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Piezometers 101: An Essential Tool for Geotechnical Monitoring

Geokon Piezometer

In the realm of geotechnical engineering, understanding the behavior of soil and rock under various conditions is crucial for the safety and stability of structures. This is where piezometers, a specialized type of geotechnical sensor, play a pivotal role. Piezometers are designed to measure the pressure of fluids, particularly water, within the ground. This data is essential for a wide range of applications, from construction site monitoring to the maintenance of dams and levees.


 

What Are Piezometers?

Piezometers are instruments that measure the pore water pressure within soil, earth fills, foundations, and concrete structures. By providing insights into the water pressure within these materials, piezometers help geotechnical engineers predict and mitigate potential failures. This is particularly important in areas prone to soil liquefaction or instability.

 

Types and Functions of Piezometers

 There are several types of piezometers, each suited for specific geotechnical monitoring needs. The primary differences between manual and electronic piezometers lie in their measurement methods, data accuracy, and ease of data collection.

Manual Piezometers

Manual piezometers require physical readings taken on-site, often using simple tools. They are generally less expensive but provide less frequent and potentially less accurate data. Types of manual piezometers include:

  • Casagrande Standpipe Piezometers: Designed for taking measurements in rock and soil where only non-time-sensitive readings are needed. They measure the water level inside a pipe using a dip meter.

  • Open Tube Piezometers: Used in simple hydrogeological conditions, consisting of a cracked or micro-slotted PVC pipe installed inside the probing hole.

Electronic Piezometers

Electronic piezometers use advanced sensors and data logging systems to provide continuous, real-time data. They offer higher accuracy and can be monitored remotely with cloud-based sensor management platforms like the Inzwa Cloud, reducing the need for frequent site visits. Types of electronic piezometers include:

  • Vibrating Wire Piezometer: Measures pore-water pressure using a diaphragm, a tensioned steel wire, and an electromagnetic coil. Changes in water pressure alter the wire's tension and its resonant frequency, which is used to calculate pressure.

  • Pneumatic Piezometer: Utilizes gas pressure to measure pore water pressure in saturated soils. It features a simple, reliable transducer free from zero drift, with long-term performance enhanced by corrosion-resistant materials.

  • Titanium Piezometer: Especially useful in corrosive environments, these piezometers are known for their corrosion resistance.

  • Hydraulic (Flushable) Piezometers: Consist of a porous filter enclosing a reservoir of water, separated from a pressure gauge by flexible, water-filled tubes. They can measure both positive and negative pore water pressures.

  • Strain Gauge Piezometers: Feature a diaphragm sensor isolated from the surrounding environment by silicon oil, making them suitable for applications where the instrument is exposed to harmful liquids or gases.


Installation of Piezometers

Installation of piezometers varies depending on the type and the specific requirements of the project. The most common methods include drilling boreholes to the desired depth and installing the piezometer, which can be a vibrating wire, pneumatic, or standpipe type. The choice of installation method—such as fully grouted, sand-packed, or push-in—depends on the soil conditions, the required measurement accuracy, and the duration of monitoring:

  • Fully Grouted Method: This method involves installing the vibrating wire piezometer directly into a borehole and completely backfilling the annular space around the piezometer with a cement-bentonite grout. The grout acts as a sealing material and hydraulic barrier between the piezometer and surrounding soil formation. This method is quick, easy to install, and provides excellent isolation between different measurement zones when multiple piezometers are installed in the same borehole.

  • Sand-Packed Method: The sand-packed method involves placing a sand filter or "sand pack" around the piezometer tip to create a permeable zone. This permeable zone is then sealed above and below by bentonite or cement-bentonite grout to isolate it from the rest of the borehole. This traditional method allows water to flow freely from the surrounding soil into the sand pack before being measured by the piezometer. It is more time-consuming than the fully grouted method but may be preferred in very permeable formations.

  • Push-In Method: Push-in or drive-in piezometers are designed with a specialized housing that allows them to be directly pushed or driven into soft, cohesive soils like clays. This avoids the need for a borehole. The piezometer has a conical tip to minimize soil disturbance and excess pore pressure generation during installation. Push-in piezometers are quick to install but have a limited depth range compared to borehole installed piezometers. They are ideal for monitoring pore pressures in near-surface soils.


Applications of Piezometers

Piezometers are versatile tools used in various geotechnical applications:

Water level monitoring with piezometers at construction site

  •   Construction Site Monitoring: They help assess soil conditions, identify risks of soil liquefaction, and inform decisions regarding construction methods and safety measures.

  • Dam Monitoring: Piezometers measure water pressure beneath the surface, providing data critical for ensuring the dam's safety and integrity.

 

  • Levee Monitoring: They are used to measure water pressure within levees, aiding in flood control and prevention efforts.

 

  • Mining and Excavation Applications: Piezometers monitor pore water pressure in surrounding geological formations, helping predict and prevent water ingress and soil or rock failure.

Top Three Manufacturers of Piezometers Globally

 

The global market for piezometers features several key players known for their innovative solutions and quality products. Here are the top three manufacturers:

 

  • Soil Instruments Limited: A leading manufacturer of premium quality geotechnical instrumentation, including piezometers. Known for their precise inclinometers and extensometers, Soil Instruments serves industries such as civil engineering and mining with comprehensive monitoring systems.

 

  • Geokon: Specializes in the manufacture of geotechnical instruments and sensors, including a wide range of piezometers. Geokon's products are used across the construction, transportation, geotechnical, and mining industries, adhering to the ISO 9001:2015 quality assurance standard.

 

  • Durham Geo Slope Indicator (DGSI): A manufacturer and supplier of geotechnical instruments, DGSI offers piezometers among its range of sensors for monitoring ground movement and structural deformation. Serving a global clientele, DGSI is known for its quality products and industry expertise.

 

Conclusion

Piezometers are indispensable tools in geotechnical monitoring, providing critical data that helps maintain the safety and integrity of structures before, during, and after construction. With advancements in technology, such as Inzwa Technologies' Cloud platform, the ease of piezometer data management continues to evolve, enhancing the efficiency and productivity of geotechnical monitoring projects. As the demand for reliable geotechnical monitoring solutions grows, manufacturers like Soil Instruments Limited, Geokon, and Durham Geo Slope Indicator remain at the forefront, offering innovative products that meet the industry's needs.


Go here to learn more about piezometer use in geotechnical monitoring.

 


 

Inzwa Cloud Simplifies Piezometer Management

Water pressure monitoring with piezometer at dam site

Our plug-and-play Cloud sensor data management platform can streamline the acquisition, analysis and reporting of all your piezometer data with:

  •  24/7 remote data access

  • Intuitive data visualizations

  • Customizable alerts - SMS & email

  • Pre-built dashboards and automated summary report templates

  • Third-party hosting

  • The ability to develop custom formulas to calculate data from multiple devices




Inzwa Cloud & GeoKon Piezometer Case Study:

FK Engineering

Zachary Carr, FK Engineering

FK Engineering used the Inzwa Cloud to provide 24/7 remote piezometer data management on a critical infrastructure rehabilitation project in Fraser, MI.


"With the criticality of monitoring water levels 24/7, Inzwa saved my bacon and reduced my stress level that weekend," lead engineer Zachary Carr said.






We can take the headaches out of your geotechnical monitoring. Connect with us today.



 

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