Civil Engineering Technical Job Interview Questions and Answers for Freshers and Experienced:
Question
No. 01
What
is civil engineering?
Answer: Civil engineering is a professional engineering discipline that deals
with the design, construction, and maintenance of the physical and naturally
built environment, including works like roads, bridges, canals, dams, and
buildings.
Civil engineering is arguably the oldest
engineering discipline. It deals with the built environment and can be dated to
the first time someone placed a roof over his/her head or laid a tree trunk across a river
to make it easier to get across.
Question
No. 02
What
does civil engineering do?
Answer: They do many interesting things. Their job has to do a lot with design
and construction. They can tell you what works and what will not for all sorts
of situations.
There is a lot of mathematics involved along
with many other disciplines. They have to have a good solid understanding of how
the environment works and how nature interacts with manmade. They are probably
best known for designing bridges, interstates, skyscrapers, canals, and so
forth.
Question
No. 03
What
is the difference between shear and tensile strength?
Answer: Tensile Strength for a Bolt is determined by applying a Force along it
long axis. Shear Strength for a Bolt is determined by applying a Force across
its diameter, as it would be loaded in a lug joint.
Question
No. 04
What
are the materials used in building a gravity dam?
Answer: There are many gravity dams constructed of compacted earth. High dams
are generally concrete. All dams require a spillway to be safe. The spillway
must be armoured.
Question
No. 05
What
does civil status mean?
Answer: Civil means like, when you do not get on with someone, but only talk
when you have to. Alternatively, when you do talk you do not argue.
Alternatively, if you are with someone who is of your both friends and family,
you do not ruin it for them.
Question
No. 06
What
are the functions of a column in a building?
Answer: A column is used to support the weight of the roof and/or the upper
floors. Now days, many columns are used for decorative purposes. A column along
with load bearing beams can support a lot of weight.
Question
No. 07
What is the
function of packing materials in the joint of concrete pipes in pipe jacking?
Answer: Packing
materials are about 10 mm to 20 mm thick and are normally made of plywood,
fibreboard or other materials. In case packing materials are absent in pipe
joints for pipe jacking, then any deflection in the joints reduces the contact
area of the concrete and it leads to spalling of joints due to high stresses
induced. With the insertion of packing material inside the pipe joints, the
allowable deflection without damaging the joint during the pipe jacking process
can be increased.
Question
No. 08
For drained
reclamation, what is the significance of smear zone induced by installation of
band drains?
Answer: During installation of band drains,
smear zones are created in which zones of soil surrounding the band drains are
disturbed. The compressibility of surrounding soils is increased and it results
in the reduction of their permeability. In fact, the surrounding soils are
remoulded during the installation process and the effectiveness of band drains
is reduced. In essence, for the reduced permeability of soils around band
drains, it takes longer time to complete the consolidation process.
Question
No. 09
What
are the causes of building collapse?
Answer: The Passage of time is one reason. Buildings also collapse due to weak
foundations. Earthquakes, hurricanes and other natural disasters can also
damage the structure of the buildings and cause it to collapse. Bombings or
demolition of buildings is also other reasons.
Question
No. 10
In
selecting screw pumps in polder scheme projects, what are the factors that
affect the design capacity of screw pumps?
Answer: The commonly used angles of
inclination for screw pumps are 30°, 35° and 38°. For screw pumps of relatively
high lifting head, like over 6.5 m, angle of inclination of 38° is normally used.
However, for relatively lower head and high discharge requirement, angle of inclination
of 30° shall be selected. In general, for a given capacity and lifting head,
the screw pump diameter is smaller and its length is longer for a screw pump of
30° inclination when compared with a screw pump of 38° inclination.
To increase
the discharge capacity of screw pumps, a larger number of flights should be selected.
In fact, screw pumps with 2 flights are more economical that that with 3
flights in terms of efficiency and manufacturing cost. Moreover, the discharge
capacity is also determined by the screw pump diameter and sizes of 300 mm to
5000 mm are available in current market.
Question
No. 11
What is
the load transfer mechanism for paving blocks in pedestrian footway?
Answer: In Hong Kong, footway is normally
designed with paving slabs/interlocking blocks instead of concrete because the
extensive use of concrete in pavement is boring. Moreover, poor appearance will
result in concrete pavement due to frequently trench openings for utility work.
In addition, owing to the prolonged setting and curing time of concrete, the
use of concrete pavement inevitably generates disturbance to the general
public.
The
pedestrian loads are taken up through the following ways:
- Load carrying capacity of paving slabs/interlocking blocks are derived from their individual strength;
- Pedestrian loads are also supported by interlocking forces provided by friction transfer through the sand in vertical joints (K. K. Tang & Robert P. Cooper (1986).
Question
No. 12
What
is the meaning of soil reinforcement?
Answer: Soil reinforcement is the act of improving soil strength to enable it
support or carry more load.
Two common examples are:
- Mixing a soil amendment such as lime into weak clayey soil and re-compacting to improve soil-bearing capacity (often done under the road base in highway construction)
- Installing plastic or composite webbing layers (called geo-grid material) alternating with compacted soil to produce a stronger sloped soil structure (often done on steep roadway embankments to improve strength and stability)
Question
No. 13
If the
construction of concrete carriageway is carried out in summer, can expansion
joints be omitted?
Answer: If the construction of concrete
carriageway is carried out in summer, expansion joints may not be necessary as
suggested by Arthur Wignall, Peter S. Kendrick and Roy Ancil. Expansion of
concrete carriageway is mainly due to seasonal changes with an increase in temperature
from that during construction to the ambient temperature (i.e. the temperature in
summer). However, if the construction of concrete carriageway takes place in
summer, the concrete carriageway will undergo contraction in the following
winter, thus the space available in contraction joints can accommodate the
future expansion in the next summer.
Question
No. 14
Why are
steel tubular marine piles often driven open-ended?
Answer: In marine structures where piles are
constantly subject to significant lateral and uplift forces induced by berthing
operation and wave action, it is necessary to drive the piles to much greater
depth. To avoid premature refusal so that insufficient soil cover may develop which
is incapable of providing the required lateral and uplift resistance, tubular
piles are normally driven open-ended so that they are driving to greater depths
than piles with closed ends.
Question
No. 15
What
is the difference between engineering stress and true stress?
Answer: In biology, Stress is something that disrupts homeostasis of an organism.
In engineering, Stress is an external force that pushes, pulls, twists, or
otherwise puts force on something.
Engineering stress assumes that the area a
force is acting upon remains constant, true stress takes into account the reduction
in area caused by the force.
Question
No. 16
Why are
high and narrow beams not desirable in concrete piers?
Answer: Based on past experience in other
countries (Carl A. Thoresen (1988)), high and narrow beams after several years
of construction showed signs of serious deterioration at the bottom of the
beams. However, the deterioration of pier slabs was not significant when compared
with that of the deep beams. The main reason to account for this is due to the close
proximity of the deep beams to the sea level. To avoid these problems, either beamless
slab or wide with shallow beams are normally designed.
Question
No. 17
Why
does the pressure increase under soil?
Answer: Soil pressure increases with depth due to the overburden or self-weight
of the soil and due to loads imposed upon the soil.
For example, the pressure variation below
the depth of soil is linear and the relation is given by pressure = unit wt ×
depth.
As depth increases, there will be a linear
increase in the soil pressure.
Question
No. 18
Geotechnical
Instrumentation is frequently employed for monitoring the condition of
reclamation. Sometimes two piezometers are installed inside the same borehole. What
is the reason behind this?
Answer: For standpipes, they normally contain
one plastic tube between its intention is to measure water level only. However,
for piezometers, they are used for measuring pore water pressure in a certain
depth below ground. For instance, if there are two clayey layers below ground
at different depths, a multiple piezometer including two separate piezometers
may be sunk at the same borehole to determine the pore water pressure at these
layers respectively. This arrangement has the advantage that it saves the cost
of installation of separate boreholes for several piezometers. However, the
installation of multiple piezometers within the same borehole is affected by
occurrence of leakage along the pipes as suggested by Marius Tremblay (1989).
Question
No. 19
What
do you mean by honeycomb in concrete?
Answer: Some people call it an air pocket in the concrete or a void.
Question
No. 20
In the
construction of pump troughs for accommodation of screw pumps, what is the
construction method to ensure close contact between the screw pumps and the pump
trough?
Answer: In the construction of screw pump
troughs, trapezoidal-shaped troughs are usually formed by using normal
formwork. In order to enhance close contact between screw pumps and troughs,
upon lifting the screw pumps into the troughs screeding works is carried out. Screw
pumps are set to rotate and screeds are placed between the gap of screw pumps’ blade
and trapezoidal-shaped troughs during the rotating action of screw pumps. After
the screed sets, it serves to prevent leakage of water during the pumping
operation of screw pumps.
Question
No. 21
How
did street originate in the plumbing term street ell?
Answer: A "street ell" may have gotten its name because it describes
a 90 fitting particularly useful in tight, street ditches. When installing
water pipes under a street, or from a water service, again under the street,
into a home or business, this street ell allows one to change pipe direction
with one less fitting, and in less space, than with a standard ell.
Question
No. 22
In
General Specification for Civil Engineering Works (1992 Edition), it specifies the
temperature requirements for bituminous material during and after mixing. What is
the reason behind this?
Answer: Temperature is one of the factors
that govern the compaction of bituminous material and the air void content is
found to decrease with an increase in compaction temperature. This phenomenon
is explained by the viscosity-temperature relations: the higher is the
viscosity of binders, the greater is the resistance to compaction. Therefore,
in normal contract for bituminous laying, the temperature requirements for
bituminous material during and after mixing are specified.
Question
No. 23
What
is diversion tunnel in a dam?
Answer: When a dam is to be built, a diversion tunnel is usually bored through
solid rock next to the dam site to bypass the dam construction site. The dam is
built while the river flows through the diversion tunnel.
Question
No. 24
What is
the function of a separation membrane between concrete pavement slab and
sub-base?
Answer: The separation membrane between
concrete pavement slab and sub-base has the following functions:
- It aids in reducing the frictional forces between concrete slab and sub-base and helps to movement of concrete slab with respect to sub-base owing to changes in temperature and moisture.
- It prevents the loss of cement and water in immature concrete which significantly affects the strength and durability of hardened concrete.
- It avoids the mixing up of sub-base materials and freshly placed concrete.
Polythene
sheeting, which is a waterproof material, is commonly used as separation membrane.
Question
No. 25
Why
was the Empire State Building made of steel?
Answer:
- Strength - Steel is very strong
- Flexibility - Ability to flex in the wind
- Cost - Inexpensive and fast to build; Prefab construction
Concrete, a possible alternative, has less
compressive strength than steel. The bottom support structure of the empire
state building would consist of a large percentage of solid concrete simply to
support the weight of the building.
Question
No. 26
Why is
sulphate-resisting cement not used in marine concrete?
Answer: The main components of Portland
cement are tricalcium silicate, dicalcium silicate, tricalcium aluminate and
tetracalcium aluminoferrite. In sulphate-resisting cement, it contains a low
amount of tricalcium aluminate in order to avoid sulphate attack. Otherwise, tricalcium
aluminate would react with sulphates to form calcium sulphoaluminate and gypsum
that cause expansion and crack the concrete structure.
However, for
marine concrete sulphate-resisting cement should not be used because tricalcium
aluminate has high affinity for chloride ions. This is based on the possible reaction
of chloride ions and tricalcium aluminate to form calcium chloroaluminate
hydrate as suggested by P. Kumar Mehta (1991) and the reduction of which may
increase the rate of chloride attack to the concrete marine structure and
result in faster corrosion of steel reinforcement in marine structures.
Question
No. 27
What
black man invented the clothes dryer?
Answer: George T. Sampson
Question
No. 28
Would
you cause a 55 gallon drum of water to weigh more by climbing in?
Answer: A person will sink in water if he is not holding enough air in his
lungs to keep him floating. Therefore, the person weighs more than the amount
of water that he will displace.
Question
No. 29
Is it
worthwhile to carry out tests on particle density of soil particles for geotechnical
design?
Answer: Particle density of soils is defined
by the ratio of soil particle mass and soil particle volume. Depending on soil
types, the range of variation of soil particle density varies not significantly,
i.e. by 4%. Therefore, it may not be worthwhile to order laboratory tests and incur
additional expenditure just to determine the particles density by recognizing
that the variation of particles density is not significant.
Question
No. 30
What
is the withdrawal force of steel nails?
Answer: In engineering, the code allowable withdrawal force is zero, because
the wood expands and contracts over time and the nail pullout force can reduce
to zero.
Question
No. 31
Are there
any differences in the methods of compaction between clayey soil material and
sandy material?
Answer: As suggested by Lars Forssblad
(1981), the three main actions of compaction are static pressure, impact force
and vibration. Different compactors contain one or more modes of these actions.
For example, vibratory tampers perform mainly by the principle of impact while
vibratory rollers work with principle of static pressure and vibration.
For sandy
soils, vibration is adequate for normal compaction because the action of vibration
sets the soil particles in motion and friction forces between soil particles
are virtually demolished. During this vibration motion, the soil particles
rearrange themselves to develop a dense state.
For normal
soils, it is necessary to combine the action of vibration together with static pressure
to breakdown the cohesion forces between soil particles in order to allow for better
compaction. The static pressure of vibratory machines is adopted to exert a
shearing force to eliminate the cohesion in clayey soils.
Question
No. 32
Are kerbs
necessary in road pavements?
Answer: In general, kerbs are essential in
road pavements due to the following reasons (based on Arthur Wignall, Peter S.
Kendrick and Roy Ancil):
- They provide strength to the sides of road pavements and avoid lateral displacement of carriageway due to traffic loads.
- In terms of road safety, they serve as a separation line between footway and carriageway and aid car drivers in driving safely.
- They act as a vertical barrier to guide the surface runoff collected in road pavements to the gullies.
Question
No. 33
Can
a wave happen in the middle of the ocean like in the movie Poseidon 2006?
Answer: Yes. Rogue waves have been known to capsize ships.
Question
No. 34
In
connecting fenders to pier structures, should single lock nuts or double lock
nuts be used?
Answer: In many pier structures the
connection offenders to piers is achieved by using single lock nuts. However,
they do not perform well because some timber fenders loosen more easily when
subject to vibrating loads due to berthing, wave and tidal actions. To solve
this problem, double lock nuts should be adopted as they prove to function
satisfactory in other structural elements which are subject to frequent
vibration loads.
Note: Double
lock nuts mean two nuts are adopted in a single bolt connection between fenders
and marine structures.
Question
No. 35
What are
the different applications of draglines, backhoes and shovels?
Answer: An excavator is defined as a
power-operated digging machine and it includes different types like shovels,
draglines, clamshells, backhoes, etc.
- A dragline possesses a long jib for digging and dumping and it is used for digging from grade line to great depths below ground. Its characteristic is that it does not possess positive digging action and lateral control of normal excavators. A dragline is normally deployed for bulk excavation.
- A backhoe is designed primarily for excavation below ground and it is especially employed for trench excavation works. It digs by forcing the bucket into soils and pulling it towards the machine and it possesses the positive digging action and accurate lateral control.
- A shovel is a machine that acts like a man’s digging action with a hand shovel and hence it is called a shovel. It digs by putting the bucket at the toe of excavation and pulling it up. Though a shovel has limited ability to dig below ground level, it is very efficient in digging above ground like digging an embankment.
Question
No. 36
What
are the advantages and disadvantages of lead products in construction?
Answer:
Disadvantages: Lead is very toxic; Its use can result in
pollution of the ground and more importantly of water supplies. This leads to
the contamination of drinking water and can cause hazards to human health as
well as disrupting entire ecosystems.
Advantages: Because of its toxicity, lead is being
bought less and less around the world, which of course results in the lowering
of its cost. In addition, lead melts at a relatively low temperature, making it
great for solder. However, recently the Chinese have shown an interest in
buying mass quantities to manufacture batteries made from a base of lead so the
price of this metal may soon rise.
Question
No. 37
In case a
road passes through a reclaimed land and an existing land, what is the main
concern regarding the design of pavements?
Answer: For an existing land, it is anticipated
that there will be no major settlement within the design life of pavement
structures. However, for a recently reclaimed land, even with surcharging and
installation of vertical drains, some settlement will still occur after the construction.
If a road pavement has to be constructed connecting these two areas, special design
has to be made in this transition region. In order to avoid the occurrence of differential
settlement which may damage the pavement structure, a transition slab may be designed
to accommodate such movement (J. S. M. Kwong (1996)).
Question
No. 38
What is
the application of inverted siphons? What are the disadvantages of using inverted
siphons?
Answer: Inverted siphons are designed at locations
in which a sewer system is blocked by underground utilities or storm-water
drains. They are sometimes called depressed sewers because it is claimed that
there is no actual siphon action. They connect the upstream and downstream
sewers with U-shaped vertical alignment such that they are always running full.
The drawbacks of inverted siphons are:
- They induce additional head loss to the sewer system which is undesirable in hydraulic performance;
- U-shaped siphons create sediment accumulation problem and previous experience showed that inverted siphons were easily blocked due to siltation;
- Maintenance of invert siphons is difficult due to its inaccessibility.
Question
No. 39
What
are the uses of Groynes?
Answer: They prevent, or slow down erosion, and stop long shore drift. This,
however, can have bad knock-on effects somewhere near.
Question
No. 40
In
selection of dams in drainage channels, what are the advantages of using rubber
dams instead of steel-gate dams?
Answer: The advantages of rubber dams are as
follows:
- Since rubber is flexible in nature it is capable of performing deflation even in the presence of dirt and sedimentation on the downstream side. However, for rigid steel-gate dams, it may not be possible to open when there is excessive sediment.
- Since the foundation of rubber dams is comparatively lighter than that of steel-gate dams, it saves both construction cost and time.
- Rubber dams can be designed with longer spans without piers while steel-gate dams require intermediate piers for long spans.
Question
No. 41
What
Tor stands for in Tor steel?
Answer: The owner’s last name
Question
No. 42
What is
the purpose of carrying out water absorption test for pre-cast concrete pipes?
Answer: Cement will mix with more water than is
required to eventually combine during hydration of cement paste. As such, some
voids will be left behind after the hydration process which affects the
strength and durability of concrete. With the presence of air voids in
concrete, it is vulnerable to penetration and attack by aggressive chemicals.
Good quality concrete is characterized by having minimal voids left by excess
water and therefore, water absorption test for pre-cast concrete pipes is
adopted for checking the quality of concrete in terms of density and
imperviousness.
Question
No. 43
What
are the advantages of building a dam on the river Nile?
Answer: It is the same as building a dam on any river. Dams are built to
control flooding downstream during the wet season, generate power year round,
and provide irrigation in the dry season.
Question
No. 44
What are
the functions of slip joints in block-work seawalls?
Answer: Slip joints are joints which are
formed through a complete vertical plane from the cope level to the toe level
of seawalls. These joints are designed in block-work seawalls to cater for
possible differential settlements between adjacent panels of seawalls. The
aggregates inside the half-round channels in slip joints allow for the vertical
movements induced by differential settlement and at the same time providing
aggregate interlocking forces among adjacent panels of seawalls to link the
panels in one unit against the lateral earth pressure exerted on seawall.
Besides,
slip joints provide a path for the relief of water pressure developed and allow
the lateral movement (e.g. contraction) due to seasonal variations.
Question
No. 45
Will
going from a 3-tap to 6-tap increase water pressure?
Answer: No, the pressure will be the same; you will get more volume only if
your pumps can handle the GPM, to increase pressure you may need a booster pump
or a single pump that is rated for your needs.
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