Soil Tests: Standard penetration test (spt) Introduction: Apparatus: Procedure: Calculations:

1. Standard Penetration Test
(SPT)
Presented By:
Faizan Tanoli

2. StandardPenetrationTest
(SPT)
Introduction:
The standard penetration test (SPT) is most commonly used in
cohesion less soils, and In-situ test which can’t be easily sampled.
This test is widely used to obtain the bearing capacity of soil, to
estimate the relative density of soils and approximate shear strength
parameters.
The test shall be made
 At every change in stratum
 At intervals not more than 1.5 m
‘’If the number of blows for 150mm exceeds 50 it is taken as a refusal
and the test is discontinuous’’

3. StandardPenetrationTest
(SPT)
Standard Penetration Test Tools:
1. Drilling Rig.
2. Split spoon (tube).
3. Drop hammer 65 kg (140 lbs ).
‘doughnut hammer’
4. Driving head (anvil).
5. Guiding rod.
6. Tripod.
7. Extension rods.
Guiding rod &
Drop hammer
Split Spoon

4. StandardPenetrationTest
(SPT)
Standard Penetration Test Tools:
Drilling
Rig

5. StandardPenetrationTest
(SPT)
1. Erect the tripod over the test hole and assemble the
unit.
2. Allow the spoon to rest on the bottom of the hole.
3. Drive the spoon with blows from the hammer falling
75 cm (30 inches), until either 45 cm (18 inches)
have been penetrated or 100 blows have been
applied.
Standard Penetration Test Procedure:

6. StandardPenetrationTest
(SPT)
4. Record the number of blows required to effect each
150 mm (6 inches) of penetration. The first 6 inches
(300mm) is considered as seating drive.
5. The number of blows required for the second and
third 150 mm (6 inches) of drive added is recorded
as the penetration resistance value N of the soil.
Standard Penetration Test Procedure:

7. StandardPenetrationTest
(SPT)
Observations and Calculations:
Depth (cm) No. of blows/ 15cm(150mm) N value
Result:
The penetration resistance value, N of the soil is
_________________blow.

8. StandardPenetrationTest
(SPT)
Formula:
q= 3.5 (N-3) [B+0.3/2B]Rw2Rd.
Where.
q= Allowable net pressure in T/m2.
N = Standard penetration number.
B = Breadth of footing in meters.
Rw2 = Water reduction factor= 0.5 [ 1+Z/B] .
Rd = Depth factor = l+D/B C or C= 2.0.
Z = Depth of water table below foundation level.

9. StandardPenetrationTest
(SPT)