Any soils that can be excavated with handtools is suitable provided that the void or pore openings in the soil mass are small enough to prevent the calibrated sand used in the test from getting into the natural voids. Moreover, the soils being tested should have sufficient cohesion or particle interlocking to maintain side stability during excavation of the test pit. Furthermore, it should also be firm enough not to deform or slough due to the pressures exerted in digging the hole and pouring the sand.

This question is taken from book named – A Self Learning Manual – Mastering Different Fields of Civil Engineering Works (VC-Q-A-Method) by Vincent T. H. CHU.

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.

This question is taken from book named – A Self Learning Manual – Mastering Different Fields of Civil Engineering Works (VC-Q-A-Method) by Vincent T. H. CHU.

For gravity pipes, air tests or water tests are carried out after completion of laying and jointing of the pipes. These tests are conducted to check the watertightness of joints and to ensure the pipelines are free from damage where leakage may occur.

Air test has the advantage that the test itself is simple and faster to be carried out. It does not require the disposal of significant quantities of water used in the test which is a mandatory requirement for water test. However, in case leakage exists in the constructed segment of gravity pipelines, the position of leakage can hardly be located in air test. Moreover, the rate of water leakage cannot be determined from air tests. In addition, air test is readily affected by atmospheric condition because air has a relatively high coefficient of thermal expansion. The test is also influenced by the moisture condition of the test pipelines because it affects the passage of air through the pipelines.

For water test, though it is comparatively slow, it can detect the location of water leakage. However, the leakage rate results from water test may not truly reflect its actual leakage because pipeline materials like concrete and clay are porous and would absorb water during the test.

This question is taken from book named – A Self Learning Manual – Mastering Different Fields of Civil Engineering Works (VC-Q-A-Method) by Vincent T. H. CHU.

Froude number is used when gravitation forces is predominant in the channel flow. Reynolds number is adopted when viscous forces are predominant in the channel flow. It is almost impossible to make Froude number and Reynolds number identical in model and prototype. Therefore, the use of these numbers should be judged case by case. For instance, in open channel flow Froude Number is used in the scale models as gravitation forces is predominant.

This question is taken from book named – A Self Learning Manual – Mastering Different Fields of Civil Engineering Works (VC-Q-A-Method) by Vincent T. H. CHU.

The concept of On-site Stormwater Detention involves the temporary storage of stormwater with limited runoff from the site. It essentially modifies the runoff behaviour of the site so as to prevent flooding in area downstream. The allowable rate of discharge from the given area is Permissible Site Discharge while the minimum storage area for water detention is called Site Storage Requirement.

Examples of storage facilities for Permissible Site Discharge are flat roof, underground pits, fish ponds etc.

This question is taken from book named – A Self Learning Manual – Mastering Different Fields of Civil Engineering Works (VC-Q-A-Method) by Vincent T. H. CHU.