Shear Strength of Soils - Concept Map
Shear Strength of Soils
Related concepts
Mohr-Coulomb Failure Criterion
Sub concepts
- Total Stress Analysis (τf = c + σ tan φ)
- Effective Stress Analysis (τf = c' + σ' tan φ')
- Cohesion Component
- Friction Component
- Principal Stress Relationships
Relationship to central
Fundamental theory defining when soil fails
Soil Types and Behavior
Sub concepts
- Sands (c ≈ 0, frictional)
- Clays (c > 0, cohesive)
- Saturated Clay Undrained (φ = 0)
- Granular Soils (always drained)
Relationship to central
Different soils exhibit different shear strength characteristics
Laboratory Testing Methods
Sub concepts
- Direct Shear Test
- Triaxial Compression Test
- Unconfined Compression Test
- Test Interpretation and Parameter Extraction
Relationship to central
Experimental procedures to measure shear strength parameters
Triaxial Test Variants
Sub concepts
- UU (Unconsolidated-Undrained)
- CU (Consolidated-Undrained with pore pressure measurement)
- CD (Consolidated-Drained)
- Pore Pressure Development
- Effective Stress Path
Relationship to central
Different drainage conditions during triaxial testing
Drained vs Undrained Conditions
Sub concepts
- Undrained Analysis (Short-term stability)
- Drained Analysis (Long-term stability)
- Pore Pressure Dissipation
- Loading Rate Effects
- Time-Dependent Consolidation
Relationship to central
Controls time-dependent shear strength behavior
Field Applications
Sub concepts
- Foundation Design (bearing capacity)
- Slope Stability Analysis
- Retaining Wall Design
- Embankment Construction
- Safety Factor Calculation
Relationship to central
Practical use of shear strength in engineering design
Key Formulas and Relationships
Sub concepts
- Mohr-Coulomb equation
- Unconfined strength cu = qu/2
- Principal stress relation
- Friction angle determination
- Deviator stress calculations
Relationship to central
Mathematical expressions for shear strength calculations
Stress States and Failure
Sub concepts
- Normal Effective Stress (σ')
- Shear Stress (τ)
- Mohr Circle Construction
- Failure Plane Orientation
- Maximum Principal Stress
Relationship to central
Understanding normal and shear stress at failure
Concept connections
- Mohr-Coulomb Failure CriterionSoil Types and BehaviorDifferent soil types exhibit different parameters (c and φ) in the same fundamental failure equation
- Laboratory Testing MethodsMohr-Coulomb Failure CriterionTests provide the experimental data needed to determine c and φ parameters for the failure criterion
- Triaxial Test VariantsDrained vs Undrained ConditionsThe choice of triaxial test (UU, CU, CD) directly determines whether drained or undrained conditions are simulated
- Drained vs Undrained ConditionsField ApplicationsDesign approach and timing (short-term vs long-term) depend on whether conditions are drained or undrained
- Key Formulas and RelationshipsMohr-Coulomb Failure CriterionFormulas mathematically express the failure criterion and related calculations
- Stress States and FailureKey Formulas and RelationshipsUnderstanding principal stresses and Mohr circles enables calculation of friction angle and cohesion
- Unconfined Compression TestKey Formulas and RelationshipsUC test uses the specific formula cu = qu/2 derived from Mohr-Coulomb principles
- Direct Shear TestMohr-Coulomb Failure CriterionTest directly plots τf vs σ to extract c and φ following the failure criterion equation
- Triaxial Compression TestMohr-Coulomb Failure CriterionTriaxial test provides principal stresses at failure used in failure criterion analysis
- Soil Types and BehaviorDrained vs Undrained ConditionsSands are always drained; clays behave as undrained under rapid loading and drained long-term
- Field ApplicationsLaboratory Testing MethodsSpecific field applications require appropriate lab tests to obtain valid design parameters
- Stress States and FailureMohr-Coulomb Failure CriterionMohr circle construction visualizes stress states and determines failure orientation using the failure criterion
- CU TestDrained vs Undrained ConditionsCU test bridges undrained and drained analysis by measuring pore pressures during consolidation-undrained shearing
- Principal Stress RelationshipsKey Formulas and Relationshipssin φ = (σ1 - σ3)/(σ1 + σ3) provides direct calculation of friction angle from principal stresses
- Field ApplicationsDrained vs Undrained ConditionsFoundation bearing capacity uses undrained cu for short-term; slopes use drained c' and φ' for long-term
Diagrams
Shear Strength of Soils - Complete Concept Hierarchy
Comprehensive mind map showing the hierarchical organization of all shear strength concepts, from fundamental theory through laboratory testing to field applications. Central concept branches into eight major categories with detailed sub-concepts.
Selecting the Appropriate Triaxial Test Method
Decision flowchart for selecting the appropriate triaxial test variant (UU, CU, or CD) based on project conditions, loading rates, and design timescale. Guides the engineer from problem identification to test selection to design application.
Determining Shear Strength from Laboratory Test Results
Process flowchart detailing how to extract shear strength parameters from each laboratory test type. Shows the calculation pathway from raw test data to design parameters ready for application in foundation and slope stability analysis.
Mohr-Coulomb Failure Criterion Application
Application flowchart for the Mohr-Coulomb failure criterion, showing how to select between total and effective stress formulations and how to apply the appropriate equation based on soil type, saturation, and loading conditions.
Soil Behavior: Drained vs Undrained State Transitions
State diagram showing the transition of soil conditions from rapid loading (undrained) through consolidation to long-term behavior (drained). Illustrates how design parameters and analysis methods change based on time and loading conditions.
Practical Design Flow: From Test Results to Foundation Design
End-to-end design workflow showing how laboratory shear strength test results transition into practical bearing capacity calculations and foundation design following NSCP 2015 guidelines. Includes test selection, parameter extraction, and design safety factors.
Unconfined Compression Test Quick Reference
Quick reference flowchart for the unconfined compression test, one of the most practical field tools for rapid shear strength assessment of cohesive soils. Shows test procedure, cu calculation, and typical design applications.