Help! type 1 sub base turned to porridge

[greenfingers]

Hi folks, my first post.

Having gleaned loads of useful info from this site, I plucked up enough courage to start digging up our gravel driveway, which over recent years has become more mud than gravel.

There is about 150m2 of it with virtually no gradient around the front and side of the house. It has not yet flooded in the 9 years I have lived here, which is a relief because the gravel is only about 70mm below DPC where it meets the house (the previous owner had all the entrances made wheelchair accessible many years ago).

My plan was to reduce the levels as much as practically possible and lay 100mm of type 1 hardcore over a terram membrane. Then after leaving it for the winter, part of the area is to be blinded and block paved, with the remainder finished in a 40mm layer of gravel.

We decided to do half the area at a time, to allow vehicular access while the works are in progress. After three 8-wheeler loads of mud had been excavated and removed, I laid the terram and spread 17 tonnes of type 1 mot limestone on top to give layer roughly 100mm thick.

The next day it rained and rained hard all day. The following day, when I tried to go over it with a wacker plate, the stones on top just disappeared into the mush. Now it resembles a gooey porridge, which is made even worse when cars drive on it.

After 1 1/2 days of dry weather, there are still pools of water sitting on top of a squidgy mess and with more rain forecast, I have no idea what to do, even after Googling for answers.

Would a sprinkling of type 3 (or hardcore without fines) help it to drain and make it more manageable? I was really hoping to have a surface suitable for walking and driving over, but don't want to raise the finished levels unnecessarily.

Any helpful advice would be much appreciated.

[seanandruby]

What is your sub soil made of? Different soil types need different methods. Maybe you should have used heavy duty geo-grid, crushed concrete to cappping level then mot.

[greenfingers]

The sub soil does have a high clay content.

When we moved here 9 years ago, being concerned about drainage, I dug a deep hole in the lowest area and filled it with broken bricks, roof tiles and pieces of stone. Like I said, drainage has not really been a major issue before now.

I did raise the question with a couple of contractors, about using a free draining hardcore for the sub base, but was advised by both to use the standard type 1, because it tends to bind together better.

[bobbi o]

The Type one is probably crap, ie its got a high clay content hidden in it.

We've had major problems as well, for a lot of this year.

There's not a lot you can do, except wait for it to dry out

or

Scrape it back and put a layer of crusher run down, then blind it with the best of the type one.

[greenfingers]

Thanks for your input Bobbi. It's slightly reassuring that I'm not the first to end up in this mess.

It is frustrating that when I explained to the supplier I didn't want any type 1 that had clay in it, he assured me that it was just limestone 40mm to dust. Actually, it doesn't seem as sticky as clay (I've had grey type 1 with claggy bits in it before). This is a creamy white colour, so perhaps it is limestone but with a hell of a lot of fines in it.

Is it reasonable to assume this might dry out enough for me to use a wacker on it in the next week? Otherwise, I'll have to do something like you suggest with crusher run.

[digerjones]

I wouldn't bother with the wacker, till it's properly dried out, it's a waist of time until then. The type one was probably wet through when it came.

[greenfingers]

Thanks for that digerjones. Your username suggests you have experience in this field, so I'll take that advice.

Is there any way to get it to dry out quicker, or am I in the lap of the gods and perhaps going to have to wait till the new year?

[digerjones]

Without digging it up and starting again I would just leave. Try to get a chanel dug, so drain the water off. Down the side or the middle. Doesn't have to be deep. Get the standing water moving

[greenfingers]

Yes, creating a makeshift drainage channel is something I hadn't thought of and it makes good sense.

I'll have a go at that tomorrow and report back

[digerjones]

OK. GOOD LUCK

[greenfingers]

Well, I managed to shift three or four puddles to lower ground, but most of the area still has water sitting in the impressions left by the digger tracks and it doesn't seem to be draining away at all.

I've got 6 tons of clean stone 40mm and smaller coming tomorrow morning. The plan is to scatter it on top and create a bit more of a slope which will encourage the water to run away to a point where I guess there will have to be a drain. Hopefully, then it will dry out enough for compacting.

If it is still too mushy to work with, what if I sprinkled a dusting of quicklime or cement powder on top and tracked over it a bit to mix it in? The thought of the whole lot going off in a mess worries me, but at least it might leave something to work with.

[Dave_L]

If the surface water has nowhere to drain to them your problem isn't going to go away.

If the sub grade doesn't drain freely i.e. It's clay, then you are going to need to install some form of land drainage to get the water away.

[lutonlagerlout]

I have got pals in OXON. it is a well know county for flooding and poor drainage,need the water to go someplace
LLL

[greenfingers]

Yes, point taken. So it sounds like I need to get a decent slope down the bit that's going to be block paved and put an aco drain at the bottom, connected to a soakaway.

[seanandruby]

Maybe you could use a composite membeane beneath your sub base to channel the water to a collector drain. The composite layer is mostly
Used on permeable paving, and can help stop saturation of the sub base. Is your ground suitable for a soakaway and if not have you somewhere to drain to. We have been getting some shite mot lately to on the South coast.