Are they reusable after being buried like that? I'd think they'd be corroded. Well, my last suggestion: do you have a big SDS drill with a side handle and a welder? Find a bit big enough you can drill a decent hole through or weld to. Like one of the flat spade type bits. Weld a couple links of chain to it, or drill/blow a hole in it big enough for a 3 piece shackle. From there, figure out the best way to connect it to the anchors you're trying to pull. Now you'll have a bit that should be positively locked into the chuck so you can pull while twisting.
Edit: here you go https://www.amazon.com/dp/B00LDYGL1Y/ref=cm_sw_r_cp_apa_fabc_3B66JTSAYQYDEB8GT35F?_encoding=UTF8&psc=1