Do Precipitation-Induced Shallow Landslides Occur under Unsaturated Conditions?

非饱和条件下是否会发生降水引发的浅层滑坡？

• 批准号: 0855783
• 负责人: Ning Lu
• 金额: $ 17.4万
• 依托单位: Colorado School of Mines
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2009
• 资助国家: 美国
• 起止时间: 2009-08-01 至 2011-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0855783&HistoricalAwards=false
• 关键词: Do; Precipitation; Induced; Shallow; Landslides

The socioeconomic impacts of natural landslides are enormous worldwide. In the U.S., natural landslides result in the loss of life, as well as property and environmental damages exceeding US$2 billion annually. Shallow landslides, typically translational slope failures a few meters thick of unlithified soil mantle or regolith, may dominate mass-movement processes in hillslope environments. They are particularly destructive when they initiate or coalesce to form debris flows. Shallow landslides and debris flows are commonly triggered by intense precipitation or strong ground shaking and may affect extensive areas during a single meteorological or seismic event. According to a recent survey, about half of the 40 most destructive landslide disasters worldwide in the past century resulted from prolonged or intense rainfall. Recent advances in the scientific understanding of landslide initiation, particularly for those landslides that occur under intense or prolonged precipitation in hillslope environments around the world, indicate that the failure surface may be above the water table and under nearly saturated conditions. The classic methodology for landslide analysis assumes that earthen materials are either fully saturated or completely dry neglecting the contribution of soil suction to the stability of slopes. Thus this methodology is overly conservative and incapable of accurately forecasting shallow landsliding. Recent advances in soil mechanics have shed light on the state of stress in partially saturated soil masses. Furthermore, physical evidence and scientific understanding in both geomechanics and geomorphology all point to the likelihood that the failure surface of infiltration-induced landslides may occur above the water table and under nearly saturated conditions.This project seeks further physical evidence and uses the new knowledge in defining stress in partially saturated soil to identify the likelihood of landslide initiation under partially saturated soil conditions. The overall goals of this research are: to test the hypotheses that (1) landslides, particularly shallow and translational slope failures under heavy precipitation conditions, can occur above the water table; and, (2) that the failure occurs when materials are nearly saturated and suction stress is reduced to nearly zero. To test these hypotheses, we will: (1) measure the unsaturated hydrologic and mechanical properties under laboratory settings, (2) conduct landslide initiation tests using an intermediate-scale shallow landslide simulator, and (3) implement a site-specific program for long-term, real-time monitoring for shallow landslide occurrence, thus examining the validity of both hypotheses at the field scale. By clarifying whether shallow landslides occur under saturated or unsaturated conditions, this work provides a physical basis for answering the important question regarding whether we need a new paradigm that includes either soil suction or effective stress or both to predict shallow landslides. Knowledge gained here is transformative to advancing the understanding of the interactions among climate change, topography, and sustainable land use. Mass movement due to shallow landslide initiation under heavy precipitation is part of long-term landform evolution, and presents a great challenge for society subject to climate change and evolving land use. Testing the concept of effective stress variation above the water table for landslide initiation analysis provides a sound physical basis for future predictive models and will enhance our ability to predict and forecast shallow landslide hazard. Collaboration with the USGS National Landslide Information Center ensures broad dissemination via outreach activities targeted toward researcher, K-12 students, and the general public. Integrating the research mission with an educational and diversity mission via graduate and undergraduate student training, proactive recruitment of underrepresented groups and incorporating the research activities into existing courses ensure broad impact to a diverse audience of students, researchers, and practitioners.

自然滑坡的社会经济影响在全球范围内是巨大的。 在美国，自然滑坡会导致生命损失，以及每年超过20亿美元的财产和环境损失。 浅滑坡，通常是几米的无用的土壤地幔或雷果地厚的翻译斜率故障，可能会在山坡环境中占主导地位。当他们启动或结合形成碎片流时，它们尤其具有破坏性。 浅水滑坡和碎屑流通常是由强烈的降水或强烈的摇动触发的，并且在一次气象或地震事件中可能会影响广泛的区域。 根据最近的一项调查，在过去一个世纪，全球40个最具破坏性的滑坡灾难中，大约有一半是由于降雨长期或强烈的降雨造成的。 对滑坡启动的科学理解的最新进展，特别是对于那些在世界各地山坡环境中发生的降水量或长时间降水下发生的滑坡，这表明失败表面可能位于地下水位上方，并且在几乎饱和的条件下。 滑坡分析的经典方法认为，泥土材料是完全饱和或完全干燥的，忽略了土壤吸力对斜坡稳定性的贡献。 因此，该方法过于保守，无法准确预测浅层滑坡。 土壤力学的最新进展揭示了部分饱和土壤质量的压力状态。此外，地质力学和地貌学的物理证据和科学理解都表明，浸润引起的滑坡的失败表面可能发生在地下水位上方并在几乎饱和的条件下发生。该项目寻求进一步的物理证据，并在陆地上降低了土壤中的部分饱和质量，以确定土壤中的份量饱和质量饱和的土壤，并利用新的知识。这项研究的总体目标是：测试（1）（1）在沉淀条件下的山体滑坡，尤其是浅层和翻译斜率故障的假设，可以发生在地下水位上方； （2）当材料几乎饱和并且吸力应力降低到近乎零时，发生故障会发生。为了检验这些假设，我们将：（1）测量在实验室环境下的不饱和水文和机械性能，（2）使用中间级的浅层滑坡模拟器进行滑坡启动测试，（3）实施现场特定的现场计划，以实时，实时监控浅层范围，从而检查了均匀的量表，从而均为估算量均高估，以下均为均无其范围。 通过阐明在饱和或不饱和条件下是否发生浅滑坡，这项工作为回答有关我们是否需要包括土壤吸力或有效压力的新范式或两者都预测浅层滑坡的重要问题提供了物理基础。 这里获得的知识是为了促进对气候变化，地形和可持续土地使用之间相互作用的理解的变革。 由于大降水量下的浅滑坡启动而引起的大众运动是长期地面进化的一部分，并为社会带来了巨大的挑战，但要受到气候变化和不断发展的土地利用。 测试在地下水位上方的有效应力变化的概念以进行滑坡启动分析，为将来的预测模型提供了合理的物理基础，并将增强我们预测和预测浅水滑坡危险的能力。 与USGS国家滑坡信息中心的合作确保通过针对研究人员，K-12学生和公众的外展活动来确保广泛的传播。 通过研究生和本科生培训，积极招募代表性不足的群体，将研究任务与教育和多样性任务相结合，并将研究活动纳入现有课程，以确保对学生，研究人员和从业人员的多元化受众的广泛影响。