Definition - What does Karst mean?
A karst is a geological formation which describes a topography that is characterized by the dissolution of soluble rock formations by ground or surface water. This formation is typically associated with carbonate and highly soluble rocks such as limestone, dolomite, gypsum and rock salt. Karst terrain can be identified by the presence of caves, sinkholes, and underground streams. In cases where erosion has resulted in worn away terrain above ground, rocky cliffs may also be visible.
Trenchlesspedia explains Karst
Karst landscape formations occupy as much as ten percent of the earth’s surface and provide water to one-quarter of the world’s population.
Conditions that promote the development of this type of terrain are:
- Dense carbonate and or soluble rocks
- Moderate to heavy rainfall and
- Good groundwater circulation
As the rainwater falls, it enters into the soil. The water then reacts with the carbon dioxide found naturally in the atmosphere and the soil to become mildly acidic. This mildly acidic rainwater then percolates through the joints, cracks and bedding planes in the carbonate rock formations, dissolving and eroding it. This continuous erosion eventually results in the formation of caves or underground stream channels.
Performing trenchless construction procedures (such as tunneling) in karstic conditions is particularly challenging and can give rise to hazardous conditions including tunnel collapse, water and slurry outburst, and buoyancy issues. Construction in this type of terrain usually involves having to cross voids and caverns filled with erodible material and often requires site-specific engineered solutions to ensure structural stability of the tunnel.