Study On Weathered And Unloaded Zones Of Rock Mass Of Kala Hydropower Station In Yalong River

Along with the Chinese Dream of national rejuvenation strategy and the advancement of China’s Western Campaign.The construction of key national projects,such as transmit the electricity form western areas to East China,has been steadily advanced.The excavation and treatment for rock mass are inevitable.It is of great significance to study the characteristics of rock mass for the smooth development of engineering construction and to give full play to engineering benefits after construction.This paper takes the slope of Kala Hydropower Station on Yalong river as the research object.First-hand field data are obtained through field measurement and geological sketch.Combined with the stratigraphic lithology and slope structural characteristics of the two banks,the characteristics of rock mass weathering and unloading in the dam site area of Kala hydropower station are studied quantitatively.At the same time,in order to enrich the detailed study of rock weathering and unloading of different lithologies in this research field,the relationship between weathering and unloading is explored and analyzed tentatively.The main research contents and achievements of this paper follow:(1)A systematic study of the slope structure was carried out.Through field investigation,field measurement and indoor statistical analysis,engineering geology classification and classification of the discontinuities of the dam site area are obtained.And the engineering geological characteristics of the various discontinuities are described and analyzed.The characters of different levels of discontinuities are obtained.And the dominant orientation of discontinuities is determined.(2)Based on the types and characteristics of weathering of rock mass in natural state,the characteristics of weathering rock mass,the study of common indicators of weathering rock mass,the quantitative division of weathering rock mass zone and its spatial distribution characteristics in dam site area of Kala hydropower station are analyzed.The method to divide the weathering zone of rock mass in the dam site area of Kala hydropower station is put forward.(3)On the basis of the types and characteristics of rock mass unloading in the natural state and combined with the unloading phenomenon developed in the deep valley in the dam site area,the spatial distribution characteristics,aperture,linear density and other characteristics of rock mass unloading in the dam site area are summarized in detail.The factors affecting the development of the unloading zone of valley slope rock mass are analyzed.And the method of dividing the unloading zone of rock mass in the dam site area of Kala hydropower station is put forward.(4)Based on the survey from surface and adits,the lithology and structure characteristics of rock mass,degree of weathering and unloading fracture characteristics of the slope are studied,the unloading zone of the slope is qualitatively analyzed.The results of acoustic speed testing and in-situ rock stress test are combined to establish a division scheme suitable for the unloading zone of the slope rock mass in the dam area of Kala hydropower station.(5)The development conditions of deep unloading of the left bank slope of Kara Hydropower Station controlled by geomorphology,lithology,rock stress,slope structure and geological structure.(6)Further study the relationship between rock mass weathering and unloading based on the results of rock mass weathered zone and unloaded zone of dam site in Kara Hydropower Station:①On the spatial distribution of weathering and unloading of rock mass,we found that the boundary of rock mass in each weathered and unloaded zone mostly parallel to the slope topography,and the weak unloading line and the upper limit depth of weak weathering are basically the same for depth;②FLAC3D software was used to simulate the unloading and weathering of the slope by reducing the parameters to analyze the changes in the stress field;③According to the comparison between numerical simulation and measured results,the reduction parameters on the simulation of the stress field is verified,and we found that unloading has a greater impact on the size of the stress field,but less impact on the distribution of the deep stress field.(7)Summarize and extract the main factor of the quality of rock mass.On the basis of on-site qualitative classification,combine with the results of weathering and unloading zone division of the dam site in this paper,conduct a comprehensive evaluation on the quality of rock mass in the dam site.