Course Meeting Times
Lectures: 2 sessions / week, 2 hours / session
Course Description
This class presents a detailed study of soil properties with emphasis on interpretation of field and laboratory test data and their use in soft-ground construction engineering. Topics to be covered include: consolidation and secondary compression; basic strength principles; stress-strain strength behavior of clays, emphasizing effects of sample disturbance, anisotropy, and strain rate; strength and compression of granular soils; and engineering properties of compacted soils. Some knowledge of field and laboratory testing is assumed for all students. 1.37 is desirable, and 1.361 is a prerequisite.
Conduct of Subjects
- Classes run as combination of regular lectures and class discussions.
- Reading assignments include class notes and papers.
- Do not consult any prior homework problems or exams.
- Homework problems, class problems, and class discussion count 30%.
- One 2-hour mid-term exam counts 30%.
- One three-hour final exam counts 40%.
Lecture Topics
Introduction (Mostly Review of 1.361)
- Scope of Course
- Soil Composition
- Water Absorption, Clay-water Forces, and Measurement of Soil Suction
- Soil Structure
- Classification Tests and USC System
Basic Strength Principles and Stress-Strain Behavior of Simple Clay; Soil Modeling
- Types of Triaxial Tests and Strength Principles
- Mechanisms of Volume (Pore Pressure) Change in Clays and Sands
- Behavior of Normally Consolidated Simple Clay (Laddite)
- Behavior of Overconsolidated Simple Clay (Laddite)
- Hvorslev Parameters and Extension Tests
- Modified Cam-Clay Model
Consolidation Behavior of Saturated Soils
- Introducation (K0 Trends and Measurement, Role of Oedometer Test)
- Amount of 1-D Settlement (Preconsolidation Mechanisms and Measurement, Disturbance, Creep, etc.)
- Rate of 1-D Consolidation
- Secondary Compression (Cα/Cc, Hypothesis A vs. B)
- 2-D and 3-D Settlement (Initial, Amount and Rate of Consolidation)
- Problem Soils (Sensitive, Organic, Expansive, Collapsing, Varved, etc.)
Stability Problems and Drained Strength Analyses
- Overview (Classes of Probems, Types of Analyses and Corresponding Strength Parameters for UU, CU and CD Cases)
- Effective Stress Parameters for Drained Analyses (Measurement and Problem Soils)
Undrained Strength-Deformation Behavior of Saturated Clays and Undrained Strength Analyses
- Conventional Practice for UU Case (In Situ and Lab Techniques)
- Sample Disturbance
- Stress System (σ2 and Anisotropy)
- Overview of MIT-E3 Model
- Time (Strain Rate and Creep)
- Conclusions and Special Problems
- Staged Construction (CU Case)
Strength-Deformation Behavior of Cohesionless Soils
- Strength Components and Steady-state Line
- Effects of Density, Confinement and σ2 on Drained and Especially Undrained Behavior
- Effects of Sand Structure (Anisotropy, Stress History, Heterogeneity etc.)
- MIT-S1 Model Overview
Compacted Clays
- Compaction Process (Fundamentals)
- Structure and Engineering Properties
- Effective Stress with S < 100%
- Constitutive Modeling
Miscellaneous
- Special Lecture on Precompression, Vertical Drains, and Case Histories
- Mid-term Exam and Discussion of Home Problems
Comparison of Laboratory and In Situ Testing: Complimentary, Not Competing
| LAB (oedometer, triaxial, etc.) | IN SITU (FV, CPTU, DMT, SBPT, etc.) |
|---|---|
|
_Advantages Can control loading and drainage conditions → property variation with stress path and drainage. Known soil type and features. |
Advantages
Testing soil at in situ conditions and usually less affected by disturbance. Usually lower cost, more rapid and some field tests (CPTU) can provide continuous profile. Best suited for spatial variability → mean trends + scatter about mean. |
|
_Limitations
_Sample disturbance - Affects properties (especially cohesionless soils) Discontinuous data on small fraction of soil High cost |
_Limitations
_Ill-defined boundary conditions (stress-strain-drainage) - Need empirical correlations for soil properties May not know soil type |
