A STUDY ON INVESTIGATIONS OF THE MECHANISM OF HOT-SPRINGS LANDSLIDE OCCURRENCE

在大分县的别府市，温泉的质量和气氛都得到了特别的改善，大量的温泉涌出，泉源（洞）的数量为2847个，每天的流量为137040千升。因此，别府市是日本最大的温泉观光景点，无论是来源数量还是排放量。Myouban区是著名的温泉区在酸性硫化氢喷泉和绿色转喷泉。但是，该地区是一个温泉滑坡区，滑坡活动是从具有特殊的地质特征条件，以及附近地区的一种所谓的硫磺粘土的组成来看的。由于处于温泉地区的特殊环境下，地下水的pH值、温度等性质与通常的滑坡地区有很大的不同，即使进行对策的审查，也需要引起重视。另外，在对滑坡体进行稳定性检验时， ...更多信息 在此基础上，对某温泉滑坡进行了现场调查，明确了温泉滑坡的发生机理，并采用不同的边坡稳定性分析方法和影响滑坡稳定性因素中的强度参数，计算了该滑坡的安全系数，得到的结果如下：1)地下水位变化大，尤其是从6月中旬到雨季和9月台风期，全年上升幅度较大。2)地下水性质处于高温、低pH、高电导率等高腐蚀环境下，并且该趋势根据钻孔而不同。3)滑动面附近的粘土在不同的季节接受不同的水温、pH和电导率的历史，其范围为水温24-29℃，pH 3 -4.5，电导率10- 30 mS/m。4)反算强度参数时，在下滑面条件下，“Fellenius法”得到的内摩擦角比Bishop法的内摩擦角增大约1.3℃。少

A lot of hot springs where the fountain quality and atmosphere were especially done spring up in Beppu City, Oita Prefecture, and the numbers of sources (hole) are 2, 847-places and amount of discharge is 137, 040 kiloliters a day. Thus, Beppu City is hot-spring sightseeing spot of the top of Japan in both, the numbers of sources, and amount of discharge. Myouban district is a famous hot-spring area in the acid hydrogen sulfide fountain and the green turn fountain. But, that area is a hot-spring landslide area where the landslide activity is seen from having peculiar geological features condition, and the composition of a near region of a so-called solfataric clay. Properties of groundwater including the pH and the temperature are greatly different from usual landslide areas because it is under a peculiar environment of hot-spring area, and even if it undertakes the examination of the countermeasure, the attention is required. Moreover, when the stability of the landslide slope is exam … More ined, it is a current state that experienced method is used.Then, we performed the site investigations at Myouban landslide area to clarify the occurrence mechanism of the hot-spring landslide and calculated the safety factor of the landslide using different slope stability analysis and strength parameters in factors influenced on the landslide stability.The result of obtaining is shown as follows. 1) The groundwater level is large the change, and rises especially greatly through year until the rainy season and the typhoon time of September from the middle of June. 2) Properties of groundwater are under the high corrosion environment like a high temperature, a low pH, and a high electric conductivity, etc., and the tendency is different according to the bore hole. 3) Clay in the vicinity of the slip surface receives the history of a different water temperature, the pH, and the electric conductivity by the season, and the range is water temperature 24-29℃, pH3-4.5, and electric conductivity 10-30mS/m. 4) When having calculated the strength parameters by the back calculation method, the internal friction angle ¢ obtained by the "Fellenius method" grows by about 1.3℃ than the ¢ of the Bishop method under lower slip surface. Less