Explanation :-

Engineering News Record (ENR) formula is used to determine the ultimate load carrying capacity (Qa) of a pile embedded in sand.

Qa = Wh/F(s+c)

Where,

• Qa = Allowable load in kN
• W = Weight of hammer in KN
• h = Height of fall in mm
• s = penetration per blow
• c = Empirical constant (drop hammer = 25 mm, single acting hammer = 2.5 mm)
• F = Factor of safety = 6

Explanation :-

• The number of blows required to drive the sampler 300 mm beyond the seating drive of 150 mm, is called as Standard Penetration Number (N).
• So, the number of blows for the first 150 mm penetration is ignored and number of blows for the last 300 mm penetration are noted as N-Value.

Standard Penetration Number (N),

= 8 + 10

= 18

Explanation :-

Time Factor,

Tv = Cv × t / H²

Time required for a certain degree of consolidation,

t = Tv × H²/Cv

t ∝ H²

t ∝ 1/Cv

Solution :-

Here,

W = 30%

Wl = 60%

Wp = 28%

Consistency Index (Ic),

= (Wl - W)/(Wl - Wp)

= (60 - 30)/(60 - 28)

= 30/32

= 0.9375 (Stiff Consistency)

Explanation :-

Assumptions for slope stability analysis:

• Friction is fully mobilized
• Total stress analysis is applicable
• Total stress analysis is used
• The resultant is tangential to the friction circle
• Resultant R is tangential to the friction circle

Explanation :-

Standard penetration test gives an idea about consistency of soil and also give idea about unconfined compressive strength of clayey soil.

Explanation :-

Thalweg Length (Channel Length)

• It refers to the line connecting the deepest points in a river channel.

Valley Length

• It is the entire depression or trough that a river flows through, including the sides and not just the deepest part.

SR = Sinuosity Ratio

Solution :-

Overburden Correction,

Corrected N-value = CN × N

Where,

N = Recorded N-value

CN = Overburden correction factor

CN = 350/(σv + 70)

Where,

σv = Vertical effective stress (kN/m²)

If, σv < 280 kN/m² ⇒ Overburden correction required

If, σv ≥ 280 kN/m² ⇒ Overburden correction not required

Here,

σv = Depth × Unit weight of soil

σv = 20 × 17.5

σv = 350 kN/m² > 280 kN/m²

Hence, Overburden correction not required.

Corrected N-value,

= Recorded N-value

= 48

Explanation :-

Coefficient of consolidation,

Cv = k/(γw⋅mv)

Where,

k = Coefficient of permeability

γw = Unit weight of water

mv = Coefficient of volume compressibility

Explanation :-

The bearing capacity of soil will not be affected by a water table located at a depth greater than the footing's width (3m) below the base of the footing.