基于非饱和土强度理论的土质边坡浅层破坏稳定性分析
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摘要
基于非饱和土强度理论,建立边坡内单元土体达到临界破坏状态的判别方程,提出土质边坡浅层失稳由上缘张拉区、中间主滑动区和下缘挤压区组成的"上、下缘顺坡曲面"组合破坏模式;论证了采用对数螺旋线描述上、下缘滑动体破裂面形态的合理性,并采用极限平衡理论建立了适用于非饱和土质边坡浅层破坏的稳定性分析方法。结果表明:"上、下缘顺坡曲面"组合破坏稳定分析方法能够较好地反映滑坡深度zw与中间主滑动区范围L2之间的变化关系;对于饱和土质边坡,内摩擦角和边坡坡度对边坡稳定性的影响非常小,土体黏聚力的影响则要大得多;对于非饱和土质边坡,土体黏聚力和内摩擦角的减小及边坡坡度的增大均会显著减弱边坡浅层土体的稳定性;土质边坡处于临界状态(安全稳定系数FS=1.0)时,随着土体饱和度的增加潜在滑坡体的破裂面逐渐向浅层迁移,说明降雨入渗导致饱和度上升的土质边坡更容易发生浅层失稳破坏;对于有限长度的土质边坡,无限长斜坡稳定分析方法得到的稳定安全系数偏于保守,考虑了滑坡体上、下缘力学作用的组合破坏稳定分析方法更为合理准确。
Based on unsaturated soil strength theory, a discriminant equation is established for the critical failure state of soil element in slope, and a combined failure mode of "upper and lower edge parallel slope curved surface" for soil slope is proposed, which includes three sliding regions composed of the tension zone at upper edge, the main slide zone in middle and the squeeze zone at lower edge. It is demonstrated that the failure surface morphology of the upper and lower edge sliding mass coincides with the logarithmic spiral. A new stability analysis method is established for unsaturated soil slope based on the limit equilibrium theory. The results shows that the relationships between landslide depth zw and main slide zone length L2 are better reflected using this combined failure mode of "upper and lower edge parallel slope curve". The stability of shallow soil slope decreases and tends gradually to the results of infinite slope stability with increase of the main slide zone length L2. For saturated soil slope,the effects of internal friction angle and slope angle on slope stability are very little, but the influence of cohesion is significant. For unsaturated soil slope, the slope stability is reduced apparently as cohesion and internal friction angle decreases and slope angle increases. As the soil slope is in critical state(i.e. safety factor FS=1.0), the sliding surface of potential landslide gradually migrates to the shallow layer with the increase of soil saturation. It indicates that the soil slope with rising saturation caused by rainfall is more prone to shallow failure. Compared with the traditional infinite length slope stability analysis method, for a finite length soil slope, this combined failure stability analysis method is more reasonability and accuracy because of the consideration of the mechanical effects of upper and lower edge zone.
Based on unsaturated soil strength theory, a discriminant equation is established for the critical failure state of soil element in slope, and a combined failure mode of "upper and lower edge parallel slope curved surface" for soil slope is proposed, which includes three sliding regions composed of the tension zone at upper edge, the main slide zone in middle and the squeeze zone at lower edge. It is demonstrated that the failure surface morphology of the upper and lower edge sliding mass coincides with the logarithmic spiral. A new stability analysis method is established for unsaturated soil slope based on the limit equilibrium theory. The results shows that the relationships between landslide depth zw and main slide zone length L2 are better reflected using this combined failure mode of "upper and lower edge parallel slope curve". The stability of shallow soil slope decreases and tends gradually to the results of infinite slope stability with increase of the main slide zone length L2. For saturated soil slope,the effects of internal friction angle and slope angle on slope stability are very little, but the influence of cohesion is significant. For unsaturated soil slope, the slope stability is reduced apparently as cohesion and internal friction angle decreases and slope angle increases. As the soil slope is in critical state(i.e. safety factor FS=1.0), the sliding surface of potential landslide gradually migrates to the shallow layer with the increase of soil saturation. It indicates that the soil slope with rising saturation caused by rainfall is more prone to shallow failure. Compared with the traditional infinite length slope stability analysis method, for a finite length soil slope, this combined failure stability analysis method is more reasonability and accuracy because of the consideration of the mechanical effects of upper and lower edge zone.
引文
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[3]Li Tuode,Zheng Liming,Han Huizeng.Predietion and prevention of disastrous slump of soil slop in flood season[J].China Railway Science,1993,14(4):108-118.[李妥德,郑黎明,韩会增.汛期土质边坡塌方灾害的预测和预防[J].中国铁道科学,1993,14(4):108-118.]
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[8]Han Tongchun,Huang Fuming.Rainfall infiltration process and stability analysis of two-layered slope[J].Journal of Zhejiang University(Engineering Science),2012,46(1):39-45.[韩同春,黄福明.双层结构土质边坡降雨入渗过程及稳定性分析[J].浙江大学学报(工学版),2012,46(1):39-45.]
[9]Cho S E.Infiltration analysis to evaluate the surficial stability of two-layered slopes considering rainfall characteristics[J].Engineering Geology,2009,105(1/2):32-43.
[10]Dou H Q,Han T C,Gong X N,et al.Effects of the spatial variability of permeability on rainfall-induced landslides[J].Engineering Geology,2015,192:92-100.
[11]Griffiths D V,Huang J,Dewolfe G F.Numerical and analytical observations on long and infinite slopes[J].International Journal for Numerical and Analytical Methods in Geomechanics,2011,35(5):569-585.
[12]Milledge D J,Griffiths D V,Lane S N,et al.Limited on the validity of infinite length assumptions for modelling shallow landslides[J].Earth Surface Processes and Landforms,2012,37(11):1158-1166.
[13]Huang Shangyan.Stability of expensive soil subgrade[C]//Proceedings of the First National Seminar on Expansive Soil Science.Emei Mountain:Southwest Jiaotong University Press,1990.[黄尚燕.膨胀土填土路堤的稳定性[C]//全国首届膨胀土科学研讨会论文集.峨眉山:西南交通大学出版社,1990.]
[14]Chen Shanxiong,Chen Shouyi.Analysis of stability of unsaturated soil slope due to permeation of rain water[J].Rock and Soil Mechanics,2001,22(4):447-450.[陈善雄,陈守义.考虑降雨的非饱和土边坡稳定性分析方法[J].岩土力学,2001,22(4):447-450.]
[15]Liu Huaqiang,Yin Zongze.Research on analytical method of stability of expansive soil slope[J].Rock and Soil Mechanics,2010,31(5):1545-1554.[刘华强,殷宗泽.膨胀土边坡稳定分析方法研究[J].岩土力学,2010,31(5):1545-1554.]
[16]Oh W T,Vanapalli S K.Influence of rain infiltration on the stability of compacted soil slopes[J].Computers&Geotechnics,2010,37(5):649-657.
[17]Lian Jifeng,Luo Qiang,Jiang Liangwei,et al.Stability analysis of shallow soil slope under effect of rainfall infiltra-tion[J].Journal of the China Railway Sociey,2017,39(4):101 -108.[连继峰,罗强,蒋良潍,等.雨水浸润软化下路基土质边坡浅层稳定分析[J].铁道学报,2017,39(4):101-108.]
[18]Fredlund D G,Morgenstern N R,Widger R A.The shear strength of unsaturated soils[J].Canadian Geotechnical Journal,1978,15(3):313-321.
[19]Fredlund D G,Rahardjo H.Soil mechanics for unsaturated soils[J].New York:John Wiley&Sons,1993,132(3):286-321.
[20]Lu N,Godt J.Infinite slope stability under steady unsaturated seepage conditions[J].Water Resources Research,2008,44(11):2276-2283.
[21]Lu N,Likos W J.Suction stress characteristic curve for unsaturated soil[J].Journal of Geotechnical and Geoenvironmental Engineering,2006,132(2):131-142.
[22]Genuchten M T V.A closed-form equation for predicting the hydraulic conductivity of unsaturated soils[J].Soil Science Society of America Journal,1980,44(5):892-898.
[23]Lin Hongzhou,Yu Yuzheng,Li Guangxin,et al.Influence of rainfall characteristics on soil slope failure[J].Chinese Journal of Rock Mechanical and Engineering,2009,28(1):198-204.[林鸿州,于玉贞,李广信,等.降雨特性对土质边坡失稳的影响[J].岩石力学与工程学报,2009,28(1):198-204.]
[24]Cho S E.Probabilistic stability analysis of rainfall-induced landslides considering spatial variability of permeability[J].Engineering Geology,2014,171:11-20.
[25]Chen W F.Limit analysis and soil plasticity[M].Amsterdarm:Elsevier,1975.
[26]Zhang Tianbao.Overall balance method of solving circular slip surface of the earth pressure of cohesive soil[J].Journal of Hydraulic Engineering,1987,18(5):53-60.[张天宝.求解粘性土土压力的圆弧滑面整体平衡法[J].水利学报,1987,18(5):53-60.]
[2]Day R W,Axten G W.Surficial stability of compacted clay slopes[J].Journal of Geotechnical Engineering,1989,115(4):577-580.
[3]Li Tuode,Zheng Liming,Han Huizeng.Predietion and prevention of disastrous slump of soil slop in flood season[J].China Railway Science,1993,14(4):108-118.[李妥德,郑黎明,韩会增.汛期土质边坡塌方灾害的预测和预防[J].中国铁道科学,1993,14(4):108-118.]
[4]Lian Jifeng,Luo Qiang,Jiang Liangwei,et al.Shallow stability analysis of soil slopes under seepage parallel to slope surface[J].Chinese Journal of Geotechnical Engineering,2015,37(8):1440-1448.[连继峰,罗强,蒋良潍,等.顺坡渗流条件下土质边坡浅层稳定分析[J].岩土工程学报,2015,37(8):1440-1448.]
[5]Skempton A W,Delory F A.Stability of natural slopes in London clay[C]//Proceedings of the 4th International Conference on Soil Mechanics and Foundation Engineering.London,1957.
[6]Ma Shiguo,Han Tongchun,Xu Riqing.Integrated effect of intense rainfall and initial groundwater on slope stability[J].Journal of Central South University(Science and Technology),2014,45(3):803-810.[马世国,韩同春,徐日庆.强降雨和初始地下水对浅层边坡稳定性的综合影响[J].中南大学学报(自然科学版),2014,45(3):803-810.]
[7]Zhang Jie,Han Tongchun,Dou Hongqiang,et al.Stability of loss slope considering infiltration zonation[J].Journal of Central South University(Science and Technology),2014,45(12):4355-4361.[张杰,韩同春,豆红强,等.基于降雨入渗分层假定的黄土边坡稳定性分析[J].中南大学学报(自然科学版),2014,45(12):4355-4361.]
[8]Han Tongchun,Huang Fuming.Rainfall infiltration process and stability analysis of two-layered slope[J].Journal of Zhejiang University(Engineering Science),2012,46(1):39-45.[韩同春,黄福明.双层结构土质边坡降雨入渗过程及稳定性分析[J].浙江大学学报(工学版),2012,46(1):39-45.]
[9]Cho S E.Infiltration analysis to evaluate the surficial stability of two-layered slopes considering rainfall characteristics[J].Engineering Geology,2009,105(1/2):32-43.
[10]Dou H Q,Han T C,Gong X N,et al.Effects of the spatial variability of permeability on rainfall-induced landslides[J].Engineering Geology,2015,192:92-100.
[11]Griffiths D V,Huang J,Dewolfe G F.Numerical and analytical observations on long and infinite slopes[J].International Journal for Numerical and Analytical Methods in Geomechanics,2011,35(5):569-585.
[12]Milledge D J,Griffiths D V,Lane S N,et al.Limited on the validity of infinite length assumptions for modelling shallow landslides[J].Earth Surface Processes and Landforms,2012,37(11):1158-1166.
[13]Huang Shangyan.Stability of expensive soil subgrade[C]//Proceedings of the First National Seminar on Expansive Soil Science.Emei Mountain:Southwest Jiaotong University Press,1990.[黄尚燕.膨胀土填土路堤的稳定性[C]//全国首届膨胀土科学研讨会论文集.峨眉山:西南交通大学出版社,1990.]
[14]Chen Shanxiong,Chen Shouyi.Analysis of stability of unsaturated soil slope due to permeation of rain water[J].Rock and Soil Mechanics,2001,22(4):447-450.[陈善雄,陈守义.考虑降雨的非饱和土边坡稳定性分析方法[J].岩土力学,2001,22(4):447-450.]
[15]Liu Huaqiang,Yin Zongze.Research on analytical method of stability of expansive soil slope[J].Rock and Soil Mechanics,2010,31(5):1545-1554.[刘华强,殷宗泽.膨胀土边坡稳定分析方法研究[J].岩土力学,2010,31(5):1545-1554.]
[16]Oh W T,Vanapalli S K.Influence of rain infiltration on the stability of compacted soil slopes[J].Computers&Geotechnics,2010,37(5):649-657.
[17]Lian Jifeng,Luo Qiang,Jiang Liangwei,et al.Stability analysis of shallow soil slope under effect of rainfall infiltra-tion[J].Journal of the China Railway Sociey,2017,39(4):101 -108.[连继峰,罗强,蒋良潍,等.雨水浸润软化下路基土质边坡浅层稳定分析[J].铁道学报,2017,39(4):101-108.]
[18]Fredlund D G,Morgenstern N R,Widger R A.The shear strength of unsaturated soils[J].Canadian Geotechnical Journal,1978,15(3):313-321.
[19]Fredlund D G,Rahardjo H.Soil mechanics for unsaturated soils[J].New York:John Wiley&Sons,1993,132(3):286-321.
[20]Lu N,Godt J.Infinite slope stability under steady unsaturated seepage conditions[J].Water Resources Research,2008,44(11):2276-2283.
[21]Lu N,Likos W J.Suction stress characteristic curve for unsaturated soil[J].Journal of Geotechnical and Geoenvironmental Engineering,2006,132(2):131-142.
[22]Genuchten M T V.A closed-form equation for predicting the hydraulic conductivity of unsaturated soils[J].Soil Science Society of America Journal,1980,44(5):892-898.
[23]Lin Hongzhou,Yu Yuzheng,Li Guangxin,et al.Influence of rainfall characteristics on soil slope failure[J].Chinese Journal of Rock Mechanical and Engineering,2009,28(1):198-204.[林鸿州,于玉贞,李广信,等.降雨特性对土质边坡失稳的影响[J].岩石力学与工程学报,2009,28(1):198-204.]
[24]Cho S E.Probabilistic stability analysis of rainfall-induced landslides considering spatial variability of permeability[J].Engineering Geology,2014,171:11-20.
[25]Chen W F.Limit analysis and soil plasticity[M].Amsterdarm:Elsevier,1975.
[26]Zhang Tianbao.Overall balance method of solving circular slip surface of the earth pressure of cohesive soil[J].Journal of Hydraulic Engineering,1987,18(5):53-60.[张天宝.求解粘性土土压力的圆弧滑面整体平衡法[J].水利学报,1987,18(5):53-60.]
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