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Xiao R.,CAS Institute of Geology and Geophysics | Xiao R.,University of Chinese Academy of Sciences | Wang S.,CAS Institute of Geology and Geophysics | He X.,CAS Institute of Geology and Geophysics | And 4 more authors.
Yanshilixue Yu Gongcheng Xuebao/Chinese Journal of Rock Mechanics and Engineering | Year: 2013

According to the characteristics of large-scale slope which may have multiple slip directions and multi-level slip surfaces, the method of safety zonation is proposed. Based on the theory of strength reduction, firstly, the typical geological section of the slope is selected to build a two-dimensional(2D) numerical model. Failure modes can be detected by applying local strength reduction to the model to search the potential failure surfaces at different depths. By using limit equilibrium method for each potential failure surface, the slope stability coefficients at varied depths and levels are obtained. Secondly, three-dimensional(3D) numerical model is established to analyze the influence area of different failure modes based on the local strength reduction. Thirdly, the safety of the slope can be zoned through aforementioned comprehensive analysis of slope stability coefficients and influence areas. Finally, the method is applied to the slope of Longjiang super large bridge; and the analysis results show that this method is effective for comprehensively demonstrating the stable state of large-scale slopes. The method can also provide guideline for the monitoring design, reinforcement design and construction design of slope. Source


He X.-H.,CAS Institute of Geology and Geophysics | He X.-H.,University of Chinese Academy of Sciences | He X.-H.,General Institute of Chemical Geology Survey of China Chemical Geology and Mine Bureau | Wang S.-J.,CAS Institute of Geology and Geophysics | And 3 more authors.
Yantu Gongcheng Xuebao/Chinese Journal of Geotechnical Engineering | Year: 2013

Since it has insufficient demonstration of theoretical basis of taking the first displacement data as the known condition, the original synergetic model is improved. Based on the improved model, a formula for displacement prediction and landslide time is deduced. In addition, the analysis results indicate that taking the maximum velocity as the forecast criterion of landslide time in the original synergetic model lacks rationality, and taking the maximum acceleration as the forecast criterion is more in accordance with the mechanism of landslides. Then the formula for the forecast value of landslide time based on the maximum acceleration criterion of synergetic model is deduced. Based on the deduced formulas mentioned above, the original and improved synergetic models and the two kinds of criteria are applied to the time forecast of some examples of actual landslides by using MATLAB software. The prediction and forecast results indicate that: (1) the forecast time of the improved synergetic model is closer to the actual occurrence time of landslides, and earlier than that of the original model. The precision of displacement prediction of the improved model is higher than that of the original model; (2) as for the forecast results of two kinds of criteria, the forecast time of the maximum acceleration criterion is earlier than that of the maximum velocity criterion, and its forecast error is smaller than that of the maximum velocity criterion; and (3) the forecast time of the improved model based on the maximum acceleration criterion is very closer and a little earlier than the actual occurrence time of landslides, and it can play a role in early warning. So, the improved model is better than the original one, and the maximum acceleration criterion is better than the maximum velocity one. The application of the improved model based on the maximum acceleration criterion to landslide prediction and forecast is feasible, and its forecast results are much better than those of the original model. Source


Xiao R.-H.,CAS Institute of Geology and Geophysics | Xiao R.-H.,University of Chinese Academy of Sciences | Wang S.-J.,CAS Institute of Geology and Geophysics | He X.-H.,CAS Institute of Geology and Geophysics | And 4 more authors.
Yantu Gongcheng Xuebao/Chinese Journal of Geotechnical Engineering | Year: 2013

In order to make a clearer description for assessing the overall steady state of an inhomogeneous slope, a multi-level method based on strength reduction is proposed. Initially, the multi-level potential slip surfaces can be found by using the local strength reduction of the rock mass at different depths or different strata, then, the slope stability analysis using the limit equilibrium method is conducted for each potential failure surface. Finally, the slope stability coefficients at various depths and levels can be obtained. This method makes full use of the objectivity advantage of strength reduction and avoids the subjectivity disadvantage of the limit equilibrium method in the course of determining multi-level potential slip surfaces. The slip surfaces obtained by this method can better reflect the failure process of slopes under the action of gravity than those by other methods. The results by the proposed method are better than those by the arc method. A case study proves that this method is effective for the comprehensive stability analysis of the inhomogeneous slope, and that it can provide guidance for the treatment, monitoring design and construction of slopes. Source


He X.-H.,CAS Institute of Geology and Geophysics | He X.-H.,University of Chinese Academy of Sciences | Wang S.-J.,CAS Institute of Geology and Geophysics | Xiao R.-H.,CAS Institute of Geology and Geophysics | And 2 more authors.
Yantu Lixue/Rock and Soil Mechanics | Year: 2013

The Verhulst biological growth model is a kind of statistical forecast model of landslide. According to the problem that there is no theoretical basis of taking the first displacement data as the known condition in the original Verhulst model; and a big error may be caused, the improved Verhulst model that other scholar proposed is firstly applied to the prediction and forecast of landslide. Based on the improved model and velocity maximum criterion, the calculation formula of displacement prediction and time forecast of landslide was deduced. Analysis of forecast results of different forecast criterions is another research content. Theoretical and case study indicates that taking maximum velocity as the forecast criterion of landslide time lacks rationality, and taking maximum of acceleration and accelerated acceleration as the forecast criterion is more in accordance with the mechanism of landslide. Then calculation formulas of forecast time based on the maximum criterion of acceleration and accelerated acceleration were deduced. Based on the deduced formulas above, the original and improved Verhulst model and the three kinds of criterion were applied to the time forecast of some actual landslides that had happened; and MATLAB software was used to calculate the time forecast. The forecast results indicate that, firstly, compared with the forecast results of the original Verhulst model, the forecast results of the improved Verhulst model are better, because the forecast time of improved model is closer to the actual occurrence time of landslide, and earlier than that of original Verhulst model. Secondly, as for the forecast results of three kinds of criterion, the forecast results of the acceleration and accelerated acceleration maximum criterion is better than that of the velocity maximum criterion, because the forecast time of acceleration and accelerated acceleration maximum criterion is closer to the actual occurrence time of landslide, and is earlier than the forecast time of velocity maximum criterion. Thirdly, it is suitable to substitute the single forecast time of the original Verhulst model with a forecast time range, and the upper limit of the rang is forecast time of the acceleration maximum criterion; and the lower limit is forecast time of the accelerated acceleration maximum criterion. Fourthly, the forecast time of the improved Verhulst model and the new time range criterion is more accurate than that of the original model, and it can play a role of early warning. In addition, the decrease of anti-slide force and increase of residual sliding force that is induced by increase of crack and decrease of friction coefficient is the reason why the acceleration of sliding mass increases gradually near failure. Source

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