Your FREE PE Civil Flashcards 2026 – 200+ Cards

A model splitting a soil sample into solids, water, and air. It is the basis for weight–volume relationships: void ratio, porosity, water content, and unit weight.

Void ratio e = volume of voids ÷ volume of solids (Vv/Vs). Porosity n = Vv ÷ total volume. They relate by n = e/(1+e).

Water content w = weight of water ÷ weight of solids (Ww/Ws), expressed as a percent. Found in the lab by oven-drying a sample.

S = volume of water ÷ volume of voids (Vw/Vv). S = 0% is fully dry, S = 100% is fully saturated.

A core phase identity: degree of saturation × void ratio = water content × specific gravity of solids. It links the four basic phase quantities.

Total stress σ = overburden weight per area. Effective stress σ' = σ − u, where u is pore water pressure. Effective stress controls strength and settlement (Terzaghi's principle).

The water contents at boundaries of fine-grained soil behavior: liquid limit (LL), plastic limit (PL), shrinkage limit. Plasticity index PI = LL − PL.

Classifies soils by grain size and plasticity into groups (e.g., GW, SP, CL, MH). Coarse soils use gradation (Cu, Cc); fine soils use the plasticity chart (A-line).

Shear strength τ = c + σ'·tan(φ), where c = cohesion, φ = angle of internal friction, σ' = effective normal stress. Sands are c ≈ 0; clays develop cohesion.

Lateral pressure when a wall moves away from soil. Coefficient Ka = tan²(45° − φ/2). Active pressure < at-rest < passive.

Lateral pressure when the wall does not move. For normally consolidated soil, K0 ≈ 1 − sin(φ).

A uniform surcharge q behind a wall adds a uniform (rectangular) lateral pressure Ka·q over the full wall height (in addition to the triangular soil pressure).

Time-dependent settlement of saturated clay as pore water is squeezed out under load. Magnitude depends on compression index Cc and stress change; rate depends on coefficient of consolidation Cv.

N is the number of hammer blows to drive a split-spoon sampler the final 12 in (the middle two 6-in increments). It indicates relative density of sands / consistency of clays.

The steepest stable slope angle of a loose granular material, roughly equal to its drained friction angle φ. Guides safe stockpile and excavation slopes.

The maximum contact pressure soil can support before shear failure. Terzaghi: qult = c·Nc + q·Nq + 0.5·γ·B·Nγ. Allowable = qult ÷ factor of safety (often 3).

Lowering the groundwater table below the excavation using well points, deep wells, or sumps so the soil stays workable and stable and uplift/boiling is prevented.

Kp = tan²(45° + φ/2). Passive pressure resists a wall pushing into the soil and is the largest of the three earth-pressure states (active < at-rest < passive).

qult = c·Nc + q·Nq + 0.5·γ·B·Nγ, where c = cohesion, q = surcharge at footing base, γ = soil unit weight, B = footing width, and Nc, Nq, Nγ are bearing factors that depend on φ.

FS = resisting forces (or moments) ÷ driving forces (or moments). FS > 1 is stable; design typically requires FS ≥ 1.3–1.5 depending on conditions.

Loss of soil strength when saturated, loose, granular soil under cyclic (seismic) loading builds excess pore pressure until effective stress drops to near zero and the soil behaves like a fluid.

PI = liquid limit − plastic limit (LL − PL). It is the range of water content over which a fine-grained soil is plastic; high PI indicates highly plastic, expansive clay.

The ease with which water flows through soil, k (length/time). Measured by constant-head (sands) or falling-head (silts/clays) tests. Gravels are highly permeable; clays nearly impermeable.

Q = k·i·A, where k = hydraulic conductivity, i = hydraulic gradient (dh/dL), A = cross-sectional area. Governs groundwater flow and seepage.

Cohesionless (sands, gravels) gets strength from friction (φ) and grain interlock. Cohesive (clays) gets strength largely from cohesion (c) and is affected by water content.

Normally consolidated clay has never carried a higher stress than its current overburden. Overconsolidated clay was once loaded more (by ice, erosion, etc.); it settles less under new load.

γd = γ / (1 + w), where γ = total (moist) unit weight and w = water content. Dry unit weight is the target measured in compaction control.

Surveying method that finds elevation differences with a level and rod: elevation + backsight (BS) = height of instrument (HI); HI − foresight (FS) = next elevation.

In a closed level loop returning to a known benchmark, the difference between the measured and known elevation. It quantifies survey error and is distributed back through the loop.

A distance of 1,250 ft along an alignment from station 0+00. Each full station = 100 ft; the number after '+' is the offset in feet.

The central angle subtended by a 100-ft arc (arc definition). Radius R = 5729.58 ÷ D (degrees). Larger D = sharper curve.

PC (point of curvature), PI (point of intersection), PT (point of tangency), T (tangent length), L (curve length), R (radius), Δ (deflection/central angle).

A parabolic curve connecting two grades (g1, g2). Used for crest and sag curves; length L is set by sight-distance or comfort criteria. Rate of change r = (g2 − g1)/L.

A plot of cumulative earthwork volume vs station. Rising = cut, falling = fill; it balances haul, locates borrow/waste, and determines economical haul distance.

Soil changes volume between states: bank (in place), loose (excavated), compacted. Shrinkage = compacted is less volume than bank; swell = loose is more than bank.

Stakes are set at a known horizontal offset from the line/grade so they survive excavation; the cut/fill to finished grade is marked on each stake.

Best management practices (silt fence, sediment basins, stabilized entrances) required by the SWPPP under the Clean Water Act / NPDES to control stormwater and sediment.

A fixed reference point of known elevation used as the basis for differential leveling and vertical control on a project.

Grade = rise ÷ run × 100%. A 2% grade rises 2 ft per 100 ft horizontal. Drainage and ADA limits are commonly specified in percent.

R = 5729.58 ÷ D (arc definition, R in ft, D in degrees). Tangent T = R·tan(Δ/2); length L = R·Δ (Δ in radians).

M = R·(1 − cos(Δ/2)), the distance from the midpoint of the curve to the midpoint of the long chord. Used for clearance and layout.

V = (L/2)·(A1 + A2), where A1 and A2 are the cross-sectional cut/fill areas at two stations a distance L apart. The standard earthwork volume method.

In leveling, HI = known elevation + backsight (BS). A foresight (FS) then gives the next point's elevation = HI − FS.

The banking of a roadway on a horizontal curve to counter centrifugal force. Relationship: e + f = V²/(15·R) in U.S. units (V in mph, R in ft).

On a parabolic vertical curve, the turning point is where grade = 0: distance x = −g1·L/(g2 − g1) from the curve's start (BVC). A crest has a high point; a sag has a low point.

Setting stakes that mark line and elevation for construction, with cut/fill to finished grade noted, usually at an offset so the stakes survive the work.

A Stormwater Pollution Prevention Plan required under the NPDES program for construction sites disturbing ≥1 acre; it specifies erosion and sediment controls.

An inverted triangle drawn beside the soil column at a noted depth (often with a date) marking the observed groundwater table elevation.

The specified 28-day compressive strength of a standard cylinder, in psi (or MPa). The basic design property for concrete; tested per ASTM C39.

The weight of mixing water ÷ weight of cementitious material. Lower w/c gives higher strength and durability but lower workability.

A measure of fresh-concrete workability (ASTM C143): the vertical drop of a molded cone of concrete in inches. Higher slump = more flowable.

Ec ≈ 57,000·√f'c (psi) for normal-weight concrete (ACI). It relates stress to strain in the elastic range.

Rebar grade equals its minimum yield strength in ksi — Grade 60 rebar has fy = 60,000 psi. The most common bar in U.S. construction.

Hot-mix asphalt is aggregate bound by asphalt cement (bitumen). Key properties: air voids, asphalt content, density, and stability (Marshall or Superpave mix design).

Gradation is the particle-size distribution from a sieve analysis. Fineness modulus = sum of cumulative percent retained on standard sieves ÷ 100; higher = coarser sand.

Chemicals that modify fresh/hardened properties: water reducers, retarders, accelerators, air-entraining agents (freeze-thaw durability), and superplasticizers.

Linear-elastic to yield (fy), then a yield plateau, strain hardening, and rupture. Mild steel is ductile; E ≈ 29,000 ksi.

Type I is general-purpose portland cement; Type III is high-early-strength (finer ground) used when fast strength gain is needed in cold or fast-track work.

fr = 7.5·√f'c (psi) for normal-weight concrete; it is the flexural tensile strength used to predict cracking.

Increases workability but lowers strength, durability, and increases permeability. Lower w/c gives stronger, more durable, less permeable concrete.

Intentional microscopic air bubbles added by an admixture to provide freeze-thaw durability by relieving internal pressure from freezing water; it slightly reduces strength.

Type I general purpose; Type II moderate sulfate resistance/heat; Type III high early strength; Type IV low heat of hydration (mass concrete); Type V high sulfate resistance.

Es ≈ 29,000,000 psi (29,000 ksi), essentially constant for all structural steels regardless of grade.

Shaking aggregate through a stack of standard sieves to determine the particle-size distribution (gradation), reported as percent passing each sieve.

RQD = sum of intact core pieces ≥4 in long ÷ total core run length, as a percent. It rates rock-mass quality; higher RQD means more competent rock.

Concrete with high-strength tendons tensioned to put the section in compression before service loads, counteracting tensile stresses. Pre-tensioned (cast on stressed strands) or post-tensioned (ducted, stressed after curing).

Measuring and counting the materials shown on the drawings (linear feet, square yards, cubic yards, counts) to build the cost estimate. The basis of bid pricing.

Direct costs are tied to a specific work item (labor, materials, equipment for that task). Indirect costs (overhead) support the whole project: supervision, office, bonds, insurance.

Volume in cubic yards = (length × width × thickness in ft) ÷ 27. Add waste allowance. Order ready-mix in whole or quarter cubic yards.

Payment based on actual measured quantities × bid unit prices. Used when quantities are uncertain (earthwork, paving); contrast with lump-sum.

Output per unit time or per crew-hour (e.g., cubic yards/hour). Cost = quantity ÷ production rate × crew or equipment hourly cost.

The hourly cost of equipment: ownership (depreciation, interest, taxes, insurance) plus operating (fuel, lubricants, repairs, tires, operator wages).

A reserve amount added to cover unforeseen but probable costs. It reflects estimate uncertainty; it is not for scope changes.

A percentage added to direct cost to cover company overhead and desired profit. Bid price = direct cost + indirect cost + markup.

Determine bank/loose/compacted volumes with shrink-swell factors, the haul distance and cycle time, the hauler capacity, then cost = volume ÷ hourly production × hourly rate.

Bank cubic yards (BCY) = in-place; loose cubic yards (LCY) = after excavation (swelled); compacted cubic yards (CCY) = after placement and compaction (densified).

P = F ÷ (1 + i)ⁿ, the value today of a future amount F received in n periods at interest rate i. The basis of engineering economics comparisons.

A = P·[ i(1+i)ⁿ ÷ ((1+i)ⁿ − 1) ]. Converts a present cost P into an equivalent uniform annual cost over n years.

Comparing alternatives by the present worth (or annual cost) of all costs over the life — initial, operating, maintenance, and salvage — not just first cost.

Finding the quantity or time at which two alternatives (or revenue and cost) are equal. Below it one option is cheaper; above it the other is.

Lump-sum: one fixed price for a defined scope (best when quantities are known). Unit-price: payment per measured quantity × unit rate (best when quantities are uncertain, like earthwork).

A breakdown of the contract sum into line items used to support progress payments; the contractor bills the percent complete of each item.

Crew cost per hour ÷ production rate × quantity, plus burden (taxes, insurance, fringe). Productivity (output per crew-hour) is the key driver.

A scheduling technique that models activities and dependencies in a network, computes early/late dates by forward and backward passes, and finds the longest (critical) path = the shortest project duration.

The time an activity can be delayed without delaying project completion. Total float = late start − early start = late finish − early finish. Critical activities have zero float.

The time an activity can be delayed without delaying the early start of any successor. Free float ≤ total float.

The longest continuous chain of activities through the network. It has zero (minimum) total float and sets the project duration; delaying any critical activity delays the project.

Forward pass computes early start/finish (left to right, taking the max at merges). Backward pass computes late start/finish (right to left, taking the min at bursts).

Finish-to-start (FS, default), start-to-start (SS), finish-to-finish (FF), and start-to-finish (SF). Lags add a delay to the relationship.

Successor B may start no earlier than 3 days after predecessor A starts (SS+3). The two activities overlap rather than running strictly in sequence.

A zero-duration event marking a key point (e.g., 'Foundation complete'). Used for tracking and contract deadlines.

Shortening the schedule by adding resources to critical activities at extra cost. Crash the lowest cost-slope critical activity first; recheck the critical path after each step.

Adjusting the schedule (using float) to smooth resource demand and avoid over-allocation, ideally without extending the critical path.

A bar chart shows activities as bars on a timeline (easy to read, weak on logic). A network diagram shows dependencies and computes float and the critical path.

Comparing planned value (PV), earned value (EV), and actual cost (AC). SV = EV − PV; CV = EV − AC; CPI = EV/AC; SPI = EV/PV. CPI/SPI < 1 means over budget / behind.

EF = ES + duration. The forward pass sets ES = max of predecessors' EF; the backward pass sets LF = min of successors' LS, and LS = LF − duration.

A path with small (low) total float that can become critical if its activities slip; schedulers monitor it because little delay turns it critical.

Cost slope = (crash cost − normal cost) ÷ (normal duration − crash duration) = the extra cost per day saved. Crash the lowest-cost-slope critical activity first.

A lag delays the successor relative to the predecessor (positive offset); a lead (negative lag) lets it start earlier/overlap. Applied to FS, SS, FF, SF links.

A schedule for repetitive work (highways, high-rise floors) plotting location vs time so production rates and crew interference are visible.

SPI = EV ÷ PV. SPI < 1 means behind schedule, = 1 on schedule, > 1 ahead. Paired with CPI = EV ÷ AC for cost performance.

A summary activity that spans (hangs between) a start and finish of a group of detailed activities, used for reporting like ongoing supervision.

Total float uses up schedule slack against the project end; free float delays only without affecting any successor's early start. Free float ≤ total float.

To collect enough representative results across a production run to characterize each lot and decide acceptance, balancing risk against testing cost.

QC is the contractor's process control (testing, inspection of the work). QA is the owner's independent verification that QC and the product meet specs.

Testing a sample from a lot to decide whether to accept or reject the whole lot, accepting some statistical risk (producer's and consumer's risk).

Standard cylinders cast from a placement and broken (ASTM C39) at 7 and 28 days; acceptance compares the average to f'c per ACI strength criteria.

Lab test (standard or modified) giving the maximum dry density and optimum moisture content used as the target for field compaction (percent of max dry density).

Compare in-place dry density (nuclear gauge or sand-cone, ASTM) to the Proctor maximum; relative compaction (e.g., ≥ 95%) must meet the spec.

A plot of a quality characteristic over time with center line and upper/lower control limits; points outside the limits or trends signal a process out of control.

The mean locates the average result; standard deviation σ measures variability. Lower σ = more uniform production and a higher chance of meeting specs.

Field measurement of fresh-concrete slump compared to the specified range; out-of-range loads may be rejected before placement.

Pay or acceptance based on the percentage of a lot's results falling within specification limits (PWL), rewarding uniform, on-target production.

Estimating in-place concrete strength from its time-temperature history (a maturity index) so forms can be stripped or loads applied based on actual strength gain.

Field dry density ÷ Proctor maximum dry density × 100%. Specs commonly require ≥ 90–95%; below it the lift is reworked.

A field instrument that measures soil/asphalt in-place density and moisture by gamma/neutron backscatter for rapid compaction QC.

Modified Proctor uses higher compactive energy (heavier hammer, greater drop, more layers), giving a higher maximum dry density at a lower optimum moisture than standard Proctor.

Visual plus nondestructive testing: dye penetrant and magnetic particle (surface), ultrasonic and radiographic (internal). Required for critical structural welds.

Confirming high-strength bolts reach required tension by turn-of-nut, calibrated wrench, direct-tension indicators, or twist-off (tension-control) bolts.

Producer's risk (α) rejects acceptable material; consumer's risk (β) accepts defective material. Acceptance plans balance both.

Strength is acceptable if every running average of three consecutive tests ≥ f'c and no single test is more than 500 psi below f'c (for f'c ≤ 5000 psi).

Dead load is the permanent self-weight of fixed components (structure, roofing, finishes). Live load is movable/temporary (occupants, furniture, snow, construction loads).

A sketch of a body isolated from its supports showing all applied forces and reactions; the basis for writing equilibrium equations.

For a 2-D body: ΣFx = 0, ΣFy = 0, ΣM = 0. A statically determinate structure is solved with these three equations.

σ = M·c / I, where M = bending moment, c = distance from neutral axis, I = moment of inertia. Max at the extreme fiber.

S = I/c. Bending stress σ = M/S. A larger S carries more moment at the same stress; it ranks beam efficiency.

τ = V·Q / (I·b), where V = shear force, Q = first moment of area above the point, b = width. Maximum at the neutral axis for a rectangular section.

For a span L with uniform load w, the maximum moment is M = w·L²/8 at midspan; max shear V = w·L/2 at the supports.

For a center point load P on span L, max moment M = P·L/4 at midspan; max shear V = P/2.

σ = P/A, the force P divided by cross-sectional area A. Tension is positive, compression negative.

Critical buckling load Pcr = π²·E·I / (K·L)², where K is the effective-length factor for the end conditions. Slender columns fail by buckling below the yield load.

Max midspan deflection δ = 5·w·L⁴ / (384·E·I). Deflection is very sensitive to span (L⁴) and stiffness E·I.

I = b·h³/12 about the centroidal axis (b = width, h = depth). Depth dominates because it is cubed — deeper beams are far stiffer.

For load P at the free end of a cantilever of length L: max moment M = P·L at the fixed support; max deflection δ = P·L³/(3·E·I).

For uniform load w on a cantilever of length L: max moment M = w·L²/2 at the support; max deflection δ = w·L⁴/(8·E·I).

r = √(I/A). It relates a section's moment of inertia to its area and appears in column slenderness, KL/r.

KL/r, where K = effective-length factor, L = unbraced length, r = radius of gyration. High slenderness means a column is buckling-controlled.

Pinned-pinned K = 1.0; fixed-fixed K = 0.5; fixed-pinned K ≈ 0.7; fixed-free (cantilever) K = 2.0. Higher K lowers the buckling load.

The slope of the shear diagram equals the negative load (dV/dx = −w); the slope of the moment diagram equals the shear (dM/dx = V). Maximum moment occurs where shear = 0.

ASD compares service loads to allowable stress (Rn/Ω). LRFD compares factored loads (Σγi·Qi) to factored resistance (φ·Rn). LRFD applies separate factors to loads and resistance.

The floor/roof area whose load is carried by a given member; multiplying it by the unit load gives the member's load. Interior beams collect from both sides.

σ = P/A ± M·c/I — superimpose the axial stress and bending stress; the extreme fiber may be in higher compression or net tension.

One with more unknown reactions/forces than equilibrium equations; it requires compatibility (deflection) conditions to solve and redistributes load when overloaded.

Open-channel flow velocity: V = (1.49/n)·R raised to 2/3·S raised to 1/2 in U.S. units (1.0 instead of 1.49 in SI). n = roughness, R = hydraulic radius (area ÷ wetted perimeter), S = channel slope. Q = V·A.

Estimates peak runoff: Q = C·i·A, where C = runoff coefficient, i = rainfall intensity, A = drainage area. In U.S. units C·i·A gives cfs when i is in in/hr and A in acres.

The fraction of rainfall that becomes direct surface runoff (rather than infiltrating). Near 0.95 for asphalt/roofs; low (0.1–0.3) for lawns and pervious ground.

The time for runoff to travel from the most remote point of a watershed to the outlet. Rainfall intensity i in the rational method is read at a duration equal to tc.

R = flow area ÷ wetted perimeter. It represents flow efficiency in Manning's equation; a circular pipe flowing full has R = D/4.

Q = V·A (flow rate = velocity × area). For incompressible steady flow, Q is constant, so velocity rises where the area narrows.

Total head = pressure head (p/γ) + velocity head (V²/2g) + elevation head (z), constant along a streamline minus head losses.

Open-channel flow has a free surface at atmospheric pressure (gravity-driven, uses Manning). Pressure flow fills the conduit (uses Bernoulli/Darcy-Weisbach with friction losses).

Specific energy E = depth + V²/2g. Critical depth minimizes E for a given Q; flow is subcritical (Fr<1) above it and supercritical (Fr>1) below it.

A plot of discharge vs time at a point during a storm, showing the rising limb, peak, and recession. The unit hydrograph scales runoff for a unit of rainfall excess.

A detention basin temporarily stores stormwater and releases it slowly (peak shaving). A retention basin holds water permanently (a wet pond), releasing mainly by infiltration/evaporation.

Fr = V ÷ √(g·D). Fr < 1 is subcritical (tranquil, depth-controlled), Fr = 1 critical, Fr > 1 supercritical (rapid, slope-controlled).

V = 1.318·C·R raised to 0.63·S raised to 0.54 (U.S. units), used for pressurized water pipe flow; C is the pipe roughness coefficient (higher C = smoother pipe).

hf = f·(L/D)·(V²/2g), the friction head loss in a pipe; f is the friction factor (from the Moody diagram via Reynolds number and relative roughness).

Net Positive Suction Head is the suction-side pressure margin above vapor pressure a pump needs. If available NPSH < required, the water vaporizes (cavitation), damaging the pump.

A runoff method where a curve number (CN, 30–98) based on soil and land use sets the runoff depth from rainfall; higher CN (impervious) yields more runoff.

An Intensity-Duration-Frequency curve giving rainfall intensity for a chosen storm duration and return period (frequency); the source of i in the rational method.

EGL = pressure head + elevation + velocity head (total energy). HGL = pressure head + elevation (the water surface in open flow). EGL is above HGL by the velocity head V²/2g.

Re = VD/ν. In pipes, Re < 2000 is laminar, > 4000 turbulent, between is transitional. It sets the friction factor.

To temporarily store stormwater and release it at a controlled (lower) rate so the post-development peak flow does not exceed pre-development, protecting downstream channels.

A conduit carrying flow under a road/embankment; capacity is governed by either inlet control (entrance geometry) or outlet control (barrel friction + tailwater), whichever gives the higher headwater.

A choker hitch reduces the rated sling capacity (about 75%–80% of vertical) because the bend and squeezing action lower the sling's effective strength.

Rated capacity depends on the load radius (horizontal distance from the center pin to the hook), boom length/angle, and configuration; capacity drops sharply as radius increases.

Gross capacity from the chart must be reduced by the weight of rigging, hook block, jib, and other below-the-boom items to get the net load the crane can lift.

As a sling angle from horizontal decreases, tension in each leg increases. Tension = load ÷ (number of legs × sin θ); shallow angles can overload slings.

Hammer energy (rated foot-pounds) drives the pile; field capacity is estimated from driving resistance (blows per inch) via a dynamic formula or wave-equation analysis.

Mass concrete requires control of heat of hydration (cooling, low-heat cement, lift heights). Placement is done in controlled lifts to manage temperature and cold joints.

An excavation is any man-made cut/cavity; a trench is a narrow excavation deeper than it is wide (≤15 ft wide). Trenches ≥5 ft deep generally require a protective system.

Sloping/benching (laying back the walls), shoring (supports like hydraulic shores), or shielding (trench boxes) to prevent cave-ins, selected by soil type and depth.

Removing or lowering groundwater (well points, sumps, deep wells) so excavation can proceed in stable, workable soil and to prevent bottom heave/boiling.

Repetitive operations gain efficiency as crews learn; unit time decreases by a fixed percent each time output doubles, improving production rates on repetitive work.

A discontinuity where fresh concrete is placed against concrete that has already begun to set, creating a weak plane; avoided by continuous placement within set time.

Total cycle = load + haul + dump + return + spot times. Production = (60 min/hr ÷ cycle min) × hauler capacity × efficiency.

Tension per leg = total load ÷ (number of legs × sin θ), where θ is the angle from horizontal. As θ decreases, tension increases sharply — a 30° sling roughly doubles leg tension vs vertical.

The horizontal distance from the crane's center of rotation to the hook. Rated capacity drops rapidly as radius increases; load charts are read by radius and boom configuration.

Outrigger loads can exceed the crane's weight at one corner; mats spread the load so ground bearing pressure stays below the soil's allowable bearing capacity.

Material type, haul distance, grade, production needed, and cost. Scrapers suit medium hauls; trucks/loaders long hauls; dozers short pushes; excavators for trenching.

A deep foundation formed by drilling a hole and filling it with reinforced concrete; carries load by end bearing and side friction. Used for heavy loads or where driving piles is impractical.

When a pile no longer advances appreciably under hammer blows (a specified small set per blow), indicating it has reached required capacity or hit a hard layer.

Average the corner cut/fill depths weighted by how many grid cells share each corner, multiply by the grid area: V = (area/4)·Σ(weighted heights).

Sloping/benching cuts back the excavation walls; shoring supports the walls (hydraulic/timber); shielding uses a trench box to protect workers without preventing wall collapse.

A reinforced-concrete wall built in a bentonite-slurry-supported trench, used for deep excavation support and cutoff in soft ground or below the water table.

A line of closely spaced shallow wells connected to a header and vacuum pump to lower the water table around an excavation in sandy soils.

Fresh (plastic) concrete acts like an equivalent fluid, giving a hydrostatic lateral pressure that increases with depth; ACI 347 caps it by a rate-and-temperature formula (Cw, Cc, pour rate R, temperature T).

Temporary molds for fresh concrete. Design for the weight of concrete and reinforcement, construction live loads, and lateral concrete pressure / wind, per ACI 347.

Vertical support carrying the weight of fresh concrete and forms until the slab gains strength. Reshoring redistributes loads to lower floors during multistory construction.

A faster pour rate (ft/hr) and lower temperature keep more concrete plastic at once, raising the lateral form pressure; slower pours let lower concrete set and reduce pressure.

Temporary framework that supports a permanent structure (e.g., bridge formwork/shoring) during construction until it is self-supporting.

Dead (self-weight, materials), construction live loads (workers, equipment, stockpiled materials), lateral loads (wind, concrete pressure, seismic), and impact.

Diagonal members that resist lateral loads and prevent buckling/racking of shoring, formwork, scaffolds, and falsework; required for stability.

A temporary watertight enclosure pumped dry to allow construction below the water table or in a waterway (e.g., bridge piers).

From the shore's rated capacity (often manufacturer tables) reduced for height, eccentricity, and bracing; a factor of safety is applied because failures are catastrophic.

Forms fail by excessive deflection, tie/wale overload, or blowout from concrete pressure; shoring fails by buckling, overturning, or foundation settlement.

A temporary elevated work platform; under OSHA it must support its own weight plus at least 4× the maximum intended load without failure.

Modeling fresh concrete (or soil) lateral pressure as if it were a fluid of an equivalent unit weight, giving a triangular pressure that increases linearly with depth.

Lateral pressure of fresh concrete is capped using Cw (unit-weight factor) and Cc (chemistry factor) with pour rate R and temperature T; faster pours and colder temps give higher pressure.

Shores reinstalled snug (not preloaded) under a slab after the original shores are removed, transferring the slab's self-weight and construction loads to lower floors during multistory work.

ASCE 37 'Design Loads on Structures During Construction' gives load combinations and magnitudes for temporary conditions (construction live loads, materials, equipment, environmental).

ACI 347 commonly uses a minimum construction live load (often 50 psf, increased for motorized buggies) plus the concrete and form dead load when designing form decks and shores.

Diagonal/horizontal bracing that resists wind, concrete pressure, and erection forces and prevents shore towers from buckling or racking; required for stability.

Sudden, catastrophic, often fatal; therefore temporary works use conservative factors of safety and a qualified engineer's design and inspection.

Wales are horizontal members backing the studs/sheathing; ties are tension members across the form spacing the two faces and resisting the concrete's lateral pressure.

Vertical steel piles (soldiers) driven/drilled at intervals with horizontal lagging between them retaining the soil face; often tied back with anchors for deep cuts.

Formwork is the mold that shapes the concrete; falsework is the temporary support system (shores, towers, framing) that holds the formwork and wet concrete until self-supporting.

Light-duty 25 psf, medium-duty 50 psf, heavy-duty 75 psf intended load; plus the 4× safety factor on capacity. The platform must be fully planked.

29 CFR 1926 — the OSHA Safety and Health Regulations for Construction. (29 CFR 1910 is general industry.)

Falls, struck-by, caught-in/between, and electrocution — the leading causes of construction fatalities and OSHA's primary enforcement focus.

Generally at 6 ft or more above a lower level in construction (OSHA 1926 Subpart M): guardrails, safety nets, or personal fall arrest systems.

OSHA requires cave-in protection for excavations 5 ft or deeper (unless in stable rock); a competent person inspects daily and classifies the soil.

Someone capable of identifying existing and predictable hazards and authorized to take prompt corrective action — required for excavations, scaffolds, and fall protection.

Type C soil (the least stable) must be sloped no steeper than 1.5 horizontal to 1 vertical (about 34°) per OSHA excavation requirements.

Most to least effective: elimination, substitution, engineering controls, administrative controls, then personal protective equipment (PPE) as the last line.

Procedures to isolate and de-energize hazardous energy (electrical, hydraulic) and lock/tag controls so equipment cannot start during service, preventing caught-in/electrocution injuries.

A scaffold and its components must support, without failure, their own weight plus at least 4 times the maximum intended load.

A step-by-step review of a task that identifies hazards in each step and the controls to eliminate or reduce them before work begins.

Top rails on supported scaffolds are 38–45 in above the platform (newer scaffolds); a midrail is required between the top rail and platform when there is no wall.

Type A is most stable cohesive soil (unconfined compressive strength ≥1.5 tsf); Type B intermediate; Type C least stable (≤0.5 tsf or submerged) — each has a maximum allowable slope.

Type A may be sloped at 3/4 horizontal to 1 vertical (about 53°) for excavations ≤20 ft deep, the steepest of the soil types.

Daily before work, after any rainstorm or hazard-increasing event, and as conditions warrant — for cave-in, water, atmosphere, and protective-system hazards.

29 CFR 1926 Subpart AA requires permit-required confined-space programs: atmospheric testing, ventilation, attendants, and rescue for spaces with limited entry and hazards.

An anchor, body harness, and connector (lanyard/lifeline) that stops a fall; OSHA limits arrest force to 1,800 lb and total fall distance, and requires a rescue plan.

Temporary traffic control in work zones per MUTCD Part 6 — signs, channelizing devices, flaggers, and tapers that protect workers and the traveling public.

Section 5(a)(1) of the OSH Act requires employers to provide a workplace free from recognized hazards that cause or are likely to cause death or serious harm, even absent a specific standard.

Hard hat, safety glasses, high-visibility vest, steel/composite-toe boots, gloves, and hearing protection as needed — PPE is the last line in the hazard-control hierarchy.

Struck-by: hit by a moving object (vehicle, falling load, flying particle). Caught-in/between: crushed/pinched between objects or in a collapse (trench, equipment). Both are OSHA Focus Four hazards.