Geotechnical Engineering and Soil Mechanics Vocabulary

Vocabulary flashcards generated from geotechnical engineering lecture notes, defining fundamental terms, equations, soil classifications, and testing parameters.

Effective Size ($D_{10}$)

The particle diameter corresponding to $10\%$ finer on the cumulative grain-size distribution curve.

Uniformity Coefficient ($C_u$)

A measure of particle size uniformity calculated as $C_u = \frac{D_{60}}{D_{10}}$.

Coefficient of Curvature ($C_c$)

A parameter evaluating the shape of the particle-size distribution curve, calculated as $C_c = \frac{(D_{30})^2}{D_{60} \times D_{10}}$.

Void Ratio ($e$)

The ratio of the volume of voids ($V_v$) to the volume of soil solids ($V_s$).

Porosity ($n$)

The ratio of the volume of voids ($V_v$) to the total volume of soil ($V_t$).

Colluvial Soil

Soil that has been transported from its parent material by gravity.

Glacial Soil

Soil transported and deposited by glaciers.

Marine Soil

Soil deposited or transported in a sea environment.

Lacustrine Soil

Soil deposited in quiet lake conditions.

Alluvial Soil

Soil transported and deposited by streams or rivers.

Aeolian Soil

Soil transported and deposited by wind.

Relative Density ($D_r$)

A parameter quantifying the degree of compactness of granular soil, given by $D_r = \frac{e_{\max} - e}{e_{\max} - e_{\min}} \times 100$.

Critical Hydraulic Gradient ($i_{\text{crit}}$)

The hydraulic gradient at which effective stress becomes zero, expressed as $i_{\text{crit}} = \frac{G_s - 1}{1 + e}$.

Plasticity Index ($PI$)

The range of moisture content over which soil behaves plastically, calculated as $PI = LL - PL$.

Liquidity Index ($LI$)

A soil consistency measure where the relationship with plasticity index is given by $PI \times LI = w - PL$.

Consistency Index ($CI$)

A measure of soil firmness related to moisture content, defined by $PI \times CI = LL - w$.

Compression Index ($C_c$)

An empirical parameter indicating soil compressibility during consolidation, estimated as $C_c = 0.009(LL - 10)$.

SW (USCS Group Symbol)

Unified Soil Classification System designation for well-graded sand.

SP (USCS Group Symbol)

Unified Soil Classification System designation for poorly-graded sand.

SC (USCS Group Symbol)

Unified Soil Classification System designation for clayey sand or clayey soil.

CL (USCS Group Symbol)

Unified Soil Classification System designation for inorganic clay.

Interstitial Velocity ($v_s$)

The actual seepage velocity of water through the soil void spaces, calculated as $v_s = \frac{v}{n}$.

Transmissibility ($T$)

The rate at which water is transmitted through a unit width of an aquifer, defined as $T = k \cdot h$.

Coefficient of Active Earth Pressure ($K_a$)

Rankine's earth pressure coefficient for active soil conditions, given by $K_a = \frac{1 - \sin(\phi)}{1 + \sin(\phi)}$.

Coefficient of Passive Earth Pressure ($K_p$)

Rankine's earth pressure coefficient for passive soil resistance, given by $K_p = \frac{1 + \sin(\phi)}{1 - \sin(\phi)}$.

Cell Stress / Confining Pressure ($\sigma_3$)

The minimum principal stress applied laterally around a soil specimen during a triaxial test.

Deviator Stress ($\Delta P$)

The additional axial stress applied to a soil sample in a triaxial test, equal to the difference between maximum and minimum principal stresses ($\sigma_1 - \sigma_3$).

Unconfined Compressive Strength ($q_u$)

The maximum compressive load per unit area that an unconfined soil specimen can sustain, where cohesion $c = \frac{q_u}{2}$.