Download Đồ án Application of mechanically stabilized earth wall to construct sai gon river wall miễn phí
TABLE OF CONTENTS
Page
ACKNOWLEDGEMENTS i
TABLE OF CONTENTS ii
LIST OF TABLES iv
LIST OF FIGURES v
LIST OF SYMBOLS viii
ABSTRACT xi
CHAPTER 1: INTRODUCTION 1
1.1 AUTHENTICITY OF RESEARCH 1
1.2 OBJECTIVES OF RESEARCH 1
1.3 SCOPES OF RESEARCH WORK 2
1.4 METHODOLOGY 2
1.5 INNOVATION 3
1.6 LIMITATION OF RESEARCH 3
CHAPTER 2: THE GEOGRAPHICAL, SOCIAL AND ECONOMIC CHARACTERISTICS OF HO CHI MINH CITY 6
2.1 NATURAL GEOGRAPHICAL CONDITIONS 6
2.1.1 Geographical Position 6
2.1.2 Topography 8
2.1.3 Climate Characteristics 8
2.1.4 Hydrological Characteristics 9
2.2 SOCIAL AND ECONOMIC CHARACTERISTICS 10
2.2.1 Population 10
2.2.2 Economy 13
2.2.3 Transportation and Traffic 15
2.2.4 Urban Planning 17
CHAPTER 3: GEOGRIDS IN GROUND ENGEERING 18
3.1 OVERVIEW OF GEOGRIDS 18
3.1.1 Uni-Axial Geogrid Properties 18
3.1.2 Bi-Axial Geogrid Properties 20
3.1.3 Tri-Axial Geogrid Properties 25
3.2 APPLICATIONS OF GEOGRIDS 30
3.2.1 Uni-Axial Geogrid Applications in Mechanically Stabilized Earth Walls (MSEW) 30
3.2.2 Uni-Axial Geogrid Applications in Reinforced Soil Slopes 31
3.2.3 Bi-Axial Geogrid Applications in Roads, Railways, Ports, Airports 34
3.2.4 Bi-Axial Geogrid Applications in reinforced sea embankments -river embankments 36
3.3 MECHANICALLY STABILIZED EARTH WALL 39
3.3.1 Historical Development 39
3.3.2 Current Usage of Mechanically Stabilized Earth Walls 41
3.4 THEORETICAL BASIS FOR MECHANICALLY STABILIZED EARTH WALLS 42
3.4.1 Analysis theories 42
3.4.2 Determination of Basic Parameters 43
3.4.3 External Stability Analysis 45
3.4.4 Internal Stability Analysis 52
3.5 Detailed instructions for using MSEW software 57
CHAPTER 4: THE DESIGN SOLUTION FOR MECHANICALLY STABILIZED EARTH WALL AT THANH MY LOI PROJECT. 65
4.1 INTRODUCTION TO THANH MY LOI RESIDENTIAL AREA PROJECT 65
4.1.1 Project Overview 65
4.1.2 Topography 66
4.1.3 Hydrological Characteristics 66
4.1.4 Result of Geotechnical Investigation. 67
4.1 PROPOSED SOLUTION FOR DESIGN 75
4.2.1 The Use of Mechanically Stabilized Earth Wall 75
4.2.2 The Basis of Calculations and Estimations 78
4. 3 OPTION FOR THE BEST SOLUTION 86
4.4 CONSTRUCTION SEQUENCE 89
4.5 THE ERRORS OFTEN OCCUR DURING CONSTRUCTION PROCESS. 93
CHAPTER 5: CONCLUSION AND RECOMMENDATION 96
5.1 Conclusion 96
5.2 Recommendation 96
References
Appendix .
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nce (figure 3.3) depending on Geogrid geometry:
Friction develops at locations where there is a relative shear displacement and corresponding shear stress between soil and reinforcement surface. Reinforcing elements where friction is important should be aligned with the direction of soil reinforcement relative movement.
Figure 3.2 Frictional stress transfer between soil and reinforcement surfaces
Passive resistance occurs through the development of bearing type stresses on "transverse" reinforcement surfaces normal to the direction of soil reinforcement relative movement. Passive resistance is generally considered to be the primary interaction for rigid Geogrid. The transverse ridges on "ribbed" strip reinforcement also provide some passive resistance.
Figure 3.3 Soil passive (bearing) resistance on reinforcement surfaces
3.1.2 Bi-Axial Geogrid Properties
The properties of Bi-Axial Geogrid made from Polypropylene (PP) with their square apertures, high tensile strength and optimized geometry of nodes and ribs make them equal to any other similar material. The reinforcing action of these Geogrids lies mainly in confining soil and increasing its shearing resistance by a process of interlocking between the square ribs and the soil. The load dispersal effect from the interlocking mechanism is highly effective and can reduce sub-base thickness and construction cost. Bi-Axial Geogrid can be used with any kind of mechanical fill material. Two aperture size ranges are available for optimum matching with project fill.
Figure 3.4 Technical shape of Bi-Axial Geogrid
The performance:
Figure 3.5 The interlocking mechanism
The interlocking mechanism means Bi-Axial Georid keeps granular materials inside the mesh. They will create a strong structure, eliminate the phenomenon of the shift of the aggregate particles should be able to prevent the phenomenon of differential settlement and improved foundation bearing capacity.
Load distribution on wide area, reduced the thickness of the layer of pavement structure and construction costs.
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Figure 3.6 The model of interlocking mechanism
(a) (b)
Figure 3.7 The use of Bi-Axial Geogrid generate interlock
Bi-Axial Geogrid can be used with any kind of engineering fill:
Under continuous wheel loading unrestrained stone fill materials can migrate downwards through soft soil sub-bases.
The use of Bi-Axial Geogrid generate interlock that confines the stone fill materials to give a stiff structure and eliminate downward migration.
Figure 3.8 The improved load distribution
The effect on load spread was evaluated and data indicated a mean angle increasing from 380 in the unreinforced case to more 500 with grid. This simple approach indicates that granular layer thickness maybe reduced by around 50% to give a similar stress on the subgrade.
Comparison with Geotextiles
Both woven and non-woven Geotextiles can improve pavement performance by providing a separation function. They can prevent contamination of the granular fill by intermixing with the subgrade soil. The only mechanism which allows Geotextiles to offer a structural contribution to a road pavement or trafficked area is as a tensioned membrane under the wheel paths. For this mechanism to work effectively, the Geotextiles must be anchored outside the wheel path and then deform sufficiently so that it can carry tension.
Figure 3.9 The use of Geotextiles reinforced the pavement
Using Geotextiles improve pavement performance. They can occur following phenomena:
The meshes of the Geotextiles are so small that granular materials can slide on them.
Uncontrolled lateral displacement of these granular materials cause the differential settlement phenomenon.
The ruts can act as invisible sumps, providing a water source to soften the subgrade.
Figure 3.10 Confinement versus membrane effect
Based on these points, the only types of application likely to benefit from the tensioned membrane approach will be roads where fixed wheel paths are followed, and large rut depths are acceptable.
As shown on figure 3.10, the interlock mechanism of Bi-Axial Geogrids is distinctly different to the tensioned membrane. By interlocking with the particles, Bi-Axial Geogrids confine the aggregate layer and prevent lateral displacement. Load is distributed from the wheel to the subgrade within the loaded area. The two materials are not directly interchangeable without design review and amendment.
3.1.3 Tri-Axial Geogrid Properties
With its unique triangular structure, Tri-Axial Geogrid is invented from the original biaxial form of Geogrid. Its multi-directional properties leverage the triangular geometry, one of construction’s most stable shapes, to provide a new level of in-plane stiffness. The transition from a rectangular to a triangular grid aperture, coupled with an increase in rib thickness and junction efficiency, offers the construction industry a better alternative to conventional materials and practices.
Figure 3.11 Technical shape of Tri-Axial Georid
Tri-Axial Geogrid deliver performance in three dimensions
Multi-directional load distribution
Tri-Axial Geogrid has three principal directions of stiffness, they are further enhanced by their rigid triangular geometry. The triangular geometry provides a significantly different structure than other available Geogrid, delivering high radial stiffness throughout the full 360 degrees.
Three-dimensional load distribution acts in a radial manner at all levels within the aggregate. This helps to ensure optimum performance of Geogrid reinforcement in a mechanically stabilized layer.
Figure 3.12 Load distribution acts radially
Triangular aperture geometry
Aggregate particles interlock within the Geogrid and confined within the apertures. These interactions create a stiffened composite layer with improved performance characteristics.
Figure 3.13 The unique structure of Tri-Axial Geogrid provides a high degree of in-plane. stiffness, improving performance
Figure 3.14 Compared with a Bi-Axial Geogrid, Tri-Axial Geogrid has a greater rib depth contributing to improved confinement
Junction integrity and efficiency
Tri-Axial Geogrids’ aperture geometry forms a hexagonal junction shape with better junction strength and stiffness to mitigate radial stress imparted from a trafficked surface.
Figure 3.15 Tri-Axial Geogrid with a hexagonal junction shape
Tri-Axial Geogrid is manufactured from an extruded sheet of polypropylene. During the manufacturing process, each sheet is punched with an array of holes and then carefully stretched to create triangular apertures with greater confinement characteristics. This process yields a Geogrid with very high junction efficiency (ratio of junction strength to ultimate tensile strength) to offer optimal rib-to-rib stress transfer. This index characterizes the need to effectively and uniformly distribute loads for both paved and unpaved applications.
The similarities and differences of Bi-Axial Geogrid and Tri-Axial Geogrid
Similarities
Materials: They made from Polypropylene (PP)
Performance:
The interlocking mechanism.
The reduction of differential settlement and improved foundation bearing capacity.
Applications: Roads, railways, ports, airport runways, paved and un-paved areas.
Table 3.1The differences are between Bi-Axial Geogrid and Tri-Axial Geogrid
Bi-Axial Geogrid
Tri-Axial Geogrid
Geometry
The square aperture geometry.
The triangular aperture geometry.
Directions
Bi-Axial Geogrid offers tensile stiffness primarily in two directions.
Tri-Axial Geogrid has three principal directions of stiffness.
The tensile properties
The conventional Bi-Axial Geogrid in TD (Transverse direction) and MD (Machine direction), with the highest strength typically in TD.
The radial stiffness describes tensile properties measured in the TD and 450 and 1350 off TD
Performance
- The evenly distributed load.
- Reduction of soil layer thickness.
- Greater ability to distribute wheel loads.
- Improved aggregate reduction factor.
- Improved applications performance.
Table 3.2 Advantages and disadvantages of Geogrids
Advantages
Disadvantages
Uni-Axial Geogrid
- High quality durable polymers.
- Consistent manufacturing process.
- Consistent data and information.
- Reliable design parameters.
- If the soft soil thickness is large and degree of consolidation is slow, they still need additional support methods such as sand drain, wick drain…
Bi-Axial Geogrid
- High quality durable polymers.
- The interlocking mechanism between Geogrid and aggregate.
- High angle of load spread through reinforced granular layers.
- Improved pavement performance.
Tri-Axial Geogrid
- Increased in-plane stiffness.
- More efficient material usage.
- Near isotropic (3600) proper...
