GeoInv_001 Case03 Fixed Poisson's Ratio
Contents
In Case02 it has been shown that inverting for Young's modulus and Poisson's ratio lead to an oscillatory behaviour in Poisson's ratio. As discussed this may indicate either or both:
1.There are more than one pair of parameter values that satisfy the convergence criteria for the chosen target solution.
2.The parameter that shows an oscillatory behaviour has a relatively low influence on the chosen target solution.
In the present case the aim is to explore the outcome of the inversion algorithm when Poisson's ratio value is fixed to a value that is different to the one used to generate the target solution. To that end two inversion analysis (Case03a and Case03b) with Poisson ratio values of 0.2 and 0.4 respectively are performed. Note that the chosen values arbitrarily correspond to the Minimum_value and Maximum_value set in Case02.
The data for the present case is provided in GeoInv_001\Case03\Data. Note that two inverse analysis data files are provided with different Poisson's ratio values (GeoInv_001_Case03a.inp and GeoInv_001_Case03b.inp respectively). Also note that both inversion analysis use the same Target and Template folders but each one uses a different Test folder to preserve the model data files for each case (this is specified in File_data).
Results
The results for the current case are provided in GeoInv_001\Case03\Results.
The inversion analyses have determined an optimal Young's modulus of 196.1 MPa for Case03a (Poisson's ratio of 0.2) and a Young's modulus of 156.3 MPa for Case03b (Poisson's ratio of 0.4). As shown in the figure below for each value of imposed Poisson's ratio, values of Young's modulus converge to a unique value. This therefore confirms that in this particular case:
1.Poisson's ratio has an influence in the vertical displacement in the monitored point.
2.The oscillatory behaviour in the inverted Poisson's ratio observed in Case02 was due to the fact that for each Poisson's ratio value there is a Young's modulus value that ensures a good match with the target solution (the pairs of inverted parameter values satisfying convergence criteria in Case02 were not unique).
Variation of misfit value as a function of trial values for Young's modulus for the two cases with fixed Poisson ratio values considered.
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