# Foundation Engineering Questions and Answers – Geotextiles

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This set of Foundation Engineering Multiple Choice Questions & Answers (MCQs) focuses on “Geotextiles”.

1. The tension T in reinforcement is given by __________
a) Ti=γKahs
b) Ti=zi Ka hs
c) Ti=γzi Ka
d) Ti=γzi Ka hs

Explanation: The tension T in reinforcement is given by,
Ti=pi A=γzi Ka hs, where A=h.s=effective area of strip
Ka=coefficient of active earth pressure
Ti=Tension in the reinforcement.

2. If F is the factor of safety and Fi is the frictional resistance, then the relation between them and tension Ti in reinforcement is ________
a) Fi=Ti F
b) Fi=$$\frac{T_i}{F}$$
c) Fi=Ti+F
d) Fi=Ti-F

Explanation: The frictional resistance of the reinforcement is,
Fi=Ti F, Where, F=factor of safety
Ti=Tension in the reinforcement.

3. If δ is the angle of surface friction, then frictional resistance Fi is ___________
a) Fi=γzi tanδ*surface area of reinforcement
b) Fi=γzi cosδ
c) Fi=γzi sinδ*surface area of reinforcement
d) Fi=γzi cotδ*surface area of reinforcement

Explanation: The frictional resistance of the reinforcement is,
Fi=Ti F, if δ is the angle of surface friction, then,
Fi=γzi tanδ*surface area of reinforcement.
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4. Geotextiles are ____________
a) permeable
b) semi-permeable
c) impermeable
d) does not permeability characterises

Explanation: Geotextiles are porous fabrics and hence they are permeable. They are made from synthetic materials that are used with geotechnical materials like soils or rocks as an integral part.

5. The geostrips are generally produced from ________
a) glycerine
b) polypropylene
c) dextrin
d) benzene

Explanation: The geostrips are a type of geotextiles. As per American Society for Testing and Materials (ASTM), the geotextiles are permeable sheets of synthetic fibres like polypropylene, polyethylene etc.

6. Geotextiles are available in thickness varying from ________
a) 1 to 5 mils
b) 5 to 10 mils
c) 10 to 20 mils
d) 10 to 300 mils

Explanation: The geotextiles are permeable sheets of synthetic fibres that are available in thickness varying from 10 to 300 mils. 1 mil=1/100 inch=0.254 mm. Due to their fine thickness, they are permeable.

7. If geotextiles are used as reinforcements, then they should have __________
a) low modulus of deformation
b) high modulus of deformation
c) low coefficient of friction
d) low breaking strength

Explanation: When the geotextiles are used as reinforcements in the soil, they should take up some of the tensile stresses and help to distribute them more evenly. Therefore, they must have high modulus of deformation.

8. The geotextiles are available in rolls of length _____
a) 100 cm
b) 5m
c) up to 600m
d) 1 km

Explanation: The geotextiles are permeable sheets of synthetic fibres that are available in thickness varying from 10 to 300 mils, widths up to 10 m and in rolls of length up to 600 m. The permeability of geotextile is comparable in range from coarse gravel to fine sand.

9. The geocells or geowebs are stitched together at _________ intervals.
a) 100 cm
b) 200 to 50 mm
c) upto 600 m
d) 1 km

Explanation: The geocells or geowebs are stitched together at 200 to 50 mm intervals. They can even be welded together. The hexagonal or rhomboidal cells can be made of geosynthetic honeycomb design.

10. The GCL is a composite of ________
a) geotextiles and bentonite clay
b) silt and gravel
c) gravel and bentonite clay
d) geotextiles and gravels

Explanation: The Bentofix Thermal Lock Geosynthetic clay liner (GCL) is a patented registered trade mark. It is a sandwiched composite of geotextiles and bentonite clay that is used to provide appositive barrier to liquids in containment applications.

11. The geotextiles can withstand differential settlements.
a) True
b) False

Explanation: Since the geotextiles are used to provide tensile strength in places where the shear stresses are generated, the use of geotextiles leads to redistribution of the stresses and hence it can withstand differential settlements.

12. The geotextiles are also used for fluid transmission and drainage function.
a) True
b) False

Explanation: Since the geotextiles are permeable materials, the geotextiles with high porosity is used for fluid transmission and drainage function. They should have substantial thickness and high horizontal permeability.

13. The exposure of the geotextiles to the elements tween lay down and covering should be a maximum of ____ days.
a) 1
b) 14
c) 150
d) 365

Explanation: The geotextiles must be protected from sun light, UV rays, debris, etc. as it can potentially damage the geotextile. The exposure of the geotextiles to the elements tween lay down and covering should be a maximum of 14 days.

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