湘西陈溪峪滑坡变形机理及稳定性评价
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摘要
浅层滑坡在我国广泛分布,但在区域范围内分布规律性较差,且具有突发性、隐蔽性和破坏性强等特点。湘西武陵山区地质条件复杂、降雨丰沛、人类工程活动强烈,突发性地质灾害频发,尤以降雨诱发的浅层滑坡为主。文章以湘西地区慈利县陈溪峪滑坡为例,开展了降雨量、基质吸力、地下水位和地表变形等的监测;结合滑坡的现场调查及监测成果,分析滑坡的形成条件和变形机理;在此基础上,考虑基质吸力对边坡稳定性的贡献,将强度折减有限元法推广到非饱和土边坡,计算得到了不同降雨工况下滑坡稳定性。结果表明:当强降雨降落到滑坡体上时,坡内基质吸力值均迅速减小,直至一定值后(9.5 k Pa左右)不再变化;坡内地下水位受季节性降雨影响显著,短时强降雨引起地下水变化幅度不如长时间降雨对地下水位造成的影响大;陈溪峪滑坡的地质力学成因为蠕滑推移式土质滑坡,运动形式为沿基覆界面的浅层滑坡;短时强降雨是诱发滑坡变形的最关键因素。陈溪峪滑坡在持续降雨条件下的降雨量预警值约为280 mm,在短时强降雨条件下的降雨强度预警值约为240 mm/d。
Shallow landslide hazards widely occur in China.The distribution regularity of this type of landslide areas is poor,and it is characterized by suddenness,concealment and destructiveness.In the Wuling Mountains,geological conditions are complex,rainfall is abundant,human engineering activities are intense,and sudden geological disasters occur frequently,especially the shallow landslides induced by rainfall.The Chenxiyu landslide in Cili county of western Hunan is taken as an example,and monitoring of rainfall,matric suction,groundwater levels and surface deformation is carried out.Combined with field investigation and monitoring results of the landslide,the formation conditions and deformation mechanism of the landslide are carried out.By considering the contribution of matrix suction to slope stability,the strength reduction finite element method is extended to the unsaturated soil slope,and the stability of landslide stability under different rainfall conditions is calculated.The results show that when heavy rainfall falls on the landslide,the matrix suction value in the slope decreases rapidly and does not change after a certain value(about 9.5 kPa).Thegroundwater level in the slope is significantly affected by seasonal rainfall and the groundwater is caused by short-term heavy rainfall.The geomechanics of the Chenxiyu landslide is due to the creeping-type soil landslide,and the movement form is a shallow landslide along the base-covered interface.Short-term heavy rainfall is the most critical factor inducing the landslide deformation.The rainfall warning value of the Chenxiyu landslide under continuous rainfall is about 280 mm,and the warning value of rainfall intensity under short-term heavy rainfall is about 240 mm/d.
Shallow landslide hazards widely occur in China.The distribution regularity of this type of landslide areas is poor,and it is characterized by suddenness,concealment and destructiveness.In the Wuling Mountains,geological conditions are complex,rainfall is abundant,human engineering activities are intense,and sudden geological disasters occur frequently,especially the shallow landslides induced by rainfall.The Chenxiyu landslide in Cili county of western Hunan is taken as an example,and monitoring of rainfall,matric suction,groundwater levels and surface deformation is carried out.Combined with field investigation and monitoring results of the landslide,the formation conditions and deformation mechanism of the landslide are carried out.By considering the contribution of matrix suction to slope stability,the strength reduction finite element method is extended to the unsaturated soil slope,and the stability of landslide stability under different rainfall conditions is calculated.The results show that when heavy rainfall falls on the landslide,the matrix suction value in the slope decreases rapidly and does not change after a certain value(about 9.5 kPa).Thegroundwater level in the slope is significantly affected by seasonal rainfall and the groundwater is caused by short-term heavy rainfall.The geomechanics of the Chenxiyu landslide is due to the creeping-type soil landslide,and the movement form is a shallow landslide along the base-covered interface.Short-term heavy rainfall is the most critical factor inducing the landslide deformation.The rainfall warning value of the Chenxiyu landslide under continuous rainfall is about 280 mm,and the warning value of rainfall intensity under short-term heavy rainfall is about 240 mm/d.
引文
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[2]刘磊,殷坤龙,王佳佳,等.降雨影响下的区域滑坡危险性动态评价研究——以三峡库区万州主城区为例[J].岩石力学与工程学报,2016,35(3):558–569.[LIU L,YIN K L,WANG J J,et al.Study on dynamic evaluation of regional landslide hazard underthe influence of rainfall-taking Wanzhou city as an example in Three Gorges Reservoir area[J]. Chinese Journal of Rock Mechanics and Engineering, 2016, 35(3):558–569.(in Chinese)]
[3]张楠,徐永强,闫慧.岩溶山区浅层基岩滑坡失稳机理研究——以大方县金星组滑坡为例[J].水文地质工程地质,2017,44(6):142-146.[ZHANG N,XU Y Q,YAN H. A study of the instability mechanism and investigation methods of shallow bedrock landslides in karst mountain areas:taking the Jinxing landslide in Dafang County as an example[J].Hydrogeology&Engineering Geology,2017,44(6):142-146.(in Chinese)]
[4]张群,许强,甯娜.降雨条件下低缓浅层土质滑坡稳定性影响因素及耦合研究[J].水文地质工程地质,2014,41(5):90-94.[ZHANG Q,XU Q,NING N. A study of the stability influence factors and coupling for inclined-shallow soil landslides under the condition of rainfall[J]. Hydrogeology&Engineering Geology,2014,41(5):90-94.(in Chinese)]
[5]周琪龙.黄土沟壑区土壤侵蚀与浅层滑坡相关关系研究[D].兰州:兰州大学,2013.[ZHOU Q L.Study on relationshio between soil erosion and shallow landslides in loess gully region[D]. Lanzhou:Lanzhou University,2013.(in Chinese)]
[6] NG C W W, ZHAN L T, BAO C G, et al.Performance of an unsaturated expansive soil slope subjected to artificial rainfall infiltration[J].Geotechnique,2003,53(2):143-157.
[7] NG C W W,LEUNG A K. Measurements of drying and wetting permeability functions using a new stresscontrollable soil column[J]. Journal of Geotechnical and Geoenvironmental Engineering,2012,138(l):58-68.
[8] RAHARDJO H,NIO A S,ENGCHOON L,et al.Effects of groundwater table position and soil properties on stability of slope during rainfall[J].Journal of Geotechnical&Geoenvironmental Engineering,2011,136(11):1555-1564.
[9]夏蒙,王家鼎,谷天峰,等.基于TRIGRS模型的浅层黄土滑坡破坏概率评价[J].兰州大学学报(自科版),2013,49(4):453-458.[XIA M,WANG J D,GU T F, et al. Evaluation of shallow loess landslide destruction probability based on TRIGRS model[J]. Journal of Lanzhou University(Natural Sciences),2013,49(4):453-458.(in Chinese)]
[10]张茂省,李同录.黄土滑坡诱发因素及其形成机理研究[J].工程地质学报,2011,19(4):530-540.[ZHANG M S,LI T L. Triggering factors and forming mechanism of loess landslides[J]. Journal of Engineering Geology,2011,19(4):530-540.(inChinese)]
[11]周杨,刘果果,白兰英,等.降雨诱发黄土边坡失稳室内试验研究[J].武汉大学学报(工学版),2016,49(6):838-843.[ZHOU Y,LIU G G,BAI L Y,et al. Model test study of loess slope instability induced by rainfall[J]. Engineering Journal of Wuhan University,49(6):838-843.(in Chinese)]
[12]李同录,习羽,侯晓坤.水致黄土深层滑坡灾变机理[J].工程地质学报,2018,26(5):1113-1120.[LI T L,XI Y,HOU X K. Mechanism of surface water infiltration induced deep loess landslide[J].Journal of Engineering Geology,2018,26(5):1113-1120.(in Chinese)]
[13]向章波,张家铭,周晓宇,等.基于Slide的某红层路堑边坡稳定性分析[J].水文地质工程地质,2015,42(4):90-95.[XIANG Z B,ZHANG J M,ZHOU X Y,et al. The slope stability analysis of red bed based on Slide[J]. Hydrogeology&Engineering Geology,2015,42(4):90-95.(in Chinese)]
[14]李江,许强,王森,等.川东红层地区降雨入渗模式与岩质滑坡成因机制研究[J].岩石力学与工程学报,2016,(增刊2):4053-4062.[LI J,XU Q,WANG S, et al. Research on rainfall infiltration models of slopes and formation mechanism of rock landslides in red stratum in the east of Sichuan province[J]. Chinese Journal of Rock Mechanics and Engineering, 2016,(Sup2):4053-4062.(in Chinese)]
[15]刘继芝娴.万州区库岸段侏罗系红层滑坡滑带土抗剪强度参数研究[D].武汉:中国地质大学(武汉),2018.[LIU J Z X. Estimation of shear strength of slip zone solis in Middle Jurassic red beds in Wanzhou reservoir area[D]. Wuhan:China University of Geosciences(Wuhan), 2018.(in Chinese)]
[16]黄波林,陈小婷.香溪河流域白家堡滑坡变形失稳机制分析[J].岩土工程学报,2007,29(6):938-942.[HUANG B L,CHEN X T. Deformation failure mechanism of Baijiabao landslide in Xiangxi River Valley[J]. Chinese Journal of Geotechnical Engineering, 2007, 29(6):938-942.(in Chinese)]
[17]连志鹏.慈利县零阳镇陈溪峪滑坡勘察报告[R].武汉:中国地质调查局武汉地质调查中心,2016.[LIAN Z P. Investigation report of Chenxiyu landslide in Lingyang Town,Cili County[R]. Wuhan:Wuhan Geological Survey Center of China Geological Survey,2016.(in Chinese)]
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