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3-dimensional slope stability analyses using non-associative stress-strain relationships

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Science China(Technological Sciences) 2009年第9期52卷 2517-2527页

作者： CHEN ZuYu SUN Ping WANG YuJie ZHANG HongTao Department of Geotechnical Engineering China Institute of Water Resources and Hydropower ResearchBeijing 100048China Department of Civil Engineering Beijing University of Science and TechnologyBeijing 430074China

The research work presented in this paper refers to a new slope stability analysis method used for landslide risk evaluations. It is an extension of the 3-dimensional upper-bound slope stability analysis method proposed by Chen et al. in 2001,which employs the Mohr-Coulomb's associative flow rule. It has been found that in a 3-dimensional area,a prism may not be able to move at friction angles to all its surrounding interfaces,as required by this associative rule,and convergence problems may occasionally arise. The new method establishes two velocity fields:(i) The plastic one that represents a non-associative and the best representative dilation behavior,and (ii) the virtual one that permits the solution for factor of safety in the work and energy balance equation. The new method can then allow any input value of dilation angle and thus solve the convergence problem. A practical application to a concrete dam foundation is illustrated.

关键词： non-associative flow rule slope stability limit analysis 3-dimension

Stability analysis of unsaturated soil slope during rainfall infiltration using coupled liquid-gas-solid three-phase model

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Water Science and Engineering 2016年第3期9卷 183-194页

作者： Dong-mei Sun Xiao-min Li Ping Feng Yong-ge Zang State Key Laboratory of Hydraulic Engineering Simulation and Safety Tianjin University

Generally, most soil slope failures are induced by rainfall infiltration, a process that involves interactions between the liquid phase, gas phase,and solid skeleton in an unsaturated soil slope. In this study, a loosely coupled liquid-gas-solid three-phase model, linking two numerical codes,TOUGH2/EOS3, which is used for water-air two-phase flow analysis, and FLAC^(3D), which is used for mechanical analysis, was established. The model was validated through a documented water drainage experiment over a sandy column and a comparison of the results with measured data and simulated results from other researchers. The proposed model was used to investigate the features of water-air two-phase flow and stress fields in an unsaturated soil slope during rainfall infiltration. The slope stability analysis was then performed based on the simulated water-air two-phase seepage and stress fields on a given slip surface. The results show that the safety factor for the given slip surface decreases first, then increases, and later decreases until the rainfall stops. Subsequently, a sudden rise occurs. After that, the safety factor decreases continually and reaches its lowest value, and then increases slowly to a steady value. The lowest value does not occur when the rainfall stops, indicating a delayed effect of the safety factor. The variations of the safety factor for the given slip surface are therefore caused by a combination of pore-air pressure, matric suction, normal stress, and net normal stress.

关键词： Coupled liquid-gas-solid three-phase model Pore-air pressure Unsaturated soil slope stability Rainfall infiltration

Scale problem:Influence of grid spacing of digital elevation model on computed slope and shielded extra-terrestrial solar radiation

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Frontiers of Earth Science 2020年第1期14卷 171-187页

作者： Nan CHEN Key Laboratory of Spatial Data Mining&Information Sharing(Ministry of Education) Fuzhou UniversityFuzhou 350108 China Spatial Information Research Center of Fujian Province Fuzhou UniversityFuzhou 350108 China

Solar radiation is the primary energy source that drives many of Earth’s physical and biological processes and determines the patterns of climate and productivity on the surface of the Earth.A fundamental proportion of solar radiation is composed of shielded extraterrestrial solar radiation(SESR),which can be computed using the slope and aspect derived from a digital elevation model(DEM).The objective of this paper is to determine the influence of the grid spacing of the DEM(the influence of the scale of the DEM)on the errors of slope,aspect and SESR.This paper puts forward the concepts of slope representation error,aspect representation error,and SESR representation error and then studies the relations among these errors and the grid spacing of DEMs.We find that when the grid spacing of a DEM becomes coarser,the average SESR increases;the increase in SESR is dominated by the grid cells of the DEM with a negative slope representation error,whereas SESR generally decreases in the grid cells with a positive slope representation error.Although the grid spacing varies,the distribution of the percentages of positive SESR representation errors on the slope,which is classified into 11 slope intervals,is independent of the grid spacing;this distribution is concentrated across some slope intervals.Moreover,the average absolute value and mean square error of the SESR representation error are closely related to those of the slope representation error and the aspect representation error.The findings in this study may be useful for predicting and reducing the errors in SESR measurements and may help to avoid mistakes in foture research and in practical applications in which SESR is the data of interest or plays a vital role in an analysis.

关键词： scale problem digital elevation model grid spacing slope shielded extra-terrestrial solar radiation

Integration of aspect and slope in snowmelt runoff modeling in a mountain watershed

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Water Science and Engineering 2016年第4期9卷 265-273页

作者： Shalamu Abudu Zhu-ping Sheng Chun-liang Cui Muatter Saydi Hamed-Zamani Sabzi James Phillip King Texas A&M AgriLife Research and Extension Center at El Paso El Paso TX 79927-5020 USA Xinjiang Water Resources Research Institute Urumqi 830049 China Civil Engineering Department New Mexico State University Las Cruces NM 88003-8006 USA

This study assessed the performances of the traditional temperature-index snowmelt runoff model(SRM) and an SRM model with a finer zonation based on aspect and slope(SRM + AS model) in a data-scarce mountain watershed in the Urumqi River Basin,in Northwest China.The proposed SRM + AS model was used to estimate the melt rate with the degree-day factor(DDF) through the division of watershed elevation zones based on aspect and slope.The simulation results of the SRM + AS model were compared with those of the traditional SRM model to identify the improvements of the SRM + AS model's performance with consideration of topographic features of the watershed.The results show that the performance of the SRM + AS model has improved slightly compared to that of the SRM model.The coefficients of determination increased from 0.73,0.69,and 0.79 with the SRM model to 0.76,0.76,and 0.81 with the SRM + AS model during the simulation and validation periods in 2005,2006,and 2007,respectively.The proposed SRM + AS model that considers aspect and slope can improve the accuracy of snowmelt runoff simulation compared to the traditional SRM model in mountain watersheds in arid regions by proper parameterization,careful input data selection,and data preparation.

关键词： Snowmelt runoff model (SRM) Degree-day factor (DDF) Aspect and slope Snow cover area Temperature Precipitation

Combined influence of nonlinearity and dilation on slope stability evaluated by upper-bound limit analysis

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Journal of Central South University 2017年第7期24卷 1602-1611页

作者：唐高朋赵炼恒李亮陈静瑜 School of Civil Engineering Central South UniversityChangsha 410075China

The combined influence of nonlinearity and dilation on slope stability was evaluated using the upper-bound limit analysis theorem.The mechanism of slope collapse was analyzed by dividing it into arbitrary discrete soil blocks with the nonlinear Mohr–Coulomb failure criterion and nonassociated flow rule.The multipoint tangent(multi-tangent) technique was used to analyze the slope stability by linearizing the nonlinear failure criterion.A general expression for the slope safety factor was derived based on the virtual work principle and the strength reduction technique,and the global slope safety factor can be obtained by the optimization method of nonlinear sequential quadratic programming.The results show better agreement with previous research result when the nonlinear failure criterion reduces to a linear failure criterion or the non-associated flow rule reduces to an associated flow rule,which demonstrates the rationality of the presented method.slope safety factors calculated by the multi-tangent inclined-slices technique were smaller than those obtained by the traditional single-tangent inclined-slices technique.The results show that the multi-tangent inclined-slices technique is a safe and effective method of slope stability limit analysis.The combined effect of nonlinearity and dilation on slope stability was analyzed,and the parameter analysis indicates that nonlinearity and dilation have significant influence on the result of slope stability analysis.

关键词： slope stability analysis nonlinear failure criterion non-associated flow rule multipoint tangent technique upper-bound limit analysis theorem

Phase transition on speed limit traffic with slope

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Chinese Physics B 2008年第8期17卷 3014-3020页

作者：李兴莉宋涛邝华戴世强 Shanghai Institute of Applied Mathematics and Mechanics Shanghai University College of Physics and Electronic Engineering Guangxi Normal University

Through introducing a generalized optimal speed function to consider spatial position, slope grade and variable safe headway, the effect of slope in a single-lane highway on the traffic flow is investigated with the extended optimal speed model. The theoretical analysis and simulation results show that the flux of the whole road with the upgrade （or downgrade） increases linearly with density, saturates at a critical density, then maintains this saturated value in a certain density range and finally decreases with density. The value of saturated flux is equal to the maximum flux of the upgrade （or downgrade） without considering the slight influence of the driver＇s sensitivity. And the fundamental diagrams also depend on sensitivity, slope grade and slope length. The spatiotemporal pattern gives the segregation of different traffic phases caused by the rarefaction wave and the shock wave under a certain initial vehicle number. A comparison between the upgrade and the downgrade indicates that the value of saturated flux of the downgrade is larger than that of the upgrade under the same condition. This result is in accordance with the real traffic.

关键词： generalized optimal speed car-following model slope phase transition

Dynamic characteristics and simulation of traffic flow with slope

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Chinese Physics B 2009年第7期18卷 2703-2708页

作者：何红弟卢伟真薛郁董力耘 Department of Building and Construction City University of Hong Kong Department of Physical University of Guang Xi Shanghai Institute of Applied Mathematics and Mechanics Shanghai University

This paper proposes a new traffic model to describe traffic flow with slope under consideration of the gravity effect.Based on the model,stability analysis is conducted and a numerical simulation is performed to explore the characteristics of the traffic flow with slope.The result shows that the perturbation of the system is an inherent one,which is induced by the slope.In addition,the hysteresis loop is represented through plotting the figure of velocity against headway and highly depends on the slope angle. The kinematic wave at high density is also obtained through reproducing the phenomenon of stop-and-go traffic,which is significant to explore the phase transition of traffic flow and the evolution of traffic congestion.

关键词： traffic flow perturbation stability analysis slope

Adaptive and intelligent prediction of deformation time series of high rock excavation slope

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中国有色金属学会会刊：英文版 1999年第4期9卷 842-846页

作者：冯夏庭张治强徐平 Institute of Rock and Soil Mechanics Chinese Academy of Sciences Wuhan 430071 China Coll. of Rsrc. and Civil Engineering Northeastern University Shenyang 110006 China Yangtze River Sci. Res. Institute Wuhan 430010 China

Deformation of high rock excavation slope has nonlinear evolution characters. It is very difficult to build mechanical model to describe this nonlinear evoution. A genetic-neural network model has been initially proposed for adaptive and intelligent prediction of deformation of slopes, which used artificial neural network to represent nonlinear evoution of slope deformation. Number 0f history points of displacement inputted to the model, topologies of neural network, and learning process of model were adaptive and automatically determined using genetic algorithm. The obtained model was thus optimal at global range, and gave predictions of horizontal displacement at succedent three months for the three measurement points with average relative error of 1. 4 % compared with the measured values. Results from one step prediction and multi-step prediction were combined with the measurements.

关键词： slope displacement adaptive genetic algorithm neural network

A comparative study of pseudo-static slope stability analysis using different design codes

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Water Science and Engineering 2018年第4期11卷 310-317页

作者： Xin-guang Yang En-di Zhai Yuan Wang Zhong-bo Hu Central Research Institute of Building and Construction Co. Ltd. MCC Group Beijing 100088 China Goldwind Science & Technology Co. Ltd. Beijing 100176 China College of Mechanics and Materials Hohai University Nanjing 210098 China China Three Gorges Corporation Beijing 100038 China

Many researchers have developed new calculation methods to analyze seismic slope stability problems, but the conventional pseudo-static method is still widely used in engineering design due to its simplicity. Based on the Technical Code for Building slope Engineering(GB 50330-2013) of China and the Guidelines for Evaluating and Mitigating Seismic Hazards in California(SP117), a comparative study on the pseudo-static method was performed. The results indicate that the largest difference between these two design codes lies in determination of the seismic equivalence reduction factor( f_(eq)). The GB 50330-2013 code specifies a single value for f_(eq) of 0.25. In SP117, numerous factors,such as magnitude and distance, are considered in determining f_(eq). Two case studies show that the types of slope stability status evaluated by SP117 are in agreement with those evaluated by the seismic time-history stability analysis and Newmark displacement analysis. The factors of safety evaluated by SP117 can be used in practice for safe design. However, the factors of safety evaluated by GB 50330-2013 are risky for slope seismic design.

关键词： Earthquake slope stability Pseudo-static method Design code