Changes in rock properties of some landform materials due to weathering

一些地貌物质因风化而发生的岩石性质变化

• 批准号: 05452340
• 负责人: MATSUKURA Yukinori
• 金额: $ 4.54万
• 依托单位: University of Tsukuba
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for General Scientific Research (B)
• 财政年份: 1993
• 资助国家: 日本
• 起止时间: 1993 至 1994
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-05452340/
• 关键词: Weathering; Rock control; Landform material science; Rock property; Mudstone; Rhyolite

To examine the mechanism of rock-strength reduction due to weathering, temporal changes in microstructure of porous rhyolite were investigated selecting Kozu-shima, a small island in the Pacific, as the study site. In this island four lava domes formed successively with eruption of rhyolite at the time of 1,100,2,600,20,000, and 40,000 y BP.These four rhyolites are mainly composed of glassy groundmass, with flow structure, which is called here "glass columns".Deep and uniform weathering in each lava dome indicates that the present-day rock properties can be assumed to represent the degree of weathering in the elapsed time from each eruption. Using rock block samples taken from the outcrop in each dome, strengths and pore size distribution (PSD) were measured, and microstructure of rocks were observed by the scanning electron microscope (SEM).Main results of the measurements are as follows : (1) Both uniaxial compressive strength and tensile strength reduce rapidly in the initial stage … More of weathering (for the first 20,000 years) ; (2) Rapid increasing in volume of large pores (about 10 mm in diameter) also occurs in this stage ; (3) A little increase in volume of medium pores (about 1 mm in diameter) occur in this stage, and the rate of the increase accelerated in the later stage (2,000-40,000 years). The SEM observations show that microcracks with a width of 1 mm, which seems to correspond to medium pores in PSD,begins to form on the surface of the glass columns in the initial stage. These evidences suggest that the rapid reduction of rock strength in the initial stage is resulted from increasing in volume of large pores and formation of microcracks.Increasing in large pores is explained to be caused by the combination of contiguous closed pores into open pores due to "dissolution" of the glassy columns. On the other hand, formation of the microcracks on the surface of the glass columns is explained to be caused by swelling pressure generated in "hydration" process. Above discussion leads to the conclusion that the changes in microstructure due to chemical weathering strongly influence on the reduction of rock strength. Less

为了探讨风化降低岩石强度的机理，以太平洋小岛小岛为研究对象，研究了多孔流纹岩的微结构随时间的变化。在岛上先后形成了4个熔岩穹隆，它们分别在1100、2、600、2万和4万年前随着流纹岩的喷发而形成。这4个流纹岩主要由玻璃质基质组成，具有流动结构，在这里被称为“玻璃柱”。每个熔岩穹顶深厚而均匀的风化表明，现今的岩石性质可以假设为代表了每次喷发所经历的时间的风化程度。对各穹顶露头岩块进行了强度和孔径分布的测试，并用扫描电子显微镜观察了岩石的微观结构。主要结果如下：(1)在…的初期，单轴抗压强度和抗拉强度都迅速下降(2)大孔体积迅速增大(直径约10 mm)；(3)中孔(直径约1 mm)体积略有增大，后期(2,000-40,000年)增大速度加快。扫描电子显微镜观察表明，玻璃柱表面开始形成宽度为1 mm的微裂纹，相当于PSD中的中孔。这些证据表明，岩石强度在初始阶段的迅速降低是由于大孔隙体积的增加和微裂纹的形成，而大孔隙强度的增加则是由于玻璃柱的溶解将毗连的闭合孔隙组合成开放孔隙所致。另一方面，玻璃柱表面微裂纹的形成是由于“水化”过程中产生的膨胀压力所致。上述讨论表明，化学风化引起的微结构变化对岩石强度的降低有很大影响。较少

项目成果

Matsukura, Y., Kimata, M., and Yokoyama, S.: "Formation of weathering rinds on andesite blocks under the influence of volcanic gases around the active crater of Aso volcano, Japan." Rock Weathering and Landform Evolution. 89-98 (1994)

Matsukura, Y.、Kimata, M. 和 Yokoyama, S.：“在日本阿苏火山活火山口周围火山气体的影响下，安山岩块上风化皮的形成。”

小口千明・八田珠郎・松倉公憲: "神津島における多孔質流紋岩の風化とそれに伴う物性変化" 地理学評論. 67. 775-793 (1994)

Chiaki Oguchi、Juro Hatta 和 Kiminori Matsukura：“神津岛多孔流纹岩的风化及其物理性质的相关变化”地理评论 67. 775-793 (1994)。

Tatahashi, K., Suzuki, T.and Matsukura, Y.: "Erosion rates of sandstone used for a masonry bridge pier in the coastal spray zone." Rock Weathering and Landform Evolution. 175-192 (1994)

Tatahashi, K.、Suzuki, T. 和 Matsukura, Y.：“沿海喷雾区砖石桥墩所用砂岩的侵蚀率。”

Matsukura,Y.,Kimata,M and Yokoyama,S.: "Formation of weathering rinds onandesite blocks undo the influence of volcanic gases around the active crater of Aso vdcano,Japan" Rock Weathering and Landform Evolution. 89-98 (1994)

Matsukura,Y.、Kimata,M 和 Yokoyama,S.：“风化层安山岩块的形成消除了日本 Aso vdcano 火山口周围火山气体的影响”岩石风化和地貌演化。

Matsukura, Y.: "A review of the studies on rock control in weathering processes." Transactions, Japanese Geomorphological Union. vol.15. 203-222 (1994)

Matsukura, Y.：“风化过程中岩石控制的研究综述。”