Engineering Geological Study On Large Quaternary Deposits In The Deeply Valley Southwestern China

The large loose Quaternary deposits is a kind of in-homogeneous geometrical, compared with rock mass or soil, it has variability of material composition, and more complicated space structure, the derivative of geological disasters is of randomness, recurrent and multiple features which concerned by the geological educational world,has become a new and special important research object. Because of complex geological conditions, the geological disasters in deep valley are developed, and a large Quaternary deposits are widely distributed in Southwestern China. With the development of social economy, human engineering activities(including water conservancy and hydro-power resources development, mining, transportation construction, etc.) more and more strong, its intensity is more than other regions at home and abroad,related to deposit geological hazards problems more and more prominent, more and more obvious influence on engineering construction, which is the one of the important problems must be solved well in the engineering development and construction. Therefore, studying to engineering geological characteristics, stability and features of hazard on large Quaternary deposits in the deep valley, and put forward prevention measures, it is not only of exploratory, and also has important practical significance.For research and explore the engineering geological characteristics, geological disaster problems and prevention measures for large deposit in deep valley under the complex geological environment in southwestern mountainous, the author has participated the engineering geological investigation and research work in more than two dozen water resources and hydro-power involving large deposit stability problems,Including field geological investigation, in-situ test, the results of audits, scheme evaluation and deposit geological disaster emergency rescue work. At the same time, the following researches was carried out combining with the research topic.(1) Study on classification of large deposit. Systematic classification has been conducted combined with geological environmental conditions in southwest and engineering geological characteristics of large deposit.(2) Analysis of formation mechanism for large deposit. Combined with the distribution characteristics of the deposit along river valley in southwest China, which formation mechanism and the space-time evolution characteristics are analyzed and summarized.(3) Research on geological comprehensive exploration technology for large deposit. Combined with a large number of engineering practice, the summary and the analysis of engineering geological survey technology, experimental means and methods, and the experience and lessons have been carried out for large deposit.(4) Research on geological feature for large deposit. Including the deposit interface morphology, material composition, structure characteristics, physical and mechanical properties and strength characteristics.(5)Research on deformation failure characteristics for large deposit. Including deformation and failure characteristics, the failure mode and deformation of time-space effect, etc.(6) Stability analysis of large deposit. Including analysis and evaluation of stability characteristics of deposit, the engineering stability of slope,bank rebuilding and foundation and comprehensive prevention and treatment measure of geological disaster.In order to study the deformation stability, characteristics of geological disasters, the comprehensive prevention and control measures for a large deposit under the engineering construction activities(such as engineering excavation, foundation treatment, reservoir storage, etc.),this paper closely combine with southwest geological environment characteristics and a large number of hydro-power engineering examples, based on the engineering geological classification and genetic mechanism analysis of deposit, take engineering survey and test research as the means, take large deposit geological feature research as the core, with large deposit stability analysis as the main line, relying on the early exploration completed and under construction or ongoing investigation and design of large hydro-power projects, and the engineering practice experience of more than 20 typical large deposits has been summarized and analyzed. Based on widely collecting, sorting and analysis dates from more than 30 large deposit research materials, more than 150 technical documentations and related procedure specification and extensive academic exchanges of the large deposit in southwestern river valley,and comprehensive analyzing and researching its space distribution, formation mechanism analysis,engineering geological classification, investigation methods, engineering geological characteristics, deformation and failure characteristics, the stability analysis and evaluation, Combines evaluation and summary on geological disasters characteristics treatment measures and effect of typical deposit geological disasters occurred recently for hydro-power projects in southwest regions including slope engineering, foundation engineering and reservoir engineering, the suggestions on the measures of the prevention and control for geological disasters of large deposit are put forward.Through the above research, analysis and summary, some methods and results with certain theoretical innovation, can guide the engineering survey and test, the deformation and stability analysis and effective engineering experience of processing for large deposit has been obtained. The main achievements including the following aspects:(1) According to geological environment conditions and geological characteristics for large Quaternary deposit in southwestern China, engineering geological classification are put forward on the basis of single factor, the particle size composition, structure features and space form features for large Quaternary deposit. According to the principle of ―concise and practical, from macroscopic to microcosmic ―, three-grade classification and engineering geological comprehensive classification based on the stability are also put forward.(2) According to the analysis and summary of distribution regularity of space development and distribution characteristics and dynamic geological processes for large Quaternary deposit in southwestern China, genetic mechanism of disaster causes, multipurpose causes, mixture causes and spatiotemporal evolution characteristics are put forward.(3) According to a large number of engineering practice of hydro-power project, prospecting technical requirements for large Quaternary deposits in different design stage are put forward.and the comprehensive exploration and experimental methods that ―taking 3S technology as the instruction, geological surveying and mapping as the basis, engineering geophysical exploration for auxiliary, with emphasis on the exploration, experiment research to support, mutual authentication for all kinds of means‖ are also put forward.(4) Study on the engineering geological features for large Quaternary deposits.Composition, structure features and seepage characteristics for different causes large Quaternary deposits are analyzed, summarized the characteristics of soil-rock mixture deposit such as composition diversity, uneven structure features, mechanical property difference and medium material discontinuity, the selection method of physical and mechanical parameter is proposed and the reference value of shear parameters for typical deposit are put forward, the strength characteristics of the deposit are also analyzed and discussed.(5) According to the deformation characteristics and induction mechanism for different large Quaternary deposits, seven basic instability mode such as excavation traction type, load type, reservoir water action, heavy rain infiltration, induced by earthquake, flood scouring and comprehensive induction are put forward. Combining with the typical engineering examples, the deformation space effect and time effect are also put forward.(6) Based on analysis and summarize of influence factor on the stability of large Quaternary deposits, the stability characteristics under the natural condition such as natural stability, potential instability, dynamic stability and spatial stability are presented which combined with specific engineering example, the safety control standards and evaluation methods of engineering slope stability, reservoir bank stability and foundation stability for large Quaternary deposit are put forward. At the same time, the comprehensive prevention and treatment measures are discussed combining with the characteristics of geological disasters for large Quaternary deposits.The research results not only have important guiding significance to survey, design, management and disaster prevention of large soil-rock mixture in deep valley for water conservancy and hydro-power engineering, highway engineering, railway engineering and mining engineering construction in Southwestern China, but also has reference value to the construction of similar engineering in Northwest and Southeast Asia. This study not only has theoretical significance, more has a wide range of practical guiding significance.