# Geotechnical Engineering Questions and Answers – Determination of Liquid and Plastic Limit

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This set of Geotechnical Engineering Interview Questions and Answers focuses on “Determination of Liquid and Plastic Limits”.

1. The grooving tool which is used for finding liquid limit is _________
a) ASTM tools
b) Grooving tools
c) All of the mentioned
d) None of the mentioned

Explanation: ASTM tool and casagrande tools are two types of grooving tools are used in determining liquid and plastic limit.

2. The depth of the groove cut by casagrande tool for determining the liquid limit is ______
a) 10 mm
b) 11.0 mm
c) 2 mm
d) 8 mm

Explanation: The casagrande tools cut a groove of size 11.0 mm wide at the bottom.

3. The type of tools which is preferred for sandy soil for the purpose of grooving is _______
a) ASTM tool
b) Casagrande tool
c) All of the mentioned
d) None of the mentioned

Explanation: ASTM tool is used only for more sandy soil, where the Casagrande tool tends to tears the side of the groove.
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4. What is the diameter of the sieve that is used for finding the liquid limit?
a) 275 microns
b) 700 microns
c) 425 microns
d) 200 microns

Explanation: 425 micron sieve is used as a standard, for filtering the given specimen.

5. The soviet liquid limit device is based on the principle of ___________
a) Station penetration
b) Soil moisture
c) Soil water content
d) None of the mentioned

Explanation: Static cone penetration method is used in operation of soviet liquid limit device.

6. The toughness index (It) is defined by the ratio of __________
a) It=WP/IP
b) It=IP/If
c) It=IF/IP
d) It=WL/If

Explanation: Toughness index (It) is determined by the ratio of plasticity index to the flow index: It=IP/If.

7. The number of revolutions per second, at which the handle is rotated in process of finding the liquid limit is _________
a) 2
b) 7
c) 4
d) 9

Explanation: In liquid limit apparatus, the handle is rotated at a rate of about 2 revolutions per second.

8. The cone which is used to penetrate the soil pat has a central angle of ___________
a) 26 degree
b) 30 degree
c) 31 degree
d) 40 degree

Explanation: The cone has a central angle of 31° since the total sliding mass is 80 g.

9. The plastic index is calculated from the relation ____________
a) IP = WP-WL
b) IP = WL-WP
c) IP= IL-IS
d) IP=IW-IS

Explanation: The plasticity index is given by the formula, IP=WL-WP.

10. One-point method, used for determining the liquid limit is majorly applicable for finding ________
a) Accurate value
b) Precise value
c) Rough value
d) None of the mentioned

Explanation: Since the liquid limit is found out by only one reading of water content and its corresponding number of blows. One point method is applicable for finding rough value.

11. The shear strength of the soil, at the liquid limit is ________
a) 1.75 kN/m2
b) 1.89 kN/m2
c) 17.9 kN/m2
d) 17.6 g/cm2

Explanation: The shear strength of the soil is about 17.6 g/cm2 which the penetrometer gives for a depth of 25 mm under a total sliding mass of 148 g.

12. The apparatus used for finding, WL value by static cone penetrometer method is _________
a) Liquid limit apparatus
b) Pycnometer
c) Cone penetration
d) Rubber balloon cylinder

Explanation: Cone penetration apparatus is used for finding WL value, according to IS: 2720 (part 5) -1965.

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