Abstract
The response of rocks to stress can be highly
non-linear, so sometimes it is difficult to establish a
suitable constitutive model using traditional mechanics
methods. It is appropriate, therefore, to consider
modelling methods developed in other fields in order to
provide adequate models for rock behaviour, and this
particularly applies to the time-dependent behavior of
rock. Accordingly, a new system identification method,
based on a hybrid genetic programming with the improved
particle swarm optimization (PSO) algorithm, for the
simultaneous establishment of a visco-elastic rock
material model structure and the related parameters is
proposed. The method searches for the optimal model,
not among several known models as in previous methods
proposed in the literatures, but in the whole model
space made up of elastic and viscous elementary
components. Genetic programming is used for exploring
the model's structure and the modified PSO is used to
identify parameters (coefficients) in the provisional
model. The evolution of the provisional models
(individuals) is driven by the fitness based on the
residual sum of squares of the behaviour predicted by
the model and the actual behaviour of the rock given by
a set of mechanical experiments. Using this proposed
algorithm, visco-elastic models for the celadon
argillaceous rock and fuchsia argillaceous rock in the
Goupitan hydroelectric power station, China, are
identified. The results show that the algorithm is
feasible for rock mechanics use and has a useful
ability in finding potential models. The algorithm
enables the identification of models and parameters
simultaneously and provides a new method for studying
the mechanical characteristics of visco-elastic
rocks.
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