RPSC AE Civil key terms

The ratio of applied pressure increase to the resulting fractional decrease in volume of a fluid or solid. It measures resistance to uniform compression and appears in water hammer and pipe-flow calculations.

The negative ratio of lateral strain to longitudinal strain when a material is stretched or compressed axially. For most metals it lies between 0.25 and 0.35; for concrete it is about 0.15 to 0.20.

The slope of the linear portion of a stress-strain curve, expressing how stiff a material is. Concrete uses a secant modulus, while steel uses the initial tangent value of about 200 GPa.

A pressure surge caused by sudden stopping or starting of flow in a pipe, producing a travelling pressure wave. It is estimated with the wave celerity formula and controlled by surge tanks, air valves, or slow valve closure.

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

A dimensionless ratio of inertial to gravitational forces in free-surface flow, equal to velocity divided by the square root of depth times gravitational acceleration. Values above one indicate supercritical flow.

The total head of flowing water per unit weight measured from the channel bed, equal to depth plus velocity head. Its curve versus depth explains alternate depths and the critical flow condition.

An open-channel velocity equation stating that velocity equals the Chezy coefficient times the square root of hydraulic radius times bed slope. The coefficient depends on roughness and is linked to Manning's n.

An empirical coefficient n representing channel boundary resistance in Manning's velocity formula. Typical values run from about 0.012 for smooth concrete to 0.030 or more for natural streams.

The cross-sectional area of a flow section divided by its wetted perimeter. It is a key length parameter in Manning and Chezy equations and is largest for hydraulically efficient sections.

The maximum pressure a soil mass can support at the base of a foundation without shear failure or excessive settlement. It is computed from shear strength parameters and footing geometry using Terzaghi or IS code methods.

A field soil test in which a split spoon sampler is driven 300 mm by a 63.5 kg hammer falling 750 mm, recording blows per 150 mm. The N value is corrected for overburden and used for strength and settlement estimates.

Loss of shear strength in saturated loose sandy soil during earthquake shaking, when pore water pressure rises until effective stress approaches zero. The ground then behaves like a fluid, causing settlement and lateral spreading.

Time-dependent volume reduction of saturated fine-grained soil as water is squeezed out under sustained load. Terzaghi's one-dimensional theory predicts the rate using the coefficient of consolidation and drainage path length.

The intergranular stress carried by the soil skeleton, equal to total stress minus pore water pressure. It governs shear strength, compressibility, and volume change in saturated soils.

Mechanical densification of soil by removing air voids at essentially constant water content, assessed by dry density and moisture content. The Proctor test defines the optimum moisture content for a given compactive effort.

Water content boundaries that separate the solid, semi-solid, plastic, and liquid states of fine-grained soil. The liquid and plastic limits give the plasticity index used to classify clays.

A structural design approach that keeps computed service-load stresses within permissible values using a single factor of safety. It assumes linear elastic material behaviour and is still used for some liquid-retaining and masonry structures.

A design philosophy checking that a structure will not become unfit for use, covering collapse and serviceability states. Partial safety factors are applied separately to loads and material strengths.

The line across a bending section where longitudinal strain and hence bending stress are zero. Its depth is found by equating compressive and tensile force resultants for the section.

Non-uniform distribution of bending stress across wide flanges, with stresses lower away from the web. It matters in box girders and wide-flange beams and is handled through an effective flange width.

Sudden lateral deflection of a slender member under compressive load when it reaches a critical value given by Euler's formula. The critical load depends on end conditions and the slenderness ratio.

A workability test in which fresh concrete in a standard cone is allowed to subside after the mould is lifted. The measured slump in millimetres indicates consistency but is unsuitable for very dry or very wet mixes.

The mass of water divided by the mass of cement in a concrete mix. Lowering it raises strength and durability but reduces workability, so it is balanced with admixtures and grading.

Separation of coarse aggregate from mortar in fresh concrete, often caused by over-vibration, long haulage, or excessive water. It produces honeycombing and weak, non-uniform hardened concrete.

The ability of concrete to resist weathering, chemical attack, abrasion, and reinforcement corrosion over its design life. It is improved by low permeability, adequate cover, and controlled water-cement ratio.

A network scheduling technique that identifies the longest-duration chain of dependent activities, which fixes the project duration. Activities on this path have zero float, so any delay extends completion.

A probabilistic project scheduling method using three time estimates per activity: optimistic, most likely, and pessimistic. The expected time and variance support assessment of the probability of meeting a target date.

The amount of time an activity can be delayed without affecting the project completion or a successor's start. Total float uses the whole network, while free float concerns only the immediate successor.

The process of working out the unit cost of a construction item from material, labour, plant, and overhead components plus contractor profit. It forms the basis of estimates and tender pricing.

An itemised schedule listing measured quantities of work with descriptions, prepared from drawings for tendering. Contractors price each item to form the tender total and later the basis for payment.

A reserve included in an estimate to cover unforeseen items, price escalation, and minor changes during execution. It is usually a percentage of the estimated cost and is not a substitute for detailed design.

A numerical integration method approximating the area under a curve by summing trapeziums between equally spaced ordinates. In surveying it estimates earthwork area or volume from cross-section offsets.

A volume adjustment applied to the end-area method to account for the difference between prismoidal and trapezoidal assumptions. It is computed from the difference of areas of end sections and the mid-section.

The constant vertical distance between successive contour lines on a topographic map. A smaller interval shows finer relief detail but increases survey effort and map clutter.

The horizontal angle a survey line makes with a reference meridian, measured clockwise from north in the whole-circle system. Local attraction in a compass survey is detected by checking fore and back bearings.

The cloudiness of water caused by suspended particles that scatter light, measured in nephelometric turbidity units. It is a key drinking-water quality parameter and affects disinfection efficiency.

Biochemical oxygen demand, the oxygen consumed by microorganisms while decomposing organic matter in a water sample over five days at 20 degrees Celsius. It indicates organic pollution strength and treatment requirement.

Gravity settling of suspended particles in still or slow-moving water, used in primary sewage treatment and water clarification. Design relies on overflow rate and particle settling velocity.