Soil Heave question?

[stevelucocq]

Hi,

 

There are 3 Cupressus macrocarpa trees ranging from 14-18 metres high and up to a dbh of 870mm. They are 10 metres from a new development that want to remove these trees. I have been reading through the NHBC 4.2 standard and I am aware that these trees are high water demanding species but a little unclear on the heave damage potential of removing these trees. I have tried to determine the soil type within this area but with no joy. Any pointers?

 

mucho gracias

[AA Teccie (Paul)]

Hi,

 

There are 3 Cupressus macrocarpa trees ranging from 14-18 metres high and up to a dbh of 870mm. They are 10 metres from a new development that want to remove these trees. I have been reading through the NHBC 4.2 standard and I am aware that these trees are high water demanding species but a little unclear on the heave damage potential of removing these trees. I have tried to determine the soil type within this area but with no joy. Any pointers?

 

mucho gracias

 

Hi Steve(?),

 

Strictly speaking the role of establishing a soil's heave potential is that of a (soils) structural engineer but, generally speaking, the higher the plasticty index meausrement the greater the shrinkage potential and therefore, presumably the greater the heave potential.

 

Other factors to consider are that heave damage is significantly less than subsidence damage, i.e. it occurs less frequently, and it usually only occurs where the tree(s) significantly pre-date the building, hence they are founded on existing dehydrated soils / ground. Further if the properties are relatively new build then they should have been constructed in such a way to take account of eventual tree removal. Nonetheless if they are under a 10yr NHBC gaurantee I guess sooner rather than later might be the way to go....if indeed a risk to the property prevails.

 

Hoping thsi to be of help.

 

Cheers..

Paul

[common lime]

Hi, you should have a look at what was posted in the recent past;

 

http://arbtalk.co.uk/forum/general-chat/15163-heave.html

 

Arb's should not be undertaking heave calculations these are for a structural engineer to carry out.

[Tony Croft aka hamadryad]

Hi, you should have a look at what was posted in the recent past;

 

http://arbtalk.co.uk/forum/general-chat/15163-heave.html

 

Arb's should not be undertaking heave calculations these are for a structural engineer to carry out.

 

Like aa teccie said its all in the plastic limits, and well within remits of a qualified arb, not just an engineer!

 

unless i am wrong? if not why the hell am i doing all this work on trees heave subsidence and plastic limits!

[stevelucocq]

thanks for everyones reply. As the property is less than five years old I would have hoped NHBC would have been used for foundation depth guidance..cheers steve

[Paul Barton]

You are right, the houses should have been put on adequate foundations if they are only 5 years old.

 

Are you doing a report or just advising about the tree work? If you are doing anything in writing I would recommend getting a soil sample lab tested for better info on the plasticity index.

[stevelucocq]

You are right, the houses should have been put on adequate foundations if they are only 5 years old.

 

Are you doing a report or just advising about the tree work? If you are doing anything in writing I would recommend getting a soil sample lab tested for better info on the plasticity index.

 

Hi thanks for the advice. yes its for a report to remove 3 trees close to a property.

 

thanks steve

[stevelucocq]

hi,

 

I was thinking of adding something like this:

 

"A soil sample test should be conducted to determine the plasticity index of the surround soil. If the plasticity of the soil is determined to be of a high volume change potential then a structural engineer should be consulted before tree removal."

 

thanks again steve

[Andy Clark]

hi,

 

I was thinking of adding something like this:

 

"A soil sample test should be conducted to determine the plasticity index of the surround soil. If the plasticity of the soil is determined to be of a high volume change potential then a structural engineer should be consulted before tree removal."

 

thanks again steve

 

Steve, You're kinda over complicating this a bit......

 

Peronally, i wouldn't go into the reams of Plasticity index, until such time as the soil type and structure has been identified - For example, if the soil is of a sandy/chalky type substrate, than the plasticity index and volume change potential would be neglegable..... therefore the heave/subsidance potential would also be neglegable.

 

If however, we're talking shrinkable clay based soils, that is when the P/I will come into play and be relevant..... as also will the heave/subs potential.

 

 

First things first mate... identify the soil, then deal with the resultant possibilities and make your recomendations based on the facts...... not on "what if's".

[stevelucocq]

Steve, You're kinda over complicating this a bit......

 

Peronally, i wouldn't go into the reams of Plasticity index, until such time as the soil type and structure has been identified - For example, if the soil is of a sandy/chalky type substrate, than the plasticity index and volume change potential would be neglegable..... therefore the heave/subsidance potential would also be neglegable.

 

If however, we're talking shrinkable clay based soils, that is when the P/I will come into play and be relevant..... as also will the heave/subs potential.

 

 

First things first mate... identify the soil, then deal with the resultant possibilities and make your recomendations based on the facts...... not on "what if's".

 

Hi andy,

 

Thanks for taking the time to explain things further. Most of the surrounding area is landscaped so making the identifying the soil type a little difficult. Is there a online free resource of soil classification available? Or just make an assessment on the soil type at the nearest area that has not been hard landscaped?

 

Cheers steve