摘要
以研究崩壁在地下水抬升与不同类型降雨联合作用下的失稳模式与渗流场特性为目标,基于野外勘查和相关物理分析获取的鄂东南崩岗区典型风化岩土体剖面各层次基本指标数据,尝试从崩壁渗流场与应力场两场耦合的角度,运用数值试验探讨单次降雨诱发下水力因素影响崩岗侵蚀的过程与机理。结果发现:长期小雨环境下,崩壁破坏方式属于崩壁中下部土层局部被淘空与砂土层上覆土体整体滑移相结合;短时强雨环境下则表现为坡面浅层(分层)流滑破坏。但无论何种降雨类型都存在一个促使崩壁砂土层被水蚀并退去后形成凹腔(龛)的降雨前期阶段,直到龛深达到一极限值,龛体积不再扩大,转为历时较短的崩壁失稳前的降雨后期阶段。强降雨入渗产生的渗流区域主要分布在崩壁浅层地表,引起浅层土体持续软化,剪应力明显增大。伴随降雨历时的延长,坡面浅土层出现暂态饱和区且湿润峰(零压面)逐渐向崩壁深处推移,地下水位线逐渐抬升并以出露泉方式对砂土层下部造成机械潜蚀。分析结果与野外观测现象较为一致。
Aiming at investigating the instability mode and dynamic response of the seepage field of the collapse wall under the combined interaction of groundwater uplift and different types of rainfall duration,on the basis of mechanical index parameters of rock and soil layers of the collapsing hill obtained from in-situ observation and relevant geotechnical physical model tests,we attempt to explore the process and mechanism of hydraulic factors affecting the collapsing gully erosion under a single rainfall from the angle of coupling seepage domain and stress field of collapse wall through performing plenty of numerical experiments.The FEM analysis results indicate that the failure mode of the collapse wall in successive light rain environment belongs to the combination of local erosion of the middle and lower soil layers of collapse wall and integral-sliding failure of the soil body above the sandy soil layer,and in shortterm heavy rain environment,the failure mode of the collapse wall is manifested by the(layered)flow sliding of the shallow slope surface.Whereas,no matter what type of rainfall,there must be an earlier stage(lasting for a long time)of precipitation that causes the sandy soil layer of the collapse wall to be eroded by water to form a concave cavity.Until the depth of the concave cavity reaches an ultimate value,the volume of concave cavity will no longer expand,and it will turn into a later stage of precipitation before the collapse wall is in critical failure status.The seepage areas generated by rainfall infiltration mainly occur in the shallow soil layers of the collapse wall,as a result,the shear strength properties of the shallow soil unceasingly weaken and the maximum shear stress increases obviously.With the prolongation of rainfall duration,a transient saturated zone appears in the surface soil layer of the catchment slope and the wetting peak(zero pressure surface)gradually moves towards the deep strata of the collapsing gully wall.The groundwater level line gradually rises and thus causes pipe erosion to the bottom of the sandy soil layer by(downward)outcropping springs.The analysis results are in good agreement with the field observation phenomena.
作者
马鹏飞
夏栋
许文年
杨威
罗婷
MA Pengfei;XIA Dong;XU Wennian;YANG Wei;LUO Ting(College of Civil Engineering&Architecture,China Three Gorges University,Yichang 443002,China;Key Laboratory of Disaster Prevention and Mitigation,Hubei Province(China Three Gorges University),Yichang 443002,China;Collaborative Innovation Center for Geo-hazards and Eco-environment in Three Gorges Area,Hubei Province,Yichang 443002,China;College of Hydraulic&Environmental Engineering,China Three Gorges University,Yichang 443002,China)
出处
《水利水运工程学报》
CSCD
北大核心
2020年第2期46-57,共12页
Hydro-Science and Engineering
基金
国家自然科学基金青年基金资助项目(41601287)
长江科学院开放研究基金项目(CKWV2016387/KY)。
关键词
崩岗崩壁
降雨入渗
失稳模式
ABAQUS耦合分析
渗流场
collapsing gully wall/collapse wall(caved wall)
rainfall infiltration
failure mode
ABAQUS coupling analysis
seepage field
