I haven’t seen the plans but here’s a fearless SWAG on how the green belt spiral will work. This is based on looking at the renderings in the OP article.
The ramp will have two zones, one for the vegetation and the second for the pedestrians. The inner zone will be for the larger vegetation so as to keep that weight closer to the center of the structure. The pedestrian zone would be more towards the outer wall.
The trick is the inner vegetation zone. I think this will be level, horizontal plats that are sort of like a staircase that steps up the spiral. It likely will be a hydroponic growing system and the surface will be more of a camouflage to mimic a forest or garden surface. Weight control is critical.
The pedestrian zone for hiking the spiral will probably be a ramp with regularly spaced horizontal, flat spots for a place to to rest and to exit the ramp to an interior elevator. It would not be good PR to have people stroking out from the stress of the hike. LOL.
What would be a blast would be a track for wheeled bobsleds. What a ride!
But is the ramp in compliance with the design and slope specifications required for wheelchair access as defined by the Americans with Disabilities Act of 1990?