22 Revision 33 October 2022
7 Driven and Foundation Post Testing Requirements
7.1 Ground Conditions
Soil testing must be carried out to establish the strength or compaction of
the ground in to which the VRS is to be installed. Tests should be carried out
in accordance with SAFEROAD test procedure as detailed below. The
frequency of testing should be as described in the contract specific appendix
4/1. As a minimum SAFEROAD recommend that at least one test is carried
out for each VRS run or one test for every 200m whichever is the greater.
There should be further tests if there is a change in ground conditions for
example if the VRS crosses a cut fill line then each ground condition should
be tested.
Assuming the ground has been compacted in accordance with MCHW VOL
1 series 600 then standard driven posts or driven foundations should record
a pass when the ground is tested.
It should be noted that the soil test takes in to account the plastic moment of
each post type when impacted at the angle of the type test which is the
design criteria for VRS. This does not take into account the plastic moment
of the post through its strongest axis. Therefore foundations installed to
meet the required test criteria may move under impact. If this occurs, they
should be replaced when the VRS is repaired
W
hen installing concrete foundations that are required by the design
organisation to be survivable (this should be made clear in appendix 4/1).
The deflection for a VRS post in a survivable concrete foundation should be
no more than 50mm thereby mitigating the risk of displacement when
impacted outside of the parameters set down in the initial type test although
there is no guarantee of this.
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