Study On Classification Of Rock-soil Bank Slope And Its Spatial Distribution Based On Remote Sensing

After completing the Three Gorges Reservoir, water level before the dam maintained at 145-175m and fluctuated within 30m. Before it is exposed, the rock-soil slope periodically comes and goes in the water. This process lead to groundwater and surface water interaction in embankment slope surface and rock-soil mediums, and produced the physical, chemical, mechanical effect to rock and soil. These effects made some differences between rock slope and soil slope. After impoundment, soil slope immersed in water periodically, or immersed in water partly, expanded after absorbing water, adding to wave erosion, caused the front of the ancient landslide or ancient rubble to dislocate and slide down, and accident landslides revived, until generated collapse or landslide. Rock slope immersed in water periodically, made the physical and mechanical properties of rock slope change, Effects of the static pressure in the reservoir water, buoyant force and hydrodynamic pressure, caused the potential sliding surface at the rock bottom to soften and clay after soaking the water; and made the gap pressure increase and shear strength decrease. The series caused the slope slide along the weak slip surface, and lead to occurrence of rock landslide, rock avalanche, etc.Researching on the rules of slope deformation and the analysis and evaluation the slope stability is based on the classifying the type of rock-soil slope and its spatial distribution. Recently, the method of classifying type of rock-soil slope and its spatial distribution mainly is through the field investigation. To the large scope, investigating the type of rock-soil slope in the Three Gorges Reservoir Area with the traditional manner, requires a lot of human, finance, and is time-consuming. Remote sensing technology can obtain multi-band, multi-temporal information quickly and efficiently, to solve the issues on the access and update of the relevant data. Because the vegetation cover over the reservoir area, and the penetration of remote sensing is poor, people can't classify the type of rock-soil slope and its spatial distribution by remote sensing directly. According to the correlation between coastal sediment concentration in the Yangtze River and type of rock-soil slope, this paper inversed the suspended sediment concentrations using remote sensing data, then classified the type of the rock-soil slope indirectly. The specific thesis research content and conclusions are as follows:(1) This paper took the Tangxun Lake in Wuhan as the experimental area, measured spectral reflectance of the different concentrations of sandy water bodies using field spectrometer, and measured the suspended sediment concentrations with the filter weighing method in the laboratory. By analyzing the correlation between sediment concentration and spectral reflectance of different band, this paper chose the optical band for the monitoring the suspended sediment concentrations by remote sensing, and established the linear model, logarithmic model, power model and the negative exponential model. then analysis the fitting accuracy of four different kinds of models. Finally, the article has a conclusion that the negative exponential model is the best.(2) Based on CBERS remote sensing data, the negative exponential model is applied to Zigui-Badong district in the Three Gorges Reservoir Area. Firstly, the paper inversed the suspended sediment concentrations from 2004 to 2006 years on research area. Then, calculated these three years average sediment concentration and classified the average sediment concentration. Finally, classified the bank slope and draw its spatial distribution by the different grades sediment concentrations.(3) To verify the accuracy of classified bank-slope type, this article selected 32 sample regions, and compared with the field data. It is proved that the accuracy is about 84.375%. After analyzing the results, part of the regions misclassified are mainly affected by regional topography, reservoir level changes, the Yangtze River flow rate, rainfall, tributaries imported, the nature of human activities (vessels and the wave its sparked), the remote sensing image acquisition time and weather conditions, etc. Classifying the spatial distribution of soil banks, not only contributes to researching the stability of slope, but also services to the analysis and evaluation of the slope stability. At the same time, the classification of bank slope has the great significance of the Disaster Prevention and Mitigation in the reservoir area.