Quantized Quality Classification Of Dam Foundation Rock Mass And Its Diagrammatic Representation

Great achievements have been made in rock mass structure research to evaluate engineering properties of rock mass in engineering geological domain of our country, and rock mass structure cybernetics becomes the basic theory of rock mass mechanics. Basing on the abundant statistic and testing data of Xiluodu Hydroelectric project, the spatial characters of rock mass structure and quality in dam foundation are detailed studied. Some progress is made in the following aspects: quantification of rock mass structure indexes, quantized quality classification of dam foundation rock mass, establishment of spatial database of rock mass quality indices and the diagrammatic representation of rock mass quality.Under the influence of original formation, tectonic reconstruction, superficial and epigene-action, network of structure planes was created in rock mass, accordingly complicated the rock mass structure. After contrasting and analyzing the two common used measure method of discontinuity, a modified method that is elaborate method of joint surveying is put forward for the first time. Rational method to get spacing of joints is researched utilizing lots of statistical results. According to the theory of minimal valid length of scanline, 5m is chose as appropriate statistical section length to obtain the successive values of those indices indicating rock mass structure, they are spacing, number and total length of joint. Although joint spacing is an important index in rock mass structure classification, it can't be obtained in some regions such as riverbed, so the practicability of using those indexes which characterizing the integrity degree of rock mass to class the rock mass structure is studied, and good coincidence is shown in rock mass structure classification by joint spacing, integrity coefficient and number of joints in dam abutment. In riverbed, RQD is an appropriate index of rock mass structure classification. Because the weathering agent causes the change of integrity and structure of rock mass, the relationship between rock mass structure indexes and weathering zoning is discussed through wave velocity ratio.Drawing lessons from internal and external successful experiences in rock mass quality classification, the scheme of quantized quality classification of dam foundation rock mass is put forward choosing quantization indices of rock mass structure as primary factors, and the consistency of single index and combined index on determine rock mass quality grade is also verified by measured data.In order to scientifically manage exploration data, three-dimensional database composed of rock mass quality indices is established under the geodetic reference frame. Those indices are obtained from adits, drill holes and outcrops. To efficiently make use of exploration data, finite testing results are spread to the extent which they can control in term of the characters of gradual change of rock mass quality. In addition, corresponding software is programmed, which makes the visualization of rock mass quality come true. From the zonal map, the burying depth and area percentage of rock mass which belong to different grades in dam abutment and riverbed can be obtained respectively. So embedded depth can be determined preliminarily according to the requirement of high arch dam for foundation rock mass. Then important data are provided for rational layout of hydraulic structures. This thought and method of studying dam foundation rock mass quality can be extended to other water-power projects.