Foundation Engg

Question 1

Nc of Skempton for clay soil

Answer 1

Nc= 5* (1+ 0.2D/B) *(1 + 0.2L/B)

D/B upto 2.5

Nc upto 9

Question 2

Net Safe bearing capacity of soil as per Teng’s equation.

Answer 2

qns= 1.4(N-3) *[(B+0.3)/2B]^2 *S.Cw.Cd

B is width of footing
S is tolerable settlement in mm
Cw is water table correction factor
= 0.5×(1+Dw2/B)
Cd is depth correction factor 
= 1+Df/B <= 2

Question 3

Efficiency of pile group by converse Labarre formula

Answer 3

Ng = 1 - ¢*[(n-1)m+(m-1)n] / 90mn

Tan(¢) = d/s

Question 4

general shear failure vs local shear failure conditions

Answer 4

parameter   --  general shear-- local shear
friction angle-- >36 -- <29
strain at fail -- <5%  -- >15%
relative density-->70%-- <30%
SPT number  -->30 -- <5 
void ratio -- <0.55 -- >0.75
UCS         -- > 100  -- < 80 KN/m^2

Question 5

plate load test

Answer 5

plate thickness is 25 mm
plate dia - 300 to 750 mm
it is used to calculate- bearing capacity, safe settlement
settlement ratio plate to footing
Sf/Sp = [(/)*(B+0.3/)]^2 sand equation
Sf/Sp = Bf/Bp
https://civiltoday.com/geotechnical-engineering/site-investigation/192-plate-load-test

Question 6

standard penetration test

Answer 6

tested in a Borehole
65 kg hammer
75 cm falling head
leave 150 mm first
150 + 150 +150 mm sampling
Df + (1.2-2)* B for overburden correction
dilatancy correction

https://www.slideshare.net/arpitkvnfc/soil-penetration-tests

Question 7

peck hension’s formula for q.net

Answer 7

q.net = 0.41 NSC

Question 8

Immediate settlement of foundation

Answer 8

S = q B(1-µ^2)If / Es

Question 9

Fender piles

Answer 9

protect water front structure against impact from ships and other floating objects

Question 10

Anchor pile

Answer 10

anchor against horizontal pull from water or…

Question 11

batter piles

Answer 11

resist horizontal and inclined forces espessially in water front structures
also called raking pile

Question 12

engineering news formula for friction piles

Answer 12

Qallow = W.h / F.(S+C)
C = 2.5 cm for drop hammer
= 0.25 for single acting steam hammer

Question 13

allowable load on a single pile

Answer 13

• 2/3 rd of load at which total settlement is 12 mm
• 2/3 rd of load at which plastic settlement is 6 mm
• 50% of ultimate load for 1/10 dia of deflection

Question 14

minimum spacing between piles according to IS code

Answer 14

for
friction pile = 3 * Dia
point bearing = 2.5 * dia
loose soil = 2 * dia

Question 15

Type of foundation - depth of exploration

Answer 15

isolated footing or raft or adjacent footing with spacing>4B = 1.5*B
adjacent footing with spacing<2B = 1.5L
piles and well foundation = 1.5 * Width of str
Road cuts = bottom Width of cut
Fill = max(2 meter or height of fill)

Question 16

types of shallow footing

Answer 16

• spread footing (strip, Isolated)
• Combined footing (Rectangular , trapezoidal plan)
• Raft footing
• Strap footing [cantilever footing]

Question 17

Depending upon their function, the different types of piles are

Answer 17

Depending upon their function, the different types of piles are:

Bearing piles
Friction piles
Sheet piles
Anchor piles
Batter piles
Fender piles
Compaction piles

https://www.theconstructioncivil.org/types-of-piles-deep-foundations/