Soil Mechanics

Soil Mechanics Lecture

Soil phase relationships describe how solids, water, and air coexist in a given volume of soil and are essential in understanding soil behavior. These relationships are crucial for assessing characteristics like density, porosity, saturation rate, and moisture content, all of which directly impact soil’s engineering performance. By examining the proportions of solids, water, and air, engineers can determine how well the soil can support loads, retain moisture, or drain. Soil that is fully saturated has no air voids, while partially saturated soils contain both air and water within their void spaces. These relationships offer insights into soil’s stability, compressibility, and permeability, which are necessary for effective design in construction and environmental applications.

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Volume of air in the voids
Volume of water in the voids
Volume of soil solids

The weight of the air is negligible
Weight of water
Weight of soil solids

Total Volume
Volume of voids
Total Weight

The water content (moisture) represents the proportion of water weight to solid weight.

The void ratio represents the proportion of void volume to solid volume.

The porosity represents the proportion of void volume to total volume.

The porosity represents the proportion of void volume to total volume.

The saturation rate represents the proportion of water volume to void volume.

The air content represents the proportion of air volume to void volume.

The percentage air voids represents the proportion of air volume to total volume.

The weight of 1 cubic centimeter of water is 1 gram.

The weight of 1 cubic centimeter of air is negligible

The weight of 1 cubic centimeter of the clay is 2.72 grams (in this example):

Specific Gravity or Relative density of soil solids:

Specific Gravity or Relative density of soil solids:

Phase 1: Unit weight of air
Phase 2: Unit weight of water
Phase 3: Unit weight of soil solids
3-Phase Soil: Unit weight

Dry Unit Weight

Moisture Unit Weight

Saturated Unit Weight

Dry unit weight
Moisture (total) unit weight
Saturated unit weight

w.Gs=Sr.e

Dry unit weight & Moisture (total) unit weight Relationship

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✅ GEOtExcel: Soil Mechanics & Foundation Engineering Excel Spreadsheets:
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✅ Soil mechanics: Seepage:Flow Nets: Flow Rate Calculation
✅ Concept-oriented Excel Spreadsheet
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soil_mechanics #soil_mechanics #seepage #foundation_engineering #excel_Spreadsheet #excel #equipotential #flow_net #flow_rate

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☑ Soil mechanics: Darcy’s law (alpha version):
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Hydraulic gradient, velocity and flow rate calculation:
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soilmechanics #soil_mechanics #Darcy_law #foundation_engineering #excel_Spreadsheet #excel #Hydraulic_gradient #flow_rate

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What is the concept of the equipotential lines in seepage?

What do equipotential lines represent in flow net?

✅ GEOtExcel: Soil Mechanics & Foundation Engineering Excel Spreadsheets:
✅ Soil mechanics: Seepage:Flow Nets:
✅ Equipotential lines: Concept
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#soilmechanics #soil_mechanics #seepage #foundation_engineering #excel_Spreadsheet #excel #equipotential #flow_net

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How can we calculate the hydraulic gradient between two points in the soil? How can we calculate the flow rate through soil using Darcy’s law?

✅ GEOtExcel: Soil Mechanics & Foundation Engineering Excel Spreadsheets:
✅ Soil mechanics: Hydraulic gradient:
✅Darcy’s Law: Hydraulic gradient, velocity and flow rate calculation
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📊 Geotechnical Excel Spreadsheets
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Excel Spreadsheet: #soilmechanics #Soil Classification #USCS :

The Unified Soil Classification System (USCS) is a widely-used method for categorizing soils based on their engineering properties. It classifies soils into two main groups: coarse-grained soils, such as gravels and sands, and fine-grained soils, including silts and clays. Within these groups, soils are further classified based on their grain size distribution, plasticity, and compressibility characteristics. This system utilizes a combination of letters and symbols to represent various soil types, such as GW for well-graded gravels, SM for silty sands, and CL for low-plasticity clays. The USCS provides engineers and geologists with a standardized framework for understanding and analyzing soil behavior in construction and geotechnical applications.

The Link on the YouTube Channel:

https://www.youtube.com/watch?v=MRlMFXpHtgw

Excel Spreadsheet: #soilmechanics #Shear Strength #Triaxial CD & CU Tests :

The triaxial shear tests, including the consolidated drained (CD) and consolidated undrained (CU) tests, are essential in geotechnical engineering. They provide valuable data on soil behavior under different loading conditions. The CD test assesses shear strength parameters like cohesion and angle of internal friction, while the CU test helps evaluate undrained shear strength, particularly important for saturated soils. Results from these tests inform foundation design, slope stability analysis, and other geotechnical considerations in construction projects.The triaxial shear tests, including the consolidated drained (CD) and consolidated undrained (CU) tests, are essential in geotechnical engineering. They provide valuable data on soil behavior under different loading conditions. The CD test assesses shear strength parameters like cohesion and angle of internal friction, while the CU test helps evaluate undrained shear strength, particularly important for saturated soils. Results from these tests inform foundation design, slope stability analysis, and other geotechnical considerations in construction projects.

The Link on the YouTube Channel:

https://www.youtube.com/watch?v=5NvPIB1CEzk&t=46s

https://www.youtube.com/watch?v=ABzuZtPJ1-o

Excel Spreadsheet: #soilmechanics #Particle_size #Gradation_curve :

A semi-logarithmic particle size graph is a valuable tool in soil mechanics, allowing engineers and geologists to visualize and analyze the distribution of soil particle sizes. By presenting particle size data on a logarithmic scale for one axis, it effectively compresses a wide range of particle sizes into a manageable space while maintaining a linear scale on the other axis. This graphical representation is instrumental in understanding soil properties, such as permeability, compaction, and drainage characteristics, aiding in the design and analysis of various geotechnical engineering projects.

The Link on the YouTube Channel:

https://youtu.be/b1LrrIB7V0k

Excel Spreadsheet: #soilmechanics #USCS #unified #soil #classification #System :

The Unified Soil Classification System (USCS) is a standardized method for categorizing soils based on their physical and engineering properties. It classifies soils into coarse-grained and fine-grained categories, further subdividing them based on grain size distribution, plasticity, and other characteristics. The USCS utilizes letters and symbols to represent soil properties, facilitating precise identification and characterization of soil types. Widely used in geotechnical engineering, the USCS aids in site investigation, foundation design, and construction planning by providing insights into soil behavior and properties.

The Link on the YouTube Channel:

https://www.youtube.com/watch?v=Z7w0dPFC9us&t=208s

Excel Spreadsheet: #soilmechanics #stress #strip #Boussinesq :

In soil mechanics, the Boussinesq method is a classical analytical technique used to determine stress distribution beneath surface loads on soil. Named after Joseph Boussinesq, it assumes soil behaves as isotropic, homogeneous, and linearly elastic. By representing surface loads as point loads or continuous strip loads, engineers can calculate stresses at various depths below the surface, aiding in analyzing settlement, bearing capacity, and soil stability. While useful for preliminary analysis, the method has limitations in complex or non-linear soil behavior and loading conditions. Nonetheless, it remains valuable in foundation design and soil structure analysis.

The Link on the YouTube Channel:

https://www.youtube.com/watch?v=PC8BQrJpbp8&t=1s