Characteristics Of Fault Gouge And Its Engineering Geological Significance

As a product of fault, fault gouge may contain a wealth of information about the activity. A huge mass of data have been accumulated on the material compositions and structure characteristics of fault gouge, as well as on the fault activity reflected, physical and mechanical properties. Exploring geochemical characteristics of fault gouge which reflected evolution process is basic research in frontier field of geology.Typical sections of the three faults near the northeastern Tibet plateau have been selected to systematic sampling in field study. The samples would be tested with experiments with XRD, XRF, and measurement of gas adsorption with MAT271 mass spectrometer, first applied BSRF to study S and Mn chemical species. The characteristics of the compositions of fault gouge and its environment of formation and engineering geological significance have been analyzed and discussed based on the experimental results and previous studies and findings. The major results are as follows:(1) The mineral and chemical composite experimental results showed that quartz, calcite and feldspar, and other rock-forming minerals are contained in fault zone, besides, there is a certain amount of clay minerals, such as illite, kaolinite, montmorillonite, muscovite and so on. From the analysis of the chemical constituents, we see that the Si, Ca, Fe, S, Mg, Mn and P et al. are contained in fault gouge, the more active elements are Si, Fe and Ca. A study of the correlation of elements in the samples reveals that Ca and Mg, Mn, Si; Al and K, Ti have high correlation.(2) From the experimental results of a test for adsorbed gas in fault gouge, it showed that CO2>N2>H2>CH4 (C2H6 or C3H8)>C4H10, and there is a correlation between content of adsorbed gases and history of fault activity.(3) Analyses of an X-ray absorption fine structure experiment with manganese and sulfur shows that the red and yellow gouge are usually formed in an oxidizing environment for they generally contain Oxidative chemical species; the gray-green and blue-gray gouge are formed in a reducing environment for they contain more reducing species.(4) By consulting a large number of structural data in fault gouge, we have analyzed the characteristics of particle size and micro-structure of the fault gouge. In this paper, the researcher tries to apply classic sediment particle size methods to analyze the characteristics of the fault gouge, the correlation between the particle size parameters and physical & mechanical parameters of fault gouge has been established.