Penetration-induced pore pressure

PENETRATION-INDUCED PORE PRESSURE MAGNITUDES - METHODS TO DETERMINE TRANSPORT PARAMETERS FROM TERRESTRIAL AND MARINE PENETROMETER TESTING... 

With magnitudes of penetration induced pore pressure, p-p available in Equation 1, substituting this relation directly into Equation 5 enables plots of Qi versus 6, to be contoured for permeability, for the case of an infinitesimal radius penetrometer. The resulting relationship is... 

Solutions are developed for the pore pressure fields that develop around penetrometers either advanced at constant or decelerating rate and under partially-drained flow conditions. The maximum pore pressure, recorded at the penetrometer is suggested as indicative of the permeability of the surrounding soil, since the peak-pressure is conditioned by the ability for fluids to escape. This full suite of solutions promotes a consistent framework to understand the processes operating during penetrometer penetration and arrest, and to enable the conventional sounding indices inclusive of tip resistance, Q friction factor, and pore pressure ratio, to be related to penetration-induced pore pressures, and therefore to permeability. 

Relations may be developed to represent the steady pore fluid pressures that develop around a penetrometer under steady penetration, at penetration rate, U. These rtKxlels necessarily employ simple linearized constitutive relations, but incorporate the important influence of a porous medium migrating past the penetrometer tip, albeit in a simplified form. Dislocation models (Elsworth, 1991 1993) may be applied to represent a penetrometer of infinitesimal-radius, but suffer the disadvantage that penetration-induced pressures become singular at the assumed penetrometer tip. The approximate solution for a finite radius penetrometer avoids this shortcoming, as explored in the following. 

Hydrophilic MF membranes can be made by the dry-wet phase inversion technique, which can also be used to make PVDF membranes. On the other hand, other hydrophobic microflltration membranes are made by the thermally induced phase separation technique. In particular, semicrystalline PE, PP, and PTFE are stretched parallel to the direction of film extrusion so that the crystalline regions are aligned in the direction of stretch, while the noncrystalline region is ruptured, forming long and narrow pores. Hydrophobic membranes do not allow penetration of water into the pore until the transmembrane pressure drop reaches a threshold called the liquid entry pressure of water (LEPw). These membranes can therefore be used for membrane distillation. The track-etching method is applied to make microfiltration membranes from PC. 

---