Research on Geologic Control of Slope Movements --- Analysis of Lithology and Geologic Structure of Basement Rocks

我们主要研究了近畿和四国地区白垩系至新近系的斜坡运动，例如新近系的神户群和北田群，以及白垩系至古近系的岛满托带。通过航空照片的图像分析，我们对上述特定地区的斜坡运动的许多地貌地质数据进行了测量和分析。特别是，我们明确了斜坡运动与基底岩石的岩性和/或地质构造之间的关系。“坡体运动”是指斜坡上物质的各种运动现象，包括滑坡。以下的地质地貌因素通常被认为是边坡运动的产生因素。(1)许多大规模的斜坡运动通常发生在泥岩或细凝灰岩等细碎屑沉积物中。这被称为岩性控制。(2)岩体主要由基岩形成的碎屑和土壤组成，主要受次生运动影响。另一方面，为了修建道路，人工切割边坡会产生新的边坡运动。(3)滑面一般含有丰富的蒙脱石、伊利石、绿泥石等粘土矿物，其形成与地下水的作用密切相关。丘陵山区地下水流动状况的分析比较困难。(4)基底岩层理平原上有大量滑块沿倾斜方向移动。这就是所谓的“永加班”构造类型，并表现出典型的构造控制。另一方面，在顺层平原的另一侧有少量的“乌克班型”斜坡运动。(5)边坡运动的发展并不总是与断层有关。然而，剧烈的构造运动广泛地引起了岩石的风化和断裂。这对边坡运动的产生有很大的影响。(6)大量的斜坡运动发生在具有特定坡角的斜坡上，即新近系10 15和前白垩纪25 30。这些角度与没有坡度运动的边坡相比较小，然后指出它们的出现形成了梯度边坡。(7)坡移区因水量充沛，常用作稻田或农田。少

We have mainly investigated slope movements of Cretaceous to Neogene formations in Kinki and Shikoku areas, for example the Kobe Group and the Hokutan Group of Neogene age, and the Shimanto Belt of Cretaceous to Paleogene age. By means of image analysis of aerophotos, we have measured and analyzed many geomorphological and geological data of slope movements in the specific areas mentioned above. Particularly, we made clear the relationship between slope movements and lithology and/or geologic structure of basement rocks. The term "slope movement" means all kinds of moving phenomena of materials found on slopes, including landslides.The following geologic and geomorphologic factors are commonly pointed out as the generating factors of slope movements. (1) Many large-scale slope movements usually occur in fine clastic sediments, such as mudstone or fine tuff. This is called the lithological control. (2) The masses are mainly composed of debris and soil derived from basement rocks, and sh … More ow the secondary movement. On the other hand, new slope movements occur by artificial cutting of Slopes in order to construction of roads. (3) Generally, a sliding surface includes abundant clay minerals, such as montmorillonite, illite and chlorite, and its formation is closely connected with action of groundwater. It is difficult to analyze flow conditions of groundwater in hilly and mountain areas. (4) Many sliding masses move along the dip direction side of bedding plains of basement rocks. This is called the "Nagareban' structure type, and show the typical structural control. On the other hand, a small number of slope movements, which belong-the "Ukeban type, slide along the opposite side of the bedding plains. (5) The development of slope movements is not always concerned with faults. However, remarkable tectonic movements widely brought about weathering and fracture of rocks. This gave great influence to generation of slope movements. (6) A large number of slope movements occur on slopes with specific slope angle, namely 10ﾟ-15ﾟ in the Neogene formations and 25ﾟ-30ﾟ in precretaceous formations. These angles are small compared with slopes without slope movements, and then it is pointed out that their occurrences form gradient slopes. (7) The slope movement areas are often used as rice field or farms, because of abundant water. Less