Ruddlesden geotechnical looks into sink hole…
How many times have we been told: “A hole has appeared on our site”?
And how many times have we wittily replied (or thought): “Would you like us to look into it for you?”?!
A mystery to solve required some research and thought to come up with the answer(s).
Despite our client’s eagerness to carry out some boreholes to “see if there are any big voids in the ground”, we persuaded them to spend some time and money on a decent desk study and walkover first, to see what we think might have caused the ‘sink holes’ and to tailor any intrusive investigation accordingly.
Having quite quickly ruled out the holes being a natural phenomenon, due to dissolution or mining, for example, our attention focussed on man-made reasons.
An archaeological report for the neighbouring site and a local history website revealed that buildings formerly on the site had cellars and at least one cellar was repurposed as an air raid shelter during World War II.
Combined with detailed field observations, which included the use of a borescope into three lateral holes, we were confident that the reason for the ‘sink holes’ was due to the collapse of the rear retaining wall of the structure, due to long-term degradation, which would have withdrawn support of the ground.
As a result, we were happy to recommend relatively simple remedial works (filling, following consultation with an archaeologist, and monitoring), without the need for an intrusive investigation, which would have been both relatively expensive and potentially dangerous.
