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研究生:王博文
研究生(外文):Wang, Bor Wen
論文名稱:圓柱型地工合成材料直剪試驗儀之修改與地工織物直剪特性之研究
論文名稱(外文):Modifications of a cylindrical Direct Shear Apparatus and the Investigation of the Direct Shear Characteristics of Geotextiles
指導教授:謝啟萬謝啟萬引用關係
指導教授(外文):Chi-Wan Hsieh
學位類別:碩士
校院名稱:國立屏東技術學院
系所名稱:土木工程技術研究所
學門:工程學門
學類:土木工程學類
論文種類:學術論文
論文出版年:1996
畢業學年度:84
語文別:中文
論文頁數:2
中文關鍵詞:直剪試驗地工合成材料地工織布界面頸縮現象
外文關鍵詞:direct-sheargeosyntheticsgeotextilesinterfacenecking phenomena
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本研究之宗旨乃在改良前期所研發之圓柱型直剪拉拔試驗儀,以檢測
地工合成材料於無頸縮條件下其直剪行為與大型平鈑直剪之差異性。因第
一階段之設計,雖改善了許多大型直剪試驗儀之缺失,但仍有數項缺點有
待改進,例如織物與中空鋼模之間有複雜的摩擦阻抗問題,直剪儀壓力室
之圍壓與土壤界面正向應力之對應關係不甚了解,原始設 計壓力控制閥
精密度不足亦需改良,因此本研究乃針對此數項缺失進行儀器之改良,並
進行一系列地工織布直剪試驗,以探討織物與土壤之直剪行為? 直剪試
驗之材料包括地工織布及針軋不織布,熱熔不織布等三種材質,試驗土壤
採用潔淨石英砂。試驗之前以不同施拉速度檢測地工織物材料抗張強度試
驗,以了解施拉速度與織物抗張強度之關係,依據試驗結果顯示,不織布
抗張試驗可採用5 mm/min.,而織布之抗張試驗則建議應採用1 mm/min.較
為理想。 本研究修改之圓柱型直剪儀之荷重乃藉由外剪力盒之氣模將壓
力經由土壤傳進至土壤-織物界面,此界面之壓應力可由荷重元量測之,
由標定試驗中發現,鬆砂狀況下,氣模之壓應力與土壤-織物界面應力之
關係近似線性行為,而緊砂狀況下,此項關係呈現弧線型的行為。 為
比較平鈑式直剪與圓柱形直剪之差異性乃於不同土壤試體之緊密度、含水
量與施剪速度之條件下,分別進行大型平鈑直剪試驗與圓柱型直剪試驗,
並比較兩者間之差異性,探討兩者對於有無頸縮現象之影響。由平鈑直剪
試驗結果分析得知,建議直剪試驗剪動速率應小於或等於1 mm/min.。
綜合直剪試驗之結果顯示,砂土中之水份對織布與砂土之界面有潤滑的作
用,將會降低土壤與織布界面間之摩擦角,且此潤滑效應,對平鈑式直剪
試驗較圓柱型直剪試驗明顯;此潤滑作用對織布、針軋不織布、熱熔不織
布其界面摩擦角約下降20-80。且於圓柱型直剪試驗中顯示 緊密濕砂所得
之界面接觸效率較高,織布與緊密砂土界面之接觸效率為0.815,而不織
布與緊密砂土界面之接觸效率則大約為0.95左右。 圓柱形直剪儀與平
鈑式剪力儀在相同狀態下所得的試驗結果顯示,無頸縮圓柱形直剪試驗結
果略低於大型平鈑式直接剪力試驗結果,其應與圓柱形直剪試驗織物試體
會承受來自輻射向和環向兩方向的張應力有關,此現象對摩擦阻抗之具體
影響仍有待後續查證。 關鍵字:直剪試驗、地工合成材料
、地工織布、界面、頸縮現象
The objective of the study is to
modify a previous developed cylindrical direct shear apparatus
for geosynthetics in order to evaluate the effect of necking
phenomena on friction behavior of soil/geotextile during direct
shear test. The use of cylindrical geometry for the apparatus
has the intention of eliminating the necking deformation of
geotextile test sample dueto longitudinal extension during
direct shear test. A series of direct shear tests between
various types of geotextiles and a white quartz sand were
performed using the modified apparatus and a traditional large
scale direct shear apparatus. The tested geotextiles included a
woven fabric, a non-woven needle-punched geotextile, and a
nonwoven heated bonded geotextile. A wide range of wide width
tensile tests with different test speeds were conducted to
evaluate the strength of the geotextiles. Based on the results
of tensile tests, it is recommended that theuse of 5 mm/min.
test speed for nonwoven wide width tensile test can significant
minimize speed effect. However, the use of 1 mm/min. test speed
rate for wide width tensile test of woven fabric is recommended.
Based on the results obtained from the traditional large scale
directshear tests between geotextiles and quartz sand, the use
of maximum displacement rate of 1 mm/min. for soil/geotextile
direct shear test is recommended. Theresults of direct shear
tests indicated that the increase of water content of granular
soils would reduce the friction resistance at soil/geotextile
interface. The increase of water content of the quartz sand from
dry condition to saturated condition would reduce the friction
angle of soil/geotextile of 2 to 8 degrees for the conditions of
tested. The effect of water content of soil on friction
resistance of soil/geotextile direct shear test is more
significant for the traditional large scale direct shear device
than that of cylindrical direct shear apparatus. The
results of the tests also shown that contact efficiencies of
friction angle of dry loose sand/geotextiles are about 0.75 and
0.85 for woven fabric and nonwoven geotextiles, respectively.
The contact efficiency of wet loose sand/geotextiles is about
0.70. The typical contact efficiencies of fri-ction angle of wet
dense sand/geotextiles are about 0.815 and 0.95 for woven fabric
and nonwoven geotextiles, respectively. Due to the presence
of longit-udinal and hoop tensile stresses on cylindrical test
sample, the friction resis-tance at soil/geotextile interface of
cylindrical direct shear test sample is less than that presence
on the geotextile sample for traditional large scale direct
shear test. However, the reasons to cause the difference of test
resultsbetween traditional and cylindrical direct shear
apparatuses required further investigation.
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