

International Conference on Soil Mechanics and Geotechnical Engineering)發表，獲得國際大地 工程界肯定，充分達成計劃目標。參與研究的碩士班研究生籍此機會，習得大型基礎模型 實驗與資料擷取之操作，以及嚴謹審慎之實驗方法與獨立思考及創造的能力，獲益匪淺。

可供推廣之研發成果資料表

□ 可申請專利 □ 可技術移轉

日期：99 年 08 月 10 日

國科會補助計畫

計畫名稱：震動夯實造成之土壤應力及密度變化（Ⅱ）

計畫主持人：方永壽 教授

計畫編號：NSC 98-2221-E-009-135- 學門領域：土木水利工程

技術/創作名稱 震動夯實造成之土壤應力及密度變化 發明人/創作人 ^{方永壽 教授}

技術說明

中文: 本研究利用國立交通大學模型擋土牆設備探討震動夯實所引 致之土體密度及應力變化。以氣乾渥太華砂作為回填土進行夯實，

回填土高 1.5 公尺。回填土初始相對密度為 34%時地表震動夯實對

砂土密度與土壓力之影響。依實驗結果可獲得以下結論。（1）對於

疏鬆砂土，土體內的垂直土壓力和水平土壓力可分別以

σ

_v =

γ z

和

Jaky 公式來進行合理的估算。（2）隨著夯實機夯實趟數的增加，條 形夯實區之地表沉陷量隨之增大。地表沉陷量和夯實趟數之間的關 係可以用雙曲線的模式來模擬。（3）砂土的相對密度變化等高線範 圍，會隨著夯實趟數增加而擴大。（4）垂直土壓力變化量的等高線

近似於同心圓的形狀，而殘餘垂直土壓力

Δσ

v會由圓心區域向外逐

漸減少。土體內最大

Δσ

_v值會隨著夯實趟數增加而增大。（5）在夯

實機夯實1 和 2 趟後，殘餘水平土壓力

Δσ

h的等高線會形成兩個較

高的應力區，水平土壓力變化量會由中心區域逐漸減少。然而在夯

實機夯實 4 和 8 趟後，殘餘水平土壓力的等高線則近似於一個同心

圓的形狀。夯實影響的區域深度會隨著夯實能量增加而增大。（6）

在夯實一趟後，土壤所受夯實影響的機制可以用基礎下方土壤之局

部剪力破壞的情況來解釋。當夯實趟數增加到 8 趟後，被夯實土壤

之機制可用方形鋼樁以振動打樁機貫入砂質地盤的情況來模擬。

英文： This report studies the variation of soil density and earth pressure due to the strip compaction with a vibratory compactor. In this study, dry Ottawa sand was used as backfill material, and the height of backfill was 1.5 m. The initial relative density of the backfill was 34 %. To simulate a 2-way plane strain condition in the laboratory, the friction between the soil and sidewalls of the soil bin was reduced as much as possible. Based on the test results, the following conclusions can be drawn.

1. For loose sand, the vertical and horizontal earth pressure in the soil mass could be properly estimated with the equation

σ

_v =

γ z

and Jaky’s equation, respectively.

2. The surface settlement increased with the increasing number of passes of the compactor. The relationship between the surface settlement and the number of passes of the compactor could be modeled by the hyperbolic model.

3. After compaction, the range of contours of relative density (Dr= 36

%) would become larger with increasing number of passes.

4. The contours of

Δσ

v were analogous to concentric circles, and the

Δσ

v would decrease gradually from the central region. The vertical stress increment

Δσ

v increased with increasing number of passages of the compactor.

5. The contours of

Δσ

h formed two circles of high stresses and

Δσ

h

decreased gradually from the center region after the first and the second passes of compactor. The contours of

Δσ

_h were analogous to concentric circles after 4 and 8 passes of the compactor. The depth of the compaction-induced zone increased with increasing compaction energy input.

6. Based on the test results, the mechanism of soils after the first pass of the compactor could be explained by local shear failure.

However, the mechanism of soils after 8 passes of the compactor could be simulated by a steel square pile driven in sand with a vibratory hammer.

行政院國家科學委員會補助參與國際學術會議報告

專題研究計畫補助編號：NSC 98-2221-E-009-135 及 NSC 97-2221-E-009-124

報告人: 方永壽教授

服務機構: 國立交通大學土木工程系所 職稱: 教授

會議名稱: 第 17 屆國際土壤力學及大地工程研討會 (17

^th

International Conference on Soil Mechanics and Geotechnical Engineering)

舉辦地點: Alexandria, Egypt 舉辦時間: 2009 年 10 月 5 日~ 9 日

主辦單位:

1. International Society of Soil Mechanics and Geotechnical Engineering (ISSMGE)

2. Egyptian Geotechnical Society 3. Government of Egypt

4. City of Alexandria

國科會專題研究計畫補助編號：

NSC 98-2221-E-009-135 及 NSC 97-2221-E-009-124

攜回資料: 研討會論文集 4 大冊及論文集光碟 1 片

一、參加會議經過

國際土壤力學及大地工程研討會 (International Conference on Soil

Mechanics and Geotechnical Engineering)是全世界最大、也是最重要的大地工程 研討會。這項研討會是由國際土壤力學及基礎工程學會(International Society of Soil Mechanics and Geotechnical Engineering)；埃及大地工程學會(Egyptian Geotechnical Society)；埃及政府(Government of Egypt)；及亞歷山卓市政府(City of Alexandria)共同主辦。本次國際會議有來自 80 餘國家大約 1,200 位代表參 與，4 大本論文集共收錄 700 多篇論文。上圖左起為中華民國大地工程學會理 事長台科大廖洪鈞教授、計畫主持人方永壽、及中興顧問公司江政恩主任合影 於研討會場。

大會於研討會前兩天(2009/10/5 及 2009/10/6)邀請數位知名的大地工 程學者發表演講，例如大會於 2009 年 10 月 5 日上午邀請澳洲 Prof. Poulos 進行 Terzaghi Oration 專題演講，介紹中東超高層建築物深基礎面臨的挑 戰，大師級學者的報告內容精采，與會者收穫甚為豐富。大會於 2009 年 10 月 5 日下午邀請美國 Georgia Tech.的 Prof. Paul Mayne 進行 State of the Art (SOA #1)專題演講，介紹大地材料行為及試驗(Geomaterial behavior and testing)，報告內容精采，甚具啟發性。下圖左起為交大黃安斌教授、

Prof. Paul Mayne、及計畫主持人方永壽於(SOA #1)專題演講後共進午餐時

所攝的照片。

本次研討會於研討會後兩天(2009/10/7 及 2009/10/8)，透過下列主題 集中的 16 個討論會場次(Parallel Sessions)，由 General Reporter, Panelists 及 Selected Authors 發表經詳細審查、具重要性的論文，進行國際水準的 論文發表，促進學術界與工業界的跨領域交流。

1A - Laboratory Testing

1B - Physical and Constitutive Modeling

1C - Problematic Soils and Geosynthetic Material 1D - In-situ Testing

2A - Deep Foundations & Retaining Walls 2B - Slopes and Embankments

2C - Underground Structures

3A - Instrumentation in Geotechnical Engineering 3B - Monitoring and Performance

3C - Interactive Design

4A - Ground Improvement, Grouting and Dredging

4B - Deep Excavation, Tunneling and Groundwater Control 4C - Natural Hazard Mitigation

5A - Owner, Engineer and Contractor Public Awareness 5B - Management of Geotechnical Data and Processes

5C - Training of Geotechnical Engineers/Future of Geotechnical Engineering Education

二、論文刊出

報告人及研究生簡煜倫合著之論文”Variation of soil density and earth

pressure due to strip compaction”，被編列在研討會主題 1B (Physical and

Constitutive Modeling)，論文被發表在研討會論文集第一冊、第 700 至 704

頁。此項研究依據實驗方法探討條型夯實振動造成砂土密度及土壓力之變

化，為國科會專題研究計畫 NSC 95-2211-E-009-199 之研究成果。

3-1 各國代表參加人數

大會公佈至 2009 年 9 月 30 日為止，已註冊報名參加研討會的各國代 表名單(List of participants)，總共有來自 81 個國家、大約 1,200 位代表與 會，其中代表人數列前 20 名的國家名稱及代表人數如下表所列：

名次 國家名稱(參加人數) 名次 國家名稱(參加人數)

1 Japan (101) 11 Netherlands (27) 2 United States (55) 12 Korea (24) 3 Egypt (53) 13 Canada (21) 4 China (47) 14 Spain (17) 5 France (38) 15 United Kingdom (16) 6 Germany (36) 16 India (16) 7 Australia (35) 17 Greece (15) 8 Italy (34) 18 Taiwan (12) 9 Brazil (31) 19 Hong Kong (12) 10 Russia (27) 20 Turkey (12)

日本是上一屆 16th ICSMGE 的主辦國，埃及是本屆 17

^th

ICSMGE 的 主辦國，所以日本與埃及代表人數特別龐大。美國、法國、德國、澳洲及 義大利是傳統工程強國，大地工程人才濟濟，所以與會代表特別多。我國 註冊出席代表 12 人，大致與我國人口成合理比例。上表中排名第 4 的 China，近年經濟及工程發展有長足的進步，由其代表團人數可以看出其 逐步跨入國際舞台之趨勢。

3-2 音樂裊繞的開幕典禮

開幕典禮乃是研討會枯燥乏味又必要的儀式，在 2009 年 10 月 5 日上 午的開幕典禮中，埃及政府長官、亞歷山卓市政府長官、國際大地工程學 會會長 Prof. Pinto、及 17

^th

ICSMGE 研討會主辦人 Prof. Hamza 依序上台 官式致詞。

在長官致詞告一段落後，舞台布幕緩緩升起，舞台上出現一個大約

20 人的弦樂團，如下圖所示。隨著飛舞的指揮棒，他們流暢的奏出具埃

式致詞，放下國界與文化藩籬，融入一片愉悅的旋律，這份別出心裁的安

排，受到與會者一致的好評。

Variation of soil density and earth pressure due to strip compaction

Variation de la densité et de la poussée du sol due à un compactage en bande

Y.S. Fang

Department of Civil Engineering, National Chiao Tung University, Hsinchu, Taiwan

Y.L. Chien

Power Projects, Civil Dept., E & C Corporation, Taipei, Taiwan

ABSTRACT

This paper studies the variation of soil density and earth pressure in a soil mass due to the vibratory compaction along a strip on the surface of the cohesionless backfill. Experiments were conducted in a non-yielding model retaining wall facility and dry Ottawa sand was used as fill material. Based on the test results, it is found that surface settlement increased with the increasing number of passage of the compactor. The relationship between the surface settlement and the number of passes could be properly described by the hyperbolic model. The contours of Δσ^v after the first passage of the compactorwere analogous to a series of concentric circles. As the number of passes increased to 8, the depth of the compaction-induced zone increased with increasing energy input. After the first passage of the compactor, the contours of Δσ^h formed two regions of stress concentration below the surface. As the number of passage increased to 8, the two high-stress regions merged. The mechanism of soils after the first passage of the compactor could be properly explained by local-shear bearing capacity failure mode. The mechanism of soils after 8 passes of the compactor could be simulated by a single pile driven into a cohesionless soil.

RÉSUMÉ

Cet article étudie les variations de la densité et de la poussée du sol après le compactage par vibration d’une bande à la surface d’un remblai meuble. Des expériences furent réalisées pour étudier les effets d’un vibro-compacteur sur la densification du sol. Basé sur les résultats des essais, la relation entre le tassement de la surface et le nombre de passages du vibro-compacteur pouvait être représentée de manière appropriée par un modèle hyperbolique. Après le compactage, les contours de l’incrément de contrainte verticale Δσ^v étaient semblables à des cercles concentriques après le premier passage du vibro-compacteur et après 8 passages, et le Δσ^{v diminuait} graduellement à partir de la zone centrale de compactage. Les contours de l’incrément de contrainte horizontale Δσ^h formaient deux zones circulaires de contraintes élevées et Δσ^h diminuait graduellement à partir de la zone centrale après le premier compactage. Les contours de Δσ^h étaient semblables à des cercles concentriques après 8 passages du vibro-compacteur. La profondeur de la zone de compaction induite augmentait avec l’accroissement de l’énergie de compactage. Basé sur les résultats des essais, la mécanique des sols du remblai après le premier passage du vibro-compacteur pouvait être simulée à l’aide d’un test de résistance au cisaillement d’une semelle peu profonde. Cependant, après 8 passages du vibro-compacteur, l’interaction entre le compacteur et le sol pouvait alors être simulée par la pénétration d’un pieu carré dans un sol meuble.

Keywords : sand, model test, compaction, settlement, relative density, earth pressure

1 INTRODUCTION

In the construction of highway embankments and earth dams, engineers would compact the loose fill to increase its unit weights. The objective of the compaction operation is to improve the engineering properties of soil such as to increase the bearing capacity or to reduce settlement. Compaction is a particular kind of soil stabilization method and it is one of the oldest methods for improving existing soil or man-placed fills.

To analyze the residual lateral earth pressure induced by soil compaction, several methods of analysis have been proposed by Ingold (1979), Duncan and Seed (1986), Peck and Mesri (1987) and other researchers. However, little information regarding the mechanism of the compacted soil has been reported.

This study simulates the two-dimensional line-compaction with a vibratory compactor on the surface of a loose granular soil in the field. Tests results obtained included the surface settlement, the change of soil density, and the change of stresses in the soil mass due to compaction. Based on the test data, the mechanism of the compacted soil due to the strip compaction on the surface of a sandy soil mass is explored.

2 EXPERIMENTAL APPARATUS

To investigate the effects of vibratory compaction on a cohesionless soil mass, the instrumented non-yielding model retaining wall facility (Chen and Fang, 2002) at National Chiao Tung University (NCTU) was used.

To constitute a plane strain condition for model testing, the soil bin was designed to minimize the lateral deflection of sidewalls and the friction between the backfill and sidewalls.

The soil bin was fabricated of steel plates with inside dimensions of 1500 mm x 1500 mm x 1600 mm as shown in Figure 1. To minimize the friction between the backfill and sidewalls, a lubrication layer consisted of plastic sheets was furnished for all model wall experiments. The lubrication layer proposed by Fang et al. (2004) consisted of one thick and two thin plastic sheets hung vertically on each sidewall of the soil bin before the backfill was deposited.

To investigate the distribution of stresses in the backfill, a series of soil pressure transducers (Kyowa BE-2KCM17, capacity = 98.1 kN/m²) were used. The transducers were buried in the soil mass to measure the variation of vertical and horizontal earth pressure during the filling and compaction process.

Y.S. Fang and Y.L. Chien / Variation of Soil Density and Earth Pressure due to Strip Compaction 701 To simulate the compaction of loose soil in the field, a

vibratory compactor was made by attaching an eccentric motor (Mikasa Sangyo, KJ75-2P) to a 0.225 m × 0.225 m steel plate.

The total mass of the vibratory compactor was 12.1 kg. The amplitude of downward cyclic vertical force (static + dynamic) measured with a load cell placed under the base plate of the vibratory compactor was 1.767 kN. The measured frequency of vibration was 44 Hz. Assuming the distribution of contact pressure between the base plate and soil was uniform, the downward cyclic normal stress σ^cyc applied to the surface of the soil was 34.9 kN/m².

Figure 1. NCTU non-yielding model retaining wall and soil bin.

Air-dry Ottawa sand was used as fill material. To simulate the effects of compaction on the surface of a loose fill, the vibratory compactor was pulled over the compaction lane from the left sidewall to the right sidewall as shown in Figure 2. Then the compactor was turned around 180 degrees to compact the same lane for the second pass. At the end, the fill below the compaction lane had been compacted for eight passes with the compactor. The compaction lane was 0.225 m-wide, 1.5 m-long and each pass took 70 seconds.

Figure 3 shows the surface settlement increased with the increasing number of passes N of the compactor. The surface settlement S shown in Figure 4 was the average settlement of the seven points (point B to H) shown in Figure 3. In Figure 4, the data points obtained from tests 0701 and 0703 indicated that the test results were quite reproducible. Based on the test results, a hyperbolic model was proposed to estimate the surface settlement S as a function of the number of passes of the compactor. The hyperbolic relationship can be expressed as:

(1)

where S is the surface settlement in mm, and N is number of passes of the compactor.

Figure 3. Surface settlement profile of compaction lane.

Figure 4. Hyperbolic model to estimate surface settlements S as a function of number of passes of compactor N.

Figure 5 shows the contours of relative density in soil mass after the first passage of the compactor. Before compaction, the fill has a uniform relative density of 34%. Under the compaction lane, the soil density became quite dense (Dr = 64%), and the soil density decreased gradually with the distance

N

Y.S. Fang and Y.L. Chien / Variation of Soil Density and Earth Pressure due to Strip Compaction 702

center of the concentric circles corresponding to the maximum Δσ^v was located at the depth of 300 mm below the surface. The Δσ^v would decrease gradually from the central high-stress region.

Figure 5. Contours of relative density after 1 – pass of compactor.

Figure 6. Contours of relative density after 8 – passes of compactor.

Before compaction, vertical stress at the depth of 300 mm calculated by σv = γz was 4.68 kN/m². The incremental vertical stress Δσv was 2.2 kN/m² and the incremental stress ratio was 53.0%.

In Figure 6, the relative density of soil changed from the initial value 34%to the maximum value of 72%. At z = 300 mm, the vertical stress increment due to the change of γ (from 15.6 kN/m³ to 16.6 kN/m³) was 0.30 kN/m². The Comparison between 2.2 kN/m² and 0.30 kN/m², indicated that the vertical

In Figure 6, the relative density of soil changed from the initial value 34%to the maximum value of 72%. At z = 300 mm, the vertical stress increment due to the change of γ (from 15.6 kN/m³ to 16.6 kN/m³) was 0.30 kN/m². The Comparison between 2.2 kN/m² and 0.30 kN/m², indicated that the vertical

在文檔中 震動夯實造成之土壤應力及密度變化(II) (頁 42-65)