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Study on the generation mechanism of landslides in terms of the weathering zones of rocks

从岩石风化带角度研究滑坡发生机制

基本信息

批准号：
11680469
负责人：
CHIGIRA Masahiro
金额：
$ 1.47万
依托单位：
Kyoto University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
1999
资助国家：
日本
起止时间：
1999 至 2001
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-11680469/
关键词：
Weathering Landslide Granite Ignimbrite Tuff Sedimentaryu rocks Rainfall Infiltratoin 気相晶出作用シラスマサ泥岩砂岩

项目摘要

To clarify the generation mechanism of shallow landslides, I studied the weathering profiles, their formative mechanisms, and the relationships between the profiles and landslide generation for granitic rocks, ignimbrite, and sedimentary rocks. The major results are as followings :1) As major weathering processes of granitic rocks, micro-sheeting and spheroidal weathering were recognized. Granitic rocks, which are micro-sheeted by unloading, are loosened intensively to a depth of a few meters with a well defined front. This loosened zone increases its thickness and finally slides. Spheroical weathering proceeds by micro-cracking and chemical leaching. Moderately weathered granite, which are made through geological time, is loosened rapidly to a depth of a few meters when it is exposed by artificial cutting or natural denudation ; rainwater infiltrates through this loosened zone preferentially. The saturation, generation of pore pressure, and the decrease of cohesion by the loss of suct … More ion of this loosened material become the basic factors for the generation of landslide.2) Ignimbrite varies from unwelded to strongly welded tuff. Unwelded ignimbrite is weathered to have a well-defined front, which acts as a capillary barrier between the fresh permeable tuff and the overlying less permeable weathered tuff. Infiltrating rainwater increases the weight of the weathered tuff and decreases its cohesion because of suction disappearance. These are the basic factors of the landslide of unwelded ignimbrite.3) Vapor-phase crystallized ignimbrite has a well defined weathering front between the fresh or hydrated impermeable tuff and the overlying strongly weathered, permeable tuff. The weathered tuff on the front is exfoliated parallel to slope surface by the intensive chmical leaching. The saturation, generation of pore pressure, and the decrease of cohesion by the loss of suction of this weathered tuff become the basic factors for the generation of landslide.4) Sedimentary rocks generally have oxidation and dissolution fronts, which are made by the sequential reaction between the rocks and the infiltrating water. This weathering process and the resultant change of mechanical properties are the major causes of the common type of landslide of sedimentary rocks, which have slip surfaces along or below the oxidation front. Less

为了阐明浅层滑坡的成因机制，研究了花岗岩、褐沸岩和沉积岩的风化剖面及其形成机制，以及风化剖面与滑坡成因的关系。主要研究结果如下：1)花岗岩的主要风化作用是微片状风化和球状风化。花岗岩岩石通过卸荷被微片化，强烈地松动到几米深的地方，具有明确的前缘。这个松散的区域增加了它的厚度，最后滑了下来。球状风化是通过微破裂和化学淋溶进行的。地质时代形成的中等风化花岗岩，在人工切割或自然剥蚀裸露时，迅速松动到几米深，雨水优先渗入松动带。吸力…损失引起的饱和度、孔压的产生和粘聚力的降低这种松散物质中的更多离子成为滑坡产生的基本因素2)从未焊接凝灰岩到强焊接凝灰岩，Ignimbrite都不同。未焊接的褐沸石被风化成具有明确的前缘，在新鲜的可渗透凝灰岩和上面渗透性较差的风化凝灰岩之间起到毛细屏障的作用。雨水的渗入增加了风化凝灰岩的重量，并由于吸力消失而降低了凝灰岩的粘聚力。3)气相结晶褐煤在新鲜的或水化的不透水凝灰岩与上覆的强风化透水凝灰岩之间具有明确的风化前锋。前缘风化凝灰岩在强烈的化学淋滤作用下平行于坡面剥落。这种风化凝灰岩的饱和度、孔隙压力的产生以及因失去吸力而导致的粘聚力下降成为滑坡形成的基本因素。4)沉积岩一般具有氧化和溶蚀前锋，这些前锋是由岩石和渗入水之间的顺序反应形成的。这种风化作用和由此引起的力学性质的变化是常见类型的沉积岩滑坡的主要原因，这些滑坡沿着或低于氧化前缘具有滑动面。较少