In reply to stp:
From the link GarethSL provided:
> The aim was to compare the performance and longevity of different anchor systems placed in natural stone, and also to investigate methods of sustainable bolting.
I assume the bolts were placed at ground level under the assumption that orientation was a minimally confounding factor and made bolt placement/testing easier.
As to why so many bolts, if you read the linked study you'll see that they're testing 4 different varieties of bolts. For each bolt type they're doing several pull out tests (1 week, 1 year, 5 years and 10 years) and each test is repeated 3 times for each bolt type. 4 bolt types x 4 tests x 3 bolts/test = 48 bolts. The study also mentions some other adhoc tests that were performed so that would count for a few more bolts.
ed: apologies, numbers were wrong in the above. corrected calc: 5 bolt types x 5 tests x 3 bolts/test = 75 bolts
Post edited at 20:10