I wrote a post of what I think is a Andrena barbilabris, a few weeks back and its behaviour whilst tunneling. Tunneling bee
By the way, this one acted alone.
Here is another short sequence of a bee at work. Also one that digs into sand but which acts very differently which make me think it is a different species although it looks very similar to Andrena barbilabris.
This happened on a sandy footpath. There were loads of bee's all skimming a couple of centimeters above the ground. Then one would land and within a second it had dug into the sand and was gone - leaving no clue (what I could see) of what had just happened. I didn't see any reemerge but it was so hectic with so many bee's dashing around my ankles.
I stood still, just following them with the camera, and they were not bothered by my presence. Some people walked along the path and the bees spread out, but as soon as the people had passed the bee's were back .
It makes you wonder how deep they go once in the sand so they are not squashed by passing feet.
Image 1. Just about to land
Image 2. Has landed
Image 3. The head has already disappered into the sand
Image 4. You can see a bee and a wasp having a fight.