Important definitions in Road Engineering
A soil Having pH value less than 7.
A soil Having pH value greater than 7.
Stone or gravel mixtures of irregular unscreened sizes which may also contain smaller materials and sand.
The part of construction resting upon, and through which load is transmitted to sub-base, Sub-grade or supporting soil.
Bitumen Emulsion:-
A colloidal suspension of bitumen in water.
Black cotton soil:-
A Black or Brown clay soil in which volume changes due to shrinkage and swelling are particularly marked.
Stone greater than 300 mm in size..
A deposit of unstratified clay or sandy clay of glacial origin containing subangular stones of various sizes scattered irregularly throughout its mass. the stones are not necessarily are of 'boulder' size.
A soil containing clay, silt and sand usually of buff or biscuit colour , homogeneous without any structure and suitable for brickmaking.
The weight of the material (including solid particles and any contained water) per unit volume including voids.
The soil in which stabilization is assisted by addition or Cement, Bitumen-Tar or Chemicals.
A soft limestone consisting principally of the remain of marine animals.
Colloidally fine, complex silicates formed by the decomposition of igneous rocks.
That fraction of soil composed of particles smaller in size than 0.002 mm.
Stone between 80 mm to 300 mm in size.
A Term indicating grading of the material; it is the ratio of sieve size through which 60% of material passes to the sieve size through which 10% passes.
Soil consisting of the finer products of rock weathering. Cohesion is derived from large number of water films associated with the fine grained particles in the soil.
Total force of Attraction between two particle (f) =
$$f={{2 {\pi} rT}\over {1+tan \left({\theta}\over 2 \right) }}$$
where r => Radius of Particle
T => Surface Tension
The process whereby the soil particles are constrained, by Rolling or other means, to pack more closely together , thus increasing the dry density of soil.
The process whereby soil particles are packed more closely together by application of pressure over a period of time.
e.g. Embankment due to its own weight or Soil under Buildings.
Course:-
Prepared material placed to form a continuous layer of the pavement.
Cut-bac Bitumen:-
Bitumen which has been rendered fluid at atmospheric temperature by addition of suitable diluent such as White Spirit, Kerosene or Creosote.
Natural or Artificial means of removal of water from the surface or subsoil of an area, usually by means of Gravitation.
The weight of dry material after drying to a constant temperature at 105oC, contained in unit volume of moist material.
The relationship between dry density and moisture content of a soil when given amount of compaction is applied.
The moisture content at any point in the soil after moisture movement have ceased.
Excavated soil, rock or refuse when dumped for the purpose of filling a depression or rising the site above the natural level of ground.
The surface of ground in its final shape after the completion of earthwork, and Consolidation ,compaction , stabilization in situ etc..
Particle size distribution.
Rounded or Water-Worn stones of irregular shape and size occurring in natural deposits with or without some finer materials.
That fraction of soil composed of particles between 4.75 mm and 80 mm in size .
The water which moves downwards under the action of gravity from soil surface to water table.
The water contained in the soil below the water table.
A Horizon of accumulation that has been thoroughly cemented to an indurated, rock like layer that will not soften when wet.
Held water:-
The water retained in the soil structure above the water table by surface tension and adsorption forces.
Hoggin:-
A deposit of sand and gravel as occurring in nature and containing a proportion of clay which is sufficient to hold the mass together.
Tropical soil in which weathering process have resulted in accumulation of sesquioxides, particularly iron.
The process by which the soluble material in soil is removed by percolation of water.
The moisture content at which the soil passes from the plastic to liquid state as determined by the liquid limit test.
The difference between natural moisture content and plastic limit expressed as percentage ratio of the plasticity index.
$$LI={{m-PL}\over {LL-PL}}\times 100$$
m => moisture content
Soil consisting of natural mixture of Calcareous clay and Calcareous silt clay.
Dry density of soil obtained by specific amount of compaction at optimum moisture content.
Soil to which imported soil or aggregates has been added to obtain desired particle size distribution and which has been compacted to a desired density.
Approximate modulus of elasticity determined from the slope of the straight line extending from origin to a given strain on a stress/strain curve.
The slope of straight line extending from the origin to a given deformation on a stress/deformation curve obtained from field bearing tests.
The loss in weight, expressed as percentage of dry material when soil is dried at constant temperature at 105oC .
Soil consisting of courser products of rock weathering in which cohesive bonds associated with smaller fractions are largely absent.
The moisture content at which specified amount of compaction will produce maximum dry density.
Particle size distribution (grading) :-
The percentage of various grain sizes present in soil as determined by sieving , sedimentation , elutriation or by other means .
Pavement:-
The whole of the artificial construction made above the surface to support the traffic.
P.C.U:-
Passenger Car Unit, its conversion factor of vehicle type to convert it into standard vehicle.
| Vehicle Type | Unit weight in Tonnes | P.C.U. Value |
|---|---|---|
| Cars, Jeeps, Vans | 1.75 | 1 |
| Buses Loaded | 9 | 3 |
| Buses empty | 5 | 3 |
| Trucks Loaded | 11 | 3 |
| Trucks empty | 5 | 3 |
| Motor cycle, scooters | 0.5 | 0.5 |
| Animal Drawn vehicles | 1.0 | 8 |
| Cycle,3 wheelers | 0.0 | 0.5 |
| 3 wheelers, Rickshaws | 0.5 | 1 |
Flexible Pavement:-
A Pavement of inconsiderable flexural rigidity or tensile strength.
A pavement having considerable Local Flexural rigidity by reason of 'Tensile' strength of one or more pavement courses.
Dark, Fibrous, Spongy soil of vegetable origin.
The pF value of held water in soil is equivalent to the common logarithm of the suction expressed in centimeters of water.
The pH of a soil is negative logarithm of Hydrogen-ion concentration in an aqueous suspension of soil .
Large stones usually 200 to 300 mm in depth, when placed by hand and compacted by rolling to form a stable base coat, with small stones or other materials to fill the interstices.
The moisture content at which the soil ceases to be in Plastic condition as determined by Plastic Limit test.
The numerical difference between liquid limit and plastic limit of a soil.
$$\text{Plasticity Index}={\text{Liquid Limit }-\text{ Plastic Limit}} $$
The pressure of water in the voids of saturated soil.
The ratio of volume of voids to the total volume of materials including voids.
The percentage of dry density of soil in situ to the maximum dry density of soil as determined by the Standard compaction tests.
Small mineral particles from natural sources, free from appreciable amount of clay and silt ranging from 0.075 to 4.75 mm.
Saturated Soil:-
A soil in which voids are entirely filled with water.
Settlement:-
Downward movement of a soil or of structure which it supports , resulting in reduction in the voids in underlying strata.
Mineral particles naturally deposited as sediment in water and having size ranging between 0.002 mm to 0.075 mm.
The reduced pressure (Below atmospheric pressure) imparted to held water by forces retaining the water above the ground table.
The vertical section showing the soil strata at a given site.
The soil treated in such a manner as to render its properties less affected by water or to increase its load bearing capacity.
A layer of material placed between foundation and formation for specific purposes such as a Porous layer or further to support the construction.
The Natural foundation or the fill which directly receives the loads from the pavements.
The course or the courses laid above the base in the form of continuous layer or layers to provide wearing surface to protect the base or to add the strength to the pavement.
Soils containing thin alternate layers of different particle sizes, formed from seasonal deposits of glacial streams.
The ratio of volume of voids to the volume of Solids in a material.
Horizon at which Pore Water Pressure is at Atmospheric Pressure.
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