Sri Lanka Engineering Service Exam key terms

The maximum pressure a soil or rock mass can safely support beneath a foundation without shear failure or excessive settlement. It is computed from soil shear strength parameters and footing geometry.

The vertical downward movement of a structure's foundation caused by compression of the supporting soil. Total and differential settlement are checked against serviceability limits in design.

The gradual reduction in soil volume under sustained load as water is squeezed out of voids. In saturated clays this process controls long-term settlement of embankments and foundations.

A field test in which a split-spoon sampler is driven into soil by a falling hammer, giving the N-value. The N-value correlates with soil density, strength and bearing capacity.

The moisture content at which a fine-grained soil changes from plastic to liquid behaviour, found by the Casagrande or cone penetrometer test. It is used to classify clays and predict compressibility.

The difference between a soil's liquid limit and plastic limit, expressing the range of moisture content over which it behaves plastically. Higher values indicate more compressible clay.

The ability of a porous material such as soil to transmit water through its interconnected voids. It governs seepage, drainage and the rate of consolidation, and is measured by Darcy's law.

The intergranular stress carried by a soil skeleton, equal to total stress minus pore water pressure. It controls soil strength, compression and shear failure.

A composite material in which steel bars carry tensile forces while concrete resists compression. Bond between the two materials allows them to act together in beams, slabs and columns.

A design philosophy that checks a structure against ultimate limit states such as collapse and serviceability limit states such as deflection and cracking, using factored loads and partial safety factors.

The strength value below which no more than a defined small percentage of test results is expected to fall, such as the 5 percent fractile for concrete cube strength. It is the basis for design strengths.

A multiplier applied to loads or load effects to account for uncertainty and overload in ultimate limit state design. It is paired with a material partial safety factor.

Graphical plots showing how shear force and bending moment vary along a beam under given loads. They identify maximum moment and shear locations needed for reinforcement design.

For a column, the effective length divided by its least radius of gyration; for a wall, effective height divided by thickness. It indicates susceptibility to buckling.

Sudden lateral failure of a slender compression member when the applied load reaches a critical value. Euler's formula predicts the elastic critical load for ideal members.

Concrete in which internal compressive stresses are induced, usually by tensioned high-strength steel, to offset tensile stresses from loads. It permits longer spans and thinner sections.

An automatically operated switch that interrupts a circuit when current exceeds a set value, protecting equipment from overload and short circuit. It can be reset after tripping.

A protective device containing a metal element that melts and opens the circuit when excessive current flows. It is sacrificial and must be replaced after operation.

Connecting exposed metalwork and the neutral point of a supply to the general mass of earth through low-resistance paths. It limits touch voltage and enables protective devices to operate.

An unintended connection between a live conductor and earth, allowing fault current to flow through the earthing system. Protective devices must clear it quickly to prevent shock and fire.

The ratio of real power to apparent power in an AC circuit, equal to the cosine of the phase angle. Low power factor increases current and losses and attracts utility penalties.

An AC supply of three voltages displaced by 120 electrical degrees, delivering constant power and enabling efficient motors and transmission. Sri Lanka's distribution uses 400 V three-phase, 230 V single-phase.

A static device that transfers electrical energy between circuits by electromagnetic induction, changing voltage and current levels with minimal loss. It operates on AC only.

A sequence of processes returning a working fluid to its initial state, used to model engines and power plants. Examples include the Rankine, Otto and Diesel cycles.

The ideal cycle for steam power plants, comprising pump, boiler, turbine and condenser processes. Efficiency depends mainly on boiler pressure and condenser vacuum.

The removal of heat from a low-temperature space and rejection to a higher-temperature sink using a reversed thermodynamic cycle. Performance is expressed by the coefficient of performance.

Stress is internal force per unit area within a material; strain is the resulting fractional deformation. Their relationship in the elastic range is given by Young's modulus.

The ratio of a material's failure strength to the working stress applied in service. It accounts for uncertainty in loads, material properties and analysis.

A tender document listing measured items of work with descriptions and quantities, prepared from drawings. Contractors price each item to form the tender sum.

A formal offer submitted by a contractor to execute specified works at stated rates or a lump sum. Tenders are evaluated against technical and financial criteria before award.

A written instruction issued by the engineer authorising a change to the scope, quantity, quality or timing of contracted works. It adjusts the contract sum and programme.

A scheduling technique that identifies the longest sequence of dependent activities determining project duration. Delays on critical path activities delay project completion.

A bar chart showing activities against a time scale, with start and finish dates and progress. It is simple to read but shows dependencies less clearly than network methods.

A published set of rules governing how construction work is measured and described in bills of quantities, ensuring consistency between designers, quantity surveyors and contractors.

The comparison of two quantities by division and the equation of two ratios. These underpin problems on mixing, scaling, rates of work and sharing in aptitude tests.

A fraction expressed as parts per hundred, used to compare quantities and compute increases, decreases and interest. Converting between fractions, decimals and percentages is a common aptitude skill.

A public service cadre of engineers recruited through a competitive examination for government departments and corporations. It covers civil, electrical and mechanical disciplines.

The constitutional body in Sri Lanka responsible for recruitment, promotion and discipline of public officers. It conducts or oversees competitive examinations for public service posts.

Sri Lanka's apex environmental regulatory body, established under the National Environmental Act. It administers environmental impact assessment and issues environmental protection licences.

A formal study predicting the environmental consequences of a proposed project and proposing mitigation. In Sri Lanka it is required for prescribed projects under the National Environmental Act.