Geotechnical Engineering

Fundamentals of Soil Behavior and Properties

Basic Soil Characteristics

• Master the definition and application of fundamental soil properties, including phase relationships: understanding solid particles, water, and air volumes and weights.
• Calculate and interpret key parameters such as void ratio, porosity, water content, specific gravity, unit weight (dry, saturated, moist, buoyant), and degree of saturation for various soil conditions.
• Apply these basic properties to assess the density and composition of different soil types, forming the basis for advanced geotechnical analysis.

Soil Formation and Classification Systems

• Understand the geological processes that lead to different soil types, including residual and transported soils, and their engineering implications.
• Perform grain size analysis using both sieve analysis for coarse-grained soils and hydrometer analysis for fine-grained soils to determine particle size distribution curves.
• Interpret grain size distribution curves to classify soils and predict their engineering behavior.
• Conduct Atterberg Limits tests (Liquid Limit, Plastic Limit, Shrinkage Limit) to characterize the plasticity and consistency of fine-grained soils.
• Calculate and apply the Plasticity Index and Liquidity Index to understand soil consistency and state.
• Classify soils accurately using the Unified Soil Classification System (USCS) and the AASHTO Soil Classification System, mastering the criteria and practical application for engineering design.

Soil Compaction and Improvement

Principles of Soil Compaction

• Understand the purpose and benefits of soil compaction in improving engineering properties, such as increasing shear strength and reducing compressibility and permeability.
• Conduct standard and modified Proctor compaction tests to determine the optimum moisture content and maximum dry density for a given soil.
• Interpret Proctor test results to establish compaction specifications for construction projects.

Field Compaction Control

• Master methods for controlling and verifying compaction in the field, including the sand cone method, rubber balloon method, and nuclear densometer.
• Calculate relative compaction and assess compliance with design specifications.
• Understand the effects of various compaction efforts and equipment on different soil types.

Ground Improvement Techniques

• Gain knowledge of various ground improvement methods to enhance soil properties for construction.
• Understand techniques like dynamic compaction, vibro-compaction, stone columns, preloading with vertical drains, and soil stabilization with admixtures (cement, lime, fly ash).
• Evaluate the suitability of different improvement methods based on soil conditions and project requirements.

Water Flow in Soils: Permeability and Seepage

Darcy's Law and Permeability

• Master Darcy's Law for describing laminar flow through porous media, understanding its assumptions and limitations.
• Determine the coefficient of permeability (hydraulic conductivity) through laboratory tests (constant head and falling head permeameters) and field tests (pump tests).
• Understand factors influencing permeability, such as void ratio, particle size, and soil structure.

Seepage Analysis and Flow Nets

• Construct and interpret flow nets for various boundary conditions, including dams, retaining walls, and excavations.
• Use flow nets to calculate seepage quantity, pore water pressure distribution, and uplift pressures.
• Apply flow net principles to analyze the stability of hydraulic structures and prevent piping failures.

Filter Design

• Learn the principles of granular filter design to prevent soil erosion and maintain drainage under hydraulic structures.
• Design filters based on particle size distribution criteria to ensure stability and functionality.

Effective Stress Principle and Consolidation

Concept of Effective Stress

• Master the concept of total stress, pore water pressure, and effective stress in saturated and unsaturated soils.
• Calculate effective stresses under various conditions, including hydrostatic pressure, artesian conditions, and fluctuating water tables.
• Understand the critical role of effective stress in controlling soil strength and deformation.
• Analyze the effects of capillary action on effective stress in partially saturated soils.

Soil Compressibility and Settlement

• Differentiate between immediate (elastic), primary consolidation, and secondary compression settlements.
• Understand the mechanics of one-dimensional consolidation using Terzaghi's theory.
• Conduct and interpret results from the one-dimensional consolidation (oedometer) test to determine consolidation parameters.
• Determine the coefficient of compressibility (a_v), coefficient of volume change (m_v), and compression index (C_c) and recompression index (C_r).
• Calculate the pre-consolidation pressure (P_c') and understand its significance in soil stress history.
• Compute primary consolidation settlement for normally consolidated and overconsolidated clays.
• Analyze the time rate of consolidation using the coefficient of consolidation (c_v) and time factors.
• Predict the degree of consolidation at specific times and estimate the time required for a certain percentage of consolidation.

Shear Strength of Soils

Mohr-Coulomb Failure Criterion

• Master the Mohr-Coulomb failure criterion for both cohesive and cohesionless soils, defining shear strength parameters (cohesion 'c' and angle of internal friction 'φ').
• Understand the relationship between effective stress and shear strength.

Laboratory Shear Strength Testing

• Conduct and interpret results from direct shear tests to determine peak and residual shear strength parameters for sands and clays.
• Perform unconfined compression tests to determine the undrained shear strength (c_u) of cohesive soils.
• Execute and analyze results from triaxial compression tests (Unconsolidated-Undrained (UU), Consolidated-Undrained (CU), and Consolidated-Drained (CD)) to determine effective and total shear strength parameters for various soil types and stress conditions.

In-Situ Shear Strength Testing

• Understand and interpret results from common field tests for estimating shear strength parameters, including the Standard Penetration Test (SPT), Cone Penetration Test (CPT), and Vane Shear Test (VST).
• Correlate in-situ test results with laboratory parameters for practical design applications.

Lateral Earth Pressure

Theories of Lateral Earth Pressure

• Understand the concepts of at-rest, active, and passive earth pressures.
• Apply Rankine's theory to calculate active and passive earth pressures for cohesionless and cohesive soils with horizontal and inclined backfills.
• Apply Coulomb's theory to calculate active and passive earth pressures for retaining walls with wall friction and inclined backfills.
• Analyze the effects of surcharge loads, groundwater table, and layered soils on lateral earth pressures.

Retaining Wall Design Considerations

• Understand the stability requirements for retaining walls against overturning, sliding, and bearing capacity failure.
• Calculate forces acting on gravity walls, cantilever walls, and counterfort walls.
• Apply lateral earth pressure theories to design stable and safe retaining structures.

Slope Stability Analysis

Mechanisms of Slope Failure

• Identify common types of slope failures, including translational, rotational, and wedge failures.
• Understand the factors contributing to slope instability, such as soil properties, pore water pressure, and external loads.

Analysis of Infinite Slopes

• Analyze the stability of infinite slopes for dry, submerged, and saturated conditions with seepage parallel to the slope.
• Calculate the factor of safety for infinite slopes based on soil properties and geometry.

Analysis of Finite Slopes (Method of Slices)

• Apply the method of slices for analyzing the stability of finite slopes, including Bishop's simplified method and the Fellenius method.
• Locate the critical slip surface and calculate the factor of safety for rotational failures in cohesive and cohesionless soils.
• Understand the iterative nature of slope stability calculations and the use of stability charts.

Shallow Foundations

Bearing Capacity Theories

• Master Terzaghi's bearing capacity theory and its extensions (Meyerhof, Hansen, Vesic) for continuous, square, and circular footings.
• Calculate ultimate bearing capacity for various soil conditions, considering the effects of groundwater, foundation depth, and shape factors.
• Determine allowable bearing capacity by applying appropriate factors of safety.

Settlement of Shallow Foundations

• Calculate immediate (elastic) settlement for footings on granular soils and clays using elastic theory.
• Estimate consolidation settlement for footings on cohesive soils using consolidation theory.
• Understand the concept of differential settlement and its implications for structural integrity.

Design of Shallow Foundations

• Design isolated footings, strip footings, and mat foundations based on bearing capacity and settlement criteria.
• Consider practical design aspects such as embedment depth, eccentric loading, and influence of adjacent foundations.

Deep Foundations

Types and Load Transfer Mechanisms

• Understand various types of deep foundations, including piles (driven, cast-in-place), caissons, and drilled shafts.
• Analyze the load transfer mechanisms in deep foundations, differentiating between skin friction (shaft resistance) and end bearing (tip resistance).

Bearing Capacity of Single Piles

• Calculate the ultimate bearing capacity of single piles in cohesive and cohesionless soils using static analysis methods (e.g., Alpha, Beta, Lambda methods).
• Understand and apply dynamic pile formulas (e.g., Engineering News Formula, Hiley Formula) for driven piles.
• Interpret results from pile load tests to verify design assumptions.

Pile Group Behavior

• Analyze the bearing capacity and settlement of pile groups, considering group efficiency and block failure.
• Calculate negative skin friction and its impact on pile design.
• Understand the interaction between piles and soil in a group configuration.

Site Investigation and Geotechnical Reporting

Planning and Execution of Site Investigations

• Develop comprehensive site investigation plans tailored to project requirements, considering geological conditions and proposed structures.
• Understand various drilling and boring methods (e.g., auger drilling, wash boring, rotary drilling).
• Master techniques for collecting disturbed and undisturbed soil samples, ensuring sample quality and integrity.

In-Situ Testing Techniques

• Interpret data from Standard Penetration Test (SPT), Cone Penetration Test (CPT), Vane Shear Test (VST), Pressuremeter Test (PMT), and Dilatometer Test (DMT).
• Correlate in-situ test results with soil engineering properties for design purposes.

Geotechnical Report Preparation

• Prepare detailed and professional geotechnical reports, summarizing site conditions, laboratory and in-situ test results, engineering analyses, and design recommendations for foundations, earthworks, and ground improvement.
• Effectively communicate geotechnical findings and recommendations to other engineering disciplines and stakeholders.