Before heading out to China in 2015 we decided to test some Hilti HKD anchors in a quarry. We'd used some similar anchors the previous year, and were impressed at advantages they appeared to offer over other spit-type anchors and throughbolts. On the flip side, we weren't really sure about their strength other than from anecdotal evidence, so it seemed like a good idea to test them out.
They're similar to the Raumer Rainox anchors with the cone held at the back of the anchor, but rather than hammering the anchor over the cone, the cone is held just at the base of the threaded section and the cone is hammered into the back of the anchor. Crucially, that avoids the problems highlighted in the 2013 Ario Caves Project report
in terms of hole depth: provided the hole is shorter than than the length of the anchor plus the length of the cone, the anchor appears to set fine, and the lip prevents the anchor from being able to be recessed into the hole. An additional bonus is that they require a 10 mm diameter hole rather than a 12 mm hole. There's plenty of detailed information at on the Hilti website
Our testing wasn't rigorous or especially systematic, but hopefully it might give a useful idea about the strength of these anchors.
We did almost all the tests axially (i.e. pulling perpendicular to the rock face) for simplicity, and over 5-10 bolts, the average force required to extract the was around 5-7 kN. The weakest anchor we tested took around 4 kN to extract, and this had been placed intentionally poorly, only tapping the cone in very lightly. For one anchor where we really belted in the cone, it held a steady 15kN, which was as much as we could test it to.
We did attempt a radial test (i.e. parallel to the rock face) which, unsurprisingly, comprised a fairly poor set-up. The anchor placement was appalling, and without even hammering in the cone at all, it held 7 kN before the rock started fracturing badly.
On the expedition itself we bolted a fair few pitches with no problems from these anchors at all. For future trips where expansion anchors are likely to be the only feasible option, I would certainly have a strong preference for these over spits, Rainox anchors or throughbolts for standard rigging.
Attached photos by Chris H - proof of the 15 kN!