As previous posts say, inspection of belled piles (also called under-reamed piles in UK) is carried out from surface now. A couple of companies over here have developed specific tools to visually inspect the base of the pile using a camera. One also allows you to recover U100 samples from the...
You're right to be careful about whether to take some/any skin resistance from the clay. Given how soft the clay is, the first thing I would check is whether this material could still be settling under any recent imposed load (raising ground level for example). If this is the case, additional...
I would agree that using another organisations interpretation within your own design is foolish, without first going back to basics and justifying the approach. However...
Reference to 'Geotechnical Report', can constitute a wide variety of information. If its a factual report that is referred...
Typically, if the piles being installed using a CFA technique, the higher alpha values will be used. When a rotary/bored technique is used, the lower values would be used. This mainly comes back to the monitoring information available on the rigs and greater control on drilling with CFA.
If...
It is normal practice within the UK to limit shaft adhesion on larger diameter piles, typically those greater than about 900mm diameter.
Auger rotatation, crowd and concreting can be closely controlled using the rig computer for smaller diameter CFA piles, however greater soil disturbance...
As gokcealtun said, the ASTM standard provides good detail on this. You could also consider the ICE Specification for Ground Improvement, or the BRE guide Specifying Vibro Stone Columns.
In the UK it is common practice to test stone columns to between 1.5 to 3 times the working load, with...
In which case...
Go = p*Vs2
Where p = Bulk density, Vs = Shear wave velocity
As dgillette says this could be misleading depending on how fractured/jointed the rock is as failure is often due to weakest plane rather than in-situ strength.
Advantages - Without them we'd be stuck up an unpleasant smelling creek without a paddle!
Disadvanages - You need to understand what the correlation is based upon and when it should (or more importantly should not) be applied.
Correlation between SPT and Cu after Stround 1974 is a good...
What type of test are you using to generate/measure the shear waves? Shear wave velocity can be used to calculate the small strain stiffness (Gmax) of a soil or rock which can then be related to it's shear modulus. Following link deals with its use in measuring ground improvement work but...