臺灣博碩士論文加值系統

摘要
本論文以實驗方法探討反復扭轉剪力夯實造成砂質填土土體內相對密度的改變及沉陷量。本研究使用自行設計建造直徑為0.45 m之剪力盤之反復扭剪夯實儀，在土層表面施加靜態垂直應力與反復剪應力。本研究以氣乾之渥太華砂為填土，填入整層高度為1.5 m或5層高度0.3 m之疏鬆砂土。填土初始相對密度為36 %。本研究採用雷射測距儀來量測土體表面沉陷量，採用密度控制盒埋置於試體內部以量測各點土壤相對密度。根據實驗結果，本研究可獲得以下幾項結論。在最初5次的反復扭轉夯實次數 (N = 5)，表面沉陷量明顯地增加。進行反復扭轉剪力夯實20次後 (N = 20)，土壤顆粒排列趨於緊密，土體達到主要地表沉陷量，後續扭剪造成之地表沉陷量趨緩。對5層厚度各0.3 m的土體分別進行反復扭轉剪力夯實後20次後，各層之平均體積應變量為9.77 %、10.53 %、10.37 %、10.05 % 與10.32 %，顯示反復扭轉剪力夯實對各土層造成之體積變化是相對地均勻。而整層的相對密度值都被成功的增加到大於70 %。對5層土層施作分層夯實，改良土體平均相對密度值為76.3 %，標準差為6.2 %。證明此反復扭轉剪力夯實方法成功的將整層土層改良。

Abstract
This paper presents experimental data on the change of volume and relative density in a cohesionless soil mass due to static vertical load and cyclic torsional shearing compaction. A cyclic torsional shearing compactor was with a 0.45 m-diameter circular shearing disc was designed and constructed at National Chiao Tung University. Air-dry Ottawa sand was used as fill material. The initial relative density of the fill was 36 %. The static vertical load and cyclic torsional shearing were applied on the surface of a 1.5 m-thick lift, and then on another specimen with five 0.3 m-thick lifts, with the rotation angles be +5°. Surface settlement of the fill was measured with a laser distance meter. Soil density cups were buried in the cohesionless specimen to monitor the distribution of relative density of with depth soil. Based on the test results, the following conclusions were drawn.
In the first 5 cycles of cyclic torsional shearing application, the surface settlement increased significantly. However, after 20 cycles, the major part of settlement was accomplished, soil particle were sheared and reached a densely-packed condition. As a result, it was difficult to increase the surface settlement any further with more cyclic shear application. For shearing compaction on five 0.3 m-thick lifts, after 20 cycles of torsional shearing with the torsional angle of =±5˚, the average volumetric strain for the lift 1, 2, 3, 4, and 5 was 9.77, 10.53, 10.37, 10.05 and 10.32 %, respectively. It was clear that the cyclic torsional shearing compaction in each lift was relatively uniform. Most of the relative density measured in compacted fill were greater than 70 %. The entire soil body was successfully compacted with cyclic torsional shearing compaction. For five compacted lifts, the mean relative density was 76.3 % with a standard deviation of 6.2 %. It was obvious that the entire soil body was successfully compacted with this ground improvement technique.

Table of Contents
Abstract (in Chinese) i
Abstract ii
Acknowledgements iv
List of Tables viii
List of Figures ix
List of Symbols xvii
Chapter 1 INTRODUCTION 1
1.1 Objectives of Study 1
1.2 Research Outline 2
1.3 Organization of Thesis 2
Chapter 2 Literature Review 3
2.1 Soil Improvement with Densification 3
2.1.1 Densification Techniques 4
2.1.2 Soil Densification with Vibratory Compactor 4
2.2 Cyclic Simple Shear Test 5
2.2.1 Study of Youd 5
2.2.2 Study of Hsu and Vucetic 6
2.3 Cyclic Torsional Simple Shear Test 6
2.3.1 Study of Ishibashi et al. 7
2.4 Densification with Cyclic Torsional Shearing 8
2.4.1 Study of Yang 8
2.4.2 Study of Ren 8
2.4.3 Study of Huang 8
2.4.4 Study of Chen 9
2.4.5 Study of Liu 10
2.5 Requirements of Soil Improvement 11
2.6 Maximum Index Density and Unit Weight of Soils Using a Vibratory Table 12
Chapter 3 Experimental Apparatus 13
3.1 Soil Bin 13
3.2 Cyclic Torsional Shear Compactor 14
3.2.1 Shearing Disc 15
3.2.2 Surcharge Weight 15
3.2.3 Torque Loading Device 19
Chapter 4 Soil Characteristics 21
4.1 Soil Properties 21
4.2 Side-wall Friction 22
4.3 Control of Soil Density 22
4.3.1 Air-Pluviation of Loose Sand 22
4.3.2 Measurement of Soil Density 23
Chapter 5 Testing Procedure 25
5.1 Specimen Preparation 25
5.2 Application of Vertical Static Load 26
5.3 Application of Cyclic Torsional Shearing 26
Chapter 6 Test Results 28
6.1 Static Load Tests on a 1.5 m-thick Lift 28
6.1.1 Volume Change Due to Static Load 29
6.1.2 Relative Density after Static Load 30
6.1.3 Relative Density Increase Ratio 30
6.2 Cyclic Torsional Shear Compaction on a 1.5 m-thick Lift 31
6.2.1 Measurement of Applied Torque 31
6.2.2 Volume Change Due to Cyclic Torsional Shear Compaction 32
6.2.3 Relative Density Distribution after Change Due to Surface Compaction 34
6.2.4 Relative Density Increase Ratio 34
6.3 Compaction on Five 0.30 m-thick Lifts 35
6.3.1 Compaction of Lift One 36
6.3.2 Compaction of Lift Two 36
6.3.3 Compaction of Lift Three 37
6.3.4 Compaction of Lift Four 38
6.3.5 Compaction of Lift Five 38
6.4 Cyclic Torsional Shear Compaction with Different Shearing Angles 39
6.4.1 Applied Torque for Different Shearing Angles 39
6.4.2 Volume Change of Soil with Shearing Angles 40
Chapter 7 CONCLUSIONS 41
References 43
Tables 47
Figures 51

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