Ground Bearing Pressures/Piling Mats
Ground Bearing Pressures/Piling Mats
(OP)
Hi
Can anybody point me in the right direction for the design of simple pile mats.
We are utilising crawler cranes that are inducing ground bearing pressures in the region of 50T/m2. We are operating on a crushed concrete piling mat (600mm deep) on top of London clay. What theoretical ground settlement would be expected under loadings of this magnitude?
We have conducted plate bearing pressure tests and are experiencing settlements in the region of 10mm - how can I calculate the theoretical settlements that are expected under loadings of this magnitude?
Can anybody point me in the right direction for the design of simple pile mats.
We are utilising crawler cranes that are inducing ground bearing pressures in the region of 50T/m2. We are operating on a crushed concrete piling mat (600mm deep) on top of London clay. What theoretical ground settlement would be expected under loadings of this magnitude?
We have conducted plate bearing pressure tests and are experiencing settlements in the region of 10mm - how can I calculate the theoretical settlements that are expected under loadings of this magnitude?





RE: Ground Bearing Pressures/Piling Mats
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.
RE: Ground Bearing Pressures/Piling Mats
Yes we are looking at settlements due to construction equipment.
We will be using a 600T crawler crane lifting a load of approx 90T at a radius of 50m. This would induce a pressure of 65T/m^2.
We have conducted plate bearing pressure tests up to 70T/m^2 and have experienced a settlement of 10mm.
Not coming from a soil engineering background (I'm mechanical) I am curious to find out information on how pile mats are designed.
RE: Ground Bearing Pressures/Piling Mats
The biggest hurdle you will have to cross is determining the sustained load. The area where the crane is stored will see the greatest settlement.
You should seek out an introductory text on geotechnical engineering for more information. I would suggest Ronald F. Scott's text; avoid Bowles' or Das' books.
There is no simple answer to your question -
Please see FAQ731-376 by VPL for tips on how to make the best use of Eng-Tips Fora.
RE: Ground Bearing Pressures/Piling Mats
If I know from empirical data the strength of the underlying clay (say 45kPA) and the thickness of the crushed pile mat (600mm) is there a formula to determine the allowable pressure on the mat?
RE: Ground Bearing Pressures/Piling Mats
A 45 kPa compressive strength results in a shear strength of 22.5 kPa - pretty weak soil. (It's still weak even if the shear strength is 45 kPa.) A straight bearing capacity calculation would indicate a bearing capacity failure at an applied pressure of about (22.5)5.14 = 115 kPa. Apply a factor of safety of at least 2.5, and your allowable bearing capacity is no more than 46 kPa. And you may need a much larger factor of safety ( because of "guessed" soil properties, risk of loss of life, etc.) That's a far cry from the 490 kPa your equipment needs...
You'll need a lot more than a 600 mm layer of stone to spread your load - probably need a geogrid reinforcement to spread the load and reduce the risk of a bearing capacity failure when simply moving the equipment. And use large timber mats under the tracks/wheels when picking up loads to spread the load and reduce the applied pressure. Depending on your loads, site layout, etc. you may also have to do a lot more site preparation to use that equipment.
Please see FAQ731-376 by VPL for tips on how to make the best use of Eng-Tips Fora.
RE: Ground Bearing Pressures/Piling Mats
I will try and keep you posted on the outcomes and thanks again!!
RE: Ground Bearing Pressures/Piling Mats
Good Luck