非饱和地震滑坡堆积体降雨破坏水-力耦合行为试验
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摘要
降雨滑坡的水-力耦合过程和机制研究是开展准确预测预报的基础和前提。选取典型滑坡模型,采用足尺人工降雨模型试验模拟了典型砾石土滑坡堆积体破坏过程,并采用Brooks-Corey(BC)和Van Genuchten(VG)模型分别建立了降雨入渗吸湿过程的土-水特征曲线,再通过一维非饱和无限边坡稳定性分析模型对滑坡开展应力状态和稳定性分析,揭示了斜坡破坏过程是优先流和基质流的双渗流场共同作用的结果,而VG模型适用于吸湿条件下宽级配砾石土优先流的土-水特征曲线的重构;稳定性计算和试验过程的对比分析表明,试验中斜坡的变形破坏过程中观测到的含水率、基质吸力和地表倾斜角度的变化过程与计算的吸力应力、稳定系数的演进过程有显著的对应关系。通过试验还揭示了非饱和滑坡堆积体渗流潜蚀现象,定量分析了细颗粒迁移程度。基于物理模型试验,揭示了降雨激发条件下滑坡堆积体形成优先流作用的土-水特征曲线和变形破坏的水力耦合过程,可为地震滑坡堆积体非饱和失稳的预测预警提供参考和基础。
A profound understanding of hydro-mechanical coupling process in rainfall-induced landslides and its formation mechanism are prerequisites for the accurate early warning. In this study, a typical landslide in Wenchuan earthquake region is selected for a series of full-scale artificial rainfall tests, to simulate failure progress on gravelly soil slope of landslide deposit. Two classical soil-water characteristic curve(SWCC) models, Brooks-Corey(BC) and Van Genuchten(VG) model, are used to establish the SWCC during rainfall infiltration. Then, the stress state and stability of slope are analyzed by one-dimensional variably saturated infinite slope model. The results reveal that the slope failure is the consequence of dual-permeability interaction between the preferential flow and the matrix flow. The VG model is capable of fitting SWCC of wide-graded gravelly soil during wetting process for preferential flow. Comparison between stability analysis and observation indicates that changes on volumetric water content,matric suction and surface inclination are consistent with calculated suction stress and safety factor. Finally, the seepage erosion in unsaturated slope is proved by the tests, and the migration of fine particles is statistically analyzed. Based on the physical model test,this study reveals the coupling process of soil-water characteristic curves and slope failure with the influence of preferential flow under rainfall conditions, which can provide reference and basis for the prediction and early warning of unsaturated slope instability.
A profound understanding of hydro-mechanical coupling process in rainfall-induced landslides and its formation mechanism are prerequisites for the accurate early warning. In this study, a typical landslide in Wenchuan earthquake region is selected for a series of full-scale artificial rainfall tests, to simulate failure progress on gravelly soil slope of landslide deposit. Two classical soil-water characteristic curve(SWCC) models, Brooks-Corey(BC) and Van Genuchten(VG) model, are used to establish the SWCC during rainfall infiltration. Then, the stress state and stability of slope are analyzed by one-dimensional variably saturated infinite slope model. The results reveal that the slope failure is the consequence of dual-permeability interaction between the preferential flow and the matrix flow. The VG model is capable of fitting SWCC of wide-graded gravelly soil during wetting process for preferential flow. Comparison between stability analysis and observation indicates that changes on volumetric water content,matric suction and surface inclination are consistent with calculated suction stress and safety factor. Finally, the seepage erosion in unsaturated slope is proved by the tests, and the migration of fine particles is statistically analyzed. Based on the physical model test,this study reveals the coupling process of soil-water characteristic curves and slope failure with the influence of preferential flow under rainfall conditions, which can provide reference and basis for the prediction and early warning of unsaturated slope instability.
引文
[1]黄润秋.汶川地震地质灾害后效应分析[J].工程地质学报,2011,19(2):145-151.HUANG Run-qiu.After effect of geohazards induced by the Wenchuan earthquake[J].Journal of Engineering Geology,2011,19(2):145-151.
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[4]KHATTAK G A,OWEN L A,KAMP U,et al.Evolution of earthquake-triggered landslides in the Kashmir Himalaya,northern Pakistan[J].Geomorphology,2010,115(1-2):102-108.
[5]SABA S B,VAN DER MEIJDE M,VAN DER WERFF H.Spatiotemporal landslide detection for the 2005 Kashmir earthquake region[J].Geomorphology,2010,124(1-2):17-25.
[6]TANG C,ZHU J,LI W L,et al.Rainfall-triggered debris flows following the Wenchuan earthquake[J].Bulletin of Engineering Geology and the Environment,2009,68(2):187-194.
[7]TANG C,ZHU J,QI X,et al.Landslides induced by the Wenchuan earthquake and the subsequent strong rainfall event:a case study in the Beichuan area of China[J].Engineering Geology,2011,122:22-33.
[8]YANG Z,QIAO J,UCHIMURA T,et al.Unsaturated hydro-mechanical behaviour of rainfall-induced mass remobilization in post-earthquake landslides[J].Engineering Geology,2017,222:102-110.
[9]贺可强,周敦云,王思敬.降雨型堆积层滑坡的加卸载响应比特征及其预测作用与意义[J].岩石力学与工程学报,2004,23(16):2665-2665.HE Ke-qiang,ZHOU Dun-yun,WANG Si-jing.Features of load-unload response ratio and its significance in predication of colluvial landslide induced by rainfall[J].Chinese Journal of Rock Mechanics and Engineering,2004,23(16):2665-2665.
[10]BUCKINGHAM E.Studies on the movement of soil moisture[J].U.S.Department of Agriculture,Bureau of Soils Bulletin,1907,38:28-61.
[11]GARDNER W,WIDTSOE J A.The movement of soil moisture[J].Soil Science,1921,6(3):215-232.
[12]RICHARDS L A.The usefulness of capillary potential of soil moisture and plant investigators[J].Journal of Agricultural Research,1928,37(12):719-742.
[13]KRAHN J,FREDLUND D G.On total matric and osmotic suction[J].Soil Science,1972,114(5):339-348.
[14]FREDLUND D G,RAHARDJO H.Determination of the shear strength parameters of an unsaturated soil using the direct shear test[J].Canadian Geotechnical Journal,1988,25:500-510.
[15]LU N,LIKOS W J.Unsaturated soil mechanics[M].Hoboken:John Wiley&Sons,Inc.,2004.
[16]LU N,W J L.Suction stress characteristic curve for unsaturated soil[J].Journal of Geotechnical and Geoenvironmental Engineering,2006,132:131-142.
[17]GRIFFITHS D V,LU N.Unsaturated slope stability analysis with steady infiltration or evaporation using elasto-plastic finite elements[J].International Journal for Numerical and Analytical Methods in Geomechanics,2005,29(3):249-267.
[18]LU N,GODT J.Infinite slope stability under steady unsaturated seepage conditions[J].Water Resources Research,2008,44(11):2276-2283.
[19]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.LIN Hung-chou,YU Yu-zhen,LI Guang-xin,et al.Influence of rainfall characteristics on soil slope failure[J].Chinese Journal of Rock Mechanics and Engineering,2009,28(1):198-204.
[20]左自波,张璐璐,王建华.降雨触发不同级配堆积体滑坡模型试验研究[J].岩土工程学报,2015,37(7):1319-1327.ZUO Zi-bo,ZHANG Lu-lu,WANG Jian-hua.Model tests on rainfall-induced colluvium landslides:effects of particle-size distribution[J].Chinese Journal of Geotechnical Engineering,2015,37(7):1319-1327.
[21]郑亚飞,张璐璐,张洁,等.基于时变监测数据的降雨滑坡多目标随机反分析[J].岩土力学,2017,38(11):3371-3377.ZHENG Ya-fei,ZHANG Lu-lu,ZHANG Jie,et al.Multi-objective probabilistic inverse analysis of rainfall-induced landslide based on time-varied data[J].Rock and Soil Mechanics,2017,38(11):3371-3377.
[22]赵建军,余建乐,解明礼,等.降雨诱发填方路堤边坡变形机制物理模拟研究[J].岩土力学,2018,39(8):2933-2940.ZHAO Jian-jun,YU Jian-le,XIE Ming-li,et al.Physical model studies on fill embankment slope deformation mechanism under rainfall condition[J].Rock and Soil Mechanics,2018,39(8):2933-2940.
[23]IVERSON R M,REID M E,LAHUSEN R G.Debris-flow mobilization from landslides[J].Earth Planet Science,1997,25:85-138.
[24]WANG G,SASSA K.Factors affecting rainfall-induced flowslides in laboratory flume tests[J].Géotechnique,2001,51(7):587-599.
[25]OKURA Y,KITAHARA H,OCHIAI H,et al.Landslide fluidization process by flume experiments[J].Engineering Geology,2002,66(1):65-78.
[26]ORENSE P R,SHIMOMA S,MAEDA K,et al.Instrumented model slope failure due to water seepage[J].Journal of Natural Disaster Science,2004,26(1):15-26.
[27]TAKE W A,BOLTON M D,WONG P C P,et al.Evaluation of landslide triggering mechanisms in model fill slopes[J].Landslides,2004,1(3):173-184.
[28]LOUREN?O S D N,SASSA K,FUKUOKA H.Failure process and hydrologic response of a two layer physical model:implications for rainfall-induced landslides[J].Geomorphology,2006,73(1-2):115-130.
[29]LU N,GODT J W.Hillslope hydrology and stability[M].New York:Cambridge University Press,2013.
[30]YANG Z,SHAO W,QIAO J,et al.A multi-source early warning system of MEMS based wireless monitoring for rainfall-induced landslides[J].Applied Sciences,2017,7(12):1234-1245.
[31]BROOKS R H,COREY A T.Hydraulic properties of porous media[D].Fort Collins:Colorado State University,1964:1-27.
[32]VAN GENUCHTEN M T.A closed-form equation for predicting the hydraulic conductivity of unsaturated soils[J].Soil Science Society of America Journal,1980,44(44):892-898.
[33]BAUM R L,GODT J W,SAVAGE W Z.Estimating the timing and location of shallow rainfall-induced landslides using a model for transient,unsaturated infiltration[J].Journal of Geophysical Research Earth Surface,2013,118(3):1999-1999.
[34]LU N,LIKOS W J,韦昌富.非饱和土力学[M].北京:高等教育出版社,2012.LU N,LIKOS W J,WEI Chang-fu.Unsaturated soil mechanics[M].Beijing:Higher Education Press,2012.
[35]LEONG E C,RAHARDJO H.Review of soil-water characteristic curve equations[J].Journal of Geotechnical&Geoenvironmental Engineering,1997,123(12):1106-1117.
[36]LEI X Q,YANG Z J,HE S M,et al.Numerical investigation of rainfall-induced fines migration and its influences on slope stability[J].Acta Geotechnica,2017,12(6):1431-1446.
[37]HORTON R E.The role of infiltration in the hydrologic cycle[J].Transactions of American Geophysical Union,1933,14:446-460.
[38]CUI Y F,ZHOU X J,GUO C X.Experimental study on the moving characteristics of fine grains in wide grading unconsolidated soil under heavy rainfall[J].Journal of Mountain Science,2017,14(3):417-431.
[39]周小军.宽级配砾石土强度、渗透特性与细观结构研究[D].成都:中国科学院水利部成都山地灾害与环境研究所,2012.ZHOU Xiao-Jun.Study on strength and permeability characteristics and meso-structure of wide-grading gravelly soil in triggering area of debris flow[D].Chengdu:Institute of Mountain Hazards and Environment,Chinese Academy of Sciences,2012.
[40]LEI X Q,YANG Z J,HE S M,et al.Hydro-mechanical analysis of rainfall-induced fines migration process within unsaturated soils[J].Journal of Mountain Science,2017,14(12):2603-2619.
[2]LIN C W,LIU S H,LEE S Y,et al.Impacts of the Chi-Chi earthquake on subsequent rainfall-induced landslides in central Taiwan[J].Engineering Geology,2006,86(2-3):87-101.
[3]KOI T,HOTTA N,ISHIGAKI I,et al.Prolonged impact of earthquake-induced landslides on sediment yield in a mountain watershed:the Tanzawa region,Japan[J].Geomorphology,2008,101(4):692-702.
[4]KHATTAK G A,OWEN L A,KAMP U,et al.Evolution of earthquake-triggered landslides in the Kashmir Himalaya,northern Pakistan[J].Geomorphology,2010,115(1-2):102-108.
[5]SABA S B,VAN DER MEIJDE M,VAN DER WERFF H.Spatiotemporal landslide detection for the 2005 Kashmir earthquake region[J].Geomorphology,2010,124(1-2):17-25.
[6]TANG C,ZHU J,LI W L,et al.Rainfall-triggered debris flows following the Wenchuan earthquake[J].Bulletin of Engineering Geology and the Environment,2009,68(2):187-194.
[7]TANG C,ZHU J,QI X,et al.Landslides induced by the Wenchuan earthquake and the subsequent strong rainfall event:a case study in the Beichuan area of China[J].Engineering Geology,2011,122:22-33.
[8]YANG Z,QIAO J,UCHIMURA T,et al.Unsaturated hydro-mechanical behaviour of rainfall-induced mass remobilization in post-earthquake landslides[J].Engineering Geology,2017,222:102-110.
[9]贺可强,周敦云,王思敬.降雨型堆积层滑坡的加卸载响应比特征及其预测作用与意义[J].岩石力学与工程学报,2004,23(16):2665-2665.HE Ke-qiang,ZHOU Dun-yun,WANG Si-jing.Features of load-unload response ratio and its significance in predication of colluvial landslide induced by rainfall[J].Chinese Journal of Rock Mechanics and Engineering,2004,23(16):2665-2665.
[10]BUCKINGHAM E.Studies on the movement of soil moisture[J].U.S.Department of Agriculture,Bureau of Soils Bulletin,1907,38:28-61.
[11]GARDNER W,WIDTSOE J A.The movement of soil moisture[J].Soil Science,1921,6(3):215-232.
[12]RICHARDS L A.The usefulness of capillary potential of soil moisture and plant investigators[J].Journal of Agricultural Research,1928,37(12):719-742.
[13]KRAHN J,FREDLUND D G.On total matric and osmotic suction[J].Soil Science,1972,114(5):339-348.
[14]FREDLUND D G,RAHARDJO H.Determination of the shear strength parameters of an unsaturated soil using the direct shear test[J].Canadian Geotechnical Journal,1988,25:500-510.
[15]LU N,LIKOS W J.Unsaturated soil mechanics[M].Hoboken:John Wiley&Sons,Inc.,2004.
[16]LU N,W J L.Suction stress characteristic curve for unsaturated soil[J].Journal of Geotechnical and Geoenvironmental Engineering,2006,132:131-142.
[17]GRIFFITHS D V,LU N.Unsaturated slope stability analysis with steady infiltration or evaporation using elasto-plastic finite elements[J].International Journal for Numerical and Analytical Methods in Geomechanics,2005,29(3):249-267.
[18]LU N,GODT J.Infinite slope stability under steady unsaturated seepage conditions[J].Water Resources Research,2008,44(11):2276-2283.
[19]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.LIN Hung-chou,YU Yu-zhen,LI Guang-xin,et al.Influence of rainfall characteristics on soil slope failure[J].Chinese Journal of Rock Mechanics and Engineering,2009,28(1):198-204.
[20]左自波,张璐璐,王建华.降雨触发不同级配堆积体滑坡模型试验研究[J].岩土工程学报,2015,37(7):1319-1327.ZUO Zi-bo,ZHANG Lu-lu,WANG Jian-hua.Model tests on rainfall-induced colluvium landslides:effects of particle-size distribution[J].Chinese Journal of Geotechnical Engineering,2015,37(7):1319-1327.
[21]郑亚飞,张璐璐,张洁,等.基于时变监测数据的降雨滑坡多目标随机反分析[J].岩土力学,2017,38(11):3371-3377.ZHENG Ya-fei,ZHANG Lu-lu,ZHANG Jie,et al.Multi-objective probabilistic inverse analysis of rainfall-induced landslide based on time-varied data[J].Rock and Soil Mechanics,2017,38(11):3371-3377.
[22]赵建军,余建乐,解明礼,等.降雨诱发填方路堤边坡变形机制物理模拟研究[J].岩土力学,2018,39(8):2933-2940.ZHAO Jian-jun,YU Jian-le,XIE Ming-li,et al.Physical model studies on fill embankment slope deformation mechanism under rainfall condition[J].Rock and Soil Mechanics,2018,39(8):2933-2940.
[23]IVERSON R M,REID M E,LAHUSEN R G.Debris-flow mobilization from landslides[J].Earth Planet Science,1997,25:85-138.
[24]WANG G,SASSA K.Factors affecting rainfall-induced flowslides in laboratory flume tests[J].Géotechnique,2001,51(7):587-599.
[25]OKURA Y,KITAHARA H,OCHIAI H,et al.Landslide fluidization process by flume experiments[J].Engineering Geology,2002,66(1):65-78.
[26]ORENSE P R,SHIMOMA S,MAEDA K,et al.Instrumented model slope failure due to water seepage[J].Journal of Natural Disaster Science,2004,26(1):15-26.
[27]TAKE W A,BOLTON M D,WONG P C P,et al.Evaluation of landslide triggering mechanisms in model fill slopes[J].Landslides,2004,1(3):173-184.
[28]LOUREN?O S D N,SASSA K,FUKUOKA H.Failure process and hydrologic response of a two layer physical model:implications for rainfall-induced landslides[J].Geomorphology,2006,73(1-2):115-130.
[29]LU N,GODT J W.Hillslope hydrology and stability[M].New York:Cambridge University Press,2013.
[30]YANG Z,SHAO W,QIAO J,et al.A multi-source early warning system of MEMS based wireless monitoring for rainfall-induced landslides[J].Applied Sciences,2017,7(12):1234-1245.
[31]BROOKS R H,COREY A T.Hydraulic properties of porous media[D].Fort Collins:Colorado State University,1964:1-27.
[32]VAN GENUCHTEN M T.A closed-form equation for predicting the hydraulic conductivity of unsaturated soils[J].Soil Science Society of America Journal,1980,44(44):892-898.
[33]BAUM R L,GODT J W,SAVAGE W Z.Estimating the timing and location of shallow rainfall-induced landslides using a model for transient,unsaturated infiltration[J].Journal of Geophysical Research Earth Surface,2013,118(3):1999-1999.
[34]LU N,LIKOS W J,韦昌富.非饱和土力学[M].北京:高等教育出版社,2012.LU N,LIKOS W J,WEI Chang-fu.Unsaturated soil mechanics[M].Beijing:Higher Education Press,2012.
[35]LEONG E C,RAHARDJO H.Review of soil-water characteristic curve equations[J].Journal of Geotechnical&Geoenvironmental Engineering,1997,123(12):1106-1117.
[36]LEI X Q,YANG Z J,HE S M,et al.Numerical investigation of rainfall-induced fines migration and its influences on slope stability[J].Acta Geotechnica,2017,12(6):1431-1446.
[37]HORTON R E.The role of infiltration in the hydrologic cycle[J].Transactions of American Geophysical Union,1933,14:446-460.
[38]CUI Y F,ZHOU X J,GUO C X.Experimental study on the moving characteristics of fine grains in wide grading unconsolidated soil under heavy rainfall[J].Journal of Mountain Science,2017,14(3):417-431.
[39]周小军.宽级配砾石土强度、渗透特性与细观结构研究[D].成都:中国科学院水利部成都山地灾害与环境研究所,2012.ZHOU Xiao-Jun.Study on strength and permeability characteristics and meso-structure of wide-grading gravelly soil in triggering area of debris flow[D].Chengdu:Institute of Mountain Hazards and Environment,Chinese Academy of Sciences,2012.
[40]LEI X Q,YANG Z J,HE S M,et al.Hydro-mechanical analysis of rainfall-induced fines migration process within unsaturated soils[J].Journal of Mountain Science,2017,14(12):2603-2619.