1. The __________ arrangement of preventing the sleep of earth in foundation trenches is used when the excavation is to be carried out in the moderately firm ground.
a) Runner
b) Stay bracing
c) Vertical sheeting
d) Sheet piling
Explanation: In case of moderately firm ground, Stay bracing is adopted when the depth of excavation does not exceed 2 metres. In this, the vertical sheets of piling boards are placed opposite each other against the wall of the trench
2. The _______ arrangement of preventing the slip of earth in the foundation trenches is adopted when a large area is to be excavated for depth greater than 10 meters.
a) Sheet piling
b) Runner
c) Box sheeting
d) Stay bracing
Explanation: Sheet piling is used when a large area is to be excavated for depth greater than 10 meters, soil to be excavated is soft or loose, width of the trench is also large and the subsoil water is present.
3. In _______ arrangement, the vertical sheets are placed nearer or sometimes, touching each other.
a) Stay bracing
b) Box sheeting
c) Vertical sheeting
d) Runner
Explanation: The Box sheeting arrangement is adopted for loose soil. In this, the sheets are kept in position by longitudinal rows of wales, usually 2 in numbers and then, the Struts are provided across the wales.
4. The _______ method is similar to box sheeting except that the work is carried out in stages and at each stage, and offset is provided.
a) Sheet piling
b) Box sheeting
c) Stay bracing
d) Vertical sheeting
Explanation: For deep trenches up to about 10 metres in soft ground, the vertical sheeting is adopted. In this for each stage, vertical sheets, horizontal wales, Struts and braces are provided as usual.
5. 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 comprises of a Riser, swinger arm, header and together work as a well point system.
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 the 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
c) Connections
d) Pumping
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?
a) Pumping
b) Well Point System
c) Freezing process
d) Electro osmosis process
Explanation: In pumping method, the pumps are installed along the foundation trenches at 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
d) Pumping
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.