L4_GEOE 281 2024_Soil Properties
GEOE 281 Physical Properties of Soils
Instructor: Bas Vriens
Semester: Fall 2024
Copyright Notice: Material is solely for use of students registered in GEOE 281; distribution prohibited.
Main Topics: Soil as a system of particles; Stress transmission through soils.
Page 1: Introduction to Soils
Soil Definition: A system of particles that hold and transmit stress.
Context of Study: Understanding physical properties to evaluate soil behavior in engineering.
Page 2: Porous Media
Concept of Porosity: Water and gas exist in pore spaces and fractures.
Porous Media: A common term across various engineering disciplines: Hydrogeology, Petroleum Engineering, Chemical Engineering, Biophysics, etc.
Properties of Porous Media (Phase Diagrams):
Definitions:
VT = total volume of the sample
VS = volume of solids
VV = volume of voids
Porosity and Void Ratio:
Porosity (n): ( n = \frac{V_v}{V_T} )
Void Ratio (e): ( e = \frac{V_v}{V_S} )
Page 3: Water Content Definitions
Water Saturation: ( s = \frac{V_w}{V_v} \times 100% )
Volumetric Water Content: ( \theta = \frac{V_w}{V_T} )
Bulk Density: ( \rho = \frac{M_S + M_w}{V_T} )
Dry Bulk Density: Definition inquiry regarding how it might be calculated.
Page 4: Soil Properties - Porosity
Average Porosity Values:
Sand: 30-50%
Sandstone: 1-5%
Mud: 70-80%
Shale: 5-20%
Chalk: 50%
Limestone: 20%
Noted sedimentary rock porosity decrease: 1.3% per 300 m.
Types of Porosity:
Fracture (e.g., igneous rock)
Matrix (e.g., sand and gravel)
Conduit (e.g., limestone)
Importance for groundwater occurrence.
Page 5: Effective Porosity
Concept of Effective Porosity:
Acknowledgement that even 'dry' rock contains immobile water (hydrated minerals).
Application Context: Soil properties relevant to engineering challenges like Earth Fill Dams.
Transition from microscale dynamics to bulk material properties and their engineering implications.
Page 6: Plasticity of Fine-Grained Soils
Atterberg Limits:
Critical measures: Shrinkage limit (LL), plastic limit (PL), liquid limit (LL).
Shrinkage Limit (LL): Water content threshold for volume change upon drying.
Page 7: Plastic and Liquid Limits
Plastic Limit (PL): Water content for soil to be rolled to 1/8” without crumbling.
Soil behaves like a plastic solid above PL, can crack below.
Liquid Limit (LL): Water content for standard groove closure after specific drops; shows liquid behavior past this point.
Page 8: Use of Atterberg Limits
Influence of water on soil particle interaction; increased water results in liquid-like behavior.
Plasticity Index (PI): ( PI = LL - PL )
Liquidity Index: Sensitivity measure for flow:
( LI = \frac{(w - PL)}{PI} )
Implications for soil's behavior during moisture changes and engineering design considerations.
Page 9: Casagrande Chart and Soil Behavior
Interpretation of Casagrande Chart for silty and clayey soils based on their plasticity characteristics.
Silt (M) and Organic (O) identification on the chart.
Page 10: Soil Strength Properties
Key Terms: Shear strength, uniaxial strength, triaxial strength.
Breakdown of forces affecting strength:
Cohesion and friction are important to understand shear strengths in varying conditions.
Page 11: Coarse-Grained Soils
Relationship between initial density and shear strength increase highlighted.*
Insights from Table 2.7 on soil strength properties with respect to granule size and structure.
Page 12: Soil Deformability
Importance of soil deformability to engineering applications, particularly for stability in construction.
Page 13: Triaxial Testing of Soils
Explanation of triaxial tests measuring soil strength under controlled conditions.
Page 14: Effective Pressure Concepts
Water pressure's effect on effective normal stress discussed.
Context of wet versus dry strength measurements.
Page 15: Fine-Grained Soil Behavior
As moisture content increases, shear strength decreases in fine-grained soils, affecting stability and structure integrity.