Vibrating Wire Piezometer Installation in an Embankment and Earth/Rockfill Dam

Piezometers are geotechnical instruments used in the measurement of pore water pressure in soil, dams, concrete structures, etc.
Many different types of piezometer are used during geotechnical monitoring and instrumentation. Piezometer installation is done accurately and with precision to avoid future disruption in the readings.

Piezometer Installation in an embankment using Model EPP-30V

Encardio-rite Model EPP-30V is recommended for installing in an embankment.
The following steps are followed for the VW piezometer installation procedure.

• The first step in the installation of a piezometer in an embankment is to accurately mark the position where the piezometer is to be installed. It is recommended to position some sand/gravel to form a plain surface in the earth/rockfill or concrete dam.
• Take a geotextile bad and fill it with 2–4 mm of saturated sand. Insert the piezometer in it and tie the bag by pulling the lace. Assemble the products into a cylinder of about 75 mm φ.

• Connect the leads to the readout unit. The reading displayed will be the “initial reading” to be entered into the sensor set-up data. It is also important to record the ambient temperature.

NOTE: Make sure to record the initial temperature and reading with the readout unit as it will form the zero reading for the piezometer. Also, note the barometric pressure at the time of initial reading.

• The next step is to completely cover the sensor and the adjoining cable all around with sand/gravel.
• In the case of earth/rockfill dam, cover the sensor with enough backfill. For a concrete dam, shovel the concrete to a depth of 0.5 m to embed the sensor before commencing the normal operations.

Also Read: How Is Vibrating Wire Piezometer Installation Done?

Piezometer Installation in an earth/rockfill dam using Model EPP-30V

The recommended piezometer for such installation is Encardio-rite Model EPP-30V Electron Beam Welded heavy-duty piezometer.

In an earth and rockfill dam, more than one piezometer and sensors are installed at marked elevations and different cross-sections, as shown in the figure below.Here, for example, nine piezometers and three soil pressure meters are installed at an elevation of 438 m.

The reason behind installing a group of piezometer is that the monitoring of readings helps to discover the phreatic line and shows how it moves with time till steady-state conditions are attained.

Also Read: Vibrating Wire Piezometer — Types and Operating Principle

At any cross-section, the dam is allowed to be filled to an elevation of about 0.5–1 m higher from where the piezometers are to be embedded.
The exact position where the piezometers are to be mounted is cautiously marked. To reach the correct required elevation, offset trenches of about 1m X 1m are dug at these positions.

Using a hand shovel, the material around the sensor is placed and pressed down using a light-duty pneumatic or petrol backfill tamper.

The height of the first layer of material shoved over the sensor should be about 250mm, compacted with precision. Using the same method, the sensor should be covered with the material until 500mm of it has been placed.

The 500 mm height permits rubber tire equipment to cross the location. However, if vibratory rollers need to be permitted to the location, the material thickness should be increased to 1m to avoid [Continue Reading…]