Question No. 01
What Tor stands for in Tor steel?
Answer: The owner’s last name
Question No. 02
What is the purpose of carrying out water absorption test for precast 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 precast concrete pipes is adopted for checking the quality of concrete in terms of density and imperviousness.
Question No. 03
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 down stream during the wet season, generate power year round, and provide irrigation in the dry season.
Question No. 04
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. 05
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.
Question No. 06
Should joints of concrete kerbs be in line with the joints in concrete carriageway?
Answer: In normal practice, joints are provided in road kerbs to cater for concrete expansion and contraction. However, the location of joints in kerbs is not arbitrary and they should match with joints in concrete carriageway. Otherwise, it is very likely that cracks may form in concrete kerbs at location of pavement joints (Ministry of Transport (1955)).
Question No. 07
In case mud waves occur during reclamation, what are the possible solutions to rectify the situation?
Answer:
(i) Option 1 Complete Removal of All Disturbed Mud: To remove all disturbed mud once mud waves occur is the fastest way to treat the problem. After that, filling material is used for replacing the disturbed mud. However, this option is a rather expensive option because it involves dredging of all disturbed mud and replacement of large amount of fill.
(ii) Option 2 Accelerated consolidation of Disturbed Mud: This option involves placement of surcharging loads on top of mud waves, together with installation of band drains to accelerate the consolidation of disturbed mud. This method suffers from the drawback that sufficient long time is required for the consolidation process of mud. =
(iii) Option 3 Partial Removal of Disturbed Mud: This option is a combination of the first two options in which the top weak layer of mud is removed while the lower mud is treated with surcharging with band drain installation.
Note: Mud waves refer to excessive displacement of mud due to successive slip failure during reclamation.
Question No. 08
For compaction of free-draining sands or gravels, what is the optimum moisture content to achieve maximum density?
Answer: The compaction curve of sandy materials is totally different from that of clayey materials. For sands or gravels, there are two situations of maximum density, namely the completely dry condition and the complete water saturation. For moisture content of sands and gravels between these two states, the dry density obtained is lower than that obtained in the above-mentioned states. The presence of capillary forces account for the difficulty of compaction sand at water contents between virtually dry and saturated state. They are formed in partially filled water void between soil particles and perform as elastic ties cementing soil particles together. Reference is made to Lars Forssblad (1981).
The compaction curve for clay is suitable for the majority of soil types except sands and gravels because a small amount of clay in soils is sufficient to make the soils impermeable.
Question No.09
What are the main reasons for conducting pull-out tests for soil nails?
Answer: There are mainly four reasons for this test:
(i) To check and verify the bond strength between soil and grout adopted during the design of soil nails. This is the main objective of conducting soil nail pull-out test.
(ii) To determine the bond strength between soil and grout for future design purpose. However, if this target is to be achieved, the test nails should be loaded to determine the ultimate soil/grout bond with a upper limit of 80% of ultimate tensile strength of steel bars.
(iii) To check if there is any slippage or creep occurrence.
(iv) To check the elastic and plastic deformations of test nails. This is observed during the
repeated loading and unloading cycles of soil nails. Note: Pull-out tests are carried out by applying specified forces in an attempt to pull out the constructed soil nails.
Question No: 10
In designing sewer pipes, why are vitrified clay pipes commonly used for pipe size less than 600 mm while precast concrete pipes with PVC lining is used for pipe size exceeding 600 mm?
Answer: The market price of vitrified clay pipes is generally less than that of precast concrete pipes with PVC lining. Therefore, for small size of pipes (pipe diameter less than 600 mm) it is more economical to use vitrified clay pipes. However, vitrified clay pipes do suffer from the problem of brittleness and its effect is even severe for larger size of pipes. Moreover, it is rather time consuming to deliver clay pipes products because the majority of them are manufactured in Europe. Hence, for larger size of sewer pipes (diameter more than 600 mm) it is customary to use precast concrete pipes with PVC lining.