Abstract:
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The estimation of soil and rock parameters based on field instrumentation
data is a common procedure in geomechanics. The use of system identification
and optimization techniques allows the performance of this type of analyses in
a more rational and objective manner. In this paper a probabilistic formulation
for the backanalysis problem is presented. The procedure described involves
the evaluation of the measurement covariance matrices, which are derived for
some geotechnical instruments used in field instrumentation. The algorithm
used to solve the mathematical problem of optimization is also presented, as
well as its coupling to a finite element code. The algorithm requires the computation
of the sensitivity matrix, which can be evaluated “exactly” in terms of
the finite element method. Finally, a synthetic example, based on the excavation
of a tunnel, is presented in which the elastic modulus E and the Ko parameter
of the material are identified from measured displacements. The effect of the
number of measurements and their error structure is also discussed. |