Highway Engineering - Chapters 6 to 10 Study Notes

Vocabulary flashcards covering key definitions, road components, failure modes, equipment, and airport terminology from Chapters 6 to 10 of Diploma Highway Engineering.

Hill Road

A road constructed in hilly or mountainous terrain characterized by steep, uneven, and unstable ground, requiring significant cutting into the hill and valley filling.

Motor Roads (Hill)

Hill roads designed specifically for vehicular traffic (cars, buses, and trucks) built with regulated width, gradient, and curvature.

Bridle Paths

Narrow tracks designed exclusively for horses, mules, and pedestrians on foot, which cannot accommodate motor vehicles.

Ruling Gradient (Hill Roads)

The normal standard design gradient adopted for hill roads, specified as $1\text{ in }20$ ($5\%$).

Limiting Gradient (Hill Roads)

A steeper hill road gradient of $1\text{ in }16.7$ ($6\%$), permitted where providing the ruling gradient results in excessive construction costs.

Exceptional Gradient (Hill Roads)

A steep gradient of $1\text{ in }14.3$ ($7\%$), permitted only for short stretches in extremely difficult topography.

Grade Compensation

The reduction in gradient on a horizontal curve calculated as $\frac{30 + R}{R}\%$, subject to a maximum of $\frac{75}{R}\%$, where $R$ is the radius of the curve in metres.

Retaining Wall

A masonry or concrete structure built on the valley (downhill) side of a hill road to support and prevent the filled earth from sliding down the slope.

Breast Wall

A masonry or concrete wall built on the hill (uphill) side to support the excavated slope face and prevent soil and rock falls onto the road.

Parapet Wall

A low safety barrier constructed along the outer valley edge of the road, commonly painted in alternating black and white bands to guide drivers at night or in fog.

Catch Water Drain

A ditch or scupper constructed uphill above the cut slope, running parallel to the road to intercept slope runoff before it reaches the roadway.

Hairpin Curve

A sharp hill road bend of approximately $180^\circ$ with a minimum radius of about $14\,\text{m}$ and a gradient not exceeding $2.5\%$, utilized to gain altitude in a short distance.

Re-entered Curve

A hill road curve that curves inward into the hill following a natural valley or gully (nala), typically requiring a culvert or bridge at the crossing.

Salient Curve

A hill road curve that bends outward around an existing projecting spur or ridge, requiring widened pavement and horn-sounding boards due to restricted sight distance.

Gabions

Stone-filled wire baskets installed as retaining or protective structures to prevent landslides and soil erosion on slopes.

Camber

The transverse cross slope provided on a road surface to facilitate rapid lateral runoff of rainwater away from the centre.

Side Drain

A longitudinal channel running alongside the road edge to collect surface runoff from the carriageway and adjacent cut slopes.

Interceptor Drain

A sub-surface drain installed on the uphill side of a road cut to capture lateral seepage flow before it penetrates the road formation.

Granular Cut-off Layer

A layer of coarse sand or gravel inserted above the water table whose large pore structure arrests the capillary rise of subsurface water into the subgrade.

Bridge

A cross-drainage structure that conveys a road across an obstacle or river, possessing a linear span exceeding $6\,\text{m}$.

Culvert

A small cross-drainage structure designed to convey water underneath a road, having a total span of up to $6\,\text{m}$.

Causeway

A low-level cross-drainage structure built across a stream bed designed to allow floodwaters to submerge and pass over the roadway during peak flow.

Potholes

Bowl-shaped hollows formed in a flexible pavement surface resulting from moisture ingress, poor mix stability, and repetitive wheel loads.

Corrugation

A flexible pavement defect consisting of transverse wave-like crests and troughs across the road, caused by unstable mix, excess binder, or vehicle braking and starting forces.

Surface Upheaval

The localized upward swelling of pavement layers caused by expansive clay soils, frost action, or trapped moisture below the pavement.

Map (Alligator) Cracks

A network of interconnected cracks resembling alligator hide caused by fatigue failure of the flexible pavement under repetitive heavy wheel loads.

Ruts

Longitudinal depressions formed along the wheel paths of a flexible pavement due to channelized traffic compaction and layer consolidation.

Through Renewal

Periodic flexible pavement maintenance executed every few years involving the application of a complete renewal coat or surface dressing to restore pavement strength.

Scaling

A rigid pavement failure where the surface mortar of the cement concrete slab peels and flakes off in patches due to high water-cement ratio, over-finishing, or de-icing salts.

Mud Pumping

The violent ejection of saturated subgrade soil through joints and cracks in a concrete pavement under the action of heavy moving wheel loads.

Warping Cracks

Cracks developing in rigid pavement slabs caused by curling stresses induced by temperature and moisture gradients between the top and bottom faces.

Blow-ups

The compressive buckling and upward shattering of concrete pavement slabs at expansion joints during hot weather when joints are choked with incompressible debris.

Crawler Tractor

A heavy power unit moving on continuous steel track chains that provides high traction and low ground pressure on soft, muddy, or rough terrain.

Dumper

A heavy-duty, off-road transport truck with a tilting body used exclusively on construction sites and quarries for hauling massive earth or rock loads.

Tipper

A highway-legal transport truck equipped with a hydraulic tipping body designed for high-speed hauling and dumping of bulk materials on public roads.

Scraper

A self-contained earthmoving machine that independently cuts a thin soil layer, loads it into a bowl, hauls, dumps, and spreads the material.

Angle Dozer

A bulldozer configuration whose blade can be set at an angle to the direction of travel to cast excavated material to the side.

Power Shovel

An excavating machine that excavates and loads material situated above the machine's operating track level.

Dragline

A cable-operated excavator equipped with a long lattice boom designed to dig materials situated below its own ground level or under water.

Motor Grader

A machine equipped with a long, adjustable moldboard blade positioned between its axles, used for surface leveling, spreading, ditching, and final profile shaping.

Sheep Foot Roller

A compaction roller equipped with projecting steel feet designed to compact cohesive clay soils from the bottom of the layer upward.

Pneumatic Tyred Roller

A compaction roller equipped with staggered pneumatic rubber tyres that provides a uniform kneading compaction action across soil and bituminous layers.

Road Paver

A specialized paving machine that accepts bituminous mix in a front hopper and spreads, screeds, and partially compacts it to an even thickness.

Aerodrome

A defined area of land or water used for the arrival, departure, and surface movement of aircraft, including all associated infrastructure, buildings, and installations.

Apron

The paved airport zone in front of the terminal building allocated for parking, boarding, baggage loading, fueling, and servicing aircraft.

Runway

A defined paved rectangular strip oriented with the prevailing wind direction, constructed to support the take-off and landing operations of aircraft.

Taxiway

A paved route established for aircraft movement under their own power connecting the runway with aprons, terminals, and hangars.

Hangar

A large enclosed building designed to house, shelter, service, and repair aircraft.

Glider

A lightweight, non-motorized aircraft that sustains flight through aerodynamic lift and ascending air currents.