HGE/PSAD Terminologies Flashcards (May 2015 – Nov 2019)

A comprehensive set of vocabulary-style flashcards covering surface properties, soil mechanics, structural concepts, signs, road planning, concrete technology, and related codes from the notes.

Surface Tension

Elastic tendency of liquids to minimize surface area, enabling objects denser than water to float or skim on the surface.

Degree of Saturation

Ratio of the volume of water to the volume of voids in a soil mass.

Porosity

Ratio of the volume of voids to the total volume of the soil mass.

Moisture Content

Ratio of the weight of water to the weight of solid particles in soil.

Archimedes’ Principle

Law of buoyancy stating that a body submerged in a fluid experiences an upward buoyant force equal to the weight of the displaced fluid.

Steady Flow

Flow where fluid velocity at a fixed point does not change with time.

Cohesion

Part of shear strength in rock/soil that is independent of interparticle friction.

Liquefaction

Loss of soil strength and stiffness due to earthquake shaking or rapid loading.

Effective Stress

Total stress minus pore water pressure; governs soil strength and deformation.

Gas (in soils)

Gas is not considered a soil solid component.

Sieve Analysis

Procedure to determine particle size distribution (gradation) of granular material.

Gravel (USCS)

Soil grains with sizes greater than 4.75 mm and less than 75 mm.

Boulders

Rock particles too large to pass a 12 inch (200 mm) opening.

Cobble

Particles that pass a 12 inch square opening but are retained on a 3 inch (75 mm) sieve.

Coarse Aggregate

Particles larger than 19 mm and up to 75 mm; passes a 3 inch sieve and is retained on a ¾ inch sieve.

Fine Aggregate

Particles between 4.75 mm (No. 4 sieve) and 19 mm; passes a ¾ inch sieve and retained on No. 4 sieve.

Groundwater Table (GWT)

Depth to groundwater; settlement of footing is affected by GWT, backfill depth, and soil plasticity.

1:2 Slope Limitation

Steepness of fill and cut shall not exceed 1 vertical to 2 horizontal.

Turbulent Flow

Flow with irregular, crossing particle paths forming a complex network.

Hydraulic Gradient

Line joining the points of highest water elevation in vertical open pipes rising from a pipeline.

Water Hammer

Pressure surge when moving fluid is suddenly stopped or its direction is changed.

Soft Cohesive Soil (0–24 kPa UCS)

Cohesive soil with unconfined compressive strength 0–24 kPa is considered soft.

Density Maximum Temperature (4°C)

Fresh water has its maximum density at 4°C.

Pascals’ Principle

Pressure applied to a confined fluid is transmitted undiminished throughout the fluid.

Bernoulli’s Principle

Along a streamline, for steady, frictionless flow, energy is conserved.

Atterberg Limits

Plastic and liquid limits used to classify fine-grained soils; No. 40 sieve (0.425 mm) is involved.

Porosity (revisited)

Ratio of void volume to the total soil volume (alternative wording in notes).

Degree of Saturation (revisited)

Ratio of the volume of water to the volume of voids in soil.

No. 40 Sieve

Sieve used for determining Atterberg limits (passes 0.425 mm sieve).

Cohesionless Soil (2018 characteristics)

Soil that is easy to compact, high shear strength, and prone to vibration-induced settlement.

Standard Penetration Test (SPT) – Medium Dense Sand

Number of blows typically ranging from 10 to 30 in the SPT.

Shear Strength vs Normal Stress

Shear strength of soil increases with increasing normal stress.

Triaxial Shear Test

Three-dimensional shear test that acts on all three principal axes (not on X and Y in some setups).

Deviator Stress

Additional stress that affects shear stress; concept often analyzed in horizontal plane.

Vane Test

A shear strength test that is not typically performed in a standard laboratory.

AASHTO Cobble Classification

Soil larger than 75 mm is classified as cobbles.

Bearing Capacity Coefficients (Nc, Nq, Nγ)

Factors in bearing capacity equations that depend on the friction angle.

Cohesion (Molecular Attraction)

Cohesion arises from molecular attraction between particles.

Metacenter (Stable Equilibrium)

Stable equilibrium occurs when the metacenter is above the center of gravity.

Porosity and Void Ratio (0.5 and 1.0)

If voids equal solids, porosity is 0.5 and void ratio is 1.0.

Angle of Shearing Resistance (φ)

In cohesionless soil, shear strength is proportional to tan(φ).

Vertical Stress from Point Load (Semi-Infinite Mass)

Vertical stress at depth is proportional to the square of depth in an idealized semi-infinite elastic mass.

Floating Body Stability

If metacenter is below the center of gravity, the body is in unstable equilibrium.

Metacentric Height (GM)

Distance between the center of gravity and the metacenter.

Negative Skin Friction

Soil-structure interaction where soft clay reduces pile capacity due to differential settlement.

Specific Weight (Planetary Variation)

Specific weight of a liquid is constant across planets described (no variation noted).

Soil as Structural Material

Soils are considered a structural material or uncemented aggregate in civil engineering.

Specific Weight

Weight per unit volume of a liquid at standard temperature and pressure.

Orthotropic Material

Material with identical composition but direction-dependent mechanical properties.

Homogeneous Material

Material that is the same at all points in the body.

Isotropic Material

Material with stress-strain response independent of orientation.

Elasticity

Tendency of solids to return to their original shape after load is removed.

Yielding

Stress level at which material begins to deform plastically.

Work Hardening

Strengthening of a metal by plastic deformation.

Buckling

Lateral or torsional instability of a member under stresses below yield/ultimate.

Toughness

Ability to absorb energy in the plastic range.

Resilience

Ability to absorb energy in the elastic range.

Ductility

Ability to undergo plastic deformation without fracture.

Center of Rigidity

Point through which the resultant resistance to lateral forces acts.

Shear Wall

The location on a structure where the resultant vertical force acts (per notes).

Eccentricity

Distance between the center of mass and the center of rigidity.

Ground Motion / Ground Displacement

Measured by a seismometer.

Inverse Stiffness

Flexibility of a structural system.

Elastic Limit

Maximum stress that can be applied to an elastic body without permanent deformation.

Torsional (Torsional) Shear Stress

Stress arising when the center of mass and center of rigidity do not coincide.

Soft Storey

A floor significantly less stiff than the floor above (or the average of the floors above).

Storey Drift

Lateral displacement of one level relative to the level above or below.

Reciprocal of Deflection

A measure that indicates the rigidity of a structure (high rigidity = small deflection).

Liquefaction (Revisited)

Described as a sudden drop in shear strength under seismic loading.

k = k1 + k2

Equivalent stiffness when two springs with stiffness k1 and k2 are in parallel.

Center of Mass

Point in a structure through which the applied seismic force acts.

Reciprocal of Stiffness (Revisited)

Flexibility of a structural system (inverse of stiffness).

Traffic Signs

Devices mounted on fixed supports conveying messages to regulate, warn, and guide traffic.

Road Work Signs

Signs warning of temporary hazardous conditions that affect road users or workers.

Special Instructions Signs

Signs instructing road users to follow specific traffic rules or conditions.

Significant Wave

Average height of the highest one-third of waves in a wave train; includes maximum height and wave period.

Seiches

Oscillations caused by strong winds and pressure changes pushing water across a body of water.

Wind Swells

Waves generated by wind blowing near the shore.

Wake Effect

Wind speed decreases and turbulence increases behind moving objects.

Wind Sea

Waves directly generated by local wind.

Caisson

Watertight structure used in underwater construction (e.g., bridges, dams).

Shoring

Temporary support system to provide structural support during excavation or renovation.

Pier

Raised platform extending over water to dock ships.

Guide Sign

Rectangular signs with white lettering on green/blue, providing routes, directions, distances, and points of interest.

Traffic Instruction Sign

Signs that convey traffic rules or directional instructions; typically rectangular.

Seven Ways to Avoid Traffic Conflicts

Separating traffic, traffic signals, roundabouts, grade separations, speed limits, proper signage/markings, education and awareness.

Delay

Difference between actual travel time and an ideal travel time for a segment.

Queue Time

Time a vehicle spends waiting in a queue (e.g., at tolls or in traffic).

Transverse Cracks

Cracks at near-right angles to pavement or centerline due to shrinkage or thermal stress.

Alligator Cracks

Interconnected cracks caused by aging, poor drainage, heavy traffic, or insufficient pavement thickness.

Block Cracks

Rectangular crack pattern due to shrinkage of asphalt concrete.

Longitudinal Cracks

Cracks running parallel to the direction of traffic or centerline.

Safety Sight Distance

Distance required for safe stopping, depending on road environment and visibility.

Safety Distance

Distance dependent on driver eye height and vehicle type.

Screeding

Leveling a layer of concrete using a straight edge.

Trowelling

Smoothing and leveling freshly poured concrete surface.

Floating

Consolidating and smoothing the surface after screeding.

Finishing

Final treatment of concrete surface for appearance and durability.

Age of Tides

Interval between highest tide at a location and a new/full moon can be up to about 2.5 days.

Diurnal Tide

Tide pattern with one high and one low tide every ~24 hours 50 minutes.