Geotechnical and Materials Engineering Standards for Bridge ...

CORE RECOVERY - During the drklling process, the bit cuttings are
removed by the drilling fluid and the core sample passes into
the core barrel. Some of the core sample may be lost by
erosion of soft or friable material resulting in a reduction in
diameter and/or length of core. The material placed in the
core box from each core run is the recovered core. If none of
the sample is Lost by erosion then the core recovery is 100%.
Core recovery is measured by length and expressed as a
percentage of the core run length.
CORE CONDITION - The state of the core recovered can be described
as solid, braken, very broken, shattered, or rounded pieces.
In some cases, poor quality Cora may be the result of the
. .
drilling method but usually reflects the state of the rock mass.
DISCONTIWI'SY SPACING - This is another quantitative description of
the natural break in the rock mass. It is count of the number
of natural di~continuities per mdt length.
Discontinuity Spacing - No. of discontirmitics/metre
A classkfication of rock vtth regard to discontfnulty spacing
has been devsloped 3,