Time-Dependent Cox Regression Analysis of Rock Salt

The main objective of this study is to analyse and predict the potential risk of rock salt breakage using the Cox proportional hazard model. Analysed according to the theory of continuous mechanics medium rock massif is a natural environment difficult to know, so the forecasts referring to its behaviour are approximate and uncertain. Such an assertion becomes a certitude, even resulting from reality; consequences of the four fundamental features of massif are multiple and involve really difficult issues in mining field and generally, in the constructions field. The concept and the way to assess the stability of underground construction involves understanding its phenomenological evolution and doubtless the character of rocks behaviour in massif. Most of the time, the analysis of the behaviour of the rocks and the possibility of their breaking requires consideration of the simultaneous effects of several factors. Rocks behave differently over time, and in any situation, there is a possibility that the break will manifest itself. Many times, we do not have complete information for the analysis of the resistance time of the rocks. To carry out such an analysis, we proposed the use of a regressive method, that is, the Cox proportional hazard model. By applying the Cox model or proportional hazard regression, we have the possibility of predicting the relative risk (potential risk) of the occurrence of rock breakage based on several variables. Risk (hazard) can have a different variation, either in the sense that it can increase in time or perhaps decrease; if over time there is no variable or factor that determines an evolution towards breaking the rock, then the risk of breaking is lower. Based on the principle scheme of rocks behaviour way to failure, we are propose a statistical analysis method of results obtained by laboratory tests using Cox regression. This method offer the possibility to provide quantitatively and qualitatively the time when the breakage occurs. The method enables us to establish the link between a certain factor through which can be forecasted rock breakage and the ability to resist; the method can be developed and applied massif scale and also in the stability analysis of underground works.