Research about the mechanism of surface slope failure in clear-cutting forest area

本研究以皆伐山地边坡为研究对象，探讨皆伐对边坡破坏机制的影响。在监测边坡中，1999年实施皆伐，2000年植树。监测系统获取的调查目标如下：a）网络摄像头图像监控; B）气象水文数据（降雨量、空气土壤湿度、地下水位）。在监测系统方面，我们开发了适用于无市电供电的自然边坡的监测系统，与降雨事件同步的图像监测系统能够有效地提供坡面破坏发生前后的一般坡面状况的图像信息，从毁林前后土壤水分随时间推移的波动数据中可以确认：1)由于森林植被蒸散量的减少，采伐后坡面土壤水分总量总体上呈增加趋势，但不同立地土壤水分波动趋势不同。2)坡面上部表层土壤含水量呈下降趋势。另一方面，边坡底部中下层土壤含水量呈增加趋势，结合入渗模型和边坡稳定性模型，利用土壤强度参数对边坡失稳风险进行了现场评估。

In this research topic, the monitoring of clear-cutting mountainous slope was carried out for the estimation of effect of clear-cutting on mechanics of surface slope failure. In the monitoring slope, clear-cutting was executed in 1999, and tree planted in 2000. The objectives of survey obtained by monitoring system are as follows, a) the image monitor with the Internet camera, b) Meteorological and Hydrological data (rainfall, air soil moisture, ground water table). As for the monitoring system, we developed the system which can be applied for the natural slope without the commercial power supply.The image monitoring system synchronized with rainfall events can effectively give the image information of general hill slope condition before and after surface slope failure occurrence.From the data of the fluctuation of soil moisture with the time lapse before and after deforestation, the following are confirmed. 1) The total amount of soil moisture in the slope after deforestation totally shows the tendency of increasing due to the decreasing of evapo-transpiration of forest vegetation, although the tendency of fluctuation of soil moisture varies by site of the slope. 2) The soil moisture content in surface soil layer at upper part of slope shows the decreasing trend. On the other hand, the moisture content in middle and lower soil layer at bottom part of slope shows the increasing trend.The estimation of slope failure risk by site is done by combining the infiltration model and the slope stability model which use the soil strength parameter.