Retaining wall for Sunk Trampoline

[Farawayview]

Hi,

I am thinking of sinking our trampoline in the grass as we are fed up with staring at its cage like enclosure. (10 m diameter X 70 cm height)

I will need to dig the circle and build a retaining wall plus dig a channel for drainage pipe. Anyone has done this before, advise appreciated.

A) Can I use block instead of brick and which type given that its all underground level?
B) Do I need to damp proof behind the retaining circle wall and why?
C) I don't intend to put a membrane sheet inside the circle base either but just hard core sloping towards the drainage pipe, is that reasonable so that the water will dispense and soak away into the ground too.
D) How deep and wide a foundation do I need for the circle wall?
E) Anything else I should worry about?

Thanks

 

[mikej2005]

10 m diameter

Do you mean 10m in circumference ?!

 

[conny]

I would suggest he means 10' (foot) in diameter.
Though 70cm in height for the netting seems awfully low!

 

[big-all]

in my humble opinion unless you have extremely well draining soil you will have a slow draining "sump" with all surrounding garden finding the easy drain route to the lowest point

 

[Farawayview]

Hi,

Sorry dims are

3.15 m diameter (circa 8 ')
10 m circumference
70 cm height of trampoline (about 3 feet deep?)

I think our problem is where to dispense of the water, several options available, but non are perfect:

a) Behind our fence in the farmer's field, maybe he will object, and we are not sure how big a trench we need to dig

b) Under our pebbly driveway (seems way too risky)

c) Under grass next to big tree (what about roots an maybe messy)

d) Dig another big hole for a water tank and lower than in to collect water, (has to be deeper than trampoline, then we can't reach its tap to get water out, what if it gets full?)

Any suggestions?

Thanks

 

[freddiemercurystwin]

So can you answer big-all's query?

Had you thought of digging down say 35cm and then using the dug out top soil to bank up to the top of the trampoline. this would save having to get rid of the soil and would effectively raise the base level of the trampoline yet it would still appear buried.

What happens if you dig a 70cm hole (or 35cm hole if you went for banking around the perimeter)? Does it fill with rain? You would need to determine the level of the water table when the ground is fully saturated. If it were below your base level then you wouldn't even need a soakaway.

If the water table was above your base level the you'd need to tank your whole structure which will make it a whole other ball game! A soakaway wouldn't work if that were the case.