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  • 學位論文

以室內直剪試驗測定麥寮砂剪力強度與壓縮性之實驗研究

An experimental study of shear strength and compressiblity of Mai-liao sand

指導教授 : 馮道偉

摘要


文獻資料顯示台灣中西部砂土含有白雲母礦物顆粒,一般的砂土室內力學試驗僅測定有限土樣的力學特性,尚不足以了解砂土的組成礦物含量及相對密度大小對內摩擦角及壓縮指數的影響。本研究利用直接剪力試驗儀與單向度壓密試驗儀來進行室內試驗,試驗砂土包括麥寮砂及渥太華標準砂,並加入10%含量之粗白雲母(<#40)或細白雲母(<#325),為了能模擬現地可能情況,麥寮砂本身含有雲母而在加入少量雲母後更能符合雲林麥寮地區之砂土情形,而在渥太華砂內加入了雲母,使兩種不同顆粒形狀之砂土進行比較,且探討相對密度及正向應力的改變對砂土剪力強度參數及壓縮性之影響。 試驗結果顯示,取凝聚力為零的情況下割線內摩擦角隨著正向應力的提升而降低。在低正向應力(9.06kPa)作用下,麥寮砂初始相對密度21%或77%,麥寮砂混合10%粗白雲母23%或62%,混合10%細白雲母40%或76%之試樣,其割線內摩擦角分別為33.2o或41.6 o、34.7o或38.2 o、32.29 o或 35.2 o;渥太華標準砂相對密度27%或72%,渥太華標準砂混合10%粗白雲母35%或67%,混合10%細白雲母36%或71%之試樣,其割線內摩擦角分別為 35.8 o或44 o、31.9 o或42.6 o、35.4 o或37.8 o。由此可見麥寮砂與渥太華標準砂在相同正向應力下割線內摩擦角隨著相對密度的提升而提升,且混合白雲母後割線內摩擦角隨之降低,而混合細白雲母後割線內摩擦角都略低於混合粗白雲母之試樣;於較高正向應力時麥寮砂與渥太華標準砂亦是如此,而混合細白雲母試樣其割線內摩擦角都稍大於混合粗白雲母之試樣。 本研究利用直剪試驗之第五階加載(最終正向應力=350.44kPa)所得之孔隙比變化而求得割線壓縮指數;利用單向度壓密儀測出麥寮砂相對密度70%和渥太華標準砂67%之割線壓縮指數分別為0.069和0.020,而直剪試驗所測定出麥寮砂相對密度55%~91%其割線壓縮指數為0.121~0.056,渥太華標準砂67%~96%則為0.051~0.030,對此楊振邦(2009)利用單向度壓密儀所測定出麥寮砂之壓縮指數為0.096¬及渥太華標準砂為0.023,相較之下利用直剪試驗所測出的壓縮指數比利用室內單向度壓密所量測出壓縮指數值稍大。麥寮砂與渥太華標準砂混合粗及細白雲母後,割線壓縮指數隨著相對密度的提升而降低,割線壓縮指數隨著正向應力的提升而提升,試驗結果顯示混合粗白雲母之試樣其割線壓縮指數都大於混合細白雲母之試樣,因混合粗雲母會增加土壤的孔隙,故混合粗雲母有較大之壓縮量。

並列摘要


Literature data show that Taiwan Midwest sand containing mica mineral particles, the average indoor sand only a limited mechanical testing of soil samples was measured mechanical properties, not enough to understand the composition of the mineral content of sand size and relative density of the internal friction angle and compression Index of. In this study, direct shear tester and one-dimensional compaction tester for laboratory tests, including tests Mai-liao sand and Ottawa sand standard sand, and 10% levels of coarse muscovite (<# 40) or thin clouds mother (<# 325), in order to simulate in situ possible, Mai-liao sand itself contains mica and mica after adding a small amount more in line with the situation Mai-liao sand areas, and in the Ottawa sand mica added, so that the two different kinds of sand particle shape of comparison, and to explore the relative impact of changes in density and normal stress shear strength parameters of sand and compressibility of. The test results show that the secant angle of internal friction with the normal stress of taking the case to improve and reduce the cohesion of zero. In the low forward stress (9.06kPa), the Mai-Liao sand initial relative density of 21%, 77%, 10% Mai-liao coarse sand mixed muscovite 23%, 62%, mixed 10% to 40% of fine muscovite, 76 % of the sample, its secant friction angle was 33.2o, 41.6 o, 34.7o, 38.2 o, 32.29 o, 35.2 o, Ottawa sand relative density of 27%, 72%, 10% Ottawa crude mixture of standard sand muscovite 35%, 67%, 10% mixture of fine muscovite 36%, 71% of the sample, its secant friction angle was 35.8 o, 44 o, 31.9 o, 42.6 o, 35.4 o, 37.8 o. Thus Mailiao Ottawa sand and sand friction angle with the relative density of the upgrade and enhance the positive stress in the same secant and mixed muscovite secant angle of internal friction decreases, while the mixed fine muscovite secant friction angles are slightly lower than the sample of mixed coarse muscovite; while at higher normal stress Mailiao Ottawa sand and sand is also true, and its mix of fine muscovite samples secant friction angles are slightly larger than the mixed coarse clouds mother of the sample. In this study, the fifth -order direct shear loading tests (the final normal stress = 350.44kPa) the proceeds of the void ratio changes obtained secant compression index ; take advantage of one-dimensional compaction meter Mai-liao sand relative density of 70% , Ottawa sand 67% of its secant compression index were 0.069,0.020 , and direct shear tests measured the relative density of the Mai-liao sand 55% to 91% of its secant compression index was 0.121 ~ 0.056 , Ottawa sand 67% to 96% , compared with 0.051 ~ 0.030 , which Yan-gzhen Bang ( 2009 ) the use of one-dimensional compaction meter measured the Mai-liao sand compression index was 0.096 and 0.023 Ottawa sand , compared to the use of direct shear tests measured compression index than with indoor unidirectional compaction the measured value of the index is slightly compressed . Mai-liao sand Ottawa sand mixed with coarse and fine muscovite , secant compression index to improve as the relative density decreases as the compression index secant upgrade and enhance the positive stress test results show samples of mixed coarse muscovite secant compression index is greater than its mix of fine muscovite samples , which had mixed coarse mica would increase soil porosity , so there is a greater mix of coarse mica compression .

參考文獻


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