Triple-GEM detectors were selected by the CMS Collaboration for instrumenting the high η region of the muon system. This region is characterized by a huge radiation background, mainly composed by neutrons and photons. In this context, a discharge probability test was performed in 2017 at the CHARM facility at CERN, to study the operation of the detector in an environment similar to the one of the CMS muon system. A Geant4 simulation was developed in parallel to the actual test, in order to evaluate the behaviour of the detector. This paper will present this simulation, from the detector geometry implementation to the results obtained in terms of sensitivity and energy deposited into the gas gaps.