SOLUTIONS TO PROBLEMS - Geotechnical Earthquake Engineering - page 633

Table 14.6: 4000 psf (200 kPa)

with no increase allowed for an increased width or depth. Therefore, static q all

For sedimentary rock, the allowable bearing pressure

200 kPa.

Since the sandstone will not be weakened by the earthquake, then a one-third increase
in allowable bearing pressure for seismic loads is usually recommended, or:

Seismic q all (200 kPa)(1 0.333) 260 kPa

11.5 Using Fig. 11.22 to obtain the bearing capacity factors:

For 40°, N c 84, N 100, and N q 72

From Eq. (8.4) with c 50 kPa, B 1 m, and assuming sandstone at elevation 19 m:

q ult 1.3 c N c 0.4 b B N b D f N q

(1.3)(50)(84) (0.4)(11.7)(1)(100) [(9.2)(9) (11.7)(3)](72)

14,400 kPa

q all q ult FS 14,400 kPa 3 4800 kPa
Q all ( q all )( r 2 ) (4800 kPa)( )(1.0 2) 2 3770 kN

Since the earthquake will not weaken the sandstone, a one-third increase in bearing
pressure is often recommended, or:

Seismic q all (4800 kPa)(1 0.333) 6400 kPa
Seismic Q all ( q all )( r 2 ) (6400 kPa)( )(1.0 2) 2 5000 kN

11.6 Based on Fig. 11.15, use c A c 0.67 (average curve for concrete piles) and
therefore c A (0.67)(1200) 800 psf.

Using Eq. (11.12):

Q ult end bearing side adhesion

9 c R 2 2 c A R z

2) 2 9 (1200 psf)(1.0 2 (800 psf)(1.0 2)(40)

8000 100,000 108,000 lb 108 kips

F

Q all Q ult 108 3 36 kips

11.7 From Prob. 9.12, the peak shear strength 1500 psf and the fully softened shear

strength 520 psf.

Using peak shear strength:
Based on Fig. 11.15, use c A c 0.50 (average curve for all piles) and therefore c A (0.50)
(1500) 750 psf.
Using Eq. (11.12):
Q ult end bearing side adhesion