Civil Engineering Glossary

A wire mesh cage or basket filled with rocks, stones, or broken concrete used for retaining walls, erosion control, and slope stabilization. Gabions are flexible, permeable structures that allow drainage while providing mass stability.

The designation of concrete based on its characteristic compressive strength (f_ck) at 28 days, expressed in MPa. For example, M20 concrete has a characteristic strength of 20 MPa at 28 days.

The process of injecting a fluid material (grout) — typically a mixture of cement, water, and sometimes fine sand or admixtures — into voids, cracks, or soil to improve strength, reduce permeability, or fill gaps.

The level below which the ground is saturated with water. It fluctuates seasonally and affects foundation design, excavation planning, and soil effective stress calculations.

A horizontal structural beam that supports the rails for overhead travelling cranes in industrial buildings. It is subjected to vertical loads (crane weight + lifted load), lateral loads (crane surge), and horizontal transverse loads (crane braking).

An additional diagonal reinforcement provided at the re-entrant corners (junctions where two members meet at an acute angle, such as beam-column or slab-drop panel junctions) to resist corner pull-out and diagonal tension caused by stress concentration.

A curve in the horizontal alignment of a road, introduced to change the direction of travel. Types include simple circular curves, compound curves, and spiral (transition) curves.

A concrete masonry unit (CMU) with hollow cores, reducing weight and improving thermal insulation compared to solid blocks. Standard sizes in India include 390×190×190mm and 390×100×190mm.

The time interval or spatial distance between two successive vehicles traveling in the same direction on a lane. Measured from the front of one vehicle to the front of the next.

The lowest interior level (bottom) of a pipe, culvert, sewer, or channel at a given point. It is a critical datum for designing drainage gradients and ensuring adequate flow.

A statically determinate structure where all internal forces and reactions can be determined solely from equations of static equilibrium. Number of unknowns equals number of available equilibrium equations.

A joint that completely separates adjacent structural elements (like a slab from a column or wall) to allow independent movement without stress transfer. Typically filled with compressible material (bitumen board, foam).

The process by which water on the ground surface enters the soil. The infiltration rate (mm/hr) depends on soil type, initial moisture content, surface cover, and rainfall intensity.

A shallow arch formed between parallel steel or RCC beams, typically used as a floor or roof construction. The arch is usually of brick or flat terracotta tiles and spans the gap between beams, resting on the bottom flange.

Planned discontinuities in concrete structures to accommodate movement, facilitate construction sequencing, or control cracking.

Natural jute fibres used as secondary reinforcement in soil stabilization, low-cost road construction, and in composite materials. Jute geotextiles reduce erosion and improve sub-grade strength.

The ratio of horizontal active earth pressure to vertical effective stress at a given depth behind a retaining wall. It represents the minimum lateral pressure exerted by soil when the wall yields slightly away from the backfill.

The ratio of horizontal passive earth pressure to vertical effective stress at a given depth when the wall moves into the soil, compressing it. Passive pressure is much larger than active pressure and provides resistance against sliding.

A raised boundary separating the road pavement from the footpath, median, or shoulder. Kerbs prevent vehicles from leaving the carriageway, channel drainage, and provide a visual guide.

A soft white clay mineral composed primarily of kaolinite (Al₂Si₂O₅(OH)₄). Used in ceramics, porcelain, refractories, and as a filler in paper, rubber, and paint industries.

Forces acting horizontally (perpendicular to gravity) on a structure, such as wind load, seismic load, earth pressure, or blast pressure. These loads cause overturning, sliding, and bending in vertical members.

A horizontal beam placed over door and window openings to support the masonry above and transfer the load to the adjacent jambs (sides) without imposing load on the door/window frame.

Variable loads on a structure due to occupancy, furniture, equipment, moving vehicles, or other temporary forces that can change in magnitude and position.

A binding material made by mixing lime (fat lime or hydraulic lime) with sand and water. It sets slowly through carbonation (absorbing CO₂ from the atmosphere) and is more flexible and breathable than cement mortar.

The simultaneous application of different load types with appropriate partial safety factors, as specified by the code to check the structure under various probable scenarios during its design life.

A low-strength concrete (typically M5 to M10) with a low cement content, used as a blinding layer below foundations or as a leveling course. It provides a clean, flat working surface and protects the reinforcement from direct contact with soil.

The water content at which a soil transitions from the plastic state to the liquid state, as determined by the Casagrande apparatus (standard 25 blows to close a 13mm groove).