This set of Construction and Building Materials Multiple Choice Questions & Answers (MCQs) focuses on “Well Point System”.
1. Which the given method is used for dewatering of the foundation trenches.
a) Deep boring
b) Geophysical method
c) Well Point System
d) Analytical method
Explanation: A Well Point is a pipe about 1 m long and diameter is about 40 mm to 50 mm. The whole system comprise of a Riser, swinger arm, header and together work as a well point system.
Explanation: A Riser is a vertical pipe driven in the ground. The well point is provided at the bottom end of the riser. The diameter of Riser is about 40 mm to 50 mm.
Explanation: A Header is a pipe to which all the swinger arms of the different well points are attached. The header, in turn, is connected to a pumping unit. The header is laid on the ground and its diameter varies from 150 mm to 250 mm.
Explanation: When the depth of excavation exceeds 5 M below the water table, the process of providing well Point is carried out in different stages known as Multi stage system.
Explanation: The vacuum process is very much useful and effective for inorganic and organic silts and very fine sand. But several weeks may be required to achieve consolidation by this method.
6. In case of releasing artesian pressure, which precaution should be taken when the system of well points is adopted.
a) Pumping rate
b) Air locks
c) Duplication of pumps
d) Blowing action
Explanation: Blowing action is adopted for release of artesian pressure. At some places, the artesian conditions exists at a certain death from the ground level. If the foundation trench reaches that depth, its bottom is likely to be blown off due to hydrostatic pressure.
7. Which precautions to be taken in case of multistage system to achieve stability of the side slope.
a) Deep well pumps
b) Duplication of pumps
Explanation: In case of multistage system of well points, the deep well pumps should be used when the instability of the side slopes is expected. As deep well pumps are expensive, they are adopted on important works.
8. The organic Chemicals include epoxy resin, polyester resin and other resins are used in which method of dewatering of the foundation trenches.
a) Well Point System
b) Cement grouting
c) Chemical grouting
d) Electro osmosis process
Explanation: In 1925, H.J. Joosten, a Dutch mining engineer, adopted for the first time the chemical grouting. He used concentrated solution of sodium silicate and calcium chloride as electrolyte.
9. From given below, which method for the dewatering of foundation trenches is portable and can be easily moved when required.
b) Well Point System
c) Freezing process
d) Electro osmosis process
Explanation: In pumping method, the pumps are installed along the foundation trenches at a suitable points. The water gaining access to the trenches is pumped out. These pumps are portable so that it can be easily moved as and when required.
10. Identify the type of Well Point System which can suck water up to 5 meters.
a) Single stage system
b) Multi stage system
c) Vacuum system
Explanation: The practical limit upto which the water can be lifted by a suction pump is about 5 meters or so. Hence, the depth of excavation is not to exceed 5 metres in single stage system well point is adopted.
Explanation: Well Point System consists of a well points, riser, swinger arm, and header. The area to be devoted is surrounded by number of well points. The minimum spacing between the well points is 1 m.
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