Drive ramp principles - Any special rules for constructing ramp

[markactive]

Hello, I am going to construct a ramp up to a platform level with the grass in my back garden . The main fabric will be between 4 to 6 inches of aggregateand 70mm thick granite slabs laid on a full mortar bed. Are there any specific rules to follow when constructing a drive ramp i.e. a partition restraint at the bottom of the ramp to prevent long term sliding ?
Many thanks.

[lutonlagerlout]

the main thing is to make sure a car can get up it without grounding
if the grass to floor level is 200mm your ramp needs to be around2 m long
I did post a calculator for this last year
lemme see if I can find it
LLL

[Ouch]

Sensible worst case ground clearance for a car is 100mm.
So if you've got a wheelbase of 2.7m (VW Passat) which has been loaded with half a ton of paving slabs (who'd do that??) then as you crest the ramp you'd need either a gradient of less than 13:1 (half of 2700/100) or a rounded transition from ramp to flat - a quick cad sketch suggests a radius of 9.1m or greater for transition.
Technically it's called a 'breakover angle' according to wikipedia..
You might also want to radius the approach (bottom) gradient in a similar way to prevent the damage to the underside of the front bumper/skirt.

[Tony McC]

A few years back, Cookie and meself had to build a ramp for a Ford GT65 with a ground clearance measured in millimetres. The access apron from the public highway sloped out to the road, while the driveway itself sloped back to the house, forming a 'peak' at the boundary.

We had permission from the local highways to re-pave the apron to match that on the driveway, but the 'hump' that had existed for 80-odd years without causing a problem had to be drastically reduced when the client arrived home one afternoon with his latest acquisition, a show-off car which turned out to be incapable of crossing the threshold without grinding down the ludicrous spoiler on the front.....and there was no way of getting a barrow in the back of it, so not a practical vehicle at all!

Without digging out my notes from back then, it was summat daft like a maximum rise of 75mm over 3 metres

[lutonlagerlout]

we have actually looked up car specifications worked out the clearance and the distance wheel to wheel and made a profile up allowing for minimum 75mm clearance (vehicles can be heavily loaded)
but bottom line every site is different but dont get it wrong
LLL