Research On Forecasting And Evaluation Of Overbreak As Well As Underbreak In Jointed Rock Mass Openings

It is a complex engineering geology problem for forecasting overbreak as well as underbreak in jointed rock mass openings. The research on forecasting and evaluation of overbreak as well as underbreak is the mainly contents in this paper. Mainly contents includes: . . (1) The basic principal, basic method and general situation of discontinuity mapping are summarized in this paper. Combined geodesic discontinuity parameters in the fields and distribution of ground stress state in situ, one discontinuity mapping method based on geological mechanics mechanism is put forward. The technology is applied in forecasting and evaluation of overbreak as well as underbreak in jointed rock mass openings. The veracity of result will be tested by an engineering example. The result shows that discontinuity mapping considering geological mechanics mechanism can reflect discontinuity characters and forecast properly overbreak in jointed rock masses openings. The key block theory is an important tool to study overbreak as well as underbreak in the openings because it researches key block from the angle of topology. However, the key block is different from overbreak block. The relation between overbreak block and key block is researched in this paper. The method for forecasting of overbreak block by using key block theory combined discontinuity mapping is applied.(2) The geological characters of rock mass and geological constitution is the mainly factors of affecting overbreak as well as underbreak in the openings. From the mechanism of rock rupture, the fractal dimension of openings perimeter is researched in jointed rock mass in this paper. The generalized fractal dimension model of openings perimeter in jointed rock mass is put forward. The relation between effecting parameters and generalized fractal dimension of openings perimeter is analyzed. According to the fractal theory, the relation between overbreak as well as underbreak and generalized fractal dimension of openings perimeter is built. Based on geological mechanics mechanism, the relation between overbreak as well as underbreak and generalized fractal dimension is built. The blasting excavation ways are the other factor of affecting overbreak as well as underbreak in the openings. So far, the research about the effect of blasting excavation to overbreak as well as underbreak is not be reported in the domestic. The openings perimeter shape that is be affecte4 by blasting is researched from the angle of rock rupture. The relations between overbreak as well as underbreak and stress as well as strain are researched. The relations among overbreak as well as underbreak and fractals and dynamic rupture of openings perimeter are consummated. At the same time, the affecting of overbreak as well as underbreak to surrounding rock stability is researched.(3) The forecasting methods of overbreak block in the openings based on wavelet neural network of geological statistics model is put forward. Firstly, two basic theories, including theory of geological statistics model and theory of wavelet neural network, are introduced. Secondly, according to two theories, the proceeding of program designing is introduced and the calculation program is designed. In these, geological statistics model relates to the probability and statistics; wavelet neural network relates to sigmoid function used by wavelet neural network. Lastly, according to geological datum in a pump-storage hydroplant,application of two theories is in forecasting overbeak of several openings. The forecasting result provides a basis for avoiding overbreak or decreasing overbreak.(4) It is important for evaluating rock mass quality correctly and classifying surrounding rock, analyzing and forecasting overbreak as well as underbreak in the openings, researching relation between rock mass quality and overbreak as well as underbreak. Both the relation between classification of Q and overbreak as well as underbreak and the relation classification of RMR and overbreak as well as underbreak are researched in this paper. The relation betw...