Permeability from piezo response in unconfined material
I am a PhD student and I am trying to find out if I can estimate permeability from the data set I have available. I have 2 piezos, each sitting in a 0.5m sand window 3m apart from each other, sealed top and bottom by bentonite and "open" to the natural material horizontally. I have data at 3 hour intervals for both piezos recorded at the same time. I know the depth to each piezo. I know the amount of head the piezo is recording. I know the average porosity of the surrounding material. I know the material is clay and there is a significant lag between the upper and lower piezo responding. I know any water entering the system is rainfall only. Q1> Can I treat the system like a crude falling head permeameter and therefore calculate permeability? (I would have to make the area of the nonexistent standpipe the same as the area I choose for the sample such that they cancel - I need them to cancel as I have an unconfined system?) Q2> I am assuming that as the rainfall will affect an area much greater than the region close to the borehole that I can treat the system as 1D vertical flow and ignore lateral drainage - is this valid? (I'm ignoring lateral drainage as I believe the rainfall influx will be a much greater flux such that lateral flow will be insignificant?) Q3> If a falling head situation can't be used is there a vertical seepage formula/theory I can use? I'm not a geotechnical guy so hopefully I've explained myself well enough, if not please let me know whatelse you need to know. Any help would be appreciated as I don't know if the assumptions I want to make are valid. Cheers Sam
