More than 30 different methods and equations for interpretation of Piezo Cone Penetration Test (CPTu) are implemented in NovoCPT software; In case there are more than one method, user can choose the favorite method from View › Preferences menu. The main reference for the following formulae is “Cone Penetration Testing In Geotechnical Practice” book written by T. Lunne, P.K. Robertson and J.J.M. Powell, 1996.

Equivalent SPT N60:

Jefferies and Davis 1993

Permeability coefficient K:

Robertson et al. 1986

Shear strength Su:

Nk

Nkt

Nke

Overconsolidation ratio OCR:

Powel et al. 1998

Lunne et al. 1989

Clay Sensitivity St:

Robertson and Campanella 1988

Rad and Lunne 1986

Schmertmann

Clay un-drained Young's modulus Es:

Duncan and Buchihmami 1976

Clay at-rest earth pressure Ko:

Kulhawy and Mayne 1990

Sand relative density Dr:

Jamiolkowski et al. 1985

Baldi et al. 1986

Tatsuoka 1990
 

Sand Young's modulus Es:

Bellotti et al. 1989

Sand at-rest earth pressure Ko:

Kulhawy and Mayne 1990

Sand internal friction angle F:

Kulhawy and Mayne 1990

Hatanaka and Uchida 1996

Robertson and Campanella 1983

Unit weight g:

Robertson et al. 1986

Fines content Fc:

Robertson and Fear 1995 (FC=1.75*IC3-3.7)

Constrained modulus M:

Robertson 2009

Soil behaviour type index Ic:

Robertson 1990

Magnitude scaling factor MSF:

Robertson 2009

Depth correction factor Rd:

Seed and Idriss 1971 (tri-linear function)

Shear wave velocity Vs:

Mayne 2006c (all soils)

Hegazy and Mayne 1995 (all soils)

Baldi 1989 (sands) and Mayne and Rix 1995 (clays)

Void ratio e:

e = 1.152 - 0.233 Log(qc1) + 0.043 Log(OCR)

using n exponent for iteration between OCR and Ic until conversion:

CPT Guide 2009, Robertson

The following parameters are also calculated according to CPTu processing references and fundamental soil mechanics equations:

Qt, qt, Qtn
Rf, Fr
Bq
Gmax