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Dictionary of Sinkhole Terms
Anomaly
A deviation from uniformity in physical properties; a perturbation from a normal, uniform, or predictable field.
In geophysics, 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 investigative methods
Aquifer
A body of soil, sediment, or rock that is saturated with water and sufficiently permeable to allow production of water from wells.
Atterberg Limits
Atterberg limits are measurements used to characterize the behavior of cohesive soils with changes in moisture content. The Atterberg limits include the liquid limit, plastic limit, and plasticity index.
Blow Count
In standard penetration testing, blow counts represent the number of times the 140 lb. hammer must fall on the anvil in order to drive the split spoon 6 inches. The blow counts for the second and third 6 inch intervals are summed to obtain the N Value.
Clay
A grain-size term to used to describe the fine-grained particles in soils, sediments, and sedimentary rocks. Clay-sized particles are smaller then 0.004 millimeters (mm) in diameter according to the Wentworth scale used by geologists. Soil scientists and geotechnical engineers use a slightly different size range, where clay is less than 0.002 mm in diameter.
Cohesive
Cohesive soils are soils that contain sufficient clay and other fine-grained material that they can be molded and exhibit plastic behavior when moist.
Consolidation
Consolidation is the increase in density (mass per volume unit) of a soil or sediment through compressive stress (loading). Typically, soils and sediments undergo a gradual reduction in volume (compaction) and porosity slowly declines with time and loading. Upon construction of a house, there may be an initial consolidation phase, during which the underlying material (especially fill) adjust to the new load. The majority of consolidation occurs in the initial consolidation phase.
Collapse Sinkhole
A sinkhole formed by the collapse of the cover materials (soil, sediment, or rock) into an underground void created by the dissolution of limestone or dolostone.
Cover Collapse Sinkhole
A cover collapse sinkhole is a sinkhole formed by cover materials (sand, clay, etc) raveling into a void in the underlying limestone.
Cover Subsidence Sinkhole
A cover subsidence sinkhole forms when the upper surface of the limestone is dissolved away, and the cover slowly subsides to occupy the space once occupied by the limestone. Voids may not be well developed in cover subsidence sinkholes because of the continued downward movement of cover materials.
Debris
Debris consists of materials contained within the soil column that are deleterious to the stability of structures. Examples of debris include landfill and construction materials and organic debris, such as yard wastes. Organic debris has the potential for decay and loss of soil support, and larger pieces of debris may bridge over voids into which cover may ravel at a future time.
Deleterious Soil
Deleterious soils are unsuitable for construction of certain types of structures because they cannot support the load created by the structure or because they change load-bearing properties with time through decay or loss of porosity. Examples include peat, muck, and debris.
Density
Density refers to the mass per unit volume of a material.
Drilling Fluid
In order to stabilize a borehole, cool the drill bit, and flush cuttings out of the bottom of the bottom of the hole, a mixture of water and drilling mud ( a preparation that contains clay and other solids ) is circulated through the borehole during drilling. This mixture is termed drilling mud or drilling fluid.
Epikarst
Epikarst is the zone of weathering at the upper surface of a limestone stratum. Weathering of limestone results in development of rubble, fine-grained carbonate-rich silt and clay, karren (including pinnacles and valleys in limestone rock surface), and other features. Epikarst is frequently associate with losses of drilling fluid circulation, low blow counts, weight of rod or hammer events, and recovery of gravel-sized particles of rock.
Expansive Clay
A clay-rich deposit that can undergo shrinkage or swelling as moisture content or water quality change.
Fill
Fill consists of soils placed on an original or prepared land surface in order to change the elevation of the land surface, alter the contours of a property, elevate the structure, or supports a slab.
Friable
An adjective describing soils or sediments that are loosely cemented and can be crumbled in hand.
Ground Penetrating Radar
A Geophysical method for mapping underground interfaces by reflecting radar frequency waves off the interfaces and recording their reflections at ground surface. Ground Penetrating Radar is often used to detect SHALLOW soil conditions that might represent sinkhole activity.
Hand Penetrometer
The hand penetrometer is a probe that measures the resistance of a soil as it is pushed into the soil by hand.
Karst
A term describing landforms that have been modified by dissolution of soluble rock (limestone or dolostone) or sediment materials. Karst terrains are characterized by many related landforms, including sinkholes, sinking streams, and land surfaces that are irregular as a result of differential dissolution of rock. Note that sinkholes occur in karst areas, but karst is not synonymous with sinkhole activity.
Limestone
A Sedimentary rock composed of Calcite (CaCO3). Limestone is soluble and often develops karst features when weathered.
Liquid Limit
The liquid limit is Atterberg limit that represents the moisture content of a cohesive soil at which it ceases to be plastic and flows as a viscous (thick) liquid.
Loss of Circulation
Loss of circulation occurs when drilling fluid, which is used to stabilize the borehole and remove cuttings as the borehole is drilled, is lost. Losses of circulation may reflect movement of fluid into unconnected porosity or conduits. When investigating subsidence causes, losses of circulation are considered an important, but not unique, piece of evidence for karst activity or fracturing.
Muck
A dark colored soil or sediment that has a high organic content. Mucks are often found in wet areas, where oxidation of the organics is inhibited by the presence of water. The term muck is commonly applied to organic-rich soils or sediments that have less than 50%, by weight organic content.
N Value
In standard penetration testing the N-Value is the sum of the number of blows required to force the split spoon sampler through 1 foot of soil. The sampler is advanced in 6-inch increments and the N-Value is the sum of the blow counts for the second and third, 6-inch intervals.
Organics
Organics constitute the fraction of the soil formed by the accumulation of plant (and animal) tissues. Organic content is measured by determining the fraction, by weight, lost upon ignition. The Florida Department of Transportation considers that soils with over 5% by weight of organics are deleterious.
Peat
An organic-rich soil or sediment, in which organics dominate. Peat deposits are found in wet areas and often contain partly decomposed plant materials. The term is restricted by some to materials with over 50% organic material by weight.
Plastic
Plastic is the term used to describe soils that are cohesive and can be molded
Plastic Limit
The plastic limit is the Atterberg limit that describes the moisture content of a cohesive soil at which it ceases to be brittle and becomes plastic, or capable of being molded.
Plastic Index
The plasticity Index is the range of moisture contents, expressed as percentages, over which a cohesive soil is plastic. It is calculated by subtracting the plastic limit form the liquid limit.
Rubble
In the context of karst, rubble describes the gravel-like debris that forms as limestone is weathered
Sand
A grain size-related term unused to describe particles in soils, sediments, and sedimentary rock. Sand size particles range from 0.0625 to 2 millimeters (mm) in diameter according to the Wentworth scale used by geologists. Soil scientists use a slightly different size range: 0.005 to 2 mm
Spread Footing
The rectangular base beneath the foundation to distribute the building load over a greater area.
Sediments
Sediment consist of geologic materials that have accumulated at or near the earth surface by deposition from a transport agent, such as seas, rivers, or lakes.
Sinkhole
A Sinkhole is a landform created by subsidence of soil, sediment, or rock as underlying strata are dissolved by ground water. Sinkholes can form by collapse into a subterranean void created by dissolution of limestone or dolostone or by subsidence as these strata are slowly dissolved away.
Sinkhole Activity
Chapter 627.07 of Florida Statutes requires that sinkhole claim investigations be conducted by professionals qualified to identify "sinkhole activity". Sinkhole activity can also be related to the formation of a sinkhole that has not yet developed.
Soil Piping
Laterally limited, vertical areas of loose soil often caused by downward vertical movement of the soil (raveling). On a ground penetrating radar section, these would appear as discrete, highly curved convex upward reflections.
Solution Sinkhole
A sinkhole formed by the slow subsidence of soil or sediment as the upper surface of the underlying, water soluble sediment or rock is removed by dissolution.
Split Spoon Sampler
The split spoon samplers placed at the terminus of the drill string for standard penetration testing. It consists of an 18-24 inch metal tube that is split longitudinally. After the penetration testing, the spoon is retrieved, broken open, and soil samples are recovered.
Stair Step Crack
A crack that follows the pattern of cement block or brick mortar joints.
Standard Penetration Test
A widely used geotechnical investigation technique in which a split spoon sampler is driven into soil or sediment by a 140 lb. hammer dropping 30 inches. The number of blows required to drive the sampler one foot is termed the blow count (N Value).
Superficial Sands
A term applied to the sandy ,marine terrace sediments found throughout Florida.
Unconsolidated
- When applied to soils and sediments in a structural sense, the term unconsolidated indicates that the soil has not completed the consolidation process and that it is subject to continued increases in density, volume reduction, or compaction. In practical terms, and unconsolidated soil or sediment is a loose material that has a low bearing strength.
- In geology, an unconsolidated soil or sediment consists of an aggregate of particles that have not been lithified or converted to rock.
Uniform Soil Classification System
The Uniform Soil Classification System is a soil classification system developed to characterize soils from an engineering perspective. Soils can be classified under the USCS on the basis of either laboratory testing for grain sizes and Atterburg limits data or by visual methods.
Water Table
The uppermost extent of saturated pores in an unconfined aquifer. The water table forms a surface that more or less parallels the land surface.
Weathering
The natural process of physically or chemically changing the structure and/or composition of a material exposed at the land surface.
Weight of Hammer (WOH)
A weight of hammer event occurs during standard penetration testing when the hammer and 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. A weight of rod event may reflect a void, naturally weak soils, or excessive weight of drill string.
Weight of Rod (WOR)
A weight of rod event occurs during 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. A weight of rod event may reflect a void, naturally weak soils, or excessive weight of drill string.
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What is a Sinkhole?
