TCM 4434 A - Soils & Foundations: Midterm Review Flashcards

Vocabulary flashcards covering core soil mechanics concepts, phase relationships, classification systems, compaction, in-place density testing, and engineering properties from TCM 4434 A (Sessions 2-9 and 14).

Sand (Particle-Size Range)

Soil particles ranging in size from $0.075\text{ to }4.75\,mm$.

Fines

Soil particles classified as silt and clay.

Sieve Analysis

The standard laboratory method commonly used to determine the grain-size distribution of coarse-grained soils.

Hydrometer Analysis

The laboratory test method used to determine the grain-size distribution of fine-grained soils.

No. 200 Sieve

A standard sieve with an opening size of $0.075\,mm$.

$$D_{10}$$

The characteristic particle diameter on a grain-size distribution curve for which $10\%$ of the soil particles by weight are finer.

Coefficient of Uniformity ($C_u$)

A measure calculated as $C_u = \frac{D_{60}}{D_{10}}$; a value close to 1 indicates that particles are approximately the same size.

Coefficient of Curvature ($C_c$)

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

Three Phases of Soil

The three constituent phases that make up a soil mass: solid, water, and air.

Total Volume of Soil ($V$)

The sum of the volume of soil solids ($V_s$) and the volume of voids ($V_v$), expressed as $V = V_s + V_v$.

Volume of Voids ($V_v$)

The space between solid soil particles composed of air volume ($V_a$) and water volume ($V_w$), expressed as $V_v = V_a + V_w$.

Unit Weight ($\gamma$)

The total weight of a soil mass divided by its total volume, defined by $\gamma = \frac{W}{V}$.

Dry Unit Weight ($\gamma_d$)

The weight of oven-dry soil solids divided by the total soil volume, defined by $\gamma_d = \frac{W_s}{V}$.

Submerged Unit Weight ($\gamma'$)

The effective unit weight of soil beneath water, calculated as saturated unit weight minus the unit weight of water ($\gamma_{sat} - \gamma_w$).

Specific Gravity of Soil Solids ($G_s$)

The ratio of the density (or unit weight) of solid soil particles to the density (or unit weight) of water.

Void Ratio ($e$)

The volumetric ratio of the volume of voids to the volume of soil solids, defined by $e = \frac{V_v}{V_s}$.

Porosity ($n$)

The volumetric ratio of the volume of voids to the total soil volume, defined by $n = \frac{V_v}{V}$.

Fundamental Phase Relationship

The identity equating specific gravity ($G_s$), gravimetric water content ($w$), degree of saturation ($S$), and void ratio ($e$): $G_s \times w = S \times e$.

Atterberg Limits

Critical water contents that define the boundaries separating different consistency states of fine-grained soils.

Consistency States

The sequential behavioral states of fine-grained soil as moisture content increases: Solid $\rightarrow$ Semi-solid $\rightarrow$ Plastic $\rightarrow$ Liquid.

Plastic Limit (PL)

The lowest gravimetric water content at which a fine-grained cohesive soil still exhibits plastic behavior.

Liquid Limit (LL)

The boundary water content above which a fine-grained soil behaves approximately as a viscous liquid.

Shrinkage Limit (SL)

The boundary water content below which further drying or loss of moisture causes no further volume reduction.

Plasticity Index (PI)

The range of water content over which a soil remains in a plastic state, calculated as $PI = LL - PL$.

Unified Soil Classification System (USCS)

A standard soil classification system designated under ASTM D2487 that categorizes soils using sieve analysis and consistency limits.

AASHTO Classification System

A soil classification system standardized under AASHTO M145 that is widely utilized in highway construction and subgrade evaluation.

SC

The USCS group symbol designating clayey sand.

OSHA Type A Soil

Undisturbed cohesive soil possessing an unconfined compressive strength of $1.5\,tsf$ or greater.

OSHA Type C Soil

Cohesive soil possessing an unconfined compressive strength of $0.5\,tsf$ or less.

OSHA Stable Rock

Natural solid mineral material that can be excavated with vertical sides and remain intact while exposed.

Compaction

The mechanical process of densifying soil primarily by expelling air from void spaces, which increases shear strength.

Standard Proctor Compaction Test

A laboratory compaction test designated as ASTM D698 used to establish the moisture-density curve of soil.

Modified Proctor Compaction Test

A laboratory compaction test designated as ASTM D1557 that applies significantly greater compactive effort than the Standard Proctor test.

Compactive Effort Effect

The principle that increasing compaction energy yields a higher maximum dry density and a lower optimum moisture content (OMC).

Relative Compaction ($RC$)

The percentage ratio of field dry unit weight to laboratory maximum dry unit weight: $RC = \frac{\gamma_{d,\text{field}}}{\gamma_{d,\max}} \times 100$.

Sheepsfoot Roller

Field compaction equipment that provides a kneading action, making it particularly effective for fine-grained clayey soils.

Vibratory Roller

Compaction equipment utilizing dynamic vibration, particularly effective for densifying clean sands and gravels.

Sand-Cone Method

A destructive field density test standardized under ASTM D1556 that uses calibrated dry sand to measure the volume of an excavated hole ($V = \frac{W}{\gamma_{\text{sand}}}$).

Nuclear Density Gauge

A non-destructive testing instrument used to rapidly measure in-place soil density and moisture content after compaction.

Constant-Head Permeability Test

A laboratory hydraulic test used to determine the hydraulic conductivity and water movement characteristics of coarse-grained soils.

Soil Strength Properties

The shear parameters of soil represented by cohesion ($c$) and internal friction angle ($\phi$).

Soil Stiffness Properties

The elastic deformation parameters of soil represented by Young's modulus ($E$) and Poisson's ratio ($\nu$).

Consolidation Test

A laboratory testing procedure used to evaluate the compressibility, volume change, and settlement behavior of fine-grained soils under sustained loads.