Ground investigations, contracts and testing 521of load testing since the failure load on the pile is not known with any certainty until the
test is made.
The ML test is best suited for contract work, particularly for proof loading tests on working
piles. It is also suitable for use where empirical methods are employed to predict the ultimate
load from measurement of residual deflections after returning the test load to zero at four or
five stages up to the maximum (see below). The load at each stage is held until the rate of
settlement has decreased to less than 0.25 mm/hour and is still decreasing.
EC7-1 Clause 7.5 deals with pile load tests in general and outlines procedures for static
and dynamic load tests, trial piles and testing working piles. BSEN 1536 refers to EC7
requirements giving recommendations for ML, CRP, dynamic and integrity testing which
are slightly different from the BS8004 procedures. For example, in ML tests the loads should
be constant at each of at least six stages for a specified duration and unless otherwise stated
the displacement rate should be less than 0.1 mm/20 minutes at the end of each stage. For
CRP tests the rate of displacement should be constant at approximately 1 mm per minute,
unless otherwise agreed. BSEN 12699 is less prescriptive for displacement piles, but
requires testing to be in accordance with the relevant parts of EC7 and the specifications.
The section of the ICE Specification dealing with static load tests defines the Specified
Working Load(SWL) as ‘the specified load on the head of a pile as stated in the relevant
Particular Specification’or in provided schedules. This is differentiated from the Design
Verification Load(DVL) which is defined as ‘a load which will be substituted for the spec-
ified working load for the purpose of a test and which may be applied to an isolated or singly
loaded pile at the time of testing the given conditions of the Site’. The DVL takes into
account special conditions which may not apply to all piles on the site such as negative shaft
friction, or variations in pile head casting level.
The ICE recommends that a proof load test should normally be the sum of the DVL plus
50% of the SWL applied in the sequence shown in Table 11.4 for multi-cyclic pile tests
(reproduced with permission of Thomas Telford Limited).
Table 11.4Loading sequence for proof load test to a
maximum of 100% DVL plus 50% SWL
Load Minimum time of holding load
25% DVL 30 minutes
50% DVL 30 minutes
75% DVL 30 minutes
100% DVL 6 hours
75% DVL 10 minutes
50% DVL 10 minutes
25% DVL 10 minutes
0 1 hour
100% DVL 1 hour
100% DVL25% SWL 1 hour
100% DVL50% SWL 6 hours
100% DVL25% SWL 10 minutes
100% DVL 10 minutes
75% DVL 10 minutes
50% DVL 10 minutes
25% DVL 10 minutes
0 1 hour