Environmental Engineering Reference
In-Depth Information
Subsequently, the reliability of the defective pile can be calculated using
Equations 14.24
assumed to be the same as that for a pile free of toe debris.
14.6.2 Survey of toe debris
To obtain the prior information on occurrence probability and thickness of toe debris in
Hong Kong, a practice survey was conducted in the form of questionnaires to solicit views
from practicing engineers on bored pile quality (Zhang et al. 2006a). The results for toe
debris are shown in
Figure 14.5a
.
The perceived occurrence probability of toe debris is gen-
erally smaller than 5%. A histogram of the occurrence probability of toe debris is plotted
in
Figure 14.5b
.
Through the Chi-square goodness-of-fit test at the 5% significance level, a
beta distribution as shown in
Equation 14.20
with parameters
q
= 2.0 and
r
= 34.2 is sup-
ported as an adequate model. The corresponding mean and standard deviation of the occur-
rence probability are 5.5 and 3.7%, respectively.
(a)
8
7
6
5
4
3
2
1
0
No idea
0%
1%
2-5%
10%
>10%
Occurrence probability of toe debris
(b)
20
Data
β distribution
q
= 2.0,
r
= 34.2
16
12
8
4
0
0.00
0.03
0.06
0.09
0.12
0.15
0.18
0.21
Occurrence probability of toe debris
Figure 14.5
(a) Histogram of occurrence probability of toe debris; (b) probability density of occurrence
probability of toe debris.
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