Geoscience Reference
In-Depth Information
Figure 4.1 Standard penetration test.
Table 4.6 Standard penetration test in soils.
Symbol
Test
7, 11, 12 (eg)
Example of blows per 150 mm penetration.
N
23 (eg)
Penetration resistance (blows for 300 mm penetration following 150 mm
=
or N SPT
seating drive, example of 11
+
12
=
23
=
N SPT (actual field value with
no correction factors).
N
>
60
Total hammer blows exceed 60.
7, 11, 25/20 mm (eg)
Partial penetration, example of blows for the measured penetration
(examine sample as either change in material here or fall in at top
of test).
N
Corrected N - value for silty sands below the water table.
N*
Inferred SPT value.
RW
Rod weight only causing penetration (N
I).
<
HW
Hammer and rod weight only causing full penetration (N
I).
<
HB
Hammer bouncing (typically N*
>
50).
(N o ) 60
Penetration resistance normalized to an effective overburden of 100 kPa,
and an energy of 60% of theoretical free fall energy. (N o ) 60
=
C N C ER N SPT
.
C N C ER
Correction factor for overburden (C N ) and energy ratio (C ER ) .
<
Typically (N o ) 60
60 for soils. Above this value, the material is likely cemented
sand, coarse gravels, cobbles, boulders or rock. However these materials may still
be present for N - values less than 60.
 
Search WWH ::




Custom Search