Combination Evaluation Method For Classification Of Rock Mass Quality Based On D-S Theory Of Evidence

In every stage of the tunnel design and construction, the accurate classification of the surrounding rock and then making an accurate assessment of its stability is the basis to carry out economic tunnel surrounding rock’s supporting design,fast and safe construction and safe operation of the project. Therefore, it’s very important to build a classification method of rock mass quality, which can satisfy the real conditions of the tunnel surrounding rock well. With the increasing scale and more and more complicated geological environment in rock engineering, there are some inconsistency issues among the evaluation results obtained by different rock mass classification quality method.According to the combination evaluation idea, several fundamental methods are introduced to build the model for classification of rock mass quality, which can absorb the advantages of each fundamental method while decrease or even avoid their weaknesses at the same time and the results are as follows;(1)Based on the analysis of the factors affecting the quality of engineering rock mass and the discussion of the existing rock mass classification methods, the reason of the inconsistency issues among the evaluation results can be found, which illustrates the necessity of conducting the combination evaluation methods. Meanwhile, considering the limited number of rock mass heterogeneity and survey samples, it will be much more meet the real rock conditions using the interval number to describe the physical and mechanical properties of rock and the geological environment and other factors.(2)It’s taken into account that the Dempster-Shafer theory of evidence is a very rigorous uncertainty reasoning method which has strong capability for information fusion and reflects the consistency and conflict of different information. The paper introduces the D-S theory of evidence to establish the combination evaluation method for classification of rock mass quality based on D-S theory of evidence.Then, due to the combination rule of D-S theory of evidence which is difficult to define the basic probability assignment, Euclidean distance is introduced to build a method for defining the basic probability assignment in this paper.In addition, a standardized method for evaluation indexes is drawn to resolve the problem that Euclidean distance hasn’t considered the overall size of the date and the influence of different physical meaning in evaluation indexes drawn by fundament methods.Finally, in the analysis of practical engineering example,comparing with the existing methods and the actual situation of the rock mass, it can be shown that the method can deal the inconsistency issues well, which proves that the proposed method is feasible and reasonable.