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
Course syllabus.| LAB (oedometer, triaxial, etc.) | IN SITU (FV, CPTU, DMT, SBPT, etc.) |
|---|
Advantages
Well defined boundary conditions → well defined soil properties via interpretation with continuum mechanics.
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)
- Misleading spatial variations.
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 |