The biggest mistake we see on Cambridge sites is assuming the Gault Clay is uniform. It is not. You hit a layer of river gravels from the Cam's old floodplain, and suddenly your open-drive sampler jams, the SPT refusal depth shifts, and your foundation design basis collapses. Our team runs SPT tests daily across Cambridge, from Chesterton to Trumpington, and we know the local ground profile intimately. We calibrate hammer energy to BS EN ISO 22476-3 and log every 75 mm of penetration so you get N-values you can trust, not numbers that look good on a spreadsheet. This is hands-on site investigation work, supported by a UKAS-accredited lab for follow-up grain size analysis when you need to confirm the fines content of those alluvial silts.
An SPT N-value without a corrected energy ratio is just a number. We apply ERi/60% corrections so your geotechnical designer works with real data, not wishful thinking.
