Application of slope failure monitoring system and prediction model in forest clear cutting slope.

本研究的目的是通过对实际天然雪坡的监测系统和数值分析来评价森林采伐对浅层边坡破坏发生的影响。除了实时监测边坡失稳发生时刻的边坡状况外，还需要长期监测森林采伐过程中土壤强度和土壤水分的变化，以明确边坡失稳发生的过程。本研究选取千叶东京大学林场的森林清林坡为研究对象。该边坡安装了以下监测系统：(A)带网络摄像头的图像监测系统，(B)边坡土层倾斜度监测系统，(C)气象水文监测系统（雨量、风速、土壤湿度、地下水位）。监测系统的应用结果表明，与森林立地的土壤水分状况相比，边坡下部土壤水分状况水平呈上升趋势。土的强度用直剪试验来评定。直剪试验结果表明，根系对土体的黏聚力和内角均有增强作用。根据监测系统和剪切试验的应用结果，用有限元法计算了边坡安全系数。随着地下水位的升高，边坡安全系数迅速降低，坡脚部分出现了边坡层剪切应变集中现象。

The purpose of this research is to evaluate the influence of forest clear cutting on a occurrence of shallow slope failure with the monitoring system on actual natural sloe and numerical analysis. In addition to the real-time monitoring of slope condition at the moment of occurrence of slope failure, long term monitoring of change of soil strength and soil moisture with forest clear cutting is necessary to clarify the process of slope failure occurrence.In this study, the forest clear cutting slope of the Tokyo University forest in Chiba is selected as the research object. This slope is installed monitoring system as follows(A) Image monitoring system with web camera, (B) Monitoring system of incline of slope soil layer, (C) Weather and Hydrological monitoring system (rainfall, wind velocity, soil moisture, ground water level).The results of application of monitoring system shows that the soil moisture condition level of lower part of the slope is going up comparison with the soil moisture condition of forest standing slope. Soil strength is evaluated with the direct shear test. The result of direct shear test shows that both of cohesion force and internal angle of the soil is reinforced by the root system.With the results of application of monitoring system and shear test, Slope safety factor is calculated with the finite elements method Slope safety factor is rapidly decreasing with the increasing of ground water level, and Concentration of shear strain of the slope layer is emerging the foot part of slope.