滑坡对降雨响应的多指标监测及综合预警探析:以赣南罗坳滑坡为例

降雨量和位移是当前降雨型滑坡监测预警最常用的指标。然而,降雨量和位移监测结果只能反映降雨作用下滑坡的变形情况,不能揭示滑坡内在物理力学性状对降雨的响应。因此,除降雨量和位移监测之外,建立包括体积含水率、基质吸力等反映滑坡动态演化过程的关键指标监测体系必将成为今后更真实地把握滑坡内在演化趋势、更准确地建立滑坡综合预警判据的最有效手段。笔者对赣南地区典型降雨型滑坡进行了多指标监测及综合预警示范研究。结果表明:(1)在降雨条件下滑坡土体内部体积含水率、基质吸力和温度等多指标均产生有规律的动态响应;(2)随着降雨的持续,滑体体积含水率与基质吸力的变化均具有显著的滞后现象;(3)体积含水率和基质吸力变化速率与滑体位移具有显著的正相关性;(4)滑体温度分布变化规律受大气温度和体积含水率的共同影响。以实测数据的滑坡稳定性分析为基准,在考虑实际降雨入渗深度与滑坡稳定性的关联度上,建立了包括日降雨量、体积含水率增加速率、基质吸力减小速率以及位移速度多元指标预警方法体系,提出了基于关键指标综合预警体系及确定方法,旨在为降雨滑坡准确预警提供新模式。

Multi-index monitoring and comprehensive early warning of landslides in response to rainfall:An example of the Luo'ao landslide in southern Jiangxi Province

Rainfall and displacement are currently the two most commonly used indicators for rain-induced landslide monitoring and warning. However, the rainfall and displacement measurements can only reflect the effect of rainfall on landslide deformation, but they cannot reveal historic landslides in response to rainfall as determined by the inherent physical and mechanical properties of these slides. Therefore, in addition to rainfall and displacement monitoring, one can establish a monitoring system that includes indicators such as water content and matric suction to monitor the dynamic evolution of historical landslides. Such a monitoring system will certainly become the most effective means to grasp the inherent trends in landslide evolution and to develop more accurate criteria for comprehensive early warning of landslides. In this paper, we conducted a demonstrative study on the multi-indicator monitoring and comprehensive early warning for a typical rainfall-type landslide, the Luo'ao landslide in southern Jiangxi Province. The results are: (1) Multiple indicators such as the moisture level, matric suction and temperature in the surface soil produced regular dynamic response to rainfall. (2) With the continuation of rainfall, the volumetric water content and matric suction strength changed after a significant delay since the onset of rainfall. (3) The rate of changes of both volumetric water content and matric suction strength showed significant positive correlation with slip displacement. (4) The soil temperature distribution pattern was influenced by both atmospheric temperature and volumetric water content. Based on the analysis of the measured landslide slope stability, a multi-indicator early warning method was established on the basis of correlating actual rainfall infiltration depth and landslide slope stability. The key indicators are daily rainfall, rate of volumetric water content increase, rate of matric suction strength decrease and displacement velocity. Furthermore, a comprehensive early warning system with defined warning thresholds for key indicators is proposed, aiming to provide a new model for accurate early warning of rainfall-induced landslides.