Problem

When the pitch was originally planned it was clear that the poor Geotechnical properties & a high water table could potentially cause issues. The client required 7,800m2 to be stabilised & for it to achieve a minimum of 5% CBR value and for the levels to be within +20mm & -30mm tolerances.  The original design planned prior to our involvement was a sub-base 280mm of 6F5 to achieve 5% CBR with a 210mm capping layer of Type 1.   The client wanted to reduce the amount of muck away and to re-use as much site won material as possible, hence our involvement.  

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Solution

The initial soil analysis results showed a high moisture content of 50% + & it was clear that parts of the site was heavily waterlogged due to adverse weather conditions the area had faced in November 2020.  After reviewing our test samples, our suggested SMR design Method was to modify the existing spoil with a mix ratio of 3% of SMR binder, stabilising at a depth of 300mm, with a capping layer of Type 1 stone at 100mm. 

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We did this by carrying out a single pass of SMR Proprietary Binder to a depth of 300mm. The Binder was rotavated into the existing ground before compacted with a 13-ton single drum roller.  The type 1 stone was then laid and compacted at a depth of 100mm. 

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After 48 hours of the curing process, the ground was already showing that it had exceeded the requirement of 5% CBR with a reading of 6.79%. After 7 days of curing the ground was showing readings of 15.86%. 

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Although we encountered continuous adverse weather conditions resulting in the host material being wetter and more unmanageable than anticipated, we persevered throughout, dealt with the inevitable delays and still achieved what we set out to achieve before handing over to South Wales Sports Ground to lay the pitch.

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