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Questions and Answers
What are stone columns used for?
What are stone columns used for?
Ground modification and load bearing support
What is Lithomargic clay?
What is Lithomargic clay?
A type of clay used in geotechnical applications
Which of these is a geosynthetic material?
Which of these is a geosynthetic material?
What is the main purpose of geocells?
What is the main purpose of geocells?
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What does the stress concentration ratio (SCR) measure?
What does the stress concentration ratio (SCR) measure?
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Geosynthetic encased stone columns can increase load-bearing capacity.
Geosynthetic encased stone columns can increase load-bearing capacity.
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What is the unit cell concept used for?
What is the unit cell concept used for?
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What is the Mohr-Coulomb model primarily used for?
What is the Mohr-Coulomb model primarily used for?
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What is the lateral deflection of GESC from the axisymmetric analysis?
What is the lateral deflection of GESC from the axisymmetric analysis?
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What does 'UCS' stand for in the context of foundation settlement?
What does 'UCS' stand for in the context of foundation settlement?
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The arrangement of stone columns is always in a square layout.
The arrangement of stone columns is always in a square layout.
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What is the effect of drainage layer thickness on foundation soil settlement?
What is the effect of drainage layer thickness on foundation soil settlement?
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Match the following models with their primary purpose:
Match the following models with their primary purpose:
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What does the term 'improvement factor' indicate?
What does the term 'improvement factor' indicate?
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What is the full title of the research thesis?
What is the full title of the research thesis?
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Who is the author of the thesis?
Who is the author of the thesis?
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What is the register number of the author?
What is the register number of the author?
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Which materials were evaluated for basal reinforcement in the study?
Which materials were evaluated for basal reinforcement in the study?
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A single geogrid encased stone column improved the load-carrying capacity of lithomargic clay by 180%.
A single geogrid encased stone column improved the load-carrying capacity of lithomargic clay by 180%.
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What effect did geogrid encasement have on column bulging?
What effect did geogrid encasement have on column bulging?
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Which software was used for numerical modeling in the research?
Which software was used for numerical modeling in the research?
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What was the percentage reduction in foundation surface settlement with geocell-sand mattresses?
What was the percentage reduction in foundation surface settlement with geocell-sand mattresses?
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Which infill material was considered the best suited in the study?
Which infill material was considered the best suited in the study?
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What does GESC stand for?
What does GESC stand for?
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What was the maximum bulging visible depth in both cases for bulging of stone columns?
What was the maximum bulging visible depth in both cases for bulging of stone columns?
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What are geocells used for?
What are geocells used for?
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Geocells are eco-friendly and have a low strength-to-weight ratio.
Geocells are eco-friendly and have a low strength-to-weight ratio.
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What is a primary benefit of using geocells?
What is a primary benefit of using geocells?
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What did the studies by U.S. Army Engineer Waterways Experiment Station in the late 1970s focus on?
What did the studies by U.S. Army Engineer Waterways Experiment Station in the late 1970s focus on?
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Which materials were found to perform better than conventional base courses according to Webster and Watkins (1977)?
Which materials were found to perform better than conventional base courses according to Webster and Watkins (1977)?
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The proposed system in this research is a Geosynthetic Reinforced _______ System (GRPES).
The proposed system in this research is a Geosynthetic Reinforced _______ System (GRPES).
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What role does the three-dimensional honeycomb structure of geocells play?
What role does the three-dimensional honeycomb structure of geocells play?
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What are stone columns commonly used for?
What are stone columns commonly used for?
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Encasement of stone columns does not provide any additional benefits.
Encasement of stone columns does not provide any additional benefits.
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Which of the following is NOT a method of ground improvement discussed in the document?
Which of the following is NOT a method of ground improvement discussed in the document?
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What is the significance of the three-dimensional confinement provided by geocells?
What is the significance of the three-dimensional confinement provided by geocells?
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What advantage does footing on geocell reinforced soil exhibit compared to unreinforced soil base?
What advantage does footing on geocell reinforced soil exhibit compared to unreinforced soil base?
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Geocells are ineffective for embankment construction over soft soil.
Geocells are ineffective for embankment construction over soft soil.
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Which methods are commonly used for remedial actions on embankment construction over weaker subgrades?
Which methods are commonly used for remedial actions on embankment construction over weaker subgrades?
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What occurs when geocells are used in reinforced railway ballast?
What occurs when geocells are used in reinforced railway ballast?
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Match the following applications with their effectiveness of geocell reinforcement:
Match the following applications with their effectiveness of geocell reinforcement:
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What is the optimum footing diameter ratio relative to geocell cell width according to Rea and Mitchell?
What is the optimum footing diameter ratio relative to geocell cell width according to Rea and Mitchell?
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Geocell height has no effect on its load-bearing capacity.
Geocell height has no effect on its load-bearing capacity.
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What pocket size of geocell is considered optimum according to Dash et al.?
What pocket size of geocell is considered optimum according to Dash et al.?
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Which material properties affect the performance of geocell reinforcement?
Which material properties affect the performance of geocell reinforcement?
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What is the main benefit of using textured geocells over smooth-walled ones?
What is the main benefit of using textured geocells over smooth-walled ones?
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Which of the following are ground modification techniques? (Select all that apply)
Which of the following are ground modification techniques? (Select all that apply)
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Geocells are a planar soil reinforcement system.
Geocells are a planar soil reinforcement system.
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What does ECA stand for?
What does ECA stand for?
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What are the two main components of the term 'geocell'?
What are the two main components of the term 'geocell'?
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The ______ is a vertical column element formed below the ground level with compacted stone fragments.
The ______ is a vertical column element formed below the ground level with compacted stone fragments.
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What is one benefit of using geosynthetic encased stone columns?
What is one benefit of using geosynthetic encased stone columns?
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What does the abbreviation GESC stand for?
What does the abbreviation GESC stand for?
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What is the maximum depth for problematic soil replacement?
What is the maximum depth for problematic soil replacement?
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Which material is commonly used as an admixture for soil modification?
Which material is commonly used as an admixture for soil modification?
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The load-bearing mechanism of the stone column involves lateral ______ of columns into surrounding soil.
The load-bearing mechanism of the stone column involves lateral ______ of columns into surrounding soil.
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What is the advantage of stone columns over conventional piling solutions?
What is the advantage of stone columns over conventional piling solutions?
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Which type of footing does Rea and Mitchell (1978) study?
Which type of footing does Rea and Mitchell (1978) study?
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What is the shape of the opening studied by Mandal and Gupta (1994)?
What is the shape of the opening studied by Mandal and Gupta (1994)?
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What is the width of the rectangular footing according to Mhaiskar and Mandal (1996)?
What is the width of the rectangular footing according to Mhaiskar and Mandal (1996)?
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Which pattern is associated with the strip footings in Dash et al. (2001b)?
Which pattern is associated with the strip footings in Dash et al. (2001b)?
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What is the width of the chevron circular footing studied by Dash et al. (2003)?
What is the width of the chevron circular footing studied by Dash et al. (2003)?
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What type of footing does Latha et al. (2006) research?
What type of footing does Latha et al. (2006) research?
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Sireesh et al. (2009) studied a circular footing.
Sireesh et al. (2009) studied a circular footing.
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The width of the square footing according to Davarifard and Tafreshi (2015) is ______.
The width of the square footing according to Davarifard and Tafreshi (2015) is ______.
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What is the opening shape for the footing discussed by Biswas et al. (2016)?
What is the opening shape for the footing discussed by Biswas et al. (2016)?
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Match the researchers with their corresponding footing types:
Match the researchers with their corresponding footing types:
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Study Notes
Research Overview
- Thesis titled "Performance Evaluation of Encased Stone Column Supported Embankments with Geosynthetic Materials as Basal Reinforcement."
- Submitted by Vibhoosha M.P. for a PhD in Civil Engineering at NIT Karnataka in December 2021.
Declaration and Certification
- Research work confirmed to be original and not submitted elsewhere.
- Supervised by Dr. Sitaram Nayak and Dr. Anjana Bhasi, both from Civil Engineering departments.
Acknowledgments
- Expressed gratitude to advisors, colleagues, family, and the broader academic community for support.
- Acknowledged contributions from faculty members, research committees, and laboratory staff.
Abstract Insights
- Focus on lithomargic clay found in the Konkan belt of India, which faces strength issues when saturated.
- Investigation of the effect of different designs of geogrid encased stone columns on the performance of lithomargic clay, using both experimental and finite element analyses.
Key Findings
-
Load Carrying Capacity:
- Single geogrid encased stone column with a basal geogrid layer increased load capacity by 180%.
- Three geogrid encased stone columns with the same surface area enhanced load capacity by 210%.
-
Column Bulging:
- Geogrid encasement reduced maximum column bulging by 38%.
- Bulging was further reduced by 82% with a basal geogrid layer compared to ordinary stone columns.
-
Geocell Reinforcement:
- Geocells demonstrated superior reinforcement capabilities due to cost-effectiveness and three-dimensional confinement.
- 3D numerical modeling was essential due to the complexity of geocell structures.
-
Performance Improvement:
- Adding a geocell layer improved stress concentration ratio by 47% at the end of consolidation compared to GESC alone.
- Foundation surface settlement reduced by 80% with geocell-sand mattresses.
Stress and Deformation Analysis
- Minimal arching behavior observed in reinforced columnar structures.
- Numerical models indicated overestimation of stress concentration ratio and bearing capacity when using equivalent composite approach.
Settlement and Bulging Reduction
- Vertical settlement reductions of 78% and 79% achieved with single and double basal geogrids, respectively.
- Maximum bulging reduction of 69% in GESC versus ordinary stone columns with a single basal layer; reductions of 52% and 54% for two basal layers and geocell, respectively.
Material Suitability
- Aggregates found to be the most suitable infill for optimal stress concentration ratios and vertical settlements.
- Mobilized tensile stress in geocell was highest for aggregates and lowest for quarry dust.
Proposed System
- Encased stone columns with geocells at the embankment base resemble a Geosynthetic Reinforced Piled Embankment System (GRPES).
- Time-dependent analyses showed that GESC plus one basal layer reduced lateral deformation near the toe by 87% compared to unreinforced structures.
Design Method Comparisons
- Terraza’s method and BS 8006 exhibited closer predictions for stress reduction ratios than other methods for low height embankments.
- Guido et al. (1987) method provided good alignment with full 3D model results for basal geogrid tension, indicating a more reliable design approach.
Overall, the thesis demonstrates significant advancements in understanding and improving the performance of embankments supported by encased stone columns and geosynthetic materials.### Ground Modification Techniques
- Various methods used to enhance the engineering properties of soil.
- Stone column technique is a common method for improving load-bearing capacity.
Stone Columns
- Function by transferring loads from the structure to deeper, more stable soil layers.
- Load-bearing mechanism is crucial for their effectiveness.
Geosynthetic Encased Stone Columns (GESC)
- Innovative design that integrates geosynthetics to enhance the performance of stone columns.
- Provides improved lateral confinement and overall load distribution.
Geocells
- Reinforcement structures made of polymeric materials, creating cellular configurations.
- History of use in geotechnical engineering for increasing load distribution and decreasing settlement.
- Mechanism involves soil confinement, preventing lateral movement and increasing shear strength.
Lithomargic Clay
- A type of clay that plays a significant role in foundation stability.
- Specific behavior under load, which affects the performance of stone columns and geocells.
Finite Element Method (FEM)
- A numerical method for solving complex engineering problems, particularly in continuum mechanics.
- Key advantages include flexibility in modeling complex geometries and loading conditions.
- Disadvantages include high computational costs and the need for expertise in modeling.
Numerical Analysis
- Critical for understanding soil-structure interaction and predicting settlement behavior.
- Case studies and models help validate design approaches and assess performance.
Experimental Studies
- Focus on understanding stress concentration ratios and load settlement behaviors of stone columns.
- Investigate the effects of column configurations on load-bearing capacities and stress distribution.
Parameters Influencing Geocell Performance
- Factors such as stiffness, drainage layer thickness, and material properties influence the effectiveness of geocell reinforcements.
- Improvement factors indicate the enhancement in load capacity achieved with geocells.
Key Concepts
- Stress Concentration Ratio (SCR): A measure of how stress is distributed in the soil and structures, critical for predicting failures.
- Soil Arching: A phenomenon where soil redistributes stresses, enhancing overall stability.
Load Transfer Mechanisms
- Effective load transfer from superficial or soft soils to more competent layers through stone columns and geocells.
Future Research Directions
- Continued exploration into the efficiency of various reinforcement techniques.
- Development of improved models and methods to predict real-world performance under varying conditions.### Overview of Structural Analysis Techniques
- Stone columns arrangement includes unit cell concept and tributary area considerations.
- Mesh discretization is critical for accurate modeling of soils and structures, ensuring precise analysis.
Mohr-Coulomb and Modified Cam Clay Models
- Mohr-Coulomb model utilized to depict stress-strain behavior and yield surfaces in principal stress space.
- Modified Cam Clay model shows yield surfaces in q–p' plane, key for understanding soil mechanics.
Geosynthetic Reinforcement and GESC
- GESC (Geogrid Encased Stone Column) systems enhance stability in embankment constructions.
- Different layout configurations (square and triangular) for stone columns affect load distribution and settlement behavior.
Finite Element Analysis (FEA) Applications
- Various FEA models developed include axisymmetric and 3D representations, aiding in the simulation of complex interactions.
- Use of membrane elements for reinforcement modeling evaluates the performance of geosynthetics in soil stabilization.
Lateral Deflection and Strain Analysis
- Analysis identifies lateral deflections and hoop strain in GESC for different modeling approaches, highlighting structural response under loads.
Soil Properties and Performance Testing
- Properties of lithomargic clay and stone aggregates significantly influence foundation behavior and consolidation.
- Compaction and gradation curves are essential for understanding material performance under structural loads.
Loading Mechanisms and Settlement Response
- Load tests on stone columns reveal detailed pressure-settlement responses, crucial for foundation design validation.
- Improvement Factors (IF) gauge the effectiveness of reinforcement methods across single and group configurations of columns.
Stress Concentration Ratios (SCR)
- SCR variations provide insights into load resilience and structural integrity under various design and layering conditions.
- The geogrid's inclusion significantly alters stress distribution across embankment systems, enhancing support capacity.
Effects of Reinforcement and Configuration
- Different arrangements of reinforcement layers lead to varied structural performance, indicating optimization through design complexity.
- The study explores effects of geogrid stiffness, drainage layer thickness, and modular ratio on settlement and stress responses.
Consolidation and Time-Settlement Analysis
- Time-settlement graphs highlight the relation of consolidation with geosynthetic reinforcement and emergent settlement patterns.
- Variations in excess pore water pressure are monitored to assess drainage effectiveness during and after loading conditions.
Arching Effects in Embankments
- Arching phenomena are analyzed to understand load transfer mechanisms, critical for the design of effective geosynthetic systems.
- The study outlines interactions between lateral bulging and vertical stress distributions under different loading scenarios.
Summary of Analytical Techniques and Findings
- The document provides comprehensive tables summarizing parameters, properties, and results critical to understanding soil reinforcement interactions.
- A full range of graphical representations elucidates complex relationships between design parameters and structural performances.
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Description
Explore the performance evaluation of encased stone columns used in embankments, with a focus on geosynthetic materials as basal reinforcement. This thesis presents findings relevant to civil engineering and offers insights into contemporary practices in terrain stabilization.
