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標題: | 飽和砂土受振引致水壓激發對靜止側向土壓之影響 Effect of Vibration-induced Water Pressure Generation on Lateral Earth Pressure at Rest in Saturated Sand |
作者: | Yi-Chen Tsai 蔡易辰 |
指導教授: | 翁作新 |
關鍵字: | 側向土壓力,靜止土壓力係數,孔隙壓力比,顆粒互鎖,齡化作用, lateral earth pressure,coefficient of lateral earth pressure at rest,pore pressure ratio,particle interlocking,aging effect, |
出版年 : | 2017 |
學位: | 碩士 |
摘要: | 擋土設施之背填土常使用排水性良好的砂性土壤進行回填,濱海或港岸區域之臨水擋土結構物常延伸至水面以下,此時背填土呈飽和狀態,孔隙水壓的變化對擋土結構物的側向推力有相當大的影響。在地震作用時,動態側向土壓與水壓力之上升,可能使擋土結構物發生傾斜或平移之破壞。而在前人研究中,較少針對飽和砂土在受振時孔隙水壓力的變化對側向土壓力的影響進行探討。
故本研究,在無側向位移,即K_0狀態下,量測飽和石英砂受振時側向土壓及水壓之變化,探討飽和砂土受振引致水壓激發對靜止側向土壓力的影響。期能了解砂土顆粒與孔隙水在受振過程中的互制影響行為,並同時觀察時間因子(aging effect)對側向土壓力的影響。 試驗結果顯示,飽和砂土受振時,側向土壓力因顆粒互鎖作用,隨著水壓之激發而同步上升,致使側向有效應力變化不大,而垂直有效應力則因水壓激發而下降,因此K_0會增大,甚至可達1.0以上,亦即振動期間側向土壓力會隨水壓激發而上升且有超過垂直土壓力之情形。此外從試體填置完成時至靜置24到48小時期間,K_0約從0.4上升至0.5 到0.7,齡化作用會使側向土壓力有增加之趨勢。本研究亦依據試驗結果,分別以顆粒互鎖作用開始消失時之孔隙水壓比r_u、水壓增量u_e、靜止土壓力係數K_0及側向土壓力σ_h評估砂土顆粒間之互鎖作用,期能了解砂土顆粒間互鎖作用之機制。 The waterfront retaining structures in coastal regions or port areas often extend below the surface of the water, where the sandy backfill materials are generally saturated. The variation of pore water pressure would have a great impact on the lateral pressure on the retaining wall. The rise of the dynamic lateral earth pressure and the water pressure may cause the deformation of the retaining structures during the earthquakes. However, in the previous studies, the effect of the change of pore water pressure on the lateral earth pressure was rarely discussed. In this study, lateral earth pressure and pore water pressure were measured within saturated quartz sand subjected to vibration under the condition of no lateral displacement, i.e., under K_0 condition. The effect of vibration-induced water pressure generation on lateral earth pressure at rest in saturated sand was investigated to understand the interaction between sand particles and pore water during vibrations. Furthermore, the effect of aging on lateral earth pressure was also evaluated. The experimental results show that the lateral earth pressure increases along with the water pressure generation simultaneously, so the effective lateral stress doesn’t change much at the beginning of vibration. This may be due to the effect of particle interlocking during pore water pressure changes. With the vertical effective stress decreasing due to the water pressure increase, K_0 would increase up to more than 1.0. Because of particle interlocking, the lateral earth pressure would rise and may exceed the vertical earth pressure. In addition, K_0 increases from about 0.4 to 0.5-0.7 during the 24 and 48 hours periods after the completion of the specimen preparation. The effect of particle interlocking is evaluated based on the results of the pore pressure ratio r_u, the water pressure increment u_e, the coefficient of lateral earth pressure at rest K_0 and the lateral earth pressure σ_h at the starting point of losing particle interlocking for a better understanding of the mechanism of particle interlocking. |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/67629 |
DOI: | 10.6342/NTU201702134 |
全文授權: | 有償授權 |
顯示於系所單位: | 土木工程學系 |
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