Cu = Undrained strenght its a parameter of coesive soils (not rock); for categorize, you must know the values (Nspt, Cu or anything else usefull -Vs_) in 30m belove the subsoil.
Its completely different from the parameter for the bearing capacity of foundations (usually 2B from the subgrade).
I't will be usefull the abacus of Bustamante and Doix, in their famous article about Micropiles.
A *resumè* can be find here, at page 26, fig. 16 .
http://carreras.frba.utn.edu.ar/civil/cimentaciones/ANCLAJES.pdf
Really in USA is cheaper to perform 100ft and relatives SPT (one each 5 ft) than perform MASW o ReMi shear wave measurements?
And at which dimension of the building or house become mandatory to dig to 100 ft ?
Thanks?
I've read the chapter of R.W. DAY Geotech. Earthqk. Eng. Hanndbk. about bearing capacity, an I've a doubt.
Surely for dense (DR>65%) to very dense granular soils is applicable the rule of tumb of increase of one third the bearing capacity in seismic analisys.
And for loose (DR<35%) soils is...
I've understand thath the USA codes doesn't tell about ER60 because all the SPT apparatus teorically are ER60.
In general, according to many manuals SPT Vs measure are conservatives.
The strange is that for NEHRP 2003 and for your IBC no correction for litostatic pressure is to do (N1)60, and...
Anyway I think it is correct to reduce the blow count to ER60.
For many building codes is not allowed use (N1)60, the correction for litostatic pressure.
According to this Building codes:
Unified Building COde
NEHRP (USA)
EC8 (European Union)
OPCM 3274 (Italy)
For seismic caracterization, the site will be classified according to the value of the average shear wave velocity, Vs30, if this is available, otherwise the value of NSPT will be used...
In Italy will be mandatory to determine Vs30 for projects. It will be admitted the use of SPT values to deterimine Vs30.
1) I' dont understand why according to USA, Nehrp, Nspt values are not to be corrected? Neither to (N60)ER. There are other raccomandations well explained ?
2) When is...
Anybody can tell me about correlation for weak or fractured rock investigated by DP or SPT
I've found only pressuremeter menard, Plim=spt/20, from Doix & Bustamente for non fractured marl and similar.
Thanks