Geology Reference
In-Depth Information
Figure 4.28 Mazier sampler with nicely recovered weathered granite
the right side third is stained
with iron oxides. Spring-loaded cutting shoe is seen extending from the rock cutting bit outside.
bit takes over the cutting.
-
recorded. Soft soils are penetrated easily, hard soils and weak rocks
with more dif
culty. The SPT data can be interpreted in terms of shear
strength and deformability (
Chapter 5)
and for making predictions of
settlement directly (
Chapter 6).
The split spoon sampler used for the
SPT is a steel tube with a tapered cutting shoe. It is lowered down the
borehole, attached to connecting rods, and then driven into the ground
by a standard weight, which drops a standard height, as illustrated in
Figure 4.30
and shown in action from a rotary drilling rig in
Figure 4.31.
The number of blows for each penetration of 75mm is
recorded; blows for the
first 150mm are recorded but essentially
ignored (considered disturbed); the blows for the
final 300mm are
