Geomechanics 1: Week 9
Site Investigation
Tests
§ Standard Penetration Test (SPT)
§ Cone Penetration Test (CPT)
§ Other in-situ testing includes
– Marchetti Dialtometer (DMT)
– Pressuremeter testing
§ Many different methods of obtaining data
– Consideration should be made to balance the cost, timeliness and quality
SPT Blow Count, N
§ 63.5 kg mass is dropped 760 mm to make one blow on the SPT spoon.
§ Number of blows to penetrate three 150 mm distances are measured given as x/y/z.
§ The blows for first 150 mm are ignored (“seating blows”).
§ The number of blows for next 300 mm is taken as the “raw” blow count, i.e., N = y +
z
Corrections to “raw” N
Correction 2 – for effective overburden pressure
N =N x C.F.
corr corr 1 corr 2
Site Investigation
Tests
§ Standard Penetration Test (SPT)
§ Cone Penetration Test (CPT)
§ Other in-situ testing includes
– Marchetti Dialtometer (DMT)
– Pressuremeter testing
§ Many different methods of obtaining data
– Consideration should be made to balance the cost, timeliness and quality
SPT Blow Count, N
§ 63.5 kg mass is dropped 760 mm to make one blow on the SPT spoon.
§ Number of blows to penetrate three 150 mm distances are measured given as x/y/z.
§ The blows for first 150 mm are ignored (“seating blows”).
§ The number of blows for next 300 mm is taken as the “raw” blow count, i.e., N = y +
z
Corrections to “raw” N
Correction 2 – for effective overburden pressure
N =N x C.F.
corr corr 1 corr 2
