 Lecture – 8
SOIL MECHANICS AND
FOUNDATION ENGINEERING-II
(CE 311)
BEARING CAPACITY OF DEEP
FOUNDATION
 Theoretical Approach
 Pile Load Test Approach
 The Pile Driving Resistance Approach
Pile Driving Resistance Approach
 Engineering News Formula
𝑊𝐻
𝑄𝑎 =
𝐹(𝑆 + 𝐶)
 Where;
Qa = Allowable Load
W = Weight of hammer
H = Height of fall
F = Factor of Safety (=6)
S = Final penetration per blow
C = 2.5 cm for drop hammer and 0.25cm for
steam hammer
Pile Driving Resistance Approach
 Hiley’s Formula
𝜂ℎ 𝑊𝐻𝜂𝑏
𝑄𝑓 =
𝐶
𝑆+
2
Qf = Ultimate Load
W = Weight of hammer
H = Height of fall, cm
F = Factor of Safety (= 2 to 2.5)
S = Final penetration in cm per blow
C = Total elastic compression
hh = Efficiency of hammer (65% to 100%)
e = coefficient of restitution
 Where;
 𝜂𝑏 =
 𝜂𝑏 =
𝑊+𝑒 2 𝑃
(when W>eP)
𝑊+𝑃
𝑊+𝑒 2 𝑃
𝑊−𝑒𝑃 2
𝑊+𝑃
−
𝑊+𝑃
(when W<eP)
P = weight of pile
Problems
1. A wooden pile is being driven with a drop hammer
weighing 20kN and having a free fall of 1.0m. The
penetration in the last blow is 5mm. Determine the load
carrying capacity of the pile according to the Engineering
News Formula
2. A reinforced concrete pile weighing 30 kN is driven by a
drop hammer weighing 40 kN and having a fall of 0.8m.
The average penetration per blow is 1.4cm. Total elastic
compression is 1.8cm. Assuming the coefficient of
restitution as 0.25 and a factor of safety of 2, determine the
ultimate bearing capacity and the allowable load for the
pile.