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基于龛深及其上覆土层稳定性的崩壁崩坍形成条件研究
马鹏飞1,2, 许文年1,2, 夏栋2, 夏露2, 严雨洁3,2, 邓羽松4
1.三峡大学 三峡库区 地质灾害教育部重点实验室, 湖北 宜昌 443002;2.三峡大学 三峡地区地质灾害与生态环境湖北省协同创新中心, 湖北 宜昌 443002;3.三峡大学 生物与制药学院, 湖北 宜昌 443002;4.华中农业大学 资源与环境学院, 湖北 武汉 430070
摘要:
[目的] 研究龛的形态与崩岗发育及崩岗侵蚀之间的关系,为崩岗治理规划、崩岗防治工程技术的改进提供一定的数据参考。[方法] 以湖北省通城县典型崩岗区崩壁土体为对象,构建崩壁连同龛二维数值模型,结合物理试验标定模拟所用的崩壁各土层基本特性参数。引入符合龛演化过程的"单元生死法",对引起天然状态下的崩壁明显崩塌(坍)所需的龛深最小(临界)值进行定量分析,并借助正交有限单元试验(ABAQUS)对诱发崩壁崩坍的因素进行主次评价,之后选取若干未降雨条件下不导致崩壁崩坍的龛深值,联合高阶插值与强度折减法导出了这些龛深与触发龛上覆红黏土体崩坍所需的极限饱和度之间的定量方程式。[结果] 龛深与崩壁的稳定性系数呈显著线性负相关;龛上覆土层的含水量是促使崩壁发生崩坍的最重要因子,坡度对崩壁稳定性影响较大,而龛相对高度及崩壁高度均对崩壁的稳定性影响极小。[结论] 崩壁崩坍的可能性在很大程度上受控于龛的凹陷深度和龛上覆红黏土体的含水状态,在崩岗侵蚀综合治理时需加以考虑。
关键词:  崩岗崩壁    凹陷深度  土壤含水量  正交试验  稳定性  治理措施  崩坍
DOI:10.13961/j.cnki.stbctb.2019.05.045
分类号:S157.1;TU457;O242.2
基金项目:国家自然科学基金项目“花岗岩风化土体微形态特征及其与崩岗发育的关系”(41601287),“花岗岩风化岩土体特性的地带性分异及崩岗形成机理研究”(41630858);国家重点研发计划项目“西南高山亚高山区工程创面生态修复关键材料制备与优化应用技术”之专题“工程创面生态修复防冲刷技术”(2017YFC0504902-04)
A Study on Formation Conditions of Collapse for Collapsed Walls in Consideration of Stability of Red Clay Weathering Soil Layers and Depth of Concave Cavities
Ma Pengfei1,2, Xu Wennian1,2, Xia Dong2, Xia Lu2, Yan Yujie3,2, Deng Yusong4
1.Key Laboratory of Geological Hazards in Three Gorges Reservoir Area, Ministry of Education, China Three Gorges University, Yichang, Hubei 443002, China;2.Collaborative Innovation Center for Geo-hazards and Eco-environment in Three Gorges Area, China Three Gorges University, Yichang, Hubei 443002, China;3.College of Biological and Pharmaceutical Sciences, China Three Gorges University, Yichang, Hubei 443002, China;4.College of Resources and Environment, Huazhong Agricultural University, Wuhan, Hubei 430070, China
Abstract:
[Objective] This study aimed to an investigation into the relationship between the dimensions of the concave cavity and the development of collapsed gullies and collapsed gully erosion in order to provide a scientific basis for the prevention of collapse and the engineering treatment of collapsed gullies.[Methods] The study focused on the collapse mound profile in Tongcheng County in Hubei Province. We calibrated the basic calculation parameters for each soil layer of the collapsed wall, through a series of indoor experiments and actual collapse conditions, introducing the "unit life and death method," which modeled the evolution of the concave cavity, and applied analytical methods to the stability of the caved wall. Initially, 2D finite (FE) numerical models of the collapsed wall-concave cavity were established, based on the ABAQUS software platform, which can be applied to quantitatively analyze the critical splash erosion pit depth value (D0) required for triggering the collapse of the wall under natural conditions. The sensitivity of the main factors that lead to the failure of the collapsed wall was evaluated by means of the orthogonal experimental design; furthermore, this article selected a series of depths of the concave cavity (less than D0). This study elucidated the quantitative relation between depths of concave cavity and the saturation threshold value that caused the collapse of the overlying red clay layer.[Results] The safety factor of the collapsed gully wall decreased linearly as the depth of the deep-cut hole increased. The water content of the red clay layer overlying the concave cavity was the most vital factor influencing collapse. In addition, the gradient of the collapsed wall had a significant impact on the stability of the collapsed wall. The relative depth of the concave cavity and the height of collapsed gully wall had little effect on the stability of the collapsed gully wall.[Conclusion] The possibility of collapse of gully walls depends largely on the size of the deep-cut hole and the moisture content of the soil above the concave cavity. Future research should apply this understanding to the prevention of collapse and to the engineering treatment of collapsed gullies.
Key words:  collapsed gully wall  concave cavity  erosion depth hollowed out by water flow  soil water content  orthogonal test  stability  control measures  collapse