3D Stability Calculation And Evaluation Of Majiagou Landslide Based On GIS

This paper takes Majiagou landslide in the three gorges reservoir as an example. The slope stability evaluation is based on grid subdivision combining with mechanics analysis.Through the extraction and analysis of the surface, boundary and drilling information, using GIS spatial interpolation to get the strata’s bottom layer and the slip plane. By taking the interpolation slip plane as sliding surface and combining mechanics formula in ArcGIS raster calculator, get the landslide stability zoning map with analysis of the weight-stability of Majiagou landslide.Then, take the whole Majiagou landslide as the research object, using embedded VB programming to establish the Majiagou landslide’s 3D stability calculation model and get 3D stability coefficient under different working conditions.Finally, the thesis adopts GEO52D profile model to simulate the Majiagou landslide stability evaluation and compares the assessment results with the method which described earlier to demonstrate GIS 3D stability analysis method’s feasible and accuracy and summarize its advantage and shortage.The achievements are as follows:(1)Because the polynomial interpolation’s surface is not strictly through the known datum points and the inverse distance weighted interpolation’s result presents local ridges and steep, while the result of the radial basis function interpolation can react more smoothly glide of the spatial distribution characteristics. So in the case of knowing a part of the sliding zone’s position, improve the slip plane speculate by using radial basis function interpolation method two times and get the space shape of slip surface.(2)Through GIS weight-stability zoning, most of Majiagou landslide is at unstable state and less stable.Unstable region is mainly distributing in the front edge, middle and trailing edge, less stable region is continuous distributing on the sliding body, stable region is mainly concentrating near the border.The stability of the slider (grid cylinder units) which above the slip plane and below the underground water level within the scope of a certain depth will decrease obviously, more than that depth the stability’s change is not obvious.The change of stability is not obvious when only considering short-term rainfall infiltration.(3)We can use drilling wire direction, the frequency value of the slip plane’s aspect and the relationship between the surface’s aspect and slip plane’s aspect as three methods to determine the main sliding direction of the landslide.Then programming GIS 3D calculation model in ArcGIS VBA, respectively calculate stability in different working conditions such as weight, weight+different underground water levels, weight+different underground water levels+rainfall infiltration.The results show that no matter what working condition is, Majiagou landslide is at less stable state (3D Janbu method of GIS) or unstable state (3D transfer coefficient implicit method of GIS).When the water level rises, the overall stability of Majiagou landslide decreases, and short-term rainfall infiltration’s effect on the overall stability is not obvious.(4)Through comparing the results of GEO5 calculation model with the 3D model of GIS shows that the borehole profile (2D calculating profile) is not always the most dangerous section, and 2D profile calculation model is more easily affected by outside condition’s change than 3D calculation model of GIS.It shows that because of considering the overall situation of landslide, the results of 3D calculation model of GIS are closer to the actual situation than 2D profile calculation.Its calculation area is more continuity and the results are more abundant.