Advanced Information Analysis And Optimization Research For Foundation Rock Of High Concrete Gravity Dam

In the previous exploration work, most of the hydropower projects were focused mainly on abutments of both shores. Whereas the highest dam, the most loaded bedrock or deeply under covered foundation rock were exposed through a handful of drillings which could not be direct observed, let alone carry out field test; the exploration through dispersed and limited point of the dam foundation site was mostly based on qualitative judgments to choose the base surface location; When it came to the construction drawing stage, in accordance with the tender design documents, people began to evacuate until it directly excavated to the designed foundation surface place. Thus, whether the use of foundation rock was reasonable, and whether the selection of base surface was the optimal and so on had left relatively much suspense.Regarding to the above issues of high concrete gravity dam foundation rock engineering in the geological evaluation, in the intermediate stage between excavation to the design base surface, with the help of large construction area and construction equipments, using the new detection methods and technical means, the paper carried out advanced information analysis on the foundation of rock as well as obtained various information of the rock foundation. Especially for the timely detection and analysis of the under excavated deep rock in the construction process, for the accurate prediction and evaluation of the dam foundation rock below the excavated surface, and timely feedback of all the information, undertaking design adjustment, making dynamic analysis and evaluation the engineering geological characteristics of rock foundation, and ultimately serving the optimizing selection of base surface. Aiming at the Long Kaikou Hydropower Station of Jinsha River as its study object, this paper carried out a comprehensive advanced information analysis of foundation rock, and presented a set of advanced information analysis methods and technologies. Ultimately the engineering foundation rock was fully and rationally utilized, and the base surface was .optimized. The study includes:(1)The advanced analysis and tracking test of controlled weak layersAiming at the large scaled weak layers revealed in the excavation process of Long Kaikou Hydropower Station, based on the detailed site investigation, this paper carried out advanced information analysis. At the meantime made tracking test along with the process of construction. And it also made prediction and evaluation of the impact of the controlled weak layers to the foundation rock, and then forecasting the width was narrower, and the size was smaller after the weak layers get to the base surface location and the base surface excavation depth does not need to be adjusted. The result of the exposed conditions after excavation to the base surface was consistent with the advanced analysis.(2)The advanced information analysis and in situ identification of gently dipping structrual faceTo make advanced information analysis of the gently dipping fault: advanced analysis and determine whether in the deep of the foundation rock existed continuity and large-scale of gently dipping fault; Made advanced information analysis of the distribution feature and scope of the partially exposed gently dipping fault in the deep rock.Carried out in situ identification of the gently dipping joint, and discovered a surface connectivity rate computing method which had practical significance to the foundation rock based on the field measurement of structural face. Meanwhile conducted analysis of the impact of the gently dipping joint to the stability of dam foundation rock.(3)Carry out the advanced information analysis of foundation rock mass quality, and make evaluation of rock mass quality by using various methods. Conduct direct visual display of the rock mass quality with the help of three-dimensional solid model. Make advanced analysis and judgment to the foundation rock mass quality. Keep the high quality rock and propose engineering treatment plan to the low quality rock. All the construction geological work is in a dynamic process. Carry out feedback test after excavation to the base surface and found that the advanced analysis results were accurate and the foundation rock mass quality met the requirements. (4)Introduced a number of new in-situ rock mechanical test technologies and applied into engineering practice:â‘ S elf-loading ground deformation testIntroduce the new self-loading test ground deformation developed by our esearch team, Discuss test methods and calculation process, Evaluate the reliability of the test results through various projects application, establish the relation of deformation modulus - acoustic velocity with the 296 test samples: Ln ( E0 )= 3.098?Ln(Vp), ? 23.53 The correlation coefficient is high, and with a certain margin of safety, it has a universal application significance. Conduct an analysis of the deformation modulus of the foundation rock of the Long Kaikou Hydropower Station in accordance with relation. Meanwhile make deformation tests after the excavation to the base surface and the result is basically consistent with the advanced analysis.â‘¡Self-loading ground Shear TestMake improvement to the traditional Shear test. Introduce the shear test method developed by our research team that can be conducted at any site. Discuss the test methods and technical means, especially for the river dam sites that have not yet carried out a large shear test. Apply the newly developed testing technology in the construction stage, and fast access to the strength parameters, and then take them as an important supplement of the project evaluation and acceptance of information system as a whole.â‘¢P rediction Research of Deformation modulus of Weak Layers under In-situ ConditionsIntroduce the test methods of unfolded weak layers overlying a more complete overall multi-media rock deformation newly created by our research team and access the theoretical formula of all levels of media deformation modulus. Conducted the corresponding contrast test in the field, and then made the finite element inversion so as to carry out prediction study of the in-situ conditions of the deformation modulus of weak layers in many ways. Made reckon of weak layers of the dam foundation of Long Kaikou Hydropower Station as per the test results and determined the deformation modulus was high.(5)Established the advanced information analysis system of foundation rock and described its analytical methods and processes. Conducted the advanced information analysis of the foundation rock of Long Kaikou Hydropower Station through the integrated a variety of information, interaction of many factors and a number of running processes in the whole system. At the meantime, determined the optimal location of base surface, the maximum optimization of depth 13m, reduced the dam foundation excavation and concrete work of about 300,000 cubic meters and saved project investment of 100 million Yuan or more. It has significant economic benefits.(6)Fully established engineering technical files, classified archive the data files and information from the advanced analysis, tracking tests to the feedback analysis . Created a huge amount of data, and rich content project files and provide a strong protection for optimization of base surfaces. Moreover it prepared sufficient information for the engineering operation and safety assessment.