- Thrust block
- A concrete mass cast against undisturbed ground behind a bend, tee, cap or valve in a pressurized pipeline. It spreads the push of the water into the soil so joints do not pull apart, and its size depends on pipe diameter, pressure and soil strength.
- Trench shield
- A steel box set in an open trench so crews work inside it. It protects people from a cave-in but does not hold the soil back, unlike shoring, which actually supports the trench walls. Knowing the difference matters for both excavation planning and the safety questions.
- Angle of repose
- The steepest slope at which a loose soil stays put on its own. Sloping an excavation back to a safe angle depends on the soil type, so wet, sandy or previously disturbed ground needs a flatter cut than stiff clay to avoid slumping into the work area.
- Pipe bedding and haunching
- The shaped, compacted material under and alongside a buried pipe. Bedding gives the barrel even support along its length, and haunching fills the sides up to the springline, preventing point loads that could crack or deflect the pipe once the trench is backfilled.
- Invert elevation
- The height of the lowest inside point of a pipe, where the flow runs. Gravity sewer and storm lines are controlled by invert elevations at each manhole, so slope between two inverts, divided by the run, tells you whether the line will actually drain.
- Cut and fill balance
- Planning a site so the soil dug from high areas roughly equals the soil needed to build up low ones. A balanced site avoids paying to import or export dirt, which is why surveys and volume calculations come before the first machine moves.
- Swell and shrinkage factors
- Percentages that describe how soil changes volume. Dug soil occupies more space than it did in the bank, and compacted fill ends up denser than loose material. Applying these factors correctly separates a truck-count estimate from an honest volume of finished fill.
- Relative compaction
- A field density expressed as a percentage of the maximum density a laboratory test finds for that same soil. Specifications call for a minimum percentage, and field density tests on each lift show whether the roller passes and moisture level were adequate.
- Hydrostatic pressure test
- Filling a newly laid pressure pipeline with water, raising it above working pressure and holding it to confirm that joints and fittings do not leak. It is the standard way to prove a water main before it is connected to the live system.
- Jack-and-bore casing
- A trenchless crossing method in which a steel casing is pushed through the ground by hydraulic jacks while an auger removes spoil inside it. It lets a pipe pass beneath a road or railway without cutting the surface open.
- Wellpoint dewatering
- A system of small shallow wells connected to a vacuum header that pumps groundwater away from an excavation. It lowers the water table ahead of the digging so trench bottoms and foundation pits stay firm enough to work and to place pipe or concrete.
- Falsework
- The temporary structure that holds forms and fresh concrete in position until the concrete gains its own strength. It must carry the weight of wet concrete, workers and equipment, so bracing, footing support and removal timing are classic planning concerns.
- Lateral form pressure
- The sideways push fresh concrete exerts on wall forms. It rises with pour rate and head height, which is why tall walls are placed in controlled lifts. Pouring too fast can blow out ties and collapse the form.
- Driven pile
- A column of timber, steel or precast concrete forced into the ground with a hammer to carry building loads through weak upper soil to firmer layers or to develop skin friction. Piles are the alternative to spread footings where surface soils cannot hold the structure.
- Aggregate base course
- A compacted layer of graded crushed rock placed over the prepared subgrade and under asphalt or concrete paving. It spreads wheel loads, drains water away and gives the surface a stable platform, so its thickness and compaction control long-term pavement performance.
- Tack coat
- A thin spray of asphalt emulsion applied to an existing pavement or between asphalt lifts. It acts as glue so the new layer bonds to the one below instead of sliding or peeling under traffic.
- Check dam
- A small barrier of rock, gravel bags or similar material placed across a drainage swale to slow runoff. Slower water drops its sediment and erodes the channel less, so check dams are a common temporary measure on graded sites.
- Temporary traffic control taper
- The angled line of cones or barricades that guides vehicles from a full lane into a closure. Its length depends on lane width and speed, and it is the first element drivers meet when approaching a work zone in a street.
- Benchmark
- A fixed point of known elevation, such as a disk set in concrete, to which all grade readings on a job are tied. Checking back to the benchmark catches instrument errors before they become wrong elevations in pipe, pavement or foundations.
- Dry utilities
- Underground or overhead lines that carry power, telephone, cable and gas rather than water or sewage. Trenches for these lines follow separation and cover rules from the utility owners, and coordinating them with wet utilities is a normal part of site work.
