Soil Stabilization and Soil Exploration

Question 1
In a soil investigation work at a site, Standard Penetration Test (SPT) was conducted at every 1.5 m interval up to 30 m depth. At 3 m depth, the observed number of hammer blows for three successive 150 mm penetrations were 8, 6 and 9, respectively. The SPT N-value at 3 m depth, is
A
23
B
17
C
15
D
14
GATE CE 2020 SET-1   Geotechnical Engineering
Question 1 Explanation: 
No. of blows for each 150 mm penetration 8, 6 and 9.
We will not consider first 150 mm number of blows.
Hence, for last 300 mm, number of blows are 15.
Hence, observed SPT number = 15.
Question 2
For the following statements:

P: The lateral stress in the soil while being tested in an oedometer is always at-rest.
Q: For a perfectly rigid strip footing at deeper depths in a sand deposit, the vertical normal contact stress at the footing edge is greater than that at its centre.
R: The corrections for overburden pressure and dilatancy are not applied to measured SPT-N values in case of clay deposits.

The correct combination of the statements is
A
P -TRUE; Q -TRUE; R -TRUE
B
P -FALSE; Q -FALSE; R -TRUE
C
P -TRUE; Q -TRUE; R -FALSE
D
P -FALSE; Q -FALSE; R -FALSE
GATE CE 2019 SET-1   Geotechnical Engineering
Question 2 Explanation: 
P: True
In the Oedometer test, stress is applied to the soil specimen along the vertical axis, while strain in the horizontal direction is prevented by the confining ring (a condition of zero lateral strain). Thus it simulates at-rest condition.

Q: True
For a perfectly rigid footing resting on surface of sand deposit, the contact pressure distribution is zero at the edges and maximum at centre. However, for a very deep rigid footing on sand, the contact pressure distribution may tend to become like that of rigid footing on clayey soil, with edge contact stress greater than at its centre.

R: True
For cohesive soil, there is no need for overburden pressure correction (Peck et al 1974). For cohesionless soil at first overburden pressure correction is made, then if it is fine sand or silt under water table with N-value \gt 15, dilatancy correction is made.
Question 3
Which of the following statement is TRUE for degree of disturbance of collected soil sample?
A
Thinner the sampler wall, lower the degree of disturbance of collected soil sample
B
Thicker the sampler wall, lower the degree of disturbance of collected soil sample
C
Thickness of the sampler wall and the degree of disturbance of collected soil sample are unrelated
D
The degree of disturbance of collected soil sample is proportional to the inner diameter of the sampling tube
GATE CE 2015 SET-1   Geotechnical Engineering
Question 3 Explanation: 
As thickness of sampler increase, disturbance increase
Question 4
The degree of disturbance of the sample collected by the sampler is expressed by a term called the "area ratio". If the outer diameter and inner diameter of the sampler are D_{o} and D_{i} respectively, the area ratio is given by
A
\frac{D_{o}^{2}-D_{i}^{2}}{D_{i}^{2}}
B
\frac{D_{i}^{2}-D_{o}^{2}}{D_{i}^{2}}
C
\frac{D_{o}^{2}-D_{i}^{2}}{D_{o}^{2}}
D
\frac{D_{i}^{2}-D_{o}^{2}}{D_{o}^{2}}
GATE CE 2014 SET-1   Geotechnical Engineering
Question 5
In the context of collecting undisturbed soil samples of high quality using a spoon sampler, following statements are made :

I. Area ratio should be less than 10%
II. Clearance ratio should be less than 1%

With reference to above statements, which of the following applies ?
A
Both the statements are true
B
Statements II is true but I is false
C
Statement I is true but II is false
D
Both the statements are false
GATE CE 2004   Geotechnical Engineering
Question 5 Explanation: 
Area ratio should be less than 10 % for a undisturbed sample. But in case of collecting a sample using split spoon sampler the area ratio is as high as 30%. So it is impossible to get a undisturbed sample with the help of a split spoon sampler. Also, the clearance ratio should be from 1 to 3 per cent.
Question 6
Match the List-I (Boring methods) with List-II (Field conditions) and select the correct answer.
A
P-3 Q-1 R-4 S-2
B
P-1 Q-2 R-4 S-3
C
P-2 Q-3 R-4 S-1
D
P-3 Q-1 R-2 S-4
GATE CE 2003   Geotechnical Engineering
There are 6 questions to complete.

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