INDUSTRY TERMINOLOGY EXPLAINED:
Axial Load
A force acting along the long axis of a member or vertically in a wall.
Anchor Bolt
A bolt anchored to rock or concrete to hold down structure or other objects.
Auger
1. A helically shaped corkscrew-like tool with a power driving head on top and cutting head on the bottom designed to bore holes in the earth by drilling, either with or without the supplementary use of water.
2. A hand operated soil sampler.
Augercast
A proprietary augered pile. High strength grout is forced down the centre of a flight auger to form a shaft as the auger is withdrawn.
Augered Pile
Concrete pile cast-in-place in an augered hole, which may be belled at the bottom. Suitable where soil is dry and hole will stand open. Also called Drilled Pier, Drilled Shaft. See Augercast.
Backfill
Soil material placed back into a space that has been excavated, such as against structures and in pipe trenches.
Bare Foot
A pile without a driving shoe.
Base Islolation
A means of limiting the seismic forces on a building by supporting it on devices that allow relative movement to occur between the building and its foundation.
An example can be viewed at Te Papa museum in Wellington, where 150 rubber and lead shock absorbers under the building let the building move up to half a metre in any direction during a big earthquake.
Base Shear
The horizontal force at the base of a structure due to inertial forces acting during earthquake ground movement.
Bearing Capacity
The maximum load a pile can sustain by soil resistance.
Bearing Pile
A supporting pile for a structure that can be of wood, concrete or steel in any number of shapes and whose bearing is reached by point or end bearing, friction, or friction and compaction, or a combination. See End Bearing Pile.
Bearing Wall
A wall that supports vertical load, as floors or roof.
Bending Moment
A bending moment occurs in a structural element (such as a beam) when forces are applied at right angles to the element so that it bends. Bending moments produce tension on one side of the element and compression on the other side.
The bending moment at any point along a beam can be calculated from all the external forces acting on the beam. The calculation is important because it can show where the greatest amount of bending will take place. If a beam has a uniformly distributed load, the bending will occur in the middle of the span.
Blow Count
The observed blows of the pile hammer per increment of pile penetration.
Brace
A structural member used in bracing.
Brace Pile
A batter pile connected to a structure in a way to resist lateral forces.
Building Classification
The standard “AS/NZS 1170.0.2002 Structural design actions – Part 0: General Principles” classifies buildings in levels of importance (IL) from 1 to 5, where 1 is the lowest level of importance. Most multi-storey buildings are included in IL 2, IL 3 includes buildings likely to contain large numbers of people and IL 4 includes hospital and other buildings that must be operational straight after a big earthquake. The IL of a building dictates the intensity of earthquake loading that it must be able to cope with.
Butt Of A Pile
The larger or head end of a tapered pile; usually the upper end of a pile as driven. Also a general term for the upper portion of a pile.
Butt-Welding
Welding two adjoining corresponding surfaces by setting them in a common place in exact position to each other while assuring that their common axis is in a straight line. See Bevel Weld
Caisson Pile
1. Large diameter steel pipe casing which is drilled, driven or vibrated open-ended to the required depth. The inside is cleaned out and filled with concrete. The outside pipe may or may not be extracted.
2. Augered pile with or without permanent casing. Also called Drilled Shaft.
Casing
1. An open-ended steel pipe installed by drilling, driving or vibrating to support the side of a hole.
2. A pipe dropped or driven into an augered pile to prevent caving temporarily.
Cast-in-Place
A concrete pile poured (either with or without a metal casing) in its permanent location in the ground. Also called Insitu Pile, Caisson
CERA
Canterbury Earthquake Recovery Authority
cfm
Cubic feet per minute.
Chemical Grout
A fluid with chemicals injected into soil or rock to improve its strength, speed of hardening or other desired characteristic, to improve its load-carrying ability to decrease permeability.
Clay
Cohesive sols which are firmly coherent, weighty, compact and hard when dry, but stiff, viscid and ductile when moist. Smooth to the touch.
Cofferdam
A waterproof wall, open at the top, enclosing a construction area below the water level.
Compaction
The process of inreasing the density or unit weight of a soil by preloading, rolling, tamping, vibrating, or other mechanical means.
Conduit
Pipe or liner used as a passage for other pipes or wires.
Cone Penetrometer Test (CPT)
A widely used test that measures the properties of soil beneath the surface in a particular location. A cone is pushed at a controlled rate into the ground, sometimes for many metres deep and measurements are taken. Soil samples are not usually taken. CPT testing can help determine the suitability of the soil for a particular type of building and whether ground improvement is required.
Confinement Reinforcement
This is used to make reinforced concrete beams and columns stronger and more ductile so they can perform better in an earthquake. Confinement reinforcement (usually in the form of spirals or stirrups) is designed so that it ‘confines’ the core concrete inside it, giving it better compressive strength and more strain capability.
Consolidation
Soil stabilisation; see grouting
Crib
A structure built of round or square timbers, or reinforced precast concrete members, laid in courses with the pockets filled with riprap or rubble.
Cross Section
The shape of a tunnel; shapes include ovoid, horseshoe, round or square
Cut and Cover
Construction method which involves excavating a large trench, building a roof structure, then covering it with earth. Commonly used for subways and relatively flat locations.
Dead Load
Weight of the structure only.
Design Engineer
The professional organization responsible for the design, plans and specifications to fulfill the cope of work to be performed to sucessfully complete the design of a project. The firm may also monitor and observe the construction of the project.
Design Load
The load which the pile is intended to carry without excessive movement and with an acceptable factor of safety against plunging failure.
Dewater
Removal of water during construction.
Dewatering
The procedure utilized to remove water from a construction area such as pumping from an excavation or location where water covers the planned surface.
Diaphragm
A flat (usually horizontal) structural element or system that transmits horizontal forces (typically from wind or earthquakes) to and from shear walls or frames. Floors often act as diaphragms.
Diesel Hammer
A pile hammer, which carries its own diesel fuel to generate power internally.
Driving Log
Field Record of each driven pile including location number, hammer model, pile type, blow count per unit of penetration, final resistance, driven length, etc. Also called Log or Pile Log.
Dynamic force
1. Energy Delivered by a pile hammer to change the state of rest of a pile. The force of the hammer is equal to the mass of the ram of the hammer times its acceleration.
2. Force applied to a pile by a rotating eccentric weight vibratory pile driver/extractor. Mathematical formula:
Double Tee
A precast/prestressed concrete unit commonly used in floors or roofs.
Drift
A horizontal, underground passage.
Drill and Blast
Construction method in which pilot holes are drilled for explosive charges. The resulting debris is carried out and the process is repeated.
Driven Pile
A driven pile can be made of timber, steel or precast concrete and is typically hammered into the ground to form foundations. They are often used in soft ground conditions. It is not unusual for driven piles to reach 10-15 metres dept. “..driven piles have significant advantages over th other pile types for reducing settlements in earthquaket-resistant design..” (Royal Commission.)
Ductile Wall
Like most reinforced concrete building elements, a reinforced concrete wall generally performs better in an earthquake if it is designed to be ductile. The ductility of a wall depends on, among other things, its proportions, the design of its reinforcement and how it is connected to other building elements.
Ductility
Originally used in metallurgy, ductility is a measure of how easily a solid material (such as a metal) deforms under stress without breaking. In earthquake engineering terms, ductile systems allow structures to deform inelastically and so absorb earthquake energy without collapsing.
Earthquake-Prone
Although people often speak of “earthquake-prone” buildings to simply mean ones that are at greater risk of damage in an earthquake, there is a specific definition of this term in the Building Act 2004 (section 122). A building is earthquake prone if it:
a) will have its ultimate capacity exceeded in a moderate earthquake (as defined in the regulations); and
b) would be likely to collapse causing i) injury or death to persons in the building or to persons on any other property; or ii) damage to any other property
The definition does not apply to residential buildings unless they are two or more storeys and contain three or more household units. In practical terms, a building is earthquake-prone if, when assessed against current standards for new buildings, it is considered that it would not sustain more than 33% of the minimum design actions for the ultimate limit state.
Earthquake-Risk Building
A building is an earthquake-risk building if, when assessed against current standards for new buildings, it would sustain only between 33% and 66% of the minimum design actions for the ultimate limit state.
In terms of its likely performance in an earthquake, a building assessed at 33% of new building strength has about 20 times the risk of failure compared with the equivalent new building, and a building at 66% has about five times the risk.
Eccentrically Braced Frame
Building framing is braced so that it copes with wind and earthquake forces. An eccentrically braced frame is one with diagonal bracing that is not concentric. The active links between the eccentric braces gie the frame a level of stiffness and ductility that allows it to better cope with big lateral loads induced by earthquakes – the framing can absorb a lot of energy without breaking. This sort of framing is very commonly used in areas of high earthquake risk.
Embedded Wall
Retaining wall constructed using sections placed side-by-side or interlocking to form a continuous structure. Includes sheet pile, soldier pile, bored pile and diaphragm wall.
Epoxy Grout
A two (or more) part resin that, when mixed, produces a high-strength bonding material.
Excavation
The process of digging or the hole which results
Falsework
A system of temporary piles, temporary whalers and bracing, or a prefabricated structure to support elements of a permanent structure during construction.
Fault
A planar fracture in the otherwise continuous rock of the earth’s crust.
Fill
1. Soil placed in an excavation or other area to raise the surface elevation or to provide a more stable base. Fill soils are usually selected for low compressability and good stability.
2. Structural earth fill refers to material which is placed and compacted in layers under carefully controlled conditions to achieve a uniform and dense soil mass which is capable of supporting structural loading. See also Backfill.
Final Blow Count
The number of blows per inch, foot or other unit length of measure at which the driving of the pile or soil sampling device was stopped.
Fixed Leads
Pile driving leads attached to the boom point of the crane, with or without a spotter. Can only be moved fore or aft for batter pile.
Footing
Type of foundation typically installed at a shallow depth and constructed to provide an area of bearing on the supporting soil or rock.
Franki Pile
A proprietary pile utilizing a compacted concrete expanded base. A Pressure Injected Footing.
Friction Pile
Pile driven until friction between pile surface and soil are great enough to support loads placed on them. Used when firm bearing is too deep to provide support for a bearing pile.
Geotechnical Investigation
An investigation by a specialist engineer or geologist into the physical properties of the rocks and soils at a particular location. This work is often necessary to determine what foundations or earthworks are required under a planned building.
Grade
The elevation of the ground surface. Often used to describe the angle or slope of the surface.
Gravity Wall
Retaining wall relying on significant mass, dimensions or modular sections. Little or no stability is gained from the natural resistance of the supported soil. May be large stone blocks, pre-fab concrete modules, or reinforced construction with spread foundations.
Grouting
Unstable rock and soil is strengthened by the injection of chemicals, cementitous grout, freezing or other methods.
Ground Improvement
Techniques to improve the strength and stability of soil so it better supports a building. Used particularly on soft soils or soils subject to liquefaction, grounds improvement techniques include:
- dropping a heavy weight repeatedly onto ground to make it denser – before Te Papa was built, 30 tonne weights were dropped onto the ground 50,000 times
- excavating the top few metres of soil then recompacting on site – cement may be added to the mix for improved performance
- inserting deep columns into the ground that will provide added support under a building
- inserting deep columns around a site to create a supporting curtain wall.
Hollow-Core Slab
Precast, prestressed concrete slabs that are often used in floor construction in multi-storey buildings. The slabs have tubular voids running through the full lengths, making them much lighter than solid slabs of equal thickness.
IEP
Initial evaluation process, usually carried out by a local building control authority to determine whether a building is likely to be earthquake-prone or an earthquake risk. It is a very simple filter that needs to be verified by a more detailed assessment usually by the building owner with the help of a structural engineer.
Impact Velocity
The velocity of the ram of a travity or single-acting steam/air hammer when it strikes the anvil. It may be computed from:
V = 2GHe1/2
V = Velocity in feet/sec.
G = Gravity 32.3 ft/sec.2
H = Height of fall in feet
e = Hammer efficiency
For a double-acting steam/air hammer, the impact velocity is:
V = (2GEe/W)1/2
E = Rated energy
W = Weight of the ram
e = Hammer efficiency
Inclined Pile
A pile that goes into the ground on an angle rather than vertically so as to better resist horizontal forces.
In-Plane and Out-Of-Plane Forces
In-plane forces act in the same plan as the fact of the wall, while out-of-plane forces act at right angles to the face of the wall.
In-situ
Formed or created in its final position.
Initial Support
Applied or installed immediately to the interior surface after excavation to maintain the opening. Includes shotcrete, rock bolts and/or steel ribs.
Intensity
A measure of the effects of an earthquake on people and buildings at a particular location. The intensity at a particular site depends on the strength (magnitude) of a quake, how far the site is from the epicentre of the earthquake and the geology under the site.
Intensity is measured with the 12 point Modified Mercalli Intensity (MMI) scale.
A classification is made by accumulating the results of many observations on the ground. the scaleis linear, not logarithmic, which means that going up the scale is a gradual process – 1 is not felt by most people; 12 results in total destruction. The September 2010 and February 2011 Canterbury erthquakes (magnitude 7.1 and 6.3 respectively) are both classified as 9 0n the MMI scale. At this level, there is panic, partial collapse of buildings and buildings thrown off their foundations.
Intensity is different from magnitude.
Internal Hammer
A gravity hammer which acts internally on a plug at the base of a pile casing and is used to advance the casing by driving at the bottom to a given set or penetration.
Inter-Storey Drift
Drift is sideways movement of a building, and inter-storey drift is the difference in sideways movement between two adjacent storeys. The measurement is usually expressed as a percentage of the storey height. For example, if a storey is 3m high, an inter-storey drift of 10% would mean that the floor of the upper storey moves by 300mm compared to the floor below. A big inter-storey drift can lead to significant damage and even collapse of a building.
Kelly Bar
A square or splined shaft which can slide vertically through a square or splined opening in a rotary driving head to turn an auger or drill bit; for a drilling rig which drives from top the Kelly bar may be a smooth cylinder.
Kip
A force unit equal to 1,000 lbs.
Lagging
- Boards placed side-by-side to retain the face of an excavation. Held in place by soldier piles.
- The horizontal members, usually of timber or concrete, spanning between two soldier piles. See Lags.
Lateral Loads
These are horizontal or sideways loads on the building. They are typically caused by the pressure of the wind on the exposed face of the building and suction on the opposite face. Lateral loads in earthquakes are caused by the inertial weight of the building when the ground accelerates beneath it.
Lateral Load
Horizontal component of a load on a pile.
Lateral Support
1. Batter piles or reinforcement to resist lateral forces on piles or footings. See Bracing.
2. Support provided by soil, which prevents column failure of a driven pile.
Leads
1. A structure of fabricated steel or wood in which or on which a pile hammer travels up and down and with which the hammer and pile assembly is aligned in driving position.
2. A complete hammer support system including lead column, brace and other components. Also called Leaders.
Leads, Swinging
Pile hammer leads topped with a bail and hung from one load line of a crane. Also called Hanging Leads, Pendulum Leads.
Line
A description of the location and grade of a tunnel.
Liner
See Casing.
Lining
Materials used to finish the inside surface of the tunnel. The initial supports and preliminary liner are placed as the tunnel is being excavated. These help stabilise the interior surface. Shotcrete may be sprayed on as a preliminary liner. Later, additional coatings may be applied or other types may be used such as prefabricated steel or concrete panels, rock bolting, steel ribs and wood lagging, or masonry. Waterproofing liners are also used.
Liquefaction
During liquefaction, soil suddenly loses strength. Not all soils liquefy. Those more likely to liquefy as the result of an earthquake are sands and silts that are made up of particles all of similar size below the water table, where all the space between the grains is filled with water.
Earthquake forces cause the sand and silt particles to rearrange themselves into a more compact volume, and the water is squeezed out of the reduced space between the particles. The loose granular soil starts to lose strength and behave like a dense fluid – hence the term ‘liquefaction’.
Liquefied soil cannot support the weight of whatever is above it – surface layers of soil or foundations of buildings. The liquefied soil under that weight is forced into any cracks and crevices it can find, including those in the soil above or the cracks between concrete slabs or paving. It flows out onto the surface and creates sand ‘volcanoes’ and streams of silt or sand.
Liquefaction can also result in:
- settlement of the ground surface (and all or part of a building on the surface) due to the compaction of the underground soil – ground lowering may be enough to make the surface close to or below the water table, creating ponds
- floating of manholes and buried tanks and pipes that are mostly empty
Where there are sloping ground surfaces, such as on riverbanks, surface soil layers can slide sideways on the liquefied soil. This is called lateral spreading and can occur even when the slope is very small. It typically results in long tears and rips in the ground surface. Lateral spreading can severely damage buildings if part of a building’s foundations are pulled sideways more than another part.
Buried services such as sewer pipes can be damaged as they are twisted or moved by lateral spreading, uneven ground settlement or flotation. Liquefied soils that are not ejected onto the ground surface redensify and regain strength. In some cases, redensified soil may be stronger than before the earthquake.
Live Load
A moving or non-permanent load which a structure is designed to support in addition to its own dead load.
Load
A force applied to a structure.
Load Test
Testing capacity and relation of load to movement by putting a load on the bearing element before actually building upon the foundation.
Longitudinal
Along the length of a structure.
Low-Damage Design
Design that means that, after a building displaces sideways in an earthquake, it will return to its original position. The non-structural elements are separated from the main structure so that they are not damaged by the deforming building.
Low Displacement Pile
Pile with minimal soil displacement, such as H, open-end pipe or sheet piles. Also called Non-Displacement Pile.
Magnitude
A measure of the strength of an earthquake (the amount of energy it releases) at the point where it occurs. It is generally measured by the movement on a seismograph, corrected for the distance between the seismograph and the epicentre of the quake.
Magnitude is measured using the Richter scale. This is a logarithmic scale, which means that each unit of magnitude represents a very big increase in strength. For example:
- a magnitude 5 earthquake releases 30 times more energy than a magnitude 4 earthquake
- a magnitude 6.7 earthquake releases over 900 times the energy of a 4.7 earthquake
Humans typically do not feel earthquakes below about magnitude 2.5.
Magnitude is not the same as intensity.
Maximum Considered Earthquake (MCE)
The MCE is generally taken as an earthquake that has a 2% probability in 50 years or a 2,500 year return period. The requirements of current New Zealand standards are such that new multi-storey buildings in New Zealand should have a small margin of safety against collapse in MCE.
Micro Piles
Small diameter piles; most often used in underpinning.
Microtunnelling
Construction method for tunnels which are too small for humans to dig inside. May be performed using tethered, remote-controlled drilling machines or pipejacking.
Moment-Resisting Frame
A structural frame typically consisting of reinforced concrete or steel beams and columns that are rigidly connected at their joints. Resistance against sideways forces of wind or earthquakes is by bending of the frame members.
Needle Piles
Very small diameter slender driven steel tubular or rail section piles used in underpinning operations.
Non-Displacement Piles
Piles formed by boring or other methods of excavation. H, open-end pipe and sheet piles are considered low-displacement piles.
Normal Force/Normal Load
A force acting at 90 degrees to an object – for example, your finger pressing straight down on a piece of wood. Compare this with shear force.
On Grade
Placed directly on the ground, or leveled or excavated to the proper elevation.
Overburden
The soil and rock supported by the roof of a tunnel.
Penetrometer
A device for measuring resistance to penetration of a point, calibrated to indicate approximate load-bearing strength of the pile. Often called Dutch Cone Penetrometer.
Pile
A structural column of timber, steel, concrete, etc., installed in the ground to resist or transfer vertical, horizontal or combination loads imposed upon it. See: End Bearing Pile, Friction Pile, Steel H-Pile, Steel Pipe Pile, Timber Pile.
Pile Cushion
Cushion placed between drive cap and top of concrete pile to protect pile from crushing and spalling. Also called Cushion, Pad.
Pile Driver
1. A rig consisting of leads, hoisting apparatus and a pile hammer.
Pile Gate
A device at the base of the pile hammer leads, which is closed around the pile to maintain alignment between the pile and the leads.
Pile Head
The top of the pile. See Butt of a Pile.
Pile Log
See Driving Log.
Plastic Hinge/Potential Plastic Hinge
The zone in a concrete beam or column or shear wall where reinforcement yields or stretches like plasticine under earthquake loading is called a plastic hinge zone or plastic hinge region. As the reinforcement yields, the energy of the earthquake is taken up. Potential plastic hinges in a building are identified during design, and structural elements outside these areas are designed to be stronger. Potential plastic hinges are therefore designed to allow some deformation during an earthquake. Similar zones may be identified in steel structures where the steel member yields to dissipate the earthquake energy.
Portal
The open end of a tunnel. Usually includes a wall to retain the soil around the opening.
Precast Structural Seismic Systems (PRESSS)
PRESSS is a design and construction technique where unbonded, tensioned cables or bars are threaded through precast concrete walls, beams and columns, with jointed ductile connections. The cables and ductile joints let the building spring back to its original position after a large earthquake. (One writer said PRESSS is like a child’s wooden doll with jointed limbs that are held together with elastic cord but are still moveable.)
The 5 storey South Cross Hospital endoscopy building in Christchurch was built with PRESSS technology. This building came through the February 2011 earthquake with relatively little damage and could be reoccupied immediately. The Alan MacDiarmid Building at Victoria University, Wellington, also uses PRESSS technology.
Some areas of PRESSS design are covered in Appendix B of NZS 3101:2006 Concrete structures standard.
Pre-stressing
Compressing a concrete member with tensioned cables or bars running through it to make it lighter for its strength and to counteract handling stresses.
Profile
A side view of the tunnel.
psi
Pounds per square inch, the English unit of measure of pressure.
p.s.i.g.
Pounds per square inch pressure shown by gauge at pressure boiler or air compressor.
Rail Pile
Usually recycled railroad rails driven.
Refusal
The condition reached when a pile or soil sampler being driven by a hammer has negligible penetration per blow (as when the point of the pile reaches an impenetrable bottom such as rock), or when the effective energy of the hammer blow is no longer sufficient to cause penetration. For piling this is often empirically taken as 8 to 12 blows per inch. Same as Practical Refusal, Pile Refusal.
Reinforced Concrete
Concrete with embedded reinforcing bars or fibrous material to provide additional tensile strength.
Reinforced Soil Wall
Retaining wall using various methods of attaching strips, mesh or other reinforcements to an excavated face. Soil nails may be driven in to attach the reinforcements and added further stability.
Reinforcing Steel
Steel bars with deformed little projecting edges to insure that they will not pull out of the concrete and that the bond between the steel and concrete will be perfect. It comes in round bars in smaller sizes and square bars in larger sizes. It is bent or straight according to where the added strength is needed.
Retaining Wall
A structure constructed to withstand the lateral pressure of earth behind it and its own weight imposed on the soil beneath it.
Return Period
The average number of years between earthquakes of a certain magnitude on a particular fault or at a particular location. Earthquakes with longer return periods are generally assumed to be bigger and release larger amounts of energy.
Rig
See Pile Drive.
Rip Rap
Large pieces of hard rock placed on a slope to minimize wave and wash erosion.
Rock
The ultimate soils material upon which to base a foundation. The compressive strength of good stone is greatly in the excess of masonry. Limestones may be subject to caving as a result of eroding ground waters.
Rock Anchors
High tensile steel bars or cables grouted into holes drilled into rock.
Rock Bolts
Steel bar with larger plates at its head. These are driven into the interior surface of the tunnel to stabilise and add strength to the rock. See soil nails.
Rotary Drill Rig
1. A drilling machine powered hydraulically, pneumatically, electrically, or mechanically to bore explatory holes or for installation of piles, caissons, or insitu piles. The equipment may utilize a continuous flight auger or a rotary table and Kelly bar with various attachments and tools to perform the work. See Continuous Flight Auger and Kelly Bar.
Safe Load
A load less than that which would cause objectional settlement, with a factor of safety as necessary to provide for variations in material, workmanship and loading. The safe load for a group of friction piles may be less than the sum of the safe loads for the individual piles comprising the group.
Sand
The category of coarse-grained soil whose particles sizes range between about 0.07 mm and 5 mm in diameter.
Scope of Work
The specific identification of what, to what standards, and where activity is to be accomplished to fulfill an agreement to perform a task and be compensated for said performance to complete a project.
Screw Pile
A pile with spiral blade fixed on a shaft or a shaped precast pile, which is screwed into ground by a rotating force.
Serviceability Limit State (SLS)
This refers to buildings that can still be used for their intended purpose after an earthquake of the magnitude that can be expected once or twice during the life of the building. If a building remains standing and is still structurally sound, but cannot be used for its intended purpose, then the serviceability limit state has been exceeded. See also ultimate limit state.
Set
1. The net penetration of a pile into the ground per blow or specific series of blows of a pile hammer.
2. The final penetration of a pile or final set, expressed in inches or millimeters per blow.
Settlement
1. The amount of downward movement of the foundation of a structure or a part of a structure, under conditions of applied loading.
2. The downward vertical movement experienced by structures or a soil surface as the underlying supporting earth compresses.
Shaft
A vertical, underground passage.
Sheet Pile
Pre-fabricated sections installed vertically side-by-side to form a retaining wall.
Sheet Pile
A pile that may form one of a continuous line or row of timber, precast concrete, or steel piles driven interlocked to provide a tight wall to exclude or resist lateral pressure of water, adjacent earth or other materials.
Silt
A fine residual soil or alluvial sediment of mud or fine soil deposited from running or standing water. Feels velvety, smooth and floury between the fingers. Silt particles range in size from 0.002 to 0.074 mm.
Site
The metes and bounds of an area of earth designated for a project.
Site Conditions
An overall description of the site for a project; ground cover, relative elevations, surrounding environment, the presence of surface water and the normal water table, soil borings, known history, as well as the available access and egress. See Soil Investigation.
Shotcrete
Quick-setting concrete is sprayed onto the bare rock surface.
Shear Force
A force acting in a direction parallel to the face of the material or to a planar cross-section of a body. See also normal face.
Shear Wall
A structural wall, commonly of reinforced concrete or timber, that often starts at the base of a building and runs for its full height. Shear walls transmit lateral earthquake forces down to the building foundation. A shear wall can also be described as a vertical diaphragm. They are typically stronger and stiffer than walls that do not serve this purpose.
Slump
A measure of consistency of fresh concrete. It is made with truncated cone 12 in. high, 4 in diameter at the top and 8 in. diameter at the bottom filled with concrete in three lifts, each lift rodded thoroughly 25 times. The cone is then lifted slowly and the concrete within falls into a slump condition. The height of the concrete in inches deducted from the 12 in. cone height is the slump expressed in inches.
Soil Anchor
A high-strength steel tendon installed in the earth with anchoring provision in soil that will resist movement and press-stressed against a wall by an anchoring device.
Soil Nail
Steel rod driven into the ground to stabilise soil. Used as part of a retaining wall and may be attached to reinforcing strips, mesh or other buried anchors (deadman). Also called a tieback.
Soil Investigation
A study of the earth in the area of a foundation consisting of sampling, classification, preparation of logs of borings and a report setting forth conclusions and recommendations. It is basic to the design of foudnations and is required by most up-to-date building codes.
Soldier Pile
- A steel H or WF section driven (or placed in drilled hole) normally vertical at intervals of several feet to hold horizontal lagging, which is installed to retain soil as excavation proceeds. Also called Soldier Beam.
- Steel H-shape beam or bored and cast concrete pile driven vertically into the ground to provide supports for lagging.
Spile
Rod driven into soft ground or unstable rock to provide stabilisation. A grouted spile is one which is inserted into a pre-drilled hole which is then backfilled with grout.
Splice
The joining of two pile segments.
Spoil
Earth, rock debris, etc to be disposed of.
Standard Penetration Test (SPT)
A thick-walled tube of 50mm outside diameter and 35mm inside diameter is driven into the ground with a slide hammer and the number of blows required to push it down over a particular depth is measured. The main purpose of this test is to provide an indication of the density of the soil.
STC
Structural Timber Innovation Company – a company set up to develop the use of post-tensioned LVL (laminated veneer lumber) structures.
Steel H-Pile
A rolled-steel section with web and flanges nearly the same thickness. The width and depth are approximately equal. Also called H-Beam.
Sump
Small excavation or pit provided in a low point of construction to serve as a collection basin for surface water and near surface underground water.
Surveyor
The professional responsible for determining and locating in the field the horizontal and vertical coordinates for the project, as defined by the design engineer.
Tension Pile
A pile designed to resist uplift.
Test Pile
1. A pile driven to ascertain driving conditions and probable required lengths.
2. A pile on which a load test also may be made to determine its capacity and the carrying capacity of the soils.
3. A pile driven as a guide for efficient design of a pile foundation. See Indicator Pile.
Timber Pile
A cut tree, usually debarked, and pressure treated with creosote or other preservative, usually driven small end down. Probably the earliest form of a pile.
Tunnel
An underground passage for vehicles or pedestrians, especially one which is created by digging into earth. Occasionally, tunnel structures are built in an excavated area then covered over.
Tunnel Boring Machine (TBM)
A tunneling machine which has cutting teeth at its front. It creates the tunnel opening while passing the waste material through the rear.
Ultimate Limit State (ULS)
This is concerned with the safety of people in buildings. To stay within its ultimate limit state, a building must still be standing after being subjected to the peak design load (the ULD load) for which it was designed.
For most multi-storey buildings, the ULS criteria are based on an earthquake with a return period of 500 years (10% probability in an assumed 50-year building life), but with buildings that provide essential services (hospitals, for example), the return period is increased, in some cases up to 2,500 years. See also serviceability limit state.
Uncased Concrete Pile
A column of concrete placed and left in the ground without encasement. See Augered Pile.
Underhung Leads
Pile hammer leads that hang from the crane boom by way of straps or cables.
Underpinning
Piles, piers, walls, sheet piling, or other supports added to or replacing foundations under an existing structure to preserve the integrity of the structure or increase its load capacity.
Unreinforced Masonry
Concrete, stone or brick masonry that has no reinforcing steel included to make it work like reinforced concrete.
Uplift Capacity
The resistance of piles to pulling out of the ground. The ability of a pile to resist uplift and overturn forces due to wind and hydrostatic pressure. See Anchor Pile.
Ventilation
Circulation of fresh air and exhaust gases.
Vibrator
Power tool used to agitate and consolidate freshly placed concrete and produce close contact with the form.
Wall Thickness
The thickness of the metal of a pile.
Watertable
The underground elevation below which the earth is saturated with groundwater. Groundwater includes rainwater which has seeped below the surface or is supplied by aquifers, water saturated layers of rock.
Whaler
A horizontal bracing member used in form construction to support the stud uprights on concrete forms.
Wing Wall
Short section of wall along the edge of an abutment. Used to retain soil, stabilize the abutment, and divert water into an opening, such as a culvert.