Pore water pressure is the pressure exerted on soil or rock from fluids (e.g. groundwater) located within the voids between the individual particles comprising the soil or rock. It is a key component of the effective stress principle, which states that the effective stress placed on a soil is a function of both the total stress and the pore pressure. As stress is placed on the soil, it is opposed by the soil's pore pressure. Thus, the overall strength of the soil formation is dependent upon the pore pressure, and changes in pore pressure can potentially lead to unstable soil formations.

Measuring Pore Pressure

An instrument used for monitoring pore pressure in soils is called a piezometer. Many types of piezometers exist, including standpipe, vibrating wire, strain gauge and pneumatic. The piezometers are installed into the soil area of interest, typically through boreholes, and are placed at a suitable depth where they will be able to detect changes in pore pressure. Multiple piezometers are often placed in an area to provide a complete picture of the soil conditions.

The piezometers may be connected to a data logger with wireless telemetry to develop an automated system for use in remote monitoring applications. An example of this type of system is a vibrating wire piezometer connected to the Cautus Logger. The system collects data on a defined interval and transmits it to the Cautus Web, which is a complete data management and early warning system for geo-monitoring projects. Data is accessed online in user-friendly graphical displays, and alarm notification messages are enabled to inform users when threshold conditions are met.

Download our data sheet on Pore Pressure Monitoring to learn more.

The figure below shows an example of such a system and how the data is transmitted.

Pore Pressure System Drawing

Pore pressure monitoring systems are useful for a wide variety of applications. Often, the measured pressures are used as part of a calculation of other values. The table below shows a list of some of the most common applications, the physical elements being measured in the applications, and the commonly calculated computations using the pore pressure.

MeasureIt personnel have many years of experience with pore pressure monitoring equipment and systems. We have the knowledge to provide you with proper equipment and work with leading manufacturers such as Geosense.

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>> Download our data sheet on Pore Pressure Monitoring