Hi Marco,
Nice to hear from you. The team wanted to narrow the field to those logos they thought most closely reflected what they were looking for, so some designs didn't make the cut. Sorry about that. The reasons that your newer designs didn't make it was that the icons didn't add clarity to what UndergroundGIS does. In fact, some didn't understand the icons at all. One of our team liked the "text" imagery that you have in entries #9, #10, #41, and #61, but I don't think his interest is strong enough to pull that imagery through to the finals.
As I said, some of the imagery looked like it was just forced geometry that didn't necessarily convey a meaning (e.g., circular arrow, sideways teardrop, etc.).
The team is liking images of networking or schematics. The current top choice (#4) is liked because the icon has meaning to the team members (location on a map with data coming from it).
I hope the feedback helps. You are a talented artist. The team had to make some choices and sadly some designs have to be removed. Please consider this feedback and the general feedback I offered and see if some other inspiration doesn't strike you.
Cheers!
~ Rick