Ketty told me that the walkway was a little wobbly and unstable when she stepped on the bars. But that's probably because you don't have enough sand, which is needed as a "cushion.
When making such a structure, the wood slices, after they have been pre-treated with hot olive and dried, should have been laid in their places and covered with sand on top so that it fills all the gaps between the circles. Afterwards, you tamp everything down and level it out.
Your driveway is now ready to use!