| 摘要: |
| 崩岗作为我国南方厚层花岗岩地区危害最严重的土壤侵蚀类型之一,它是一种重力和水力交互作用下的综合侵蚀形式。崩岗壁是崩岗侵蚀的主体,降雨和地表径流对土壤的溅蚀以及随后岩土体在自身重力荷载下的崩塌将导致崩壁不断后退,进一步影响并促进崩岗的形成乃至演变。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域特性为目标,基于野外观测和相关物理试验获取的崩岗岩土层强度指标数据,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条件下水力因素影响崩岗侵蚀的过程与机理。分析发现：长期小雨环境下崩壁破坏方式属于中下部土层局部被淘空与整体滑移相结合,短时强雨环境下则表现为坡面浅层流滑破坏,但无论何种降雨类型都必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,龛的体积不再扩大,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,引起浅层土体持续软化,剪应力明显增大。伴随着降雨历时的延长,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的方式对砂土层下部造成潜蚀。成果与野外观测现象较为一致,可为崩壁安全预警理念提供新思路,即对每一个肉眼可识别的龛进行集中处理。 |
| 关键词: 崩岗崩壁 降雨入渗 地下水位 失稳模式 ABAQUS耦合分析 侵蚀龛 渗流场 鄂东南 |
| DOI： |
| 分类号:P642;TB115 |
| 基金项目: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(CKWV2016387/KY) |
|
| Application of ABAQUS Program in Analysis for Collapsing Gully Erosion Function in Southeastern Hubei Considering the Conditions of Rainfall |
|
MA PENG FEI1,2, XIA DONG, XU WEN NIAN1,2, yang wei3,4, LUO TING5
|
|
1.School of Civil Engineering &2.Architecture，China Three Gorges University;3.School of Hydraulic &4.Environmental Engineering，China Three Gorges University;5.Hubei Collaborative Innovation Center for Geo-hazards and Eco-environment in Three Gorges Area
|
| Abstract: |
| As one of the most seriously soil erosion disasters in the weathered area of thick granite in southern China,collapsing gully is a compound erosion form characterized by both hydraulic erosion and gravity erosion. Collapsing gully wall is one of significant component of collapsing hill,which is of great vital to the occurrence of Benggang erosion phenomenon. The foregoing water infiltration as well as surface runoff softened soil strength of collapsing gully wall,after that,collapse of the red clay soil mass above the hollow cavity under its self-gravity will directly cause the caved wall to fall back continuously,which further promoting the formation and progressive evolution of the Benggang topography. In this research,in the aim of investigating the instability mode and dynamic response of the seepage field of collapsed wall under the interaction of groundwater and different types of rainfall duration,on the basis of mechanical index parameters of rock and soil layers of collapsing hills obtained by in-situ observation and relevant geotechnical tests,we harbour the ongoing endeavor towards considering the coupling effect of unsaturated seepage domain and stress field of collapsed wall,the mechanism of hydraulic factors contributing to Benggang erosion during single rainfall had been emphatically discussed through performing plenty of numerical experiments. The FEM analysis results indicated that:under the condition of successive low-intensity rainfall,the middle and upper part of sandy soil layer was emptied by water flow to form a deep-cut hole which also known as concave cavity,and subsequently the soil body above the concave cavity will occur deep integral slip failure；while in short-term heavy rainfall environment,the failure form of collapsed wall appeared as shallow soil layered flowing. Whereas,no matter what type of rainfall it belongs to,there must be an earlier stage(lasting for a long time) of precipitation that facilitating the appearance of the splash erosion pit owing to the sand layer eroded by torrent and then retrogress,which is precisely the prerequisites for the collapse of caved wall. Until the erosion depth of concave cavity reaches a ultimate value,the rainfall process turned into a later stage at once,during this period,the collapse of the wall would going to be in critical failure status. The seepage areas generated by rainfall infiltration mainly occurs in the shallow soil layers of the caved wall,as a result,the shear strength properties of shallow soil unceasingly weakened and the maximum shear stress increased obviously. With the prolongation of rainfall duration,transient saturated zone appears on the surface soil of catchment slope and the wetting peak gradually moves towards the deep stratal of the collapsing gully wall,the groundwater diving line gradually rises and thus causes pipe erosion to the bottom of the sandy soil layer in the way of downward springs. The computed achievements in this paper were compared with the phenomena observed in practice to verify its rationality,which can be applied as a scientific basis for providing an unconventional idea of the safety forewarning concept of caved wall,that is to say,centralized management of each identifiable hollowed cavities. |
| Key words: collapsing gully wall(caved wall) rainfall infiltration groundwater level failure type ABAQUS coupling analysis deep-cut hole(concave cavity) seepage field Southeastern Hubei |
