Can My Pebble Floor Project Be Saved?

Picture this...Hardwood floors were laid in a basement which subsequently got wet and warped. They warped so bad, the front door couldn't be opened. We cut out a large area shaped like an octagon at the door and laid travertine tile. This left a small space between the tile and wood floors and something had to be put there to fill in the space. I came up with the idea to put small pebbles in this area which would fill in that space and possibly look kind of cool. I did it and yes it looks real good, the only problem is getting the pebbles to stay in place. I keep having to sweep them back in place into the "hole". My question is, how do I get them to stay in place? When I step over the space where the rocks are, I always knock a few out and especially when my dogs trample over the area pebbles go everywhere. I thought about pouring some clear polyurethane over the pebbles but eventually I plan on tearing all the wood floor out and making the entire room travertine. If anyone understood what I just said and has any suggestions, please help. Thanks!