Hydraulic Conductivity

This page is not intended to be a substitute for professional geotechnical advice and should not be relied on as geotechnical advice by individuals or other professionals to make site-specific decisions. Always seek advice from professional geotechnical engineers.

Hydraulic conductivity or permeability testing is a fundamental measure of water passage through soil or rock. This testing method provides a high-value indication of a permeable material through which water can pass, whereas low values indicate a less permeable material. Denoted by the letter ‘K’, this parameter has units of velocity, such as meters per second or meters per day. BHM Geotechnical is well-equipped to conduct permeability tests or infiltration testing across greater Sydney.

It is crucial to understand that hydraulic conductivity can range widely, from 10-2 m/s for very open gravels and cobbles, to 10-11 m/s in natural soils and rocks. This range is significantly broader than most other geotechnical characteristics, such as shear strength or compressibility, would suggest.

Furthermore, it is important to note that the manner in which a fluid (such as water) travels through a soil or rock mass is determined by both the soil/rock properties and the qualities of the permeating fluid. As such, if a given soil or rock is permeated by different fluids, such as water or hydrocarbons, it will react differently. Therefore, the term hydraulic conductivity is particularly useful as it explicitly refers to water flow.

However, the term ‘permeability’ is widely used in geotechnical engineering and is commonly misunderstood by many industries, such as the oil and gas industry, to mean ‘intrinsic permeability’, which is dependent of the permeating fluid. Intrinsic permeability has SI units of m2, though it is commonly described in Darcys (where 1 Darcy = 1 x 10-12 m2), and is a significantly different parameter from hydraulic conductivity.

While hydraulic conductivity is certainly an intriguing topic from a theoretical standpoint, it is also of practical important to geotechnical engineers. Specifically, knowledge of hydraulic conductivity is necessary for designing effective groundwater control and dewatering systems. By understanding how water flows through soil or rock, engineers can develop appropriate measures to mitigate any potential problems or hazards that may arise. Therefore, hydraulic conductivity testing is an essential tool for ensuring the success and safety of geotechnical projects.