CEE42 Exam 1 Review: Soil Mechanics and Geotechnical Engineering

Vocabulary practice cards covering fundamental soil mechanics concepts, phase relationships, weight-volume properties, soil classifications, compaction tests, and stress equations for CEE42 Exam 1.

Liquid Limit ($LL$)

The boundary moisture content representing the transition of soil behavior from a plastic state to a liquid state.

Plastic Limit ($PL$)

The boundary moisture content representing the transition of soil behavior between a semi-solid state and a plastic state.

Plasticity Index ($PI$)

A measure of the plasticity of a soil, calculated as the numerical difference between the liquid limit and plastic limit.

Water Content ($w$)

The ratio of the weight or mass of water to the weight or mass of soil solids: $w = \frac{W_w}{W_s}$ or $w = \frac{M_w}{M_s}$.

Void Ratio ($e$)

The ratio of the volume of voids to the volume of solids: $e = \frac{V_v}{V_s} = \frac{n}{1 - n}$.

Porosity ($n$)

The ratio of the volume of voids to the total soil volume: $n = \frac{V_v}{V_t} = \frac{e}{1 + e}$.

Specific Gravity ($G_s$)

The ratio of unit weight of solid particles to the unit weight of water at $4^\circ\text{C}$: $G_s = \frac{\gamma_s}{\gamma_0}$ (where $\gamma_0 = \gamma_w$ at $4^\circ\text{C}$).

Degree of Saturation ($S$)

The ratio of the volume of water to the volume of voids: $S = \frac{V_w}{V_v}$.

Phase Relationship: $G_s \cdot w$

A fundamental soil mechanics relationship establishing that specific gravity multiplied by water content equals degree of saturation multiplied by void ratio: $G_s \cdot w = S \cdot e$.

Total Unit Weight ($\gamma_t$)

The total weight of a soil mass divided by its total volume: $\gamma_t = \frac{W_t}{V_t}$.

Saturated Unit Weight ($\gamma_{\text{sat}}$)

The total unit weight of a soil mass when its voids are fully filled with water: $\gamma_{\text{sat}} = \frac{W_t}{V_t}$ when $S = 100\%$.

Dry Unit Weight ($\gamma_d$)

The weight of soil solids divided by the total volume of the soil mass: $\gamma_d = \frac{W_s}{V_t}$.

Unit Weight of Solid ($\gamma_s$)

The weight of soil solids divided by the volume of solid particles: $\gamma_s = \frac{W_s}{V_s}$.

Unit Weight of Water ($\gamma_w$)

The weight of water per unit volume: $\gamma_w = \frac{W_w}{V_w} = 62.4\,\text{pcf}$.

Buoyant Unit Weight ($\gamma_b$ or $\gamma'$)

The submerged unit weight of soil, defined as saturated unit weight minus the unit weight of water: $\gamma_b = \gamma' = \gamma_{\text{sat}} - \gamma_w$.

Total Density (‘‘pt’’ / $\rho_t$)

The total mass of soil divided by its total volume: $\rho_t = \frac{M_t}{V_t}$.

Saturated Density (‘‘psat’’ / $\rho_{\text{sat}}$)

The density of soil when degree of saturation is complete: $\rho_{\text{sat}} = \frac{M_t}{V_t}$ when $S = 100\%$.

Dry Density (‘‘pd’’ / $\rho_d$)

The mass of soil solids divided by the total soil volume: $\rho_d = \frac{M_s}{V_t}$.

Density of Solid (‘‘ps’’ / $\rho_s$)

The mass of soil solids divided by the volume of solid particles: $\rho_s = \frac{M_s}{V_s}$.

Density of Water (‘‘pw’’ / $\rho_w$)

The mass of water divided by its volume: $\rho_w = \frac{M_w}{V_w} = 1000\,\text{kg/m}^3$.

G Soil Classification

Gravel classifications consisting of GW (well graded gravel), GP (poorly graded gravel), GM (silty gravel), and GC (clayey gravel).

S Soil Classification

Sand classifications consisting of SW (well-graded sand), SP (poorly graded sand), SM (silty sand), and SC (clayey sand).

C Soil Classification

Clay classifications consisting of CL (lean clay) and CH (fat clay).

M Soil Classification

Silt classifications consisting of ML (silt) and MH (elastic silt).

O Soil Classification

Organic soil classifications consisting of OL (organic silt/clay) and OH (organic clay/silt).

P Soil Classification

Peat soil classification designated as PT (peat).

Standard Penetration Test (SPT)

An in-situ geotechnical test that determines soil bearing capacity and evaluates soil density and consistency.

Darcy's Equation

The hydraulic flow law expressed as $Q = k \cdot i \cdot A = k \left(\frac{\Delta h_t}{L}\right) A$ and $q = \frac{Q}{A} = k \left(\frac{\Delta h_t}{L}\right)$.

Standard Proctor Test (ASTM D698)

A laboratory soil compaction test performed using a $5.5\,\text{lb}$ rammer compacted in $3$ layers.

Modified Proctor Test (ASTM D1557)

A laboratory soil compaction test performed using a $10\,\text{lb}$ rammer compacted in $5$ layers.

Proctor Test Purpose

A laboratory compaction method used to determine a soil's maximum dry density and optimum moisture content.

Specific Surface

The geometric ratio of soil particle surface area to its unit volume ($\text{surface area} / \text{unit volume}$).

Total Stress

The overall stress within a soil mass, calculated as the sum of effective stress and pore water pressure: $\sigma = \sigma' + u$.