GLOSSARIES - Geotechnical Earthquake Engineering - page 499

Cone Penetration Test (CPT) A field test used to identify and determine the in situ properties of

soil deposits and soft rock.
Electric Cone A cone penetrometer that uses electric-force transducers built into the apparatus
for measuring cone resistance and friction resistance.
Mechanical Cone A cone penetrometer that uses a set of inner rods to operate a telescoping pen-
etrometer tip and to transmit the resistance force to the surface for measurement.
Mechanical-Friction Cone A cone penetrometer with the additional capability of measuring
the local side friction component of penetration resistance.
Piezocone A cone penetrometer with the additional capability of measuring pore water pressure
generated during the penetration of the cone.
Core Drilling

Also known as diamond drilling, the process of cutting out cylindrical rock samples

in the field.
Core Recovery (RQD) The Rock Quality Designation (RQD) is computed by summing the lengths
of all pieces of the rock core (NX size) equal to or longer than 10 cm (4 in.) and dividing by the total
length of the core run. The RQD is multiplied by 100 to express it as a percentage.
Deposition The geologic process of laying down or accumulating natural material into beds, veins,
or irregular masses. Deposition includes mechanical settling (such as sedimentation in lakes), precip-
itation (such as the evaporation of surface water to form halite), and the accumulation of dead plants
(such as in a peat bog).
Detritus Any material worn or broken down from rocks by mechanical means.
Diatomaceous Earth Usually fine, white, siliceous powder, composed mainly of diatoms and
their remains.
Erosion

The wearing away of the ground surface as a result of the movement of wind, water, and/or

ice.
Fold Bending or flexure of a layer or layers of rock. Examples of folded rock include anticlines and
synclines. Usually folds are created by the massive compression of rock layers.
Fracture A visible break in a rock mass. Examples includes joints, faults, and fissures.
Geophysical Techniques Various methods of determining subsurface soil and rock conditions
without performing subsurface exploration. A common geophysical technique is to induce a shock
wave into the earth and then measure the seismic velocity of the wave's travel through the earth mate-
rial. The seismic velocity has been correlated with the rippability of the earth material.
Groundwater Table (also known as Phreatic Surface) The top surface of underground
water, the location of which is often determined from piezometers, such as an open standpipe. A
perched groundwater table refers to groundwater occurring in an upper zone separated from the main
body of groundwater by underlying unsaturated rock or soil.
Horizon One of the layers of a soil profile that can be distinguished by its texture, color, and structure.
A Horizon The uppermost layer of a soil profile which often contains remnants of organic life.
Inorganic colloids and soluble materials are often leached from this horizon.

B Horizon The layer of a soil profile in which material leached from the overlying A horizon is

accumulated.

C Horizon Undisturbed parent material from which the overlying soil profile has been devel-

oped.
Inclinometer An instrument that records the horizontal movement preceding or during the move-
ment of slopes. The slope movement can be investigated by successive surveys of the shape and
position of flexible vertical casings installed in the ground. The surveys are performed by lower-
ing an inclinometer probe into the flexible vertical casing.
In Situ Used in reference to the original in-place (or in situ) condition of the soil or rock.
Iowa Borehole Shear Test (BST) A field test in which the device is lowered into an uncased
borehole and then expanded against the sidewalls. The force required to pull the device toward ground