From the Hixtra archive · 15th November 2023
To help get the most out of plate bearing tests to establish ground performance for mobile cranes here are a few simple guidelines:
• Ask to use the widest diameter plate available as the wider the plate, the more accurately the test will replicate outrigger ground pressure zones. We have up to 760mm diameter plates!
• Calculate your maximum ground pressure under each outrigger, specific to the lift, and ask that the test pressures are at least 1.5 times higher than this; the higher the test pressure the better.
• Test all over the area where the crane may be used, not just directly under the planned outrigger locations.
• Test at the edges of fabricated pile mats as often outriggers end up there and the edges can be the weakest point.
• Ask that your testing company is UKAS accredited for plate bearing tests to ensure their competence
• Ignore CBR values for the top of a crane mat, they are for road subgrade construction and have nothing to do with ground stability for mobile cranes; pressure and resulting settlement are key.
• Ensure you have access to a competent person to assess the plate bearing test results who can check that:
the maximum ground pressure has been calculated correctly
the tests have exceeded this pressure by at least 1.5 times
the test plate diameter is appropriate for the size of outriggers used
the tests have been conducted in the correct location
the tests are UKAS accredited
the resulting maximum measured ground settlement is within acceptable parameters
If you need any further assistance you know where we are!
Please get in touch at enquiries@hixtra.co.uk or give us a call.
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