Instruments
Standpipe Piezometer
“Casagrande" Piezometer
Slope Indicator’s standpipe piezometer consists of a filter tip joined
to a riser pipe that communicates with the surface. The low air entry
filter has 60-micron pores and a permeability of 3 x 10
-4
m/sec.
A sand cell is formed around the filter tip at the bottom of the bore-
hole. A bentonite seal is placed above the sand to isolate the
pore-water pressure at the tip. As pore-water pressure increases or
decreases, the water level inside the standpipe rises or falls. The
height of the water above the filter tip is equal to the pore-water
pressure.
“Observation wells” use the same components as the standpipe
piezometer, but are installed differently. The tip is not sealed off and
the borehole is backfilled with gravel or sand. Unlike the standpipe
piezometer, the observation well can collect water from any eleva-
tion above the filter tip. The water level inside the pipe rises or falls
with the ground water level.
Advantages
q
Simple and reliable.
q
Low cost.
q
Can be used in permeability tests.
Limitations
q
Slow response in low permeability soils.
q
Cannot measure negative pore pressure.
q
Expensive to automate – requires transducer or bubbler.
q
On construction site, top of standpipe interferes with construction
activity and may be damaged.
3-11
Vented Cap
Groundwater Level
Bentonite/Cement
Grout
Filter Tip
Standpipe
Bentonite Seal
Piezometric
Water Level
Vented Cap
Bentonite/Cement
Plug
Groundwater Level
Sand or Gravel
Backfill
Filter Tip
Standpipe
Casagrande Piezo
(Monitoring Well)
Observation Well
Pore Water
Pressure
Rembco Geotechnical Contractors specializes in
slope stabilization,
soil nail wall,
foundation repair
and support,
grouting,
shoring,
micropile
construction,
rock drilling, and we remediate
sinkholes. We use a
problem-solving approach in the geotechnical portions of buildings, bridges, water plants, sewage plants, tunnels,
installing caisson bottom, and roads. We are experienced in these applications:
micro piles,
sinkhole repair,
permeation and
pressure
grouting,
soil nails,
cement grouting,
chemical grouting,
micropiles,
compaction grouting, and
rock anchors.
Rembco techniques apply when adding new structures: especially
rock anchor,
microfine cement,
soil nailing, and
micropile
installations for foundation support. Our specialties are
soil nails,
rock anchor,
chemical and
compaction grouting,
mini piles,
sinkhole repair,
micropiles, and
soil nailing.
