Here below you can find the GATE Civil Engineering solved question with explanations in the topic of **Soil Mechanics – Phase relations | Origin of soil | Soil classification. **Which is very useful for the upcoming GATE 2021 examination.

**Question No. 1: The avoid ratios at the densest, loosest and the natural states of a sand deposit are 0.2, 0.6, and 0.4, respectively. The relative density of the deposit is
**(A) 100% (B) 75% (C) 50% (D) 25%

**Answer: 50%**

**Explanation: **

**Question No. 2:**** A soil has void ratio = 0.72, moisture content = 12% and G _{s}= 2.72. Determine its**

**(a) Dry unit weight**

**(b) Moist unit weight, and the**

**(c) Amount of water to be added per m**

^{3}to make it saturated.**Use**

**Solution: **

**(a)** = 15.51 kN/m^{3}

**(b)**

= = 17.38 kN/m^{3}

**(c)** =

= = 19.62 kN/m^{3}

Water to be added per m^{3} to make the soil saturated

= = 19.62 – 17.38 = 2.24 kN

**Question No.3: The undrained cohesion of a remoulded clay soil is 10 kN/m2 . If the sensitivity of the clay is 20, the corresponding remoulded compressive strength is
**(a) 5 kN/m2 (b) 10 kN/m2 (c) 20 kN/m2 (d) 200 kN/m2

**Answer: 20 kN/m2**

**Explanation:**Compressive strength = 2C =20 kN/m2

**Question No.4: The dry density of a sand with porosity of 0.387 is 1600 kg/m ^{3}. Find the void ratio of the soil and the specific gravity of the soil solids. [Take ]
n = 0.387
= 1600 kg/m^{3}**

*Solution:*

(a) e = = = 0.631

(b) =

G_{s} =

**Question No.5: Match list-I (type of soil) with list-II (mode of transportation and deposition) and select the correct answer using the codes given below the lists:
List – I**

A. Lacustrine soils

B. Alluvial soils

C. Aeolian soils

D. Marine soils

**List-II**

1. Transportation by wind

2. Transportation by running water

3. Deposited at the bottom of lakes

4. Deposited in seawater

**Codes:**

A B C D

a. 1 2 3 4

b. 3 2 1 4

c. 3 2 4 1

d. 1 3 2 4

**Answer: b. 3 2 1 4**

**Question No.6: The liquid limit and plastic limit of samples are 65% and 29% respectively. The percentage of soil fraction with grain size finger than 0.002 mm is 24. The activity ratio of the soil sample is
**(a) 0.05 (b) 1.00 (c) 1.50 (d) 2.00

**Answer: 1.50**

**Explanation:**

**Question No.7: Lacustrine soils are soils
**(a) Transported by rivers and streams

(b) Transported by glaciers

(c) Deposited in sea beds

(d) Deposited in lake beds

**Answer: (d) Deposited in lake beds**

**Question No.8: The dry density of a soil is 1.5 g/cc. If the saturation water content were 50% then its saturated density and submerged density would, respectively, be
**(a) 1.5 g/cc and 1.0 g/cc

(b) 2.0 g/cc and 1.0 g/cc

(c) 2.25 g/cc and 1.25 g/cc

(d) 2.50 g/cc and 1.50 g/cc

**Answer: (c) 2.25 g/cc and 1.25 g/cc**

**Explanation:**

**Question No.9: Consider the following statements: A Well-graded sand should have
1. Uniformity coefficient greater than 6
2. Coefficient curvature between 1 and 3
3. Effective size greater than 1mm
Which of the statements are correct?
(a) 1, 2 and 3 (c) 1 and 2
(b) 1 and 3 (d) 2 and 3**

**Answer: (c) 1 and 2**

**Question No.10: Based on grain distribution analysis, The D10, D30 and D60 values of a given soil are 0.23mm, 0.3mm and 0.41mm respectively. As per IS code, the soil classification will be
**a) SW b) SP c) SM d) SC

**Answer: b) SP**

**Explanation:**