聚丙烯纖維土壤攪拌改良體之力學行為

Mechanical Behaviors of PP Fiber-Reinforced Cemented Soil

林家銓(Jia-Quan Lin)

指導教授 ： 葛宇甯

共同指導教授 ： 鄭世豪(Shih-Hao Cheng)

國立臺灣大學/工學院/土木工程學研究所/碩士(2022年)

https://doi.org/10.6342/NTU202202408

摘要

土壤攪拌(柱或壁)幾乎是地盤改良工法中最簡單和最具經濟性的操作方法，惟在減碳意識和都市化的發展下，無論施工目的是阻水或加勁功能，設計量體或改良體直徑(厚度)若能縮減，將是推動價值工程的重要指標。土壤攪拌工法主要以水泥材料進行施工，故實現的改良體雖大都為具承壓能力的脆性材料，而低抗拉和低抗彎矩能力也是其特性。因此，如何縮減水泥量體，其攪拌改良後之力學性質可滿足工作荷載下的強度，將是重要的研究課題。有鑑於此，本研究透過室內試驗，使用標準砂、波特蘭水泥和聚丙烯纖維作為加勁材料，探討不同水泥添加量、不同水灰比和不同纖維添加比例對攪拌改良體的抗拉和抗彎矩性能的貢獻。最後，本研究藉由改良試體之無圍壓縮強度試驗、巴西人抗拉試驗和抗彎矩強度試驗數據，使用尖峰強度增幅比例、破壞時應變之增幅比例、脆性指數、韌性指數與韌性增幅比例等指標來量化聚丙烯纖維的加勁效果。本文由試驗成果發現，當砂質(標準砂)土壤在水泥與水灰比為5 %和100 %使用0 %、0.25 %、0.5 %與1.0 %(重量比)情況下，最高可提升改良體的抗壓強度17 %、抗拉強度提升13 %和抗彎矩強度提升28 %，反映著施工尺度可以縮減21 %。

關鍵字

聚丙烯纖維 ； 土壤攪拌(柱/壁) ； 無圍壓縮強度試驗 ； 巴西人拉抗試驗 ； 抗彎矩強度試驗

並列摘要

Soil mixing column is almost the simplest and most economical operation method in site improvement construction methods. However, with the development of carbon reduction awareness and urbanization, if the designed volume of the improved body that used to stiffen the soil can be reduced, it will be an important indicator for promoting value engineering. The cement is mainly used in soil mixing method for construction, and most of the improved bodies are brittle materials with great pressure bearing capacity but low tensile and low bending moment resistance. Therefore, how to ensure the mechanical function of the reduced-scale agitated improved body and maintain the strength under the loads in field will be an important research topic. In view of this, this study uses standard sand, Portland cement and polypropylene fibers as stiffening materials through laboratory tests to explore the tensile and bending performance contributed by the agitated modified body with different cement additions, different water-cement ratios and different fiber addition ratios. Finally, in this study, the unconfined compressive strength test, the Brazilian tensile test and the bending moment strength test were used, and the data will be determined by the following six parameters: (1) improved peak strength ratio; (2) improved deformation ratio; (3) brittleness index; (4) toughness index; and (5) improved toughness ratio, to evaluate the fiber reinforced performance. In this study, it is found from the test results that when the sandy (standard sand) soil uses 0 %, 0.25 %, 0.5 % and 1.0 % (weight ratio) fiber content in the cement to water-cement ratio of 5% and 100%, the compressive strength of the improved body can be appropriately increased (increased by 17 %), tensile strength (increased by 13 %) and bending moment strength (increased by 28 %), reflecting that the construction scale can be reduced by 21 %.

並列關鍵字

Polypropylene fiber ； soil agitation (column/wall) ； unconfined compressive strength test ； Brazilian tensile test ； bending moment strength test

參考文獻

何冠德 (2013)，『低黏性砂土張力強度之探討』，碩士論文，國立台灣大學土木工程學系。

蔡秉諺 (2015) ，『砂質水泥改良土剪脹之依時性.』，碩士論文，國立中央大學土木工程學系。

李俊葦 (2016)，『利用三軸無圍壓縮試驗探討纖維與水泥對粉土剪力強度與纖維握裹力的影響』，碩士論文，國立台灣科技大學營建工程系。

ASTM C39/C39M-10 (2010), “Standard Test Method for Compressive Strength of Cylindrical Concrete Specimens,” ASTM International, West Conshohocken, PA, USA.

ASTM C1018-89 (1989), “Standard Test Method for Flexural Toughness and First-Crack Strength of Fiber-Reinforced Concrete,” ASTM International, West Conshohocken, PA, USA.