welcome to the engineering video series this tutorial describes how to conduct
inverse modeling in Geo Studio 2019 inverse modeling is an important
practice in both the science and engineering fields the objective for
inverse modeling is to find an optimal set of parameters that provide the
minimum value of an objective function in order to do this the inverse modeling
process must start with the results of a model already known and then the causal
factors that produced those results are calculated generally this means that the
inverse modeling process is formulated as an optimization problem using an
objective automatic estimation procedure inverse modeling is also referred to as
parameter estimation or parameter identification two of the industry
standard inverse modeling software packages NGO environmental engineering
are pests and you code which include numerous tools to assist with the
inverse modeling process for the purpose of this video the inverse modeling
software package pest is used to conduct an optimization of a previously defined
Geo Studio file like you code the pest software package is model independent
which allows pests to interact with a model through its own input and output
files this requires that instruction and configuration files are created prior to
running pests to ensure that pests is able to find the desired parameters and
calculate the objective function based on the result output from the model the
objective function calculates the difference between the observed and
simulated model responses in pests and some other software the objective
function is defined as the sum of weighted least squares
peste must be launched from a command line prompt the instruction and
configuration files must also be checked using the pest tools via the command
prompt prior to running the optimization process in order for the input and
output files to be accessed by pest the Geo Studio file must be in the XML file
format in this tutorial video we will be discussing the setup of the accompanying
example file called multi-step outflow it is highly recommended that the pest
website and manual are reviewed prior to conducting inverse modeling with Geo
Studio
we will start with the Geo Studio file multi-step outflow already opened in Geo
Studio 2019 this example considers a one dimensional analysis based on a
multi-step outflow experiment please refer to the associated example files to
review the experiment setup and background information we will quickly
review all of the material properties and boundary conditions present within
the file
you
next we will save the file type in an XML file format initially we will try to
save the new XML file in the same folder as the existing GSM file instantly we
note the error that explains an XML file must be saved in an empty folder we will
return to the save as window and create a new folder to house the XML file for
simplification we will name the folder ms o the warning then serves as a
reminder that the new folder is meant for Geo Studio to use when solving and
saving the file therefore no other files should be added to the folder
now that we have saved the file in the XML file format we can go ahead and
solve the analysis
once the analysis is fully solved we can review the result graphs that were
created in the original GSM file in the XML file format we will be able to use
the results in these graphs within the optimization process of pests by
referring to their CSV file location in the results folders let's close geo
studio and take a look at these folders prior to setting up pests
we will go into the folder that contains all of the files downloaded from the
multi-step outflow example web page on the Geo slope web site this includes the
original GSM file along with the instruction and configuration files
required by pests saved as a zip file for more information on these required
files please refer to the associated example document and the pests website
first we will extract the files so that they are saved within the same folder as
the GS edge file this will make them available to pests to run the inverse
modeling process once extracted we can next take a look at the Geo studio files
that will be used by pests if we click on the new folder that we created for
the XML file we will see the XML file along with the mesh file the experiment
folder was created by Geo studio when we solved the analysis and holds the result
files for each saved time step of the analysis if we scroll down past all of
the folders representing the save time steps within the XML file we will find
the csv files for the results graphs that were created in the original GS ed
file these files will be called by pests to calculate the objective function
value during the optimization process
the pest executable files must be downloaded from the pest home page it is
recommended to also review the documentation available on the pests
website prior to running the optimization process to ensure that the
process is well understood once the files are downloaded only a few of the
executable files are required for this particular example so we will move them
into the folder where the GS said file and the instruction files are located
you
a bat file has been included in the downloaded files from the multi-step
outflow example web page we will open this file next using the Windows notepad
but this file could also be opened using any text editor the file location for
the pest executables and the XML file must be updated within the bat file
prior to running pests we will copy and paste the folder location and save the
bat file for more information about running batch files in command prompt
please refer to the solving with batch files using geo command tutorial video
we will also need to update the file location in the configuration files we
will first open the PST file with the same text editor
you
once the location is updated we will save the file and then open the TPL file
to update the last file location
you
now that all of the files are ready we will open the command prompt window
first we need to enter the file location since the file location is still on my
clipboard I will use the paste command next we will run the executables from
pest that will do a check of the instruction and configuration files to
ensure that all of the files are set up correctly in this case we will first run
pest check on the PST file next we will check the TPL files using the temp check
you
lastly we will check the AI NS files using ins check
once all of these checks pass with no errors we are ready to start the
optimization process in The Associated example file the shuffled complex
evolution algorithm from the University of Arizona is being used to run the
optimization process to do this we need to use the command as shown on the
screen as well as in the example document note this optimization process
can take a long time so we will not wait for the process to finish in this video
please refer to the example document for a discussion on the results of the
optimization process and comparison with laboratory data thanks for watching and
enjoy using geo Studio 2019