First lets consider a few reasons for this rethink:
Pavements and roads are concrete - they do not breathe.. Could that space be used more efficiently?
Whenever piping or cabling is altered - miles of paving is dug up and recast/replaced. Manhole covers come in an odd variety of shapes and sizes( cute but not useful).
Here is my proposal - it is not cheap to implement, but will pay off well in the long run - reducing works costs and times (thus traffic problems from works), improving environment, and they would also look very cool. It makes drainage much simpler.
Pavement and roads will be build in precast sections - mostly rectangular - but some variations/curves are included.
The sections (about 2 meters square generally) will have a high strength top level - a kind of mezzanine - which has support structs, and can take the kind of pressures exerted by people (or cars). This has a mesh, which lets light and rain through.
Under this (about a foot or so) is the next level - a mesh with grass growing in it - yes I really mean vegetation.
Below this is a meter or so of crawl space- which can be used for the piping, cabling and other such junk. These crawl spaces then interlink - so one road has a section with a big door and a ramp to descend to this level for maintenance - whether this area is lit or not is in the implementation - it is probably better unlit, and those using it take their own lighting with them(have hooks for hanging works lamps).
This is the bottom layer of the section. Under the sections would be cast a system of lugs - connecting to the four corners of a section, and the mid support strut. The sections could be placed, and removed from the lugs (watch any piping in them is remove first). The lugs have run-offs to the drain system, although there is a possibility the grasses may indulge themselves first.
To remove the sections - there will be some gripping sockets(for a crane with attachment). These are normally covered by a cover to keep them flush with the top. The plugs for these have a mechanical catch - so they slide in, and engage with some of the high strength struts - allowing the whole section to be removed. Since workmen and small machines can freely go down entrance ramps, this should only be needed for maintenance and replacement of the segments or city planning - rarely.
This can be used for city/private garage/car park design. It could be used on a smaller scale on gardens and terraces.
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What about curves?
Should curved sections be made? Why not.
Most complex road setups could be made with a set of components, for an example of a system built like this, one only need look at rail systems.
What about cost?
The cost of this - in terms of an initial investment, would be a lot, and city planners would have to put this up front, but the time and cost saved in pulling up the road with diggers, disposing of the broken tarmac/concrete, relaying and resurfacing the road just to get a burst water main or some similar problem sorted would make it worth it in a very short time scale.
Now given that the actual blocks are mostly uniform, with the exception of a few, they could actually be mass produced - which would save money. The actual plant area could be laid as turf.
Digging as deep as 1/2 meters may cause interruption. Wouldn’t it?
No. first - the intention is that all pipework, be it gas, water or cabling as well goes in the crawl space under the grassy area. This may also be organised with clips, racks or ties or what ever - but it is no longer just through solid earth, which makes laying cable a doddle - you don’t even need to pull the stuff up, just run it through the crawl space with a reel.
In terms of earth displacement, we are talking a mezzanine layer of soil and grass/vegetation here. This means that there is actually more growing here than would be in a normal road and cabling setup - which do go fairly deep and make no provision for the vegetation.
How would the vegetation be tended?
In terms of watering, it would be partially watered by draining, but may require some built in sprinklers in dried times. It would not be difficult to send small robots along this space to dib new seeds, spread compost or tend the plants in other ways. Because the top surface is a thoroughfare, it will be cropped off at the top level as its maximum height. Even on a busy road, there should be enough sunlight. However - how plants would cope with such a close and immediate source of petrol fumes and oil run off (something the construction material itself must be resistant) would depend on the choice of plants.
Occasionally - a robot may need to also go and grade it - as the soil/deposit layer would tend to get higher.
If you have any other questions on this concept, or know of something similar please let me know.