This set of Construction and Building Materials Multiple Choice Questions & Answers (MCQs) focuses on “Deep Excavations – Dewatering of Foundation Trenches”.
1. Identify the Method used for the dewatering of the foundation trenches.
a) Pumping
b) Freezing process
c) Electro osmosis process
d) Well Point System
View Answer
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.
2. Identify the Method used for the dewatering of the foundation trenches.
a) Pumping
b) Providing sumps and side drains
c) Well Point System
d) Cement grouting
View Answer
Explanation: In providing sumps and side drains, the side drains are constructed along the bottom of the foundation Trenches. The sumps are constructed at a distance of 45 M to 60 M and the side drains are given such as slope that water is collected in the sumps.
3. Identify the Method used for the dewatering of the foundation trenches.
a) Electro osmosis process
b) Chemical process
c) Cement grouting
d) Freezing process
View Answer
Explanation: In the freezing process method, the area surrounding the excavation is frozen and thus a solid wall of frozen Earth is formed. The principle of ground freezing is the use of refrigeration to convert in-situ pore water to Ice.
4. Identify the Method used for the dewatering of the foundation trenches.
a) Vacuum system
b) Single stage system
c) Pumping
d) Multi stage system
View Answer
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.
5. Identify the Method used for the dewatering of the foundation trenches.
a) Vacuum system
b) Single stage system
c) Multi stage system
d) Pumping
View Answer
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 which method a refrigeration plant of required capacity is needed to be installed near the site of work?
a) Pumping
b) Well Point System
c) Freezing process
d) Electro osmosis process
View Answer
Explanation: The principle of ground freezing process is the use of refrigeration to convert in-situ pore water to Ice. Hence, refrigeration plant of required capacity is installed near the site of work to perform the process of refrigeration.
7. ________ process consists of making a number of holes in the ground and then filling these holes by the cement grout under pressure.
a) Chemical grouting
b) Cement grouting
c) Freezing process
d) Electro osmosis process
View Answer
Explanation: In cement grouting method, the cement grout, which is a mixture of sand, cement and water is used. The term grouting is used to indicate a process of injecting the cementing materials into the cracks.
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
View Answer
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. According to him, the chemical must be able to modify the properties of soil as desired or expected.
9. The ________ can be adopted as an aid in construction to stop rock movements and to increase the permeability of the strata as in the case of oil wells.
a) Chemical grouting
b) Cement grouting
c) Pumping
d) Well Point System
View Answer
Explanation: As the chemical grouting has been developed recently, the precise information of its long-term after effects is not available. Hence it has yet not become an established technique as the conventional grouting.
10. The _______ can be effectively adopted for excavation in or at the foot of the slope of a hill.
a) Freezing process
b) Cement grouting
c) Pumping
d) Well Point System
View Answer
Explanation: The freezing is a powerful versatile tool for foundation engineering for temporary ground support, groundwater control and structural underpinning. A portion of the slope is frozen and this position act as a temporary Dam to support the soil and it prevents the earth slides.
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