Sinkhole
Terminology
A
deviation from uniformity in physical properties; a perturbation from a
normal, uniform, or predictable field. An anomaly represents an area or
volume of geologic materials that have unusual physical properties that
can be detected by ground penetrating radar, electrical resistivity,
seismic, or other investigation methods.
In a Standard Penetrating Test, a blow count represents the number of
times the 140 pound hammer must fall 30 inches onto the anvil in order to
drive the split-spoon 6 inches. The blow counts for the second and third,
6-inch intervals are added up to obtain N-value.
This is a sinkhole formed by the collapse of cover materials such as
sediment, soil, or rock. These cover materials collapse into an
underground void created by the dissolution of limestone or dolostone.
A
geophysical method for mapping interfaces underground by reflecting
frequency radar waves off the interfaces and recording their reflections
at the ground surface. This method is often used to detect shallow soil
conditions that might represent sinkhole activity.
A
sediment rock composed primarily of calcite. This rock is soluble and
often develops karst features when weathered.
A
column used to support a structure and transfer its load to the soil
through a footing as opposed to direct embedment in the soil.
This is a sinkhole formed by the slow subsidence of sediment or soil as
the upper surface of the underlying, water-soluble rock or sediment is
removed by dissolution.
A
geotechnical investigation technique that is widely used in which a
split-spoon sampler is driven into a soil or sediment by a 140-pound
hammer dropping 30 inches. The number of blows required to drive the
sampler one footed is called the blow count (N).
A
subsidence sinkhole forms when the upper surface of the limestone is
dissolved away, and the thin cover overburden slowly subsides to occupy
the space once occupied by limestone. Because of the continued downward
movement of cover materials, voids may not be well developed.
This is an event that occurs during a standard penetration testing when
the drill string (drilling rod and split spoon sampler) are allowed to
rest on the bottom of the borehole and they sink under their own weight.
This event may reflect a void, naturally weak soils, or excessive weight
of drill string.
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