RRB JE CBT 2 Civil key terms

The maximum pressure a soil mass can safely carry at the base of a foundation without failing in shear or settling excessively. It governs footing size and is calculated from shear strength parameters and depth.

The allowable soil pressure obtained by dividing the ultimate bearing capacity by a factor of safety, also checking that settlement stays within permissible limits. Designers use it to size footings.

Vertical downward movement of a foundation caused by compression of soil under load. It may be immediate (elastic), primary consolidation, or secondary; differential settlement causes cracking and distortion of structures.

Gradual reduction in soil volume due to expulsion of pore water under sustained load, typical of saturated clays. It is time-dependent and is assessed with an oedometer test using void ratio versus pressure curves.

The ratio of the volume of voids to the volume of solids in a soil mass, denoted e. It is a fundamental phase parameter used to compute porosity, unit weight, and compressibility of soils.

The percentage of void space filled with water, expressed as the ratio of water volume to void volume. A value of 100 percent indicates fully saturated soil; zero indicates dry soil.

The water content at which soil changes from plastic to liquid state, determined by the Casagrande apparatus or cone penetrometer. It is an Atterberg limit used to classify fine-grained soils and predict compressibility.

The numerical difference between liquid limit and plastic limit of a soil. It measures the range of water content over which the soil remains plastic and is used in soil classification and swelling prediction.

A field test in which a split-spoon sampler is driven by a 63.5 kg hammer falling 750 mm, and the number of blows for 300 mm penetration (N value) is recorded. N values correlate with density and bearing capacity.

Grouping soils by engineering behaviour, commonly using the Unified Soil Classification System or Indian Standard system based on grain size and Atterberg limits. It guides selection of fill, subgrade, and foundation treatment.

A workability test for fresh concrete in which a standard cone is filled and lifted, and the vertical drop of the concrete is measured. Slump indicates consistency and suitability for placing conditions.

The mass of water divided by the mass of cement in a concrete mix. Lower ratios increase strength and durability but reduce workability; the ratio is the single strongest predictor of concrete strength.

The ratio of the mass of concrete partially compacted by free fall to the mass fully compacted by vibration. It gives a more reliable workability measure than slump for dry, low-workability mixes.

A concrete mix proportioned by fixed volume ratios of cement, fine aggregate, and coarse aggregate, such as 1:2:4. Used for ordinary grades where batching by weight and testing are not specified.

A designation such as M20 or M25 where the number is the characteristic compressive cube strength in N/mm2 at 28 days. It determines structural use and required quality control.

Maintaining adequate moisture and temperature in concrete after placing so cement hydration continues. Proper curing improves strength gain, reduces shrinkage cracking, and increases durability and impermeability.

The distance between supports used in structural analysis and design, taken as clear span plus effective depth or centre-to-centre distance, whichever is smaller. It determines bending moments and shear forces.

The internal moment at a section of a beam equal to the algebraic sum of moments of forces about that section. It produces flexural stresses and governs reinforcement in concrete and steel members.

The internal transverse force at a section of a beam, equal to the algebraic sum of vertical forces on one side of the section. It controls shear reinforcement and diagonal cracking in beams.

A structural design philosophy checking that a structure satisfies both safety (collapse) and serviceability (deflection, cracking) requirements under factored loads. It is the basis of current Indian concrete and steel codes.

A multiplier applied to loads or material strengths in limit state design to account for uncertainty and variability. Load factors exceed one while strength factors are below one, ensuring adequate reliability.

The surveying operation of determining the relative elevations of points, commonly with a level and staff using height of instrument or rise-and-fall methods. It underpins setting out, earthwork, and drainage design.

A fixed reference point of known reduced level from which other elevations are determined in levelling. Permanent bench marks are established by survey departments and used to start and close level runs.

An imaginary line on a map joining points of equal elevation. Contour spacing indicates slope steepness and is used for route alignment, reservoir capacity, and cut-and-fill estimation.

The horizontal angle a survey line makes with a reference meridian, measured clockwise from north in the whole circle system. It fixes direction and is used with distances to compute coordinates.

A precision surveying instrument with a movable telescope for measuring horizontal and vertical angles. Modern versions are optical or electronic and are used for traversing, setting out, and triangulation.

A soil property expressing the velocity of water flow through a unit cross-section under a unit hydraulic gradient, commonly found by constant or falling head tests. It controls seepage, drainage, and stability.

A rapid transition in open-channel flow from supercritical to subcritical state, accompanied by turbulence and energy loss. It is used in stilling basins below spillways to dissipate energy.

A dimensionless ratio of inertial to gravitational forces in open-channel flow, equal to velocity divided by the square root of gravitational acceleration times depth. It classifies flow as subcritical, critical, or supercritical.

An empirical formula for average velocity in open channels, relating velocity to hydraulic radius, channel slope, and a roughness coefficient. It is widely used for designing drains, canals, and sewers.

Biochemical oxygen demand: the oxygen consumed by microorganisms to decompose organic matter in a water sample over a set period, usually five days at 20 degrees Celsius. It indicates organic pollution strength.

Chemical oxygen demand: the oxygen equivalent of organic matter oxidised by a strong chemical agent under acidic conditions. It is measured faster than BOD and includes non-biodegradable organics.

A sequence of physical, biological, and sometimes chemical processes removing suspended solids, organic matter, and nutrients from wastewater. Typical stages are screening, grit removal, sedimentation, activated sludge, and disinfection.

Any substance introduced into the atmosphere in concentrations that harm health, vegetation, or materials. Common examples include particulate matter, sulphur dioxide, nitrogen oxides, carbon monoxide, and ozone.

Fine solid or liquid particles suspended in air, classified by size such as PM10 and PM2.5. Fine fractions penetrate deep into lungs and are linked to respiratory and cardiovascular disease.

A dust-control device that spins particle-laden gas in a vortex so centrifugal force throws particles to the wall for collection. It is efficient for coarser particles but weak for fine dust.

Warming of the earth's surface because certain gases absorb and re-emit outgoing infrared radiation. Carbon dioxide, methane, nitrous oxide, and water vapour are the principal contributors.

Environmental impact assessment: a formal process of predicting the environmental consequences of a proposed project before approval, and proposing mitigation. It typically includes screening, scoping, baseline study, and public consultation.

The relation stating that current through a conductor is directly proportional to potential difference and inversely proportional to resistance, at constant temperature. Expressed as V equals IR.

The intrinsic resistance of a material to current flow, equal to resistance times cross-sectional area divided by length. It identifies conductors, semiconductors, and insulators and varies with temperature.

Two ways of connecting components: in series the same current flows and resistances add, while in parallel the same voltage applies and reciprocal resistances add. Each arrangement gives different current and voltage distribution.

The cosine of the phase angle between voltage and current in an AC circuit, equal to real power divided by apparent power. A low value means poor utilisation of supply capacity.

A static device that transfers electrical energy between circuits by electromagnetic induction, changing voltage and current levels at nearly constant frequency and power. It works only on alternating current.

A logarithmic scale from 0 to 14 measuring hydrogen ion concentration, where 7 is neutral, below 7 acidic, and above 7 basic. It strongly affects chemical reactions, corrosion, and biological treatment.

The concentration of dissolved calcium and magnesium salts in water, expressed as calcium carbonate equivalent. It causes scale formation and reduces soap lather; it may be temporary or permanent.

The deterioration of a metal by chemical or electrochemical reaction with its environment, such as rusting of iron in moist air. It is accelerated by acids, salts, and dissimilar metal contact.

Computer storage directly accessible by the processor, comprising RAM and ROM. It is fast but limited in size and, except for ROM, loses its contents when power is switched off.

Non-volatile storage such as hard disks, solid-state drives, and optical media used to retain data and programs permanently. It is slower than primary memory but far larger and cheaper per unit.

System software that manages hardware, memory, files, and processes and provides a platform for application programs. Examples include Windows, Linux, and Android; it schedules tasks and controls input and output.

Application software organising data in rows and columns of cells that can hold values, text, or formulas. It recalculates results automatically and supports charts, sorting, and basic data analysis.

The supreme law of India, adopted in 1949 and effective 26 January 1950, establishing the framework of government, fundamental rights, and directive principles. It is the longest written national constitution.

A set of basic freedoms guaranteed to citizens under Part III of the Indian Constitution, including equality, speech, religion, and constitutional remedies. They are enforceable through writ petitions in courts.

A three-tier system of local self-government in rural India at village, block, and district levels, given constitutional status by the 73rd Amendment. It handles local planning and development functions.

The permissible variation in a dimension or fit between mating parts, specified as upper and lower limits. It ensures interchangeability in manufacture while controlling cost and functional performance.

The relationship between the sizes of a hole and shaft before assembly, classified as clearance, interference, or transition. It determines whether parts move freely or are held tightly together.

A precision measuring instrument using a calibrated screw and spindle to measure small dimensions, typically to 0.01 mm. It is used for checking shaft diameters, thickness, and wire gauges.

A measuring tool with a main scale and a sliding vernier scale for internal, external, and depth measurements, usually reading to 0.02 mm. It is a versatile instrument for workshop inspection.