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Monthly Archives: June 2017

General Basic Civil Engineering

What is the difference between working stress approach and limit state approach?   For working stress approach, service loads are used in the whole design and the strength of material is not utilized in the full extent. In this method of design, stresses acting on structural members are calculated based …

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Piles and Foundation

It is not necessary to design nominal reinforcement to piles. Is it true?   In BS8110 and BS5400 Pt.4, they require the provision of nominal reinforcement for columns. However, for pile design the requirement of nominal reinforcement may not be necessary. Firstly, as piles are located underground, the occurrence of …

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Pipe Jacking and Microtunneling

In the design of pipe jacking, what particular areas on pipe joints should engineers take care of?   Since in pipe jacking, the jacked pipes could hardly be jacked in the designed level and alignment and some deviation from the original one is commonly acceptable provided that the deviation are …

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Water Retaining Structure and Waterworks

When designing a water storage tank, should movement joints be installed?   In designing water storage tanks, movement joints can be installed in parallel with steel reinforcement. To control the movement of concrete due to seasonal variation of temperature, hydration temperature drop and shrinkage etc. two principal methods in design …

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Reclamation

What are different approaches for reclamation in deep water region and shallow water region?   To illustrate the different approaches adopted for reclamation in deep water and shallow water region, the following example is used:   In deepwater region, consider the seabed level is –8.5mPD. After laying of geotextiles and …

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Pumping Station

What is the difference among cement plaster, cement render and cement screed? Under what situations should each of the above be used?   The purpose of plastering, rendering and screeding is to create a smooth, flat surface to receive finishes like paint, wallpaper etc.   Plastering is the intermediately coating …

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Roadworks

How can unreinforced concrete pavement function without mesh reinforcement?   For concrete carriageway, it is normally classified into two types: reinforced and unreinforced concrete pavement. The reinforcement in reinforced carriageway (in the form of mesh) is used for controlling cracking. Then one may query how unreinforced pavement can control cracking …

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Piers and Marine Structures

Why is sulphate-resisting cement not used in marine concrete?   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 …

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Earthworks

In soil compaction test, if a test result exceeds 100%, should engineers accept the result?   Soil compaction is the process of increasing the soil density by reducing the volume of air within the soil mass.   Soil compaction depends mainly on the degree of compaction and the amount of …

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Drainage Works

What is the function of waterstops in joints of box culverts and drainage channels?   The principal function of waterstops is to prevent liquids (e.g. water), water-borne materials and solids to pass through concrete joints. In essence, it aims at providing watertightness to the drainage channel.   Besides, waterstops in …

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