雲母含量影響砂土壓縮性之研究

A Study on the Influence of Mica Content on the Compressibility of Sands

楊振邦(Jen-Bang Yang)

指導教授 ： 馮道偉

中原大學/工學院/土木工程研究所/碩士(2009年)

https://doi.org/10.6840/cycu200901298

摘要

隨著時間作用的加長，砂土顆粒與顆粒間在載重不變情況下會產生顆粒重排，這種土壤行為一般稱為二次壓縮，屬於潛變現象之一種。砂質土於實驗室主要壓密完成後顯示出動態剪力模數隨時間增加而增加之行為，此種時間效應之合理解釋為砂土顆粒在二次壓縮階段連續重新排列，致使砂土顆粒之粗糙表面互鎖作用增加，而導致砂土之摩擦阻抗隨時間增加而增加。過去研究指出台灣中西部地區之砂土含有雲母礦物，且相關文獻中針對雲母質砂土大多著重於壓縮指數之測定，對二次壓縮指數之測定則不多，故本研究將對於雲母質砂土之壓縮指數與二次壓縮指數進行探討。
本研究使用單向度壓密儀量測土壤之壓縮性，試樣以麥寮砂為主，加入粗細不同含量之白雲母與絹雲母；另以渥太華砂加入雲母。並以不同比例之雲母混合砂土，進行X光繞射分析(XRD)，利用試驗結果之雲母含量與強度之關係線性迴歸得一β值，以探討砂土中雲母含量之推估方法。試驗結果顯示，當試樣雲母含量愈高，其初始孔隙比亦愈高，壓縮指數也相對愈大。麥寮砂與雲母混合土之壓縮指數及二次壓縮指數，隨著壓密應力之增加而增大；但是，渥太華砂與白雲母混合時，其壓縮指數及二次壓縮指數與白雲母有相同之行為，即隨著壓密應力的增加先上升而後下降。Cα/Cc之比值隨雲母含量增加而減少，最低值甚至低於0.01。XRD試驗結果顯示，以已知比例混合之渥太華砂與白雲母，利用公式可迴歸得一β值為1.736，並以此值驗證麥寮砂之雲母含量約為8%~12%

關鍵字

壓縮性 ； 砂 ； 雲母 ； X光繞射分析

並列摘要

Secondary compression is the rearrangement of sand particles with time under a constant effective stress. This soil behavior also called creep. Laboratory measurements of dynamic shear modulus after primary consolidation in sands show an increase with time. A reasonable mechanism for this time-effect in sands is a continued rearrangement of sand particle during secondary compression. Improved frictional resistance to deformation develops with time with a gradual increase in interlocking of particle surface roughness. The past researches indicated the sand included mica minerals in West-Central Taiwan. These researches almost focused on measurement of compression index in micaceous sand, ignoring the secondary compression index.
This study used Mia-Liao sand、Ottawa sand to mix with muscovite and sericite at different percentages to make oedometer specimens. In addition, known percentages of Ottawa sand and muscovite were used to perform the XRD test, and the results were used to get a β value by linear regression. The results show that the higher the mica content, the higher the initial void ratio, and the higher the compression index. Compression index and secondary compression index of the mixtures of Mai-Liao sand and mica almost increase with consolidation pressure. But, there is a situation of rising first then drop for compression index and secondary compression index of the mixtures of Ottawa Sand and mica. The ratio of Cα/Cc decrease with increasing in mica content. The lowest value even less than 0.01 . The results of XRD show that there is a β value of 1.736 by regression, and use the β value to estimate the mica content to be 8% to 12% for Mia-Liao sand.

並列關鍵字

Sand ； Mica ； Compressibility ； X-ray Diffraction Analysis

參考文獻

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