Humboldt 5000 BLU Light Weight Deflectometer - Manual (Page 29)

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4.7 Proposal for the Correlation of Static / Dynamic Plate Load Test
The static and the dynamic plate load test differ from each other especially in the load speed and the
pressure exerted on the ground. Therefore there is no constant correlation between the parameters E
v1
/
E
v2
and E
vd
.
In order to achieve the most accurate reading possible, we recommend performing site-specific correlation
tests for every construction project directly on-site. To determine correlation values for the required
backfill material we advise you to adhere to the following procedure: After the first phase of compaction
work has been sufficiently completed, perform a static plate load test on the test area. Make sure that the
loading vehicle leaves the area very carefully to avoid any ground disturbances. Afterwards, determine the
water content of the backfill material. Then, in a circle around this first testing point, carry out eight
dynamic plate load tests – four tests 30 cm away from the first testing point, and four 60 cm away, each
with a 45 degree distance from the next. Several test sequences must be performed in succession along
the centre of the compaction line; the required number depends on the size of the construction site. In all
cases, at least three test sequences, at a distance of 20 metres from each other, should be performed.
The procedure must be repeated at other points of the test area. If the water content at the different testing
points does not vary widely, compare the mean values of the measured E
vd
values with the mean values
of the E
v
values obtained through the static test.
For the calculation of the E
vd
mean value, ignore the two highest and the two lowest test results and
consider only the four test results which show parameters close to each other. After having determined the
correlation values E
vd
/ E
v
all other tests can be performed with the Light Weight Deflectometer, provided
that it is used on the same type of soil. Contractor and client should perform the correlation procedure
together, so that they can both agree on the standard test method.
4.8 Interpreting the Test Results
According to German standards ZTV E-StB 09, ZTV A-StB 12 and RIL 836 Deutsche Bahn AG as well as
Austrian standard RVS 08.03.04, an inspection with the dynamic plate load test (in accordance with ‘TP BF-StB
Part 8.3 for Soil and Rock Mechanics in Road Constructions’) can be conducted instead of the static plate load
test. Please strictly follow the instructions of ZTV-E, ZTV-A and/or RVS 08.03.04 (Austria).
For every static plate load test at least three dynamic tests must be performed. However, these must not
be conducted side by side, but can be spread over the entire test area.
The evaluation of the measured Evd value depends on the material and the subsoil being tested. It is always
necessary to determine correlation values of the static plate load test on a trial basis for the pre-existing
ground or the ground intended for backfilling. Homogeneous ground is a prerequisite for properly correlating
the two measuring methods. Accordingly, the water content of the soil must not vary widely.
ATTENTION (Quotation from ZTV E-StB 09)
‘The deformation modulus Ev2 is to be assessed by the static plate load test in accordance with DIN
18134 and the dynamic deflection module Evd with the dynamic plate load test in accordance with TP
BF-StB Part B 8.3.... The specifications of the building contract should state whether the static or dynamic
deflection modulus is to be established. If no such statement is to be found in the contract, the static
deformation modulus will need to be established.’
According to German standard TP BF-StB Part B 8.3 Light Weight Deflectometers must be calibrated at
least once a year at a calibration institute accredited by the German Federal Road Research Institute
(Bundesanstalt für Straßenbau). Send the device back to TERRATEST GmbH for calibration at least once
a year, otherwise test results may be imprecise. Test results of a device that has not been calibrated, or
of a device with an expired calibration date, must not be used for evaluating the bearing capacity of soil
and rock. Abide by the mandatory calibration intervals.