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Practical - construction questions
Construction (University of Technology Sydney)
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SITE AND MEASURE
Apart from a pump, name ONE specific way of keeping a site free of surface water.
Drainage
Dykes
Ditches
Drains
Generators generally provide a cheaper source of power than existing power grid
False
Apart from water, what are TWO other services that MUST be supplied on site?
Power
Communications
The only way to provide sufficient security for a site is to employ a security firm
False
Which of the following type of containers have become popular for storing small
items of equipment and material in on site?
Second hand shipping containers
Time sheets for plants are primarily kept for
Costing purposes
Payment purposes
Which of the following tapes is suitable for MAJOR building work?
Steel
Tension variations in a 30m steel tape should NOT be ignored
False
What is a wheel attached to a handle to measure long distances called
Pedometer
Slopes should never be checked with a spirit level
False *you just need to construct a template
Stringlines can be used to check line AND level for STRAIGHT grades
True
For less critical work, it is suitable to use a batter profile for ____ construction
Fill
Cut
The builder’s level can be used to accurately measure horizontal angles
False *old levels can ROUGHLY measure them
If a level is not available, can theodolite be used in its place
Yes * just fix the vertical angle to 90 degrees
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Lasers commonly consist of tubes filled with two gases
Helium
Neon
The laser is so accurate that it eliminates the need for survey equipment
False *it is wise to CHECK level and alignment periodically
The laser beam is always straight
False *the beam can bend with different air densities
Construction machinery can be guided by a laser
True *machine fitted with a sensor
Apart from improving morale and productivity, what does a good safety record result
Cheaper insurance premiums
Project cost records are primarily useful for
Expenditure cost
Technique comparison
Forward estimates
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EARTHMOVING
Trucks are a cheap way of moving material over long distances
True
Highway vehicles usually have a higher payload capacity than off-road vehicles
False
An articulated truck is allowed to be longer than a truck with a trailer attached
False *both allowed to be 17m long
The biggest off-road truck available has a struck capacity of about
130 tonnes
The biggest off-road truck is capable of travelling at up 100km/hr when loaded
False *maximum speed is about 75km/hr
Apart from maximum tonnage, what are TWO ways of expressing capacity
Struck capacity
Heaped capacity
What is the term used for when the load is filled level with the sides of the truck
Struck capacity
Heaped capacity of a truck is measured by
Volume
Rear dump trucks are really only suitable for sand and gravel
False *good for many other materials
Rear dump trucks are generally quicker to unload than bottom dump trucks
False *they can unload while moving
Generally, the SMALLER the truck, the cheaper the operation
False *the bigger the better
What is the maximum excavation depth that a front end loader can generally work
efficiently
2m
Front end loaders are best suited to small volumes of excavation
True
Which loader possesses the best manoeuvrability
Crawler loader
The crawler loader is bigger than the biggest wheel loader
False *wheel is bigger, 24tonnes v 86 tonnes
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The ARTICULATED wheel loader is more productive than the WHEEL tractor
loader in good working conditions
True *because they manoeuvre faster
The biggest wheel loader has a heaped bucket capacity of about
10 cubic metres
___ can be attached to the bucket when working in harder materials
teeth
Excavators can be used to transport material
True *act as a crane
POWER SHOVELS are best suited for excavations which are
Vertical
The POWER SHOVEL is good in loose soil
False *may become engulfed in slides
With the POWER SHOVEL, what lines pulls the dipper up the excavation face
Hoist line
Is it suitable to use a DRAGLINE in loose soil
Yes
When using a DRAGLINE, tension on what cables keeps the bucket lip in the air
during hoisting
Drag cable
DRAGLINE and CLAMSHELL BUCKET are not precise in their movement
True
Which of these lines on the CLAMSHELL BUCKET prevent it from rotating
Tag line
The CLAMSHELL BUCKET has a
Dropped descent *dropped from a crane
What are the TWO principal components of BACKHOE
Bucket
Hoe
Which of these cylinders is present on a HYDRAULIC EXCAVATOR
Bucket, Hoist, Stick cylinder
Trenchers are suitable in what type of ground
Firm sand, Clay
A TRENCHER commonly can excavate to about what depth
2m
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GRADING & COMPACTING
Scrapers are usually crawler units
False *usually rubber tyres
What machine is self-moving, and can dig, carry and spread material
Scraper
Do ‘standard’ scrapers have sufficient power to load themselves
No *usually need a dozer in the rear
For a push loaded scraper, the depth of the cut is set by the
Bowl lift cylinder
The part of the push loaded scraper that holds the load inside when the scraper is
moving is called
Apron
The __ is the part of the scraper that pushed the material out when unloading
Ejector
In general, which is the slower moving scraper
Elevating scraper *slower because heavier
Which scraper can be loaded quicker
Push loaded *25% quicker
Poorly graded, non-cohesive material is usually most easily loaded by which type of
scraper
Elevated
What is the maximum economical travel distance for a dozer transporting soil
100m
the angle dozer is one type of dozer. What is the other
Tilt
Another name for the drive sprocket on a dozer is a ____
Bullwheel
The blade of the tilt dozer can also be set at ‘sideways’ angles
False
The THREE types of blades that a dozer can have are the
‘U’ blade
Rake blade
‘V’ blade
Which of the following blade sidecasts as it moves forward
‘V’ blade
A ____ can be attached to the back of a dozer to loosen material
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Ripper
What are the TWO main types of rippers
Radial
Parallelogram
A D10 dozer weighs approximately how many tonnes
87 tonnes
The compound front axle of a grader allows the front wheel to be ___ to increase their
resistance to skidding sideways when the blade is angled
Angled
Leaned
Titled
Inclined
Sloped
Articulated graders can give greater stability against side thrust
True *since front and rear wheels are offset
What angle is the blade of a grader commonly set at for sidecasting
25 degrees
With which angle of the blade of a grader can deeper cuts be made
A greater one *since less material is carried
The frame of the grader is raised. What other part of the grader is it providing
clearance for
Mouldboard
Blade
The back of the frame of the grader splits into two beams. This is support what parts
of the grader
Engine
Powertrain
A ____ can be mounted in front of the circle of a grader to break up hard surfaces
Scarifier
With rollers, what does pressure, impact, vibration and kneading (manipulation) result
in
Compaction
What is the main compacting force that a grid roller provides
Pressure
With the smooth steel drum roller, the contact pressure is very small. Because of this,
you should restrict the lift thickness to
100mm
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A PNEUMATIC TYRED ROLLER can have its wheels mounted slightly out of line
in the axle. This gives them a weaving action. The term given to this effect is called
the ____ wheel effect
Wobble
Wobbly
With the PNEUMATIC TYRED ROLLER, what forces are utilised to produce
compaction
Pressure
Manipulation
What forces of compaction are produced by TAMPING FOOT roller
Pressure
Impact
Manipulation
Vibration
The SHEEPSFOOT roller performs better than the TAMPING foot roller in clay soil
True
Which rollers utilise vibration to produce compaction
Tamping foot
Vibrating
The autograde moves on wheels
False *crawler
How many mouldboards does the autograde have
2 *one at the front, one at the back
Does the autograde require a driver
Yes
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NETWORK DIAGRAMS
A dummy activity in a network diagram always has zero duration
True
In a project diagram, a sequence of activities may form a loop
False
In a project network diagram, every outgoing activity at a node is necessarily a
successor to all incoming activities at the same node
True
In project planning, it is possible to delay the completion of critical activities without
delaying the entire project
False
In a project network diagram, a critical path need not constitute a connected chain of
activities between the start and terminal nodes
False
In a project network diagram, a critical activity must have its total float or slack equal
to zero
True
In project planning, a network may include more than one critical path
True
In a network diagram, if the network has more than one critical path, the duration of
the different paths may not be equal
False
In a network diagram, a non-critical activity may or may not have zero free float.
(Free float is defined as the spare time available to an activity such that all following
activities will still begin at their earliest start time)
True
A non-critical activity cannot have zero total float or slack
True
A non-critical activity can be scheduled anywhere between its earliest start and latest
completion time
True
A zero free float for a non-critical activity is a signal that the start time for one or
more succeeding activities depend on when this non-critical activity will be finished.
(Free float is defined as the spare time available to an activity such that all following
activities will still begin at their earliest time.)
True
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The start and completion times for critical activities cannot be changed without
necessarily increasing the duration of the entire project
True
Information about float or slack time is essential for effecting resource levelling
True
Resource limitations can affect the critical path computations by requiring an
expansion of one or more critical activity
True
The use of CPM schedule requires periodic updating to reconcile differences between
the schedule and the actual progress in the field
True
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SHORING
What is the maximum depth of trench that you can have BEFORE shoring is required
1.5 metres
Rank the following materials from the STEEPEST to FLATTEST batter required,
when they are NOT supported
Compact earth
Moist sand
Dry sand
Welt silt
Liquid clay
Often the sides of excavations are battered to the natural slope of the material and left
free standing
True *yes soils are quite stable at their natural angle of repose. The decision to shore
or batter back is an economic one.
Close timbering is a good shoring technique for
Unstable ground
The biggest problem with leaving tools at the side of the trench is that
They can fall into the trench
What sorts of pressures do heavy materials cause when they are placed alongside the
sides of a trench
Surcharge
Would you usually provide shoring when working in rock
No
Which of the following type of rocks are likely to require investigation before
deciding where shoring is required
Sedimentary
Which end of the Mooney Mooney Creek Bridge superstructure
Sydney
How many rock anchors were installed to secure the Mooney Mooney bridge
superstructure
25
What was the length of the longest rock anchor installed on the Mooney Mooney
creek bridge
35m
Pot bearings are positioned between the superstructure of the Mooney Mooney Creek
Bridge and the abutment. What type of movement do they allow?
Rotational
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During construction of the Mooney Mooney Creek Bridge, the holes drilled doe the
rock anchors were tested for watertightness by filling them with water and measuring
the ‘depth’ of the water lost in 10 minutes
For the 35m deep hole, what was the maximum level that the water level was allowed
to drop, before it had to be waterproofed
1.2m
The rock anchors for the Mooney Mooney Creek Bridge were manufactured on-site
True
When were the Mooney Mooney Creek Bridge rock anchor stressed
After the grout was cured *untouched until grout strength >30MPa
The rock anchors of Mooney Mooney Creek Bridge were tested for slippage. This
was done by subjecting each anchor to a load of 5400kN in five equal stages. Load vs
extension was measured and all of the rock anchors passed, since their plots were
straight.
What was the maximum deduced displacement that was allowed for any anchor?
2mm
The rock anchors of the Mooney Mooney Creek Bridge were retested 9 months after
initial testing. It was found that they lost an average of 8.5% of their load. Why?
Relaxation of the strands
A change in ground temperature
Consolidation of clay seams
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OPEN PIT SHORING
BRACED TIMBER SHORING is economical in which type of material?
Moist sand
*that’s right, braced timber shoring is usually only economical when the material will
stand up by itself while the shoring is being installed. Moist sand will often stand
almost vertically for a short time, but eventually the face breaks up in lumps or
slumps to take a natural resting position.
Clay should not be trusted to support itself, especially if it is wet. So it isn’t
economical if the batter is likely to collapse while you trying to support it.
And rock can often support itself for the full duration of the job, unless it is badly
fractured. So it is a waste of money to provide braced timber shoring.
The beams used in SOLDIER PILES are usually made of:
Steel
*yes, steel i-beams are commonly used. Keep in mind that the beams are often driven
into the ground – steel can withstand this better than many other construction
materials. For hard ground, the holes for the beams are drilled, and the beams
concreted in. Steel is still the most suitable material.
Sophisticated shoring system using ground anchors and often sprayed concrete walls
use back to back steel channels or concrete soldier piles.
____ piling is the most suitable piling in unstable ground?
Sheet
*it can be installed while excavating
Interlocking and ___ are the two most common types of sheeting
Flange
What is the typical range of the width (length along the wall) of a section of flangetype sheeting?
300-400mm
Flange sheeting is easy to drive and extract because there is no chance of ____ ?
Binding
Catching
Sticking
Snagging
Grabbing
Which type of system minimises the flow of soil and water through the sheeting wall?
Interlocking
*interlocking provides a positive joint?
A ____ is a simple apparatus that can be used to attain adequate alignment of the
sheet piling.
Frame
Guide
Template
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It is best to place and drive most of the wall sections to a moderate depth before any
sheeting is driven all the way.
This is to ensure that joints are properly interlocked, and also to improve the
alignment of the wall.
This technique is called ___ driving?
Stage
Staged
Greasing the interlocks of sheet piling is sometimes undertaken but it provides little
benefit.
False
*yes, it helps to reduce friction in the interlock and also helps to reduce corrosion in
the interlock which would make extraction more difficult
When you strike an obstacle whilst driving, you can wait until the excavation reaches
that depth before you do anything about it.
True
*yes, you haven’t got much choice unless it is possible to drive though the obstacles.
However heavy driving might force the interlocks to spring or buckle the tip of the
sheet.
BANK ANCHORING involves tying the sheeting into the soil mass. By doing this,
you can leave out one of the usual trench shoring components. Which one?
Strut
Struts
Strutting
Prop
Props
Propping
Brace
Braces
Bracing
*no strut = better access
Soil anchor are now a common back anchor system. What is the system that used
before the development of soil anchors?
Deadman blocks
Deadman block
Deadman
Deadman anchor
Deadman anchors
If the height of the completed piling above ground level has to be 6m, how far would
you need to drive underground to conform to ‘typical’ deadman anchor requirements?
2m
*one third of the height is typical
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Place the following soil anchor steps in their correct order
Drill a hole
Ram in temporary casing
Place the anchor
Inject grout
Tension the anchor
Soil anchors are placed with their top section encased in a protective writing
This encased length is known as the ____ length
Free
*free lengths allows the load to be transmitted deep into the soil mass
Soil anchors are usually installed using a temporary casing. When do you take the
temporary casing out?
During grouting
The anchor is ____ so that a large concentrated force is produced (this concentrated
force propping to help carry the loads that the shoring experiences)
Tensioned
Stressed
Sometimes grouting is carried out in two stages. First the bond length and then after
stressing from the lowest point of the free length sheathing (this is known as
secondary grouting). Why is the free length grouted?
To protect the anchor from corrosion
Now we’re up to CONCRETE DIAPHRAGM (OR CUT-OFF WALLS).
Lets start with some trivia.
Concrete walls have been used extensively in Europe for what range of depth?
0 - 50 metres
*Although cut-off or diaphragm walls of up to 100m are used, most walls are less
than 50 metres
About what thickness diaphragm wall can be built without temporary works?
0.5 – 1.5m
What type of clay slurry is used to fill narrow excavated sections before concreting?
Bentonite
What type of pressure is produced by the clay slurry to support the excavation?
Hydrostatic
Hydrostatic pressure
What is often used to seal a trammie?
Plate
Rubber ball
Steel plate
Ball
*rubber ball or steel plate taped to the base with grease impregnated tape are two
common techniques
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the top layer of concrete placed by the tremmie method is often contaminated because
it has come into contact with _____
Water
Slurry
CONTIGUOUS PILES are installed by:
Boring
CONTIGUOUS PILES are good for controlling groundwater.
False
*the mating of the piles is not perfect
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TRENCH SHORING
What are the THREE components of timbering?
Struts
Wales
Sheathing
Can you dig a trench and THEN shore it?
Yes
*in stable materials!
What is the typical thickness range of the TIMBER sheathing?
50-75mm
The size of the struts depends primarily on what feature of the excavation?
The width of the trench
*struts are usually slender compression members in which buckling is a major
consideration
steel props with screw jacks are used as what traditional ‘timber shoring component?
Struts
Strut
Strutting
Props
Prop
Propping
*strong, durable, easily adjustable
Do PROPRIETARY SYSTEMS allow timber to be used?
Yes
*some systems are based on timbering. It is possible to attach brackets to the narrow
steel sheeting panels. This allows easy placement of the timber wales.
About how long is a typical fabricated shoring panel?
5m
Whereabouts are the struts placed for fabricated shoring panels?
At the ends *easier access/where there is easy access
The ____ trench lining system consists of soldier slide rails and ‘add-in’ side panels.
Krings
What are the ADVANTAGES of modular systems?
They increase productivity
They provide safe conditions
The DRAG BOX can be varied in width during trench construction
False
*that’s right, its usually of a fixed width. Although if removed from the trench new
longer struts could be installed
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Output with the DRAG BOX is usually quite low
False
*output can be high if the excavator is big enough
Keep in mind that UNDERPINNING is a means of supporting an existing structure’s
foundation loads.
Underpinning is for:
Temporary or permanent support
What is the MOST COMMON reason for underpinning?
An adjacent excavation has removed supporting soil
A suitable width for an underpinning pit is usually;
1 – 3metres
*generally the pit should be small so that the remaining foundation material can
continue to take the load during the construction of new supports.
When the depth to the new founding stratum is SMALL, what type of support would
you construct?
Brick piers
Concrete piers
When the depth to suitable strata is GREAT, what type of support would be required?
Steel tube piles
Concrete piles
A gap is often left between the existing footing and the new support during
construction
Name ONE thing that this is usually packed with.
Mortar
Grout
Steel wedge
Freyssinet
Flat jack
*ensure good positive bearing
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PUMPS
The atmospheric pressure at sea level is equivalent to what height of water (in metres)
10.3
Even though the theoretical suction lift for any pump is 10.3 metres, what is the
practical suction lift usually limited to?
6m
During the DOWNSTROKE of a reciprocating pump cycle, is the value in the
PLUNGER open or closed?
Open
*water gets in
During the UPSTROKE, is the value in the SUCTION PIPE open or closed?
Open
During the DOWNSTROKE of the reciprocating pump, is the discharge valve open or
closed?
Open
What are the advantages of the reciprocating pump, when compared to some other
type?
Quite high efficiency
The DIAPHRAGM PUMP consists of a diaphragm stretched of a cylinder.
When does the water flow IN – when the diaphragm is lifted or when it is depressed?
Lifted
*forms a vacuum
There must be water in the chamber of a diaphragm pump before it can be used.
True
*must be primed before use.
The CENTRIFUGAL pump consists of a revolving impeller, with its vanes throwing
out water from the centre.
Does the centrifugal pump need to be primed before use?
Yes
What are the TWO type of centrifugal pump?
Closed impeller pump
Open impeller pump
What pump is more efficient?
Closed impeller pump
*less water pumped thru open impeller
Which pump is MORE prone to damage by soil and other debris?
Closed impeller pump
*flows thru the open impeller
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What do multistage centrifugal pumps have more of than ‘standard’ centrifugal
pumps?
Impellers
Is a SUMP PUMP primed before used?
No
*no as they are positioned under water
What is the SUMP PUMP a small version of?
Centrifugal pump
The discharge produced by a given VARIES with the head against which it must
work.
Manufacturers give out data sheets of their pump so that you can determine which the
right pump is for you.
The force that must be supplied by a pump to overcome the resistance set up the
motion of water through the system is known as the:
Friction head
Pressure head is the height that the water must be lifted:
False
*that’s static head
Pressure head is the energy required to discharge the water at a desired pressure.
It is calculated by multiplying the outlet pressure by the unit weight of water. True or
false?
False
*it is divided by the unit weight.
With regard to FRICTION HEAD, is the following associated with major or minor
losses:
Increased turbulence and resistance to the flow caused by fittings.
Minor
*yes, they are often ignored for long pipes.
major losses occur continuously along the pipe. They are generally regarded a
function of the roughness of the interior surface, and the velocity of the flow.
Losses need to be calculated around the fitting and bends. What is one simple way of
doing this?
Convert the fittings and bends to equivalent lengths of pipe
To calculate energy losses, the Hazen-Williams formula is used:
S = k * Q^1.852
Where, s = energy loss per unit length of pipe
K = a factor you get from a table
Q = the capacity of the flow
K is found by first determining what C is for the type of pipe material. The bigger the
C the smaller the K.
Which of the following materials has the highest value of C?
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Plastic
Rank the following from GREATEST loss to LEAST loss when used in a pipeline.
Standard elbow
Medium sweep elbow
Long sweep elbow
45 degree elbow
lets say that you have pipelines of diameter 100mm and 600mm.
if you place the same type of fitting on both pipelines, which will have the
SMALLER loss?
100mm pipeline
Keep the following things in mind when choosing your pump. Put them in order of
priority.
It must be able to provide the desired rate of discharge
It must be dependable (or have a standby)
Replacement parts must be easy to get hold of
Maintenance should be straightforward
It must be cheap
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GROUNDWATER
The height of the water table varies with the season. When is it usually at its
LOWEST?
Summer
*if you can, do your excavating in summer.
What is the simplest way of controlling ground water on a site?
Ditches and Dykes
With a gravel blanket, is the stone well-graded or poorly-graded?
Poorly graded
About what thickness would the gravel blanket be, if it were comprised of 25mm
diameter gravel (in mm)?
150mm
Can a gravel blanket be used on a slope?
Yes
*slope cannot be too steep
Which of the following are significant properties of a GEOTEXTILE?
Drainage capacity
Filtration capacity
Separation capacity
Tensile strength
Are geotextiles of any use when installed vertically?
Yes
*they are excellent as vertical drains
Filter wells are placed around the excavation. They are connected to the header main
by ____ pipes?
Riser
What is going to get into the pump besides water in a wellpoint operation?
Air
*debris is filtered out as much as possible
Because air gets into a pump in a wellpoint operation, you cant use just any type of
pump. Which of the following is best to use?
Centrifugal
Reciprocating
*if you use centrifugal pump, it must be equipped with an auxiliary positive
displacement pump to remove any air from the water.
Is it detrimental to have small uniform pulsations in the discharge from a wellpoint
system?
False
*vibration helps to prevent clogging of the filter screen.
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After a while, coarse material accumulates on the filter screen of a wellpoint. Is this
good?
Yes
*acts as an additional porous screen
What is the common capacity of a single wellpoint in litres/second?
1 to 1.5
What is the typical length of filter screen section of a wellpoint?
1m
at what centres would you place the wellpoints for maximum drawdown in SILTY
SAND?
1.5m
At what centres would you place the wellpoints for maximum drawdown in COARSE
GRAVEL?
0.3m
Deep wells are usually of small diameter.
False
*up to 1m
Rank the steps for the installation of a deep well. Some of the steps are missing to
make it a little harder.
Install a large diameter pipe
Excavate the material in the pipe
Install a small perforated pipe
Place gravel between the pipe
Place a pump in the pipe
_____ wells of a smaller diameter are sometimes used to measure the DRAWDOWN
of the water table in a large scale dewatering operation.
Observation
Keep in mind that JET EDUCTOR systems are basically large wellpoints.
Jet eductor can lift groundwater from much greater depths than a normal wellpoint
can. From what range of depths can jet eductor achieve this?
20-30m
*yes, a vacuum is created in the riser near the constriction. This, along with the
pressure of the water pumped in through the high pressure water line, ifs the
groundwater from these incredible depths.
The pressure in the riser pipe of a jet eductor is ____ kPa.
100
Jet eductor are relatively inexpensive.
False *heaps expensive
Jet eductors DO NOT eliminate the need for multistage wellpointing.
False
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STABILISATION and CONSOLIDATION
Sand drains are used to consolidate what material?
Silt and organic material
*used in swampy conditions
Are sand drains quick to install?
No
What diameter is the steel pipe casing used for installation of sand drain?
400-500mm
What is the range of centres that is usually adopted for a sand drain dewatering
operation?
2 to 3 metres
Should the sand used in sand drains be of a high or low void ratio?
High void ratio
Do you remove sand drains after the material has consolidated?
No
ELECTRO OSMOSIS and ELECTROCHEMICAL CONSOLIDATION are ways of
stabilising and consolidating similar to sand drains.
In electro osmosis, a direct current is passed through the soil. Does the water flow
with or away from it?
With it
In ELECTRO OSMOSIS, the moisture content in the excavation is reduced due to the
water moving away with the current.
This results in an increase of what type of strength?
Shear
*This increases in shear strength enables excavation in silts and weak silty clays to be
made with steeper batters.
In ELECTRO OSMOSIS soil consolidation, the ANODE is placed closest to the
excavation.
True
*water flows from away from +ve to –ve
Is electro osmosis a cheap form of stabilisation of soil?
No its rather expensive
*installation and running costs are high
Stabilisation of soil by electro osmosis is achieved relatively quickly.
False
*it can take months.
Electrochemical consolidation is quite complex, so heres some background
information.
It uses a similar setup to osmosis, but a salt solution is introduced at the anode.
Stability is improved due to ionic permeation. This either changes the chemical
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arrangement in the clay mineral, or increases the bonding between the particles and
the water.
There are many chemical additives that can be fed through an opening in the anode
during electrochemical consolidation for particular clays. What is the most common
additive?
Calcium chloride
Cooling in the subsurface results in the pore water freezing. This results in
strengthening of the soil.
Which is the most common system of freezing?
Recirculatory system
What is the temperature of the liquid inside the brine pump of a recirculatory system?
-30
What temperature can liquid nitrogen reach when it is allowed to evaporate into the
atmosphere?
-196
What freezes the ground in the RECIRCULATORY system?
Brine
Which system freezes the ground the quickest?
Non-recirculatory system
Which system is the more expensive?
Non-recirculatory system
*due to the liquid nitrogen
Ground freezing is a very time consuming process.
False
*it can be quite speedy, especially if very small probe centres are used.
Ground freezing is economical when the cost of delays is great. It is quick to install,
which is its attraction. But remember it is only temporary.
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SHALLOW FOUNDATIONS AND SPREAD FOOTINGS
Usually SHALLOW FOUNDATIONS are uses when reasonable foundation materials
is located within how many metres of the surface?
3m.
Which of the following are types of spread footing?
Single
Raft
Strip
Spread footings aim to:
Spread the load over a wide area
*you need to reduce the pressure on the founding strata
An AXIAL LOAD alone produces:
Uniform bearing pressure
*going straight down
Non-uniform bearing pressure is created by:
Axial loads combined with being moment
What type of resistance is required when a shallow foundation is subject to a
horizontal load?
Friction
Frictional
Sliding
Is clay a good foundation material?
Yes
*some settlement must be acceptable, you need to control moisture by providing
drainage or a moisture barrier
For a hard, dry clay what is the typical allowable bearing pressure?
300MPa
Rank the following foundation materials in terms of their allowable bearing pressure.
Loam
Sandy clay
Shale
Medium sandstone
Igneous stone
Which why does SYNCLINE face?
Downwards (sagging)
*anticline goes up
With anticline and syncline, cracking can occur in some of the layers. Can this rock
provide adequate bearing strength (in general) for smaller to medium sized footings?
Yes
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*substantial strength can be achieved, but it is wise not to excavate any deeper than
you have to for the footing. The deeper you go, the greater the chance of disturbing an
unstable layer.
Joints and faults in rock are of greatest significance in earthquake zone. But what
excavation method can unwary engineer employ that might convert a passive fault
into an active one?
Blasting
Explosive
Explosives
A ‘binding layer’ or ‘mud mat’, which is just a mass concrete layer, is often placed
over foundation materials when the excavation work is complete. Generally how thick
is it (in mm)?
50mm.
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DEEP FOUNDATIONS 1
Piles are used to transmit loads to deeper levels when the strata at the surface isn’t
strong enough.
Which of the following are resisted by the end bearing and friction between the pile
and the bearing strata?
Axial loads
How do TENSION PILES resist the load?
Shaft friction
Which of the following are counteracted by the passive resistance of the surrounding
soil?
Bending moments
Horizontal loads
Raked pile together with a stiff pilecap can be used to form a frame. How are the
moments which act on the pile cap resisted?
By axial forces in the piles
Which of the following are ADVANTAGES of a REINFORCED CONCRETE pile
over a prestressed concrete pile?
Long term durability
Lower transportation cost
More easily spliced
The head and toe of a reinforced concrete preformed large displacement pile is
heavily reinforced for the following reason?
To resist driving force
A plane of weakness between the wood and the bark forms during the decomposition
of the bark. What is the major implication of this on the pile?
Reduced shaft friction
*bark should be stripped off
Timber piles are limited in that they only come in short lengths.
False
*yes, they can be spliced by using a steel cylinder and bolting the first section into the
bottom half of the cylinder and the second section into the top half.
Select the following which are features of timber piles.
Lightweight
Susceptible to decay
Renewable resource
How much do you know about the FRANKIPLIE system?
Place the following in order:
Consolidate the plug
Drive the tube
Form the base
Place the reinforcement
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Concrete the pile
There are two types of STEEL driven piles. One is tubular, and the other is UBP.
What does UBP stand for?
Universal bearing pile
Do bored piles have to be cased?
No
*Boring piles can be cased, but they don’t NEED to be in ‘stable’ ground. Of course,
the chance of something going wrong during construction of the pile is increased
without the casing, so you need to consider this.
Keep in mind that the casing can be temporary. This is cheaper than providing a
permanent casing, and less risky that having no casing at all.
Now, lets move onto CLASSIFICATION of piles.
There are four classification:
Large displacement, preformed
Large displacement, formed in place
Small displacement
No displacement
Which of the following are large displacement, preformed piles?
Timber
Which of the following are ADVANTAGES of a large displacement, preformed pile?
Groundwater isn’t a problem
You can inspect all of the pile
Which of the following DISADVANTAGES apply to large displacement, formed in
place piles?
Need a lot of head room
Need a firm site
*Pile lengths are easily adjusted – just vary how deep you drive the section
*the plant is cumbersome – you need a firm, level site with plenty of overhead room
*shaft friction is increased due to the increased bonding of the concrete with soil
Small displacement piles, such as UBP’s and open ended steel tubes, have many
ADVANTAGES. Which of the following apply to steel small displacement piles?
Toe anchoring
Minimal wastage
Hard driving allowed
Easy lengthening
Which of the following are DISADVANTAGES of a NO DISPLACEMENT pile?
Non-cohesive soil may be loosened
Cannot inspect the pile
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DEEP FOUNDATIONS 2
PILE SECTION is very important.
Which type of pile would you use in a GRANULAR material?
Large displacement
*Large displacement is the best due to the faults in other methods.
*Small displacement – limited surface area.
*No displacement – requires temporary casing.
Which type of pile would use in COHESIVE material?
No displacement
*No displacement offers good shaft friction, and can also be cheap.
The following must also be taken into account when selecting the type of pile:
Cost
Pile loading
Expected founding level
Ground condition
Plant access
Adjacent structures
How for PILING EQUIPMENT. The two ‘type’ of equipment are Pile Frame and
Hanging Leaders.
The two type of hammers commonly used with their equipment are the drop hammer
and the _____ hammer.
Diesel
The drop hammer doesn’t necessarily operate by free falling.
True
*may be an attached falling
For effective pile driving, the weight of the hammer has to be GREATER than onethird of the weight of the pile.
True
The drop hammer is a quick way to drive a pile.
False
*blow rate is usually 5 to 15 blows per minute
Is the drop hammer suited to drive piles in high resistance soils?
Yes
A diesel hammer is:
Semi-automated
*the ram must be first lifted by winch rope. Once the fuel begins to explode under the
blow, the operation will continue automatically.
The diesel hammer is impractical in soft ground:
True
*because the ram does not strike the anvil with enough force to vaporise the fuel.
A pile can be specified that it must be driven to ‘nominal refusal’. This is generally
specified as 25mm in ____ blows.
20.
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A pile can be also be driven to a ‘specified set’ this is a common specification
requirement for concrete driven piles. For example once a 35-45 tonne piles has
reached contract level, it is driven with a further four blows to establish ‘set’.
How many millimetres is the pile to move under these four blows for the pile to be
considered to have reached ‘set’?
6mm
If you stop driving the pile for an extended period of time, can you expect the
penetration per blow to be greater or lesser when you resume?
Lesser
*It will take a lot of blows to get going.
It is wise to avoid any stoppage during driving the pile, simply because it does take so
long to get going again.
Finally remember that it is wise to measure the ‘set’ just after you finish driving,
rather than after a long period of time. This is because of the same reason as given
above.
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FORM and FALSEWORK
Does the height of the concrete pour have any effect on the lateral pressure produced
on the vertical forms?
Yes
*higher pour = higher pressure
Does the rate of vertical placement of the concrete have any effect on the lateral
pressure?
Yes
*because concrete stiffens over time
Does the lateral pressure on vertical forms always keep increasing with depth, or can
it level off?
Levels off
*hydrostatic pressure can be curtailed by other factors.
The smaller the slump of the concrete, the GREATER the lateral pressure experienced
on the forms.
False
For vertical formwork, which component usually is horizontal and runs left to right?
Wales
What are the main support members of formwork called when they are vertical?
Soldiers
In formwork that can be resisted, the further the wales are spaced apart, the LOWER
the design lateral pressure?
True
In vertical formwork, usually ties are used to join what components?
Wales
In vertical formwork, ties support a proportion of the area of the formwork. The
proportion is a fraction of: horizontal tie spacing x vertical tie spacing.
What is proportion?
Four quarters
For formwork, can the maximum deflection allowed for VISIBLE concrete surfaces
any different to that for hidden concrete surfaces?
Yes, it can be smaller
In formwork, should the grain of the outer plies of the plywood run parallel or
perpendicular to the studs?
Perpendicular
How many of the following do you consider when assessing the STRENGTH that
will be obtained from a proprietary system prop.
Allowable axial loads
Addition of lateral bracing
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How many of the following do you consider when assessing the DEFLECTION that
will be experienced by proprietary system falsework?
Pre-camber
Foundation settlement
FOUNDATION DESIGN for falsework must include consideration of:
Bearing pressures
Settlement
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CONCRETING
Generally for 4m3 of concrete mixing, time should not be less than:
3 minutes
Air temperature is a very important parameter affecting the success of concrete
placement.
What is the MINIMUM temperature that you should place concrete at?
5
What is the MAXIMUM temperature that you would place concrete at?
40
Fresh concrete is subject to PLASTIC SHRINKAGE. What can you do to reduce its
effect?
Erect wind and sun shields
Cool the materials before mixing
keep the concrete surface wet
Concrete is also subject to PLASTIC SETTLEMENT. Which of the following can
help reduce it?
Revibrate the concrete after placement
Cast the concrete in layers
COMPACTION of concrete is important. Keep in mind that the idea is to get as much
air out of the mix as possible.
It is said that you should not leave a vibrator in the same place for too long. What is
the recommended MAXIMUM time?
30
When compacting concrete, the immersion vibrator should be inserted at regular
intervals. What is the maximum spacing recommended for a large vibrator?
500
When using an immersion vibrator, should the vibrator be inserted:
Vertically
*that is so that ALL concrete is compacted.
It is OK to angle the vibrator for thin slabs to maximise the contact length of the
vibrator with the concrete. But this procedure has one particular disadvantage. What is
it?
Fines may rise to the surface
*worry is the segregation
You should not move concrete around the vibrator. You could segregate the concrete
so that there are pockets of aggregate, with no mortar to bind it.
Often you need to pour a layer of concrete over another one. Assuming that the
previous layer has not set, is it wise to get the vibrator down to that layer as well?
Yes
*this practice prevents detrimental cold joints.
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When placing concrete, how long can concrete be kept in the truck after mixing
before being placed in its final position?
90 minutes
*provided the concrete is kept agitated.
Ready mix concrete can be ordered in increments of:
0.2 cubic metres
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COMPRESSORS AND AIR OPERATED TOOLS
Compressed air is used on construction sites to operate pneumatic breakers, rock
drills, pumps and small equipment.
Is compressed air a cheap form of power?
Yes
Is compressed air a relatively safe form of power?
Yes
*although relatively safe, care must be taken to ensure an air stream is never directed
at anybody and dust or debris is not blown into the eyes.
And now let’s get to onto the theory of compressed air. It is almost impossible to test
you on the process, so here’s a quick explanation of the principals using a
reciprocating compressor to describe the process.
1) the piston cylinder is filled with air at atmospheric pressure
2) the piston moves in, compressing the air
3) the air pressure in the cylinder and the discharge pipe are now the same
4) the discharge valve opens, and the compressed air is delivered
5) the piston moves out
6) the suction valve opens when the pressure drops below that in the suction pipe,
and fresh air comes in
… and the whole process starts again.
Now, when the compressed air is discharged, a small amount is kept behind. The
expression give to this volume of air is called the ____ volume?
Clearance
*the chamber cannot be fully evacuated because there must be clearance to ensure
valves are not damaged.
A compressor operates between two limiting processes. Compression takes place
under what theoretical conditions for ISENTROPIC compression.
No heat exchange with the surroundings
Air is usually compressed in two stages. The air passes through a tubular radiator on
the way from stage 1 to stage 2 compression.
Does the tubular radiator heat or cool the air?
Cool
The tubular radiator that cools the air in two stage reciprocating compressor is also
known as the _____?
Intercooler
In a multistage air compressor, what does cooling the air do to its volume?
Decreases it
Which of the following reciprocating compressors exist?
Single stage
Double stage
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If the air pressure going into the second stage of a double stage compressor was
200kPa, what would be the pressure at the outlet?
700kPa
Which type of intercooler is the more convenient in a portable reciprocating
compressor?
Air cooled
It is true that air receivers are actually defined as boilers, and as such are subject to
specific safety regulations?
Yes
What happens when air demand is substantially reduced?
Suction valve opens
*compression stops
What valve adjusts the compressor speed to the air consumption?
Fuel valve
*pressure regulated
Select the relevant advantages of a reciprocating compressor.
Easy to maintain
Tough
What are the reciprocating compressors mostly used as?
Stationary units
*relatively heavy and bulky
Just how fast does the rotor spin in a sliding vane rotary compressor?
1500-1800rpm
In a sliding vane compressor, how is the rotor mounted in the cylinder?
Eccentrically
Just in case you aren’t sure, in sliding vane compressor, compression takes place with
spinning of the rotor. Large air pockets are turned into small one  compression!
The centrifugal force keeps the vanes in contact with the casing, producing
compressed air.
What fluid is sprayed into the compression space to serve as both a lubricant and a
sealer?
Oil
What usually wears out first in a sliding vane compressor?
The vanes
Why does compression stop when a sliding vane compressor idles?
The centrifugal force is too low
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Which of the following statements are TRUE for a sliding vane compressor?
It is quiet
Low vibration
How many helical rotors are there in rotary screw compressor?
2
In a rotary screw compressor, as the rotors intermesh, the air gets force into smaller
and smaller spaces. Hey presto  compressed air.
Now, do the inlet and outlet ports automatically seal themselves off?
Yes
*they are sealed off by the ends of the rotor.
Which rotary compressor system is more efficient? One where the rotors are:
Non-symmetrical
*They are more efficient by about 10-15%
Rotary screw compressors are more efficient than sliding vane compressors.
True
Are rotary screw compressors very reliable?
Yes
Breakdowns of a rotary screw compressor are cheap to repair.
False
*close machine tolerances are required
Are large compressor installations popular? (A large installation is where there is one
central compressor, and pipelines are fed off them to different areas of the site.)
No
*that’s right, portable units are usually preferred. Large compressors systems are now
not very popular, due to being inefficient (losses in the pipe are very high), and the
pipelines getting in the way of everything!
A BLOWPIPE is used to clean dirt and debris off reinforcement and formwork.
An AIRLIFT is another simple tool that uses compressed air.
What is an air lift best described as?
A pump
Which of the following components can be found on an air lift?
Riser pipe
Air supply line
What type of conditions is an air lift designed for?
Water charged excavations
The air lift is only efficient if the submergence of the riser is LESS than 30% of the
lift.
False
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The operation if a JACKPICK is quite simple. Please have a look at the diagram in
your notes to ensure that you are familiar with it.
Jackpicks have steels on the end of them (to pick with). One type is the tamping pad.
The other two are the moil point and the __ ___ spade.
Chisel point
In a jackpick, when the piston is driven DOWN, is the exhaust port open or closed?
Open
*yep it is so the lower chamber gases can escape
Iin a jackpick, when the piston is driven UP, is the exhaust port open or closed?
Open
*air from the upper chamber is expelled. The exhaust port services bother upper and
lower chambers.
The action of the jack hammer (or hand rock drill) is:
Rotary and percussion
When using a rock drill, which action chips the rock?
Hammering
*rotation gives fresh striking surfaces
In rock drills, the drill stem is hollow.
True
*this is where the air comes out
A ‘blower’ valve is present on the jack hammer. Its purpose is to turn all of the air
that through the throttle down to the stem (if that is what is desired). This process is
very useful in which of the following situations?
Deep holes
Soft rock
In a jack hammer, what does the rifle bar move on the upstroke or downstroke?
Downstroke
A pusher leg is simply an ___ ____ that provides pneumatic support for a jack
hammer.
Air cylinder
A jack hammer with a pusher leg can only drill vertical holes.
False
Are drifters bigger or smaller than jackhammers?
Bigger
Are drifters hand held or supported?
Supported
*they are supported on a cradle and get fed into the work.
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In a drifter, rotation of the drill is powered by a rifle bar assembly.
True
A WAGON DRILL is just a tool mounted on a mobile frame. Which tool?
Drifter
Which of the following are true for wagon drills?
Poor manoeuvrability
Slow to set up
CRAWLER DRILLS have replaced wagon drills, and they are much more mobile
and flexible in use.
What direction(s) can the mast of a crawler move in?
Sideways AND up and down
Can the crawler drill up used to drill angled holes?
Yes
There two common types of DRILL STEEL used in drifters. They are integral and
___ drill steels.
Extension
What is an integral drill steel for a drifter made from?
Alloy steel
What is the most common cross-sectional shape of the integral drill steel used in a
drifter?
Hexagon
The integral drill steel is hollow.
True
*to allow air to remove cuttings and cool the bit.
Which drill bit used in a jack hammer or drifter is easiest bit to sharpen?
Chisel bit
Which drill bit used in a jack hammer or drifter has the best penetration?
Button bit
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