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4.4 Installation by Pushing or Driving into Soft Soils
The Model 3400DP piezometer is designed to be pushed into soft soils. In soft soils, it can be
difficult to keep a borehole open. The 3400DP may eliminate the need for a borehole altogether.
The unit is connected directly to the drill rod (AW, EW, or other) and pressed into the ground,
either by hand or by means of the hydraulics on the rig. (See Figure 5.) The units can also be
driven into the soil, but there is a possibility that the driving forces may shift the zero reading.
The ground conditions need to be relatively soft for the 3400DP to be effective. Soft soils (like
clays or silts) with SPT blow counts under 10 are ideal. In stiffer soils, it is possible to drill a
hole and then push the 3400DP only a few feet below the bottom of the hole, but if the soil is too
stiff, the sensor may overrange or break.
The piezometer should be connected to a readout box and monitored during the installation
process. If pressures reach or exceed the calibrated range, the installation should be stopped.
Allow the pressure to dissipate before continuing.
The drill rod can be left in place or it can be removed. If it is to be removed, a special five-foot
section of EW (or AW) rod with reaction wings and a left hand thread are attached directly to the
piezometer tip. This section is detached from the rest of the drill string by rotating the string
clockwise. The reaction wings prevent the EW rod from turning. A LH/RH adapter is available
from Geokon. This adapter is retrieved along with the drill string.
Figure 5 - Typical Soft Soils Installation
