| Popis: |
The Pacific Northwest National Laboratory (PNNL), in collaboration with The Space and Naval Warfare Systems Center (SPAWAR) proposed to develop a rapid, robust and reliable tool for in situ measurement of hydraulic properties in heterogeneous, anisotropic, variably saturated porous media. A critical component of this project was the modification of the existing SCAPS/GeoVIS system to function as dual field-of-view video camera system for sub-surface soil imaging. One camera is used to capture grain size data in the silt-sized fraction and the other to capture information in the sand-sized fraction. These two levels of magnification provide fields of view ranging from 2 to 20 mm diagonal. Digital images of sediments were converted into particle size distributions and their moments using the Pixel-Vernier, a suite of photogrammetric algorithms. A subatmospheric borehole permeameter proved successful in overcoming limitations in subsurface conductivity measurements. Use of a subatmospheric pressure permeameter reduced the effect of macropores and fissures on matrix flow. For the analysis of data, a new method using the Brooks-Corey hydraulic model was developed to solve the steady-state infiltration equation. This approach will lead to a better understanding of the measurements available for permeability characterization and help to establish the validity of permeability predictions in untested intervals based on measurements like grain size distributions that are easier to make. The data obtained using the direct push sensors will be invaluable in the design and evaluation of remedial systems and the prediction of future contaminant migration. |
