CONE PERMEAMETER? – IN-SITU PERMEABILITY MEASUREMENTS WITH DIRECT PUSH TECHNIQUES

摘要

Soil permeability, which defines the magnitude of fluid flow (gas or liquid) underimposed pressure gradients, is one of the most important hydrologic parameters tomeasure when predicting fluid or contaminant movement in the subsurface, designingenvironmental remediation systems, or simply characterizing a geologic site. Scienceand Engineering Associates, Inc. (SEA), has developed the Cone Permeameter?, a conepenetrometer technology that measures the in-situ air permeability or hydraulicconductivity in unconsolidated media. The cone permeameter rod incorporates awell-defined injection zone and multiple pressure ports placed at discrete locations fromthe injection zone. A permeability value is obtain by injecting a known flowrate of air orwater, measuring the pressure response along the permeameter rod, and then applying aone-dimensional, spherical, steady-state Darcy flow model to the measured injection rateand pressure profile. Near to the injection point the pressure field is distorted by acombination of the cylindrical injection zone and the compacted soil near the rod surface.A fundamental premise of the measurement is that, as the distance from the injectionpoint is increased, the resulting pressure distribution will become spherical. This methodmeasures the pressure gradient far enough from the injection point to avoid the distortedfield.The Cone Permeameter? measurement system has the following benefits overexisting in-situ permeability methods:1. All the advantages of direct push: minimal waste, risk reduction, fast emplacement,low unit measurement cost2. 3 to 10 minute measurement time per elevation3. Rapid mobilization and minimal site disturbance4. Complements standard CPT geophysical measurements5. Higher spatial resolution possible than borehole techniques (<10 vs. 50+ cm.)6. Potentially more accurate and quantified permeability measurements7. Compared to the pore pressure dissipation technique, which can only measure in lowpermeability water saturated media, the Cone PermeameterTM system can measurefive orders of magnitude in both saturated and unsaturated environmentsThe initial research and feasibility assessment of this system was completed inearly 1997 as the first phase of a contract supported by the DOE Characterization,