Application Research Of Uncertain Statistic Model For Discontinuities Trace Length

The stability of rock mass has a very close internal relationship with degree of development in discontinuities, development positions, assemblage characteristics, engineering properties and so on. And trace length is one of the important parameters to reflect the rock mass structure. The study of trace length estimation is limited to theoretical research at present, and the literature is quit rare, which uses the investigation results of full-trace length to verify and study the trace length estimation models. In this paper, the evaluation on the reliability of the existing nondeterministic trace length estimation models is done through the verification research in hydro-junction of Shuangjiangkou project, and furthermore the discussion on the adaptability of trace length estimation model is done.In this paper, according to the field measured data, the fracture statistic of full-trace length in hydro-junction of Shuangjiangkou project and the adits is done, and based on the classification according to the predominant direction of fracture statistic, statistical sofeware-SPSS is used to establish the statistical model of trace length, combined with the occurrence, trace length and the weathering conditions of discontinuities. The calculations of mean value and the variances of trace length are done, and the calculation results are used as actual value. And then, in the adits which have some difficult in investigation, using four different trace length estimation methods, lengths of traces are calculated in different weathering zones, and the nondeterministic statistical model is established. After that, considering the influence of the weathering and the size effect of statistic window, verification and analysis are done, which are for the nondeterministic statistical model based on the statistic of the fracture in the adits, comparing with the results done by the whole trace length method. At last, the suitable nondeterministic statistical model for different weathering zones is provided.In this paper, different calculation methods of nondeterministic models are done in different weathering zones, and the results are compared with the one of the full-trace length method. The conclusion is obtained that: the calculation method of Laslett is proper in hightly weathering zones; the calculation method of H-H is proper in moderately weathering zones; the calculation method of H-H₂ is proper in slightly weathering zones.