The mechanical parameters and initial stress of coal have predominant influences on the stability of the surrounding coal of an entry in the coal seam. In practice, however, it is very difficult to determine the values of time-dependent soft coal mass parameters. To obtain these values of the time-dependent soft coal mass parameters based on very limited amounts of measured data, back-analysis is the most commonly used approach worldwide. Field measurement data may include displacements, strains, and stresses.
Because the displacements of a rock mass can be measured easily and reliably, back-analysis based on displacements has long been an active topic of research. The basic methods used in most of the studies have been numerical simulation methods and optimization algorithms. In these methods, numerical simulations were used to compute the displacements of the surrounding rock based on certain assumed values of the mechanical parameters and the initial stress. Then, by optimizing the error between the computed displacements and the measured displacements via an optimization algorithm, the initially assumed values were corrected into real values.
However, there are few papers that deal with back-analysis method based on timber load and displacement measured in the entry when the rock pressure and displacement of the entry increase continuously owing to the coal softening with time in very soft coal such as anthracite coal.
In order to ensure the accuracy in determining the mechanical parameters of time-dependent anthracite coal and to ease consideration and calculation in a set of algorithm, Sin Myong Nam, a researcher at the Faculty of Mining Engineering, has conducted a FLAC3D numerical simulation based on measured load and displacement, established a three-layer BPNN from it and found a methodology for predicting the mechanical parameters by SSA.
The proposed method can provide a useful basis for predicting time-dependent behavior of media surrounding the drift or chamber driven in such soft rock as the anthracite coal.
You can find the details in his paper “Determination of Mechanical Parameters of Anthracite Coal using Flying Squirrel Search Algorithm with Timber Load and Displacement Data” in “Journal of Mining and Environment” (EI).
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