Deformation Analysis of Embankment Foundation Soil Supported by DCM (Deep Cement Mixing) Columns and Geotextiles
- Abstract
- Recently, due to a rapid increase in population, traffic volume; various construction activities (such as highways, airports, embankments, industries and others) are taking place in an accelerated rate in low land or low and swampy areas which are composed of highly compressible weak organic soils. These kinds of soils have low shear strength and low permeability creating difficulties in construction over it. Soil improvement and the evaluation of the stability of the structure are very important for the construction work. Ground improvement technique using a preload is often needed to rapidly improve the strength of the soft ground. In the recent years, DCM (Deep Cement Mixing) method has been widely used as an alternative to reduce the lateral displacement of soil as well as improve the soft soil foundation under the embankment. Different patterns of DCM columns (such as block type, wall type, lattice type, and column type) could be installed. But all of them, the column type is the most commonly used for improving the soft foundation under the embankment as well as lateral displacement of soil because of its simplification in installation on land and construction machine. A two-dimensional FEM analysis, which is conventionally used for the practical design applications, has been conducted to evaluate the vertical and lateral displacement of soil under the embankment. In this study, the ‘replacement weighted area’ in plane strain element has been used to simulate the DCM columns effects in analyzed 2-D models from actual configuration are investigated. The results have been compared with the existing rule ‘same area replacement ratio’ in plane strain and beam elements analysis. In this study, ‘replacement weighted area’ in plane strain gives the reasonable values compared to the ‘same area replacement ratio’ rule in the plane strain and beam elements as well as field observation data in the ‘A’ industrial complex project. All of these analysis are performed with PLAXIS computer software. The ‘replacement weighted area’ has been applied to analyze the vertical settlement and lateral displacement of embankment foundation soil in the ‘B’ highway expansion project. The analyses have been performed and the results have been compared with the field measured data. In addition, a parametric study of the stability of geotextile-reinforced soil has been conducted in different layers in the embankment. The effects of tensile stiffness, number and length of reinforcement layers have been investigated. Settlements and lateral displacement have been reduced with increasing in tensile stiffness, number and length of reinforcement but there is a critical value for the number and the length of geotextile. Exceeding this critical value the inclusion of geotextiles has not significant effect on the reduction of settlements and lateral displacement. Finally, according to the results of the analysis, some recommendation would be suggested for reducing the vertical and the lateral displacement of soft soil as well as the stability of the embankment.
- Issued Date
- 2011
- Awarded Date
- 2011. 8
- Type
- Dissertation
- Keyword
- Vertical settlement
- Publisher
- 부경대학교
- Affiliation
- 부경대학교 일반대학원 토목공학과
- Department
- 대학원 토목공학과
- Advisor
- Lee Young Dai
- Table Of Contents
- LIST OF CONTENTS
ABSTRACT i
ACKNOWLEDGEMENT iv
LIST OF CONTENTS vi
LIST OF TABLES x
LIST OF FIGURES xii
LIST OF SYMBOLS xiv
CHAPTER 1
1.0 Introduction
1.1 Background 1
1.2 Objectives of the study 4
1.3 Scope of the study 5
1.4 Methods 5
CHAPTER 2
2.0 Literature Review
2.1 Evaluation of soil settlement 7
2.1.1 Instantaneous settlement or elastic compression 8
2.1.2 Primary consolidation settlement 8
2.1.3 Secondary compression settlement 8
2.2 Soils consolidation theories 9
2.2.1 Vertical consolidation 9
2.2.2 Redial (or horizontal) consolidation 9
2.2.3 Vertical and horizontal consolidations 10
2.3 Horizontal displacement 10
2.3.1 Mechanism of horizontal displacement in soft grounds 11
2.3.2 Lateral displacement measurement with inclinometer 12
2.4 Deep cement mixing (DCM) 13
2.4.1 Conventional deep cement mixing (CDCM) 14
2.4.2 In-situ stabilization with deep cement mixing 15
2.4.3 Deep cement mixing applications 15
2.4.4 Deep cement mixing conclusions 16
2.5 Geosynthetics 16
2.5.1 Classification of geosynthetics 16
2.5.2 Effect of geosynthetics (geotextile) 17
2.5.3 Application of geosynthetics 17
2.6 Back analysis 18
2.6.1 Final settlement prediction by hyperbolic method 19
2.6.2 Tarzaghi’s consolidation settlement equation 20
2.6.3 Underground internal stress (Osterberg, 1957) 20
2.7 PLAXIS computer software 21
2.7.1 Lateral earth pressure at rest 22
2.7.2 Safety analysis 22
2.8 Soil classification 23
2.8.1 Engineering use chart 23
2.9 Soil parameters 24
2.10 Literature of the pre-study 28
CHAPTER 3
3.0 Data collection and analysis
3.1 Data collection 32
3.1.1 ‘A’ industrial complex 32
1) General information of zone-3 33
2) Surface settlement from the settlement gauge plate 37
3) Horizontal displacement measured by inclinometer 37
4) Summary of observation data 38
3.1.2 ‘B’ highway expansion Project 39
1) General information of the project 40
2) Vertical settlement 41
3) Horizontal displacement measured by inclinometer 42
4) Summary of the observation data 42
3.2 Numerical analysis by PLAXIS 43
1) Proposed plane strain element (replacement weighted area) rule 43
2) Plane strain and Beam elements (same as and Ic rule) 44
3.2.1 ‘A’ industrial complex project 45
1) Plane strain (replacement weighted area) rule 45
2) Plane strain element (same area replacement ratio) rule 46
3) Beam element (same area replacement ratio) rule 47
3.2.2 ‘B’ highway expansion project 49
1) Analysis without lateral protection 49
2) Analysis with DCM column as lateral protection 50
3) Analysis of effect of geosynthetics (geotextile) 51
CHAPTER 4
4.0 Result and discussion
4.1 Result 52
4.1.1 ‘A’ industrial complex project 52
4.1.2 ‘B’ highway expansion project 53
4.2 Discussion 56
4.2.1 ‘A’ industrial complex 56
1) Settlement analysis 56
2) Horizontal displacement analysis 58
4.2.2 ‘B’ highway expansion project 60
1) Effect of DCM (Deep Cement Mixing) column 60
2) Effect of using geosynthetics 62
i) Effect of tensile stiffness of geotextile 62
ii) Effect of length of geotextile layer 64
iii) Effect of number of geotextile layer 65
CHAPTER 5
5.0 Conclusions 67
- Degree
- Master
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