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The rates of increase in weathered zones and decrease in rock strength

风化带的增加率和岩石强度的降低率

基本信息

批准号：
07640609
负责人：
SUZUKI Takasuke
金额：
$ 1.6万
依托单位：
CHUO UNIVERSITY
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
1995
资助国家：
日本
起止时间：
1995 至 1996
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-07640609/
关键词：
Weathering Weathered zones Decrease in rock strength Weathering rates Rock properties Mudstone Sandstone 強度劣化

项目摘要

The weathering rates of bedrock under dated erosional terraces were concluded as follows.(1) The empirical equations were established to express the rates of increase in the thickness of each of four weathered zones, i.e.highly, moderately, slightly and faintly weathered zone. The relationships between the thickness of weathered zone (Z) and the weathering time (t) are expressed as Z=alphat^<beta>, Whera alpha and beta are constants. It is concluded that (1) the rates of increase in thickness of each weathered zone (dZ/dt) are not constant, but decelerate with time (t) gradually, and (2) the zones with lower weathering grades have a faster weathering rate.(2) Comparism with mudstone and sandstone in the weathering rates (dZ/dt) shows that at first mudstone have larger weathering rates which increase in thickness of weathered zones than sandstone. The weathering rates of mudstone are decelerate with time and finally are passed by sandstone.(3) The empirical equation that shows the rate of decrease in strength at arbitrary depth from the bedrock surface are established. Mudstone and sandstone have no change in strength from the start of weathering to the point where decrease in strength rapidly (t=7.8d^<1.2> in sandstone, t=4.2d^<1.4> in mudstone).(4) Compare with mudstone and sandstone in the rate of decrease in strength (dR/dt), at the point near the bedrock surface, mudstone have larger than sandstone in weathering rates. On the order hand, at the deep point where deeper than 30cm from the surface, sandstone have lager than mudstone in weathering rates.

年代久远的侵蚀阶地下基岩的风化速率如下。(1)建立了强风化带、中风化带、弱风化带和弱风化带厚度增长率的经验公式。风化带厚度（Z）与风化时间（t）之间的关系可表示为Z= α t ^<beta>，其中α和β为常数。结果表明：（1）各风化带的厚度增长率（dZ/dt）不是常数，而是随时间（t）逐渐变慢;（2）风化等级低的风化带风化速率快。(2)与泥岩和砂岩的风化速率（dZ/dt）的比较表明，泥岩的风化速率首先大于砂岩，风化带厚度增加。泥岩的风化速率随时间的推移逐渐减慢，最终被砂岩所超越。(3)建立了基岩面任意深度处强度衰减率的经验公式。泥岩和砂岩从风化开始到强度迅速下降（砂岩t=7.8d^<1.2>，泥岩t=4.2d^<1.4>），强度没有变化。(4)与泥岩和砂岩的强度衰减率（dR/dt）相比，在靠近基岩面处，泥岩的风化速率大于砂岩。在距地表30 cm以上的深部，砂岩的风化速率大于泥岩。