freshy Posted August 24, 2020 Share Posted August 24, 2020 Can anyone help me interpret the results below for dynamic probe tests? Link to comment Share on other sites More sharing options...
Declan52 Posted August 24, 2020 Share Posted August 24, 2020 Basically the probing has confirmed that the ground is decent until you get to over 2m where it becomes rock solid. Any test that takes over 50 blows is when you stop it as that is perceived to be something like rock. But due to the limitations of the test as you can't actually see what you probing you might need to dig trial pits to confirm that it is actually rock and not a large boulder at 2.1m. Did you only get one test done or does the data from a few tests all look pretty similar?? 1 Link to comment Share on other sites More sharing options...
freshy Posted August 24, 2020 Author Share Posted August 24, 2020 These are actual test results from the previous owner, he had some Geobear stabilisation work done to one room. Link to comment Share on other sites More sharing options...
Declan52 Posted August 24, 2020 Share Posted August 24, 2020 So the house has had some issues with subsidence and geobear came in to do some remedial work to improve the ground conditions. The left table is how many blows it took before they started work and then the right after. You can see it's had an improvement, The higher the number the better. The test involves driving a metal probe into the ground and counting the blows it takes to move it 100mm. So more blows means harder ground. Are you having issues with cracks etc?? 1 1 Link to comment Share on other sites More sharing options...
freshy Posted August 25, 2020 Author Share Posted August 25, 2020 No issues as such, I'm planning to knock down the 1930's bungalow & rebuild a 1.5 storey dwelling. A neighbour mentioned that there was clay in the ground, when he extended his house and had to dig deeper than 1.2m for his footings. So since I managed to get this report from the previous owner I'm just trying to gauge what type of foundations or issues I may face when I'm doing my new foundations. Link to comment Share on other sites More sharing options...
ToughButterCup Posted August 25, 2020 Share Posted August 25, 2020 9 hours ago, freshy said: These are actual test results from the previous owner, he had some Geobear stabilisation work done to one room. Did the previous owner also have some cores taken? In which case you might have access to an analysis of those cores perhaps? As @Declan52 says, beware of the boulder. It happened to us on the last pile. Took hours to sort out. Link to comment Share on other sites More sharing options...
Declan52 Posted August 25, 2020 Share Posted August 25, 2020 5 hours ago, freshy said: No issues as such, I'm planning to knock down the 1930's bungalow & rebuild a 1.5 storey dwelling. A neighbour mentioned that there was clay in the ground, when he extended his house and had to dig deeper than 1.2m for his footings. So since I managed to get this report from the previous owner I'm just trying to gauge what type of foundations or issues I may face when I'm doing my new foundations. As your plot will have a marker beside it due to issues with subsidence your really going to have to push the boat out and be extra careful. A few trial pits to confirm what's down there is a must and maybe some proper boreholes to give a structural engineer real data to design your foundations correctly so you don't suffer the same fate. Link to comment Share on other sites More sharing options...
freshy Posted August 25, 2020 Author Share Posted August 25, 2020 1 hour ago, ToughButterCup said: Did the previous owner also have some cores taken? In which case you might have access to an analysis of those cores perhaps? As @Declan52 says, beware of the boulder. It happened to us on the last pile. Took hours to sort out. No cores taken. The subsidence was on a relatively small section of the original 1930's bungalow and was picked up during mortgage survey. Hence, Geobear carried out £7-8k worth of warrantied work to support the area from further movement. 8 minutes ago, Declan52 said: As your plot will have a marker beside it due to issues with subsidence your really going to have to push the boat out and be extra careful. A few trial pits to confirm what's down there is a must and maybe some proper boreholes to give a structural engineer real data to design your foundations correctly so you don't suffer the same fate. A marker? Do you know where will this marker maybe? This is historical movement before the previous owner moved in 40 yrs ago. He extended the bungalow in 1985/86 with 1 mtr deep x 600mm wide foundations. I'm expecting the worst and hoping for the best! Worst case piling or 2m-deep trenchfill foundations in some places. Link to comment Share on other sites More sharing options...
Mr Punter Posted August 25, 2020 Share Posted August 25, 2020 The probes are fairly quick and easy to do, especially if you only need to probe 2.5 metres. I would want to make sure the solid strata was uniform around the foundation extents, with no voids. The probe table you have would have been more reassuring if the soil was more consistent, whereas there is very little capacity for the first 2.0m. I doubt there will be much cost difference between probes and trial pits. I would want at least 4. If the results vary a lot, you may need to install piles. 1 Link to comment Share on other sites More sharing options...
joe90 Posted August 25, 2020 Share Posted August 25, 2020 @freshy have you considered a passive slab for your new build, plenty of info here about them especially @Jeremy Harris thread. Link to comment Share on other sites More sharing options...
Declan52 Posted August 25, 2020 Share Posted August 25, 2020 46 minutes ago, freshy said: No cores taken. The subsidence was on a relatively small section of the original 1930's bungalow and was picked up during mortgage survey. Hence, Geobear carried out £7-8k worth of warrantied work to support the area from further movement. A marker? Do you know where will this marker maybe? This is historical movement before the previous owner moved in 40 yrs ago. He extended the bungalow in 1985/86 with 1 mtr deep x 600mm wide foundations. I'm expecting the worst and hoping for the best! Worst case piling or 2m-deep trenchfill foundations in some places. As there has been an insurance claim on it there will be a record of it on file. Where its kept I couldn't tell you but I'm sure they would soon find it if they needed it to fight a claim. As you will have a digger on site to knock the house down a trial pit to 2.2m would take 5 mins extra work. A few of these around the site, not on the actual footprint of the new house will confirm that hopefully rock is at this depth. Link to comment Share on other sites More sharing options...
freshy Posted August 25, 2020 Author Share Posted August 25, 2020 29 minutes ago, joe90 said: @freshy have you considered a passive slab for your new build, plenty of info here about them especially @Jeremy Harris thread. Not sure at the moment about the slab type, I'm still in the planning phase, but will take time to read, thanks. ? 2 minutes ago, Declan52 said: As there has been an insurance claim on it there will be a record of it on file. Where its kept I couldn't tell you but I'm sure they would soon find it if they needed it to fight a claim. As you will have a digger on site to knock the house down a trial pit to 2.2m would take 5 mins extra work. A few of these around the site, not on the actual footprint of the new house will confirm that hopefully rock is at this depth. Good to know, no insurance claim was made against the property (the previous owner paid out of his own pocket) so assume no marker. ? Trial pits certainly make sense since I will have a digger on site during the demolition (fingers crossed) in spring 2021. Link to comment Share on other sites More sharing options...
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