Effect of saturated permeability on drawdown problem

This example constitutes a simple demonstration of how to conduct a parametric study. The Rapid Drawdown example problem GeoStudio website is used. The parametric study consists of analyzing the effect of the saturated hydraulic conductivity of the dam on the dissipation of the pore water pressure following a instantaneous drawdown.

We first import PyGeoStudio library, open the GeoStudio study and get hydraulic permeability function of the dam fill material.

import PyGeoStudio as pgs

src_file = "../GeoStudio_files/Rapid drawdown.gsz"
geofile = pgs.GeoStudioFile(src_file)
mat = geofile.getMaterialByName("Dam fill")
Kfunction = mat["Hydraulic"]["KFn"]

Then we define the saturated hydraulic conductivity to test in our parametric study and initiate Python list to get the results of the simulation.

Ksats = [1e-7, 1e-6, 1e-5, 1e-4]
Ts = []
PWPs = []

We now enter in the parametric study loop to analyze the pore water pressure dissipation for the different Ksat. Note there is no way in GeoStudio to define the saturated hydraulic conductivity of the unsaturated material. The saturated hydraulic conductivity is rather specified through the hydraulic function. So the approach is to scale the whole conductivity function.

for new_Ksat in Ksats:
  # scale hydraulic conductivity
  # note relative permeability is defined through the function,
  # not by the KSat attribute which is for saturated only model
  actual_relK = Kfunction.getYData()
  actual_Ksat = Kfunction.getYData()[0]
  Kfunction.setYData(new_Ksat/actual_Ksat * actual_relK)
  # run GeoStudio
  geofile.save()
  instant_drawdown = geofile.getAnalysisByName("2 - Instantaneous drawdown")
  pgs.run(geofile, analyses_to_solve=[instant_drawdown])
  # get results
  T,PWP = instant_drawdown["Results"].getVariablesVsTime(
    "PoreWaterPressure",
    locations=[[25,2]]
  )
  # store it for future plotting
  Ts.append(T)
  PWPs.append(PWP)

The PWPs list now contains the pore water pressure dissipation curves for the different conductivity tested. We can plot these curves using matplotlib library:

import matplotlib.pyplot as plt
fig,ax = plt.subplots()
for T,PWP,Ksat in zip(Ts,PWPs,Ksats):
  ax.plot(T, PWP, label=f"Ksat = {Ksat}")
ax.grid()
ax.legend()
ax.set_ylabel("PoreWaterPressure")
ax.set_xlabel("Time (s)")
plt.tight_layout()
plt.show()