Page 46 - Unit2.docx

0.5 620 680 0.6 550 620

0.3 580 640 0.4 550 600
5 TON 0.4 670 740 0.5 620 660
0.5 760 840 0.6 670 730

© It's Engg. Life

Example 5.2

A concrete pile with length 26 m and cross-sectional area (235)⋅ (235) is
subjected to a vertical loading of 390 kN (ultimate) load. Determine appropriate
condition to halt hammering. Type of hammer Drop hammer activated by rope and
friction winch. Class 2, GC 2, pile length 20 m

solution:

FRsp≥ γ n. Fsd

γ n = 2.2 (table 20-3)

vertical load 390 kN ⇒ FRsp≥ (2.2)390/0.9***= 477kN

2
2
Pile cross-sectional area ⇒ 0.235 = 0.055 m ⇒

type of hammer: Drop hammer activated by rope and friction winch ⇒

***For piles 20m - 30m length, the bearing capacity should be reduced by
20%

∴ Table value (table 5-2): Hammer weight = 4 ton ⇒ fall height
0.45m (interpolation)

Hammer weight = 3 ton ⇒ fall height 0.54 m

4 ton hammer with fall height 0.45m is an appropriate choice.

5.2 Friction piles

Load on piles that are driven into friction material, for the most part the weight
is carried by friction between the soil and the pile shaft. However considerable
additional support is obtained form the bottom part.

In designing piles driven into friction material, the following formulas can be used