Installation of piezometers

The grout mixture used in the test was the same bentonite-cement mix that Slope Indicator recommends for inclinometer casing. A one-inch layer of water was left on top of the grout. The other piezometer and the fittings for the pressure source were installed in the top half of the chamber. The top half was then sealed to the bottom half, and a 5 psi pressure was applied and maintained to simulate a confining pressure.

Tests were run on day 2, 7, 14, and In each test, pressure in the upper chamber was increased by 10 psi. Afterwards, pressure was returned to the constant 5 psi confining pressure. The plot below shows the results from a typical test in the first series.

The piezometer in air responds instantly to the increase in pressure, while the piezometer in grout responds more slowly. Results are shown in the table below:. The second series of tests was run for days. In this series, the geotextile protection for the filter was eliminated.

This dramatically shortened response times. We believe that air trapped in the geotextile slowed response time in the first series. While response time still increases with curing days, the time-lag at 30 days is only 2.

A low air entry value ceramic flat filter with a thickness of 3 mm and a grain size of microns is normally provided. The water oozes through internal pores or seams in rock formations of dam foundations, mass concrete of structures, foundation soil of structures, reclaimed land soil etc.

A locking nut holds the filter in position. For filling up the cavity behind the filter with de-aired water before installation and for saturating the filter with water, a bent nose plier is used to remove and again assemble the locking nut.

Depending upon the application filters with different porosity and air entry values are available. The leads from the coil magnet are terminated on the glass to metal seal which is integrally welded to the stainless steel body of the piezometer. The two pins marked red and black are connected to the coil magnet. The other two pins are connected to a thermistor. A cable joint housing and a cable gland are provided for the connection. Normally, the piezometer is supplied without any cable attached to it.

Cable jointing with the required length of appropriate cable can be easily done at the site. The vibrating wire and coil magnet assembly is enclosed in a corrosion resistant stainless steel body which is an electron beam welded to the diaphragm.

A low air entry value ceramic filter of 40 micron porosity is provided. Other types of filters are available as an option. Leads from the coil magnet are terminated on a glass to metal seal which is an electron beam welded to the stainless steel body of the pore pressure meter. Two pins marked red and black are connected to the coil magnet. A cable joint housing and suitable cable gland is provided for the cable connection.

The piezometer working is achieved by:. The vibrating wire pressure sensing capsule is sealed under high vacuum. The capsule and coil magnet assembly is housed in a stainless steel body. Leads from the coil magnet are terminated on the glass to metal seal which is an electron beam welded to the stainless steel body of the piezometer. A cable joint housing and suitable cable gland are provided for the cable connection.

The sensor can also be supplied with the required length of cable attached. The pressure sensor is individually temperature compensated making the requirement of a thermistor for temperature correction redundant. However, a thermistor is provided for monitoring temperature.

The Encardio-rite Model EPPV vibrating wire low range piezometer is specially designed to measure low water pressure and water levels in boreholes. The capsule and coil magnet assembly is housed in a stainless steel body with two small openings provided on the glass to metal seal. The sensor with range 7 m is supplied with the required length of vented tube cable attached.

This shielded cable has two vent tubes running through it which connect the inside of the sensor to the outside atmosphere, thus ensuring that sensor reading is unaffected by any change in barometric pressure. The open end of the vent tubes in the cable terminates into a moisture trap assembly consisting of a terminal box and desiccant chamber at the top of the borehole thus preventing any moisture from migrating into the vent tube or the sensor.

Model EPPV piezometers are individually temperature-compensated making the requirement of a thermistor for temperature correction redundant. The uplift pressure measurement system is used for monitoring uplift pressure of water in the foundation of dams and concrete structures and the stability of foundations of embankments in dams, tunnels and other underground works. It provides significant quantitative data on the magnitude and distribution of uplift pressure of water and its variations with time.

It also provides the pattern of seepage, zones of potential piping and the effectiveness of seepage control measures undertaken. The pipe is inserted in a drilled hole in the foundation from the instrumentation gallery to the required depth. To the other end of the pipe in the gallery is connected the uplift pressure meter or a Bourdon pressure gauge. It is similar to the model EPPV piezometer except some changes in piezometer specification. Instead of the special filter, a 25 mm BSP adapter is provided for the pipe connection.

When threaded into a drill rod, the piezometer can be pushed into soft soil directly. The cable attached to the piezometer is passed through the drill rod. The piezometer must be monitored to ensure that the pressure created during vibrating wire piezometer installation does not exceed the maximum rated pressure. The pore pressure meter is individually temperature-compensated making the requirement of a thermistor for temperature correction redundant.

This is how the piezometer works! The vibrating wire and coil magnet assembly is enclosed in a corrosion-resistant stainless steel body which is an electron beam welded to the diaphragm. A low air entry value stainless steel filter of micron porosity is provided.

The diameters selected for the drilled holes shall depend on the intended configuration of the borehole and depth of drilling. The top of filter pack shall not be higher than the top of thelayer of interest.

The filter pipes and solid- walled pipes shall be installedwith centring devices to ensure that the annulusis completely filled. A seal shall be installed above the filter pack to avoid any pressure equalisation via the area outside the pipe. The construction of the screen shall be chosen as a function of the filter pack. Filter packs are generally required in open systemsto prevent soil particles from entering the filter and clogging it.

They shall be filter-stable against the surrounding ground and the sealing. Typical Standpipe Piezometer Installations. Model Main Page Get a Quote. Direct-Push Equipment.