Evaluation of The Effective Rainfall Consideing Slope Factors

为了评价考虑坡面因素的有效降雨量，1975年考察了小时雨量、连续雨量或有效雨量等单一因素作为判断边坡崩塌可能性的标准，1996年对同样的可能性第二年也采用了两种因素的组合，得到了如下结果：(1)将Logit模型应用于边坡破坏，可将边坡的抗滑能力表示为包含坡角、对策的存在和坡体土质等条件的判据。(2)降雨因子模型：用阻力势与降雨因子的比值(以上三种降雨中的每一种)表示的Logit模型所表示的边坡失稳概率是判断边坡失稳可能性的有效方法。(3)判定降雨因子的指标(小时降雨量和有效降雨量的组合)是判断边坡是否失稳的最佳方法。为了实现这一点，绘制了横坐标、小时雨强和纵坐标的图形，在图中我们得到了一条边界线(Lm线)来判断边坡是否失稳。(4)Lm线的特征(斜率和切割纵坐标)代表了以上阻力势的大小。结果表明，对于抗力很强的边坡，有效雨量对稳定性的影响大于小时降雨量，而对于弱抗力边坡，小时降雨量对稳定性的影响大于有效降雨量，相应地，稳定边坡与危险边坡的区分标准由坡度系数模型、雨量系数模型和小时/有效雨量组合表示。

For evaluation of the effective rainfall considering the slope factors, uni-factor such as hourly rainfall, continuous rainfall or efficient rainfall is examined as the criterion to judge possibility of slope failure in 1975, and combination of two-factors were also used for that same possibility second year 1996, and following results are obtained.(1) (Slope factor model) By means of applying Logit model to slope failure, resistance potential of slope against failure can be expressed as a criterion containing the slope conditions like angle, existence of countermeasure and constituent soils of slope, etc.(2) (Rainfall factor model) The probability of slope failure expressed by logit model using the ratio of resistance potential to rainfall factor (each of above three kinds of rainfall) is fairly effective to judge the possibility of slope failure.(3) The index of judging rainfall factors (combination of hourly rainfall and efficient rainfall) is best way to discriminate whether or not slope fails. To realize this, the graph with the abcissa, hourly rainfall intensity, and the ordinate, efficient rainfall, is drawn, in which we get a boundary line (LM-line) to judge whether or not slope fails.(4) The characteristics of LM-line (slope and cutting ordinate) represents a magnitude of above resistance potential. It becomes clear that for the slope of very strong resistance, efficient raifall is greater effect on the stability than hourly rainfall, and for the slope of weak one, hourly rainfall have greater effect than efficient rainfall.Accordingly, the criterion that discreminates between stable slope from dangerous one, is expressed by the slope factor model, rainfall factor model and combination of hourly/efficient rainfall.