Verification of geotechnical reliability using load tests and integrity tests - Risk and Reliability in Geotechnical Engineering - page 545

of the piles will be changed after these tests. This chapter describes procedures for quan-
titatively evaluating the impact of routine load tests and integrity tests on the reliability of
piles using the Bayesian approach and illustrates the proposed procedures by considering the
effect of proof load tests and interface coring on the reliability of piles.
In the proof load test example, whether or not a load test is carried out to failure, the
test outcome can be used to ensure that the acceptance reliability is met using the methods
described in this chapter. Thus, contributions of load tests can be included in a design in a
systematic manner. Although various analysis methods could arrive at considerably different
designs, the reliability of the designs associated with these analysis methods is rather uniform
if the designs adopt the same FOS of 2.0 and are verified by consecutive positive proof tests.
In the example of reliability analysis of bored piles with defective toes, the occurrence
probability and mean thickness of toe debris are updated with the information from the
interface coring tests. The test information can improve the reliability of pile foundations
significantly in the example. The degree of reliability improvement depends on outcomes of
the tests, actions taken after the tests, the pile length, and the pile diameter.

aCknoWleDgMent

The research described in this chapter was substantially supported by the Research Grants
Council of the Hong Kong Special Administrative Region (Project No. HKUST6126/03E).

lISt oF SYMbolS

β reliability index

β T target reliability index

ξ standard deviation of logarithm of a random variable

η mean of logarithm of a random variable

κ and ν parameters for a gamma distribution

λ R bias factor for resistance

λ QD bias factor for dead load

λ QL bias factor for live load

μ mean value of random variable

μ′ prior mean of the mean value when the mean value is also a variable

μ″ posterior mean of a random variable

σ standard deviation of a random variable

σ′ prior standard deviation of a random variable

σ″ posterior standard deviation of a random variable

Φ() cumulative distribution function

COV Q coefficient of variation for load effect

COV R coefficient of variation for resistance

D pile diameter

L pile length

k ratio of the maximum load in a load test to the design load

m number of pile tests with unsatisfactory test outcome

n total number of pile tests

p d occurrence probability of toe debris

p f probability of unsatisfactory performance

q and r parameters for a beta distribution