Hello, and welcome to the thread. Early refusal in dense sand with gravel lenses is a common headache, and the usual first suspects are a gravel layer or cemented zone above the design tip, pile-to-soil friction building faster than expected, or a hammer that isn't delivering full energy.
Some checks crews commonly run before calling refusal: confirm the hammer's stroke or blow count against its rated energy, look at pile head damage and cushion condition, compare blow counts across neighboring piles, and check whether a few restrikes after a pause (setup) show the resistance easing. If it doesn't ease, it's more likely real.
Whether a pile is refused, and whether to switch to predrilling or a bigger hammer, is a call for your geotechnical engineer and the pile designer, based on your boring logs and load criteria. A quick question: do you have the boring data showing where those gravel lenses sit relative to the refused piles?
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