| 摘要: |
| 黄土是具有“水敏性”的特殊土，水是诱发黄土滑坡最积极的因素，黄土水敏性的力学机制及致滑机理已成为黄土地区生态文明建设中迫切需要解决的重大基础问题。本文在搜集大量文献的基础上，将黄土水敏性及水致黄土滑坡研究现状按照黄土水敏性、考虑优势通道的黄土斜坡水分运移规律和刻画方法、水致黄土滑坡失稳力学机制、基于水的黄土滑坡防控关键技术共四方面内容加以总结归纳。建议明确黄土水敏性的概念和内容，以黄土水敏性力学本质为突破口，研究建立基于吸应力理论的黄土水敏性参数和指标体系，开展考虑优势入渗的黄土斜坡稳定性有限元分析，并建立一套基于水的水致黄土滑坡风险防控关键技术体系。 |
| 关键词: 黄土 水敏性 黄土滑坡 研究现状 展望 |
| DOI：10.7515/JEE201604001 |
| CSTR：32259.14.JEE201604001 |
| 分类号: |
| 基金项目:国家自然科学基金项目（41530640）；中国地质调查局地质调查子项目（12120114025701） |
| 英文基金项目:National Natural Science Foundation of China (41530640); Geological Survey Project of China Geolgocial Survey (12120114025701) |
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| Advances and prospects of water sensitivity of loess and the induced loess landslides |
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ZHANG Maosheng, HU Wei, SUN Pingping, WANG Xuelian1,2,3
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1. Key Laboratory for Geo-hazard in Loess Area, Ministry of Land and Resources, Xi’an 710054, China;2. Xi’an Center of China Geological Survey, Xi’an 710054, China;3. Chang’an University, Xi’an 710064, China
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| Abstract: |
| Background, aim, and scope Loess is a typical type of soil with high water sensitivity. In the early age of engineering practices in loess areas, however, water sensitivity was unsuitably replaced by the concept “collapsibility”, which shrinks the special features of deformation and strength of loess after interaction with water. Moreover, water is one of the most active factors in inducing loess landslides. The recent outbursting hazards in Tianshui and Yan’an reveal the severe mitigatioin problems due to shortage of the knowledge of loess water sensitivity. Materials and methods In this study, we reviewed the achievements of studies on water sensitivity of loess and related topics on water-induced loess landslides in four aspects and bring out questions to be solved in future studies. Results Firstly, on the aspect of study on water sensitivity of loess, the angels can be summarized in three groups, including physical microstructure of loess, physico-chemical interaction between soil and water, as well as macroscopic mechanical properties. Researchers across the globe have studied the microstructure of loess mostly via SEM means, most of which were conducted towards collapsing behavior of loess, while seldom studied the changes of microstures under other water sensitive behaviors of loess. In terms of methodology, all of them were done via SEM, which is limited by both the sampling location and human experience. Hence, both the representativeness and reliability are greatly reduced. Furthermore, due to low resolution, traditional CT scanning technique is only able to observe macroscopic cracks while incapable of studying particle and pore scale. Some practice proved that Xray CT scanning capable of constructing three-dimensional micro-model of loess is a worthy trend. The major view about physico-chemical interaction between loess and water is that water dissolves soluble salt in loess, triggering compositional and structural changes and consequently, mechanical property changes. Concerning macroscopic mechanical properties of water sensitivity of loess, it is deemed that suction-stress defined unsaturated soil mechanics theory is a powerful theoretical tool. Secondly, on the aspect of water flow laws on the slopes due to advantageous channels, it is demonstrated to be the dominating mode of infiltration in loess region. Since the groundbreaking work by Beven and Germann in 1982, researchers have conducted multi-means of studies on advantageous flow, ranging from theoretical model to numerical analysis, to in-situ monitoring, to laboratory model tests. The theoretical model means has the problem of acquiring acurate model parameters, as well as lacking solid consideration of the random distribution of advantageous channels, leading to inacurate calculation. Physical model is the major means of study. Compared with laboratory model, the in-situ test is more favorable due to its straightforwardness. Although numerous studies already exist, more effort needs to be paid especially for its fundamental influence on water-induced loess landslides. Thirdly, the water-induced loess landslide is the major type of disaster in recent years due to water sensitivity of loess. Whatever the origin of water, the core of the study focuses on the responses of shear strength parameters and pore water pressure due to water impact, as well as the overall action on slope instability. Moreover, investigations after lots of loess landslides have revealed the fact that sliding bodies and sliding planes were partially saturated, indicating the urge of mechnical mechanism study of loess landslides from the unsaturated soil mechanics angle. Fourthly, the mitigation measures of water-induced loess landslides should be decided based on the type of water. For precipitation-induced landslides, the most widespread way is to forecast potential landslides through establishing the statistical relationship between precipitation and landslide displacement or probability. The problem of uncertain thredshold of precipitation for a particular region still remains. To overcome it, some researchers recommended that observation of the intrinsic factors such as changes of seepage and stress fields should replace the conventional method. For irrigation-induced landslides, the key is to effectively control the groundwater table. The problem relies on lacking of monitoring and experimental data. For loess landslides due to impoundment of water, the trend is to carry out landslide risk mangement based on reservoir water table. Discussion To summarize, three fundamental problems remain. The mechanical mechanism of water sensitivity of loess is still vague, leading to lacking theoretical support for the mechanism of water-induced loess landslides. Studies on the mechanism and depicting methodology of water influx, rapid infiltration and diffusion under complex topographical conditions are deficient. Also, the risk mitigation measures of water-induced loess landslides need to be further studied. Conclusions Therefore, it is urgent to discuss the definite concept and content of water sensitivity of loess, which is fundamental for discussioin of mechanism of water-induced loess landslides and related mitigation measures. Recommendations and perspectives It is recommended that suction stress theory be utilized to characterize water sensitivity of loess. Also, quantitative depictions of water influx on the slope surface and rapid infiltration and diffusion in the slope need to be studied. On the basis of the above two aspects, we will carry out loess slope stability analysis based on soil element stability, as well as key mitigation measures of loess landslides according to different origins of water. |
| Key words: loess water sensitivity loess landslide research advances prospect |
