Rock mass parameters based doline susceptibility mapping in gypsum terrain
Rock in nature is observed as a rock mass that is a discontinuous medium with features including joints, faults, fissures, fractures and bedding planes. Interaction of the intact rock blocks with the discontinuities mainly controls the rock mass behaviour under applied stress. Therefore a detailed description of the discontinuities in rocks, their structure and their condition can provide valuable insights into potential rock mass behaviour. Although the rock mass characteristics in terms of discontinuities are very important for the stability of underground openings, they have never been considered as a conditioning factor of doline susceptibility analyses. In this paper, preparation of a doline susceptibility map based on the rock mass parameters is proposed. Three doline susceptibility models (based on conventional affecting factors (geological, hydrological, topographical, land use factors and vegetation cover), rock mass parameters, and both sets of factors combined) were produced and their validation performances and accuracies were compared. According to the comparison of the three models, the most realistic and accurate doline susceptibility model was implemented from the combined parameters. However, the accuracy of the model obtained from the doline susceptibility map based on rock mass parameters was distinctly higher than that of the first model, which is based on conventionally used conditioning factors. Validation analyses of the maps indicated that the method and conditioning factors in terms of rock mass parameters included in the models can be considered as satisfactory. Although a precise map was obtained in this study considering the rock mass parameters, the results of this paper do not claim that the parameters considered are sufficient to construct a precise doline susceptibility map, as there may be other site-specific factors affecting doline occurrence that were not included in the analyses in this study because of the characteristics of the study area. This paper particularly points out that the rock mass parameters must be included in doline susceptibility analyses together with the other factors.