Spongy ground a nightmare

[williams]

I remember years ago you would dig a job out and you would very occasionally get the odd spongy patch of ground which would reflect in the sub base, I.e it would be like a sponge when you walk on it.

To remedy this you would dig the stone out, maybe dig some of the ground out, chuck a barrow of concrete in and then type one on top, compact etc then fine.

What I've noticed the last couple of years is that this is more frequent, the last few jobs have been ridiculous, one being dug out to over 14" deep all over - and still being spongy.
A recent patio was fine when dug out, it rained heavily and then when based is like a sponge again? Very odd.

Why is this happening? Who else is having this and how are you getting round it? It does seem to improve if left for a while.

My theory is that because we have had so much rain the ground is just sodden, when you stone it and compact it's just bringing the water up getting caught in the stone and acting like a sponge and due to the nature of type one being dusty water is trapped. To be fair I've dug out deeper, put in 50mm crushed as an oversite and it's still spongy so not even sure if it's the type 1.

It's worrying, expensive and a real pain.

[rab1]

One of the small sites were on (new build school) scrapped the ground around the site 4 times since xmas. 1000t type one put down today and rolled

[Kuts]

i always give stone a good roll the day i get, when its wet you've no chance

[williams]

i always give stone a good roll the day i get, when its wet you've no chance

So do I, without fail, but even recently it's gone from just wet sub soil to spongy type one straight away.

[Kuts]

since its pissed it down every night lately it could be abit wet before you get it i suppose, i get mine from the tarmac plant and its all covered

[williams]

I have never ever seen as much rain as this in my working life (16 years).

I almost want it to snow, at least you know your not even attempting it :p

[lutonlagerlout]

too much rain
LLL

[GB_Groundworks]

Been lucky to be in factories last 14 months so missed the worst of the weather,

You could use a macintosh probe to establish ground conditions before you start I bought a get for about £500 basically a fancy slide hammer but let's you determine ground baring capacity.

Do you specify the assumption of say 150mm dig out and 100mm mot any more is extra in your quote

Our you could lay a 100mm cbm using a c7.5/c15 dry mix compact it then that'd act as a sudo raft footing

[Tony McC]

But are we really having that much more rain?

Much of the dramatic flooding splashed (literally!) across the front pages and the TV news stems not from there being more rain but from our crap attitude to handling it. We 'urbanise' ever more ground, we insist on building on flood plains, and, as we see almost every day on this website, we want un-waterlogged back gardens and puddle free driveways.

We had a scorcher of a summer last year, so any residual groundwater should have been at a relatively low level, and even with a wetter-than-average winter, the ground in most places shouldn't be struggling to cope, but if we insist on working against nature by dumping water straight into escape routes rather than allowing it to recharge natural aquifers, then we are bound to get wetter ground in those low-lying areas.

There needs to be a more rational long-term approach to water management. Building more and more flood barriers is reactive, it's bolting the stable door after the horse has fled. As a society, we need to be pro-active and deal with the surface water at source, whether that's achieved through wider use of permable paving or community soakaways.

If we are, as some seem to suspect, getting ever wetter weather, then our current strategy of 'mopping up' is bound to fail, so maybe we actually will end up with a scenario where we are required to use ever deeper permeabble or bound sub-bases just to give us a reliable platform on which to build. This raises costs but given the current mindset of government, expecting individuals to absorb additional costs is preferable to sharing considerably lower costs across a wider community. Short-sighted, as usual!

[GB_Groundworks]

absolutely agree

this is our friends in Rochester's NY garden, hes got 12 acres including a stream running through it, but 2 acres of it is an attenuation pond (the low lying areas where the bow hunting animal target are) there are willow and other water loving tress in it and most the time he can use it as garden but then under heavy rain it fills up, if it over fills it runs out through the concrete chamber you can see into the stream, if not it just saoks in over time.

hes on a sub division of about 50 house so takes most the surface run off of these, he showed me the plans of his new 1m sp foot metal working shed he wa shaving built at work, very large roof area and all was to be run into a series of casading large ponds to hold it and let it back into the ground naturally. they are way more up on their water handling than we are.

i say we need more of it rather than straight into the drains, plus itd be more work for us





Edited By GB_Groundworks on 1390413303

[rab1]

Most of my mates live in a scheme lol

[Dave_L]

Without access to the figures, I would say we are experiencing MORE rainfall and perhaps in a shorter timeframe.

[lutonlagerlout]

or a project Rab :;):

we visited some relatives in yorktown heights New York state, and they all have their own borehole for water
drilled 300ft down ,lined and then pumped through a series of 3 filters
it blew me away but cheaper than digging a water main in from 5 miles away
LLL

[williams]

Without doubt the last few months rainfall has been above average. I know this because I'm on a big job with deadlines, the rain has been flooding the place making it impossible to do stuff. So for my defence I actually looked up average rainfall for those months compared to the usual average and it was higher, by quite a bit. Infact it wasn't too far off of the tropics at certain times!

I've never seen so much rain (Essex here).

[Tony McC]

I think we're more accustomed to the wet here in Lankysheer. It's been wet, admittedly, but I don't think it's been any wetter than normal. The Met Office says England had 134% of normal rainfall in December, but that's across the whole country. I can't find the data for the regions but If you've had it wetter than average down in that Essex, then if we've been 'on target' that would be about right, I s'pose.