Coal Seam

[SiBoyle]

Hello.

 

My wife and I are in the process of purchasing some land in Durham.

 

As with most land up these parts, it's been mined, and there is a coal seam 11.5m down, 1m in depth.

 

We have quotes to grout the land, one at 21k and one at 27k, however this is fixed price.

 

Has anyone ever dealt with this before? And what foundations are suitable following this? Just a raft or trench? 

 

The bore hole report is attached if anyone reaaaalllly wants to help out ?.

 

Thanks.

Fern Meadows Bore Hole Report.pdf

[markc]

This is an odd situation to be in 11.5m is a shallow seam, but too deep to be worth stripping and re compacting. But also too shallow to forget about it.

Piles are an option but at 15m (Ish) metres each would be expensive.

Assuming old mine workings, these would be bell or tunnel pits as opposed to face working so voids should be relatively small and unlikely to affect a floating raft.

Several options im affraid, non of them cheap

 

[SiBoyle]

We've come to terms with the grouting fee, I the land price is reflected in this.

 

It was just the concern of buildability once grouted, if the land can be treated as any other. 

 

Would gravelly clay be suitable for shallow founds?

[markc]

In that case grouting is the easiest way forward. No problem with build afterwards as the bulk of the grout should be well below your founds and pipework.

Gravelly clay is good if the site drains ok. 

[Gus Potter]

On 12/03/2021 at 12:50, SiBoyle said:

Hello.

 

My wife and I are in the process of purchasing some land in Durham.

 

As with most land up these parts, it's been mined, and there is a coal seam 11.5m down, 1m in depth.

 

We have quotes to grout the land, one at 21k and one at 27k, however this is fixed price.

 

Has anyone ever dealt with this before? And what foundations are suitable following this? Just a raft or trench? 

 

The bore hole report is attached if anyone reaaaalllly wants to help out ?.

 

Thanks.

Fern Meadows Bore Hole Report.pdf 886.35 kB · 11 downloads

Hello SiBoyle.

 

Interesting stuff. I have clicked on the download link but only get the results for rotary borehole 2. Can see the void. The void shown in the pdf doc I can down load may be localised.

 

Mods.. Is this a tech failure at my end not being able to download all 11 pdf's?

 

SiBoyle. To get a more comprehensive response on BH you can identify the site and post all the info you have. It's up to you but if you feel ok actually identifying your site, assuming the deal is done then BH folk will chip in.

 

I'm not Columbo but when a grouting contractor offers a fixed price then they probably have a good idea that they are not going to loose money on the job. I can see that the site is named on the RBH record as "The Old Coop" The Coop are not daft and have to my knowledge employed competant SE advisors... you may not need to grout at all.. just gather evidence and off the back of that make an engineering judgement.. After all, both the grouting contractor and an SE will cover you insurance wise.. with a good bit of fine print in the policy. But.. the differance could be a fair bit? The grouting contractor will let you sort out the rest on your own. The SE will take a holistic view and consider the foundation cost and options too, strip / raft etc

 

SiBoyle  "and what foundations are suitable following this? Just a raft or trench?" that comes later. The first thing to do is to dig (excuse the pun) deeper and look at all the info, go back to basics.. desk top study of the site and surroundings..look at the surrounding buildings say and see if they are moving about..

 

Can you see signs of movement. Bell pits were often dug in clusters... long and fascinating story.  Start to form a view of what could be under the ground. It sounds like a lot of work but the cost of this research can suddenly save you a pile of money. 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

[Declan52]

8 hours ago, Gus Potter said:

Hello SiBoyle.

 

Interesting stuff. I have clicked on the download link but only get the results for rotary borehole 2. Can see the void. The void shown in the pdf doc I can down load may be localised.

 

Mods.. Is this a tech failure at my end not being able to download all 11 pdf's?

 

SiBoyle. To get a more comprehensive response on BH you can identify the site and post all the info you have. It's up to you but if you feel ok actually identifying your site, assuming the deal is done then BH folk will chip in.

 

I'm not Columbo but when a grouting contractor offers a fixed price then they probably have a good idea that they are not going to loose money on the job. I can see that the site is named on the RBH record as "The Old Coop" The Coop are not daft and have to my knowledge employed competant SE advisors... you may not need to grout at all.. just gather evidence and off the back of that make an engineering judgement.. After all, both the grouting contractor and an SE will cover you insurance wise.. with a good bit of fine print in the policy. But.. the differance could be a fair bit? The grouting contractor will let you sort out the rest on your own. The SE will take a holistic view and consider the foundation cost and options too, strip / raft etc

 

SiBoyle  "and what foundations are suitable following this? Just a raft or trench?" that comes later. The first thing to do is to dig (excuse the pun) deeper and look at all the info, go back to basics.. desk top study of the site and surroundings..look at the surrounding buildings say and see if they are moving about..

 

Can you see signs of movement. Bell pits were often dug in clusters... long and fascinating story.  Start to form a view of what could be under the ground. It sounds like a lot of work but the cost of this research can suddenly save you a pile of money. 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

I can only find the report for a single borehole as well @Gus Potter.