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碩士論文公告區 |
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| 年度： | 91 | |
| 姓名： | 莊棓凱(Pou-Kai Zhuang) | |
| 論文題目(中)： | 砂土中傾斜擴座地錨之錨碇行為 | |
| 論文題目(英)： | Anchorage Behaviour of Inclined Underreamed Anchors in Sand | |
| 摘要(中)： | ||
| 本文乃使用SHSE 模式(Strain Hardening-Softening and Volume Expansion Model)配合FLAC3D 軟體進行傾斜擴座地錨於緊砂中之受力行為研究。 由研究結果發現，在Dr=70%之砂土中，當地錨直徑D=0.076m、長徑比 L/D=4.5、及覆土深徑比H/D=8 時，地錨之總拉力、面承力和摩擦力隨埋入深 度之增加而增加，而總拉力和面承力亦隨傾斜角度之增加而減少，但傾角為o 20 時，摩擦力最大。摩擦型地錨之最佳傾角為2 45 f - o 。發揮地錨尖峰拉拔力、 尖峰摩擦力與尖峰面承力所需的位移量並非一致。地錨之摩擦力具有明顯之尖 峰值與殘餘值，發揮尖峰摩擦力所需之位移量約為15%D達到殘餘摩擦力所需 之位移量為50%D；面承力於埋入深徑比Z/D≧5之後，將無明顯之尖峰值，因 此，面承力之臨界埋入深度Zcr=5D。經由定義地錨發揮降伏面承力Qqy所需之 位移量Sq≒35%D。 研究的結果亦顯示，地錨之面承力係數Nq隨埋入深度和傾斜角度的增加而 減少。尖峰摩擦力之側土壓力係數Kf小於被動土壓力係數Kp，但大於靜止土 壓力係數K0。地錨荷重傳遞曲線呈凹向上之方式由錨底向錨頂傳遞，埋入深徑 比Z/D＜10 之傾斜地錨，摩擦應力在錨頂會有應力集中現象，因此地錨之埋入 深徑比不宜小於10D。從錨碇段周圍土壤之降伏過程可得知，錨底土壤會因解 壓而先達到降伏，錨碇段上方土壤較下方之土壤先達降伏且降伏範圍較大。當 地錨的埋入深度較淺時，面承前方土壤之降伏面將會觸及結構壁體。當地錨之 覆土深徑比H/D≦8 時，其降伏範圍仍可能會發展至地表，因此傾斜地錨之覆 土深度不宜小於8D。 |
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| 摘要(英)： | ||
| A constitutive model for sand named “SHSE” and FLAC3D software were used to study the anchorage behavior of inclined underreamed anchors in dense sand. The anchor has a diameter D of 0.076mm, length-to-diameter ratio L/D of 4.5, and overburden head of 8D, all anchors were placed in sand with Dr=70%. It was found that the total load, end resistance, and shaft friction were increased with increasing embedded depth. Total load and end resistance were increased with decreasing inclined angle, too. The maximum shaft friction occurs when the inclination angle “a ” equals to 20o, an inclination angle of 2 / 45 f - O may be the optimum angle for a friction type anchor. Total load, end resistance, and shaft friction do not reach peak values at the same anchor displacement. Evident peak value and residual value can be seen when anchors were pulled. An anchor displacement equals to 15%D is need for the shaft friction reaches peak value. Shaft friction reaches residual state at an anchor displacement of about 50%D. No peak value of end resistance can be found when free length of an anchor is greater than 5D and named a depth anchor herein. According to the definition of yielding end-resistance, the yielding end-resistance of deep anchor develops at an anchor displacement of about 35%D. The end resistance coefficient Nq was decreased with increasing embedded depth and inclination angle of an anchor. The coefficient of lateral earth pressure Kf is less than coefficient of passive earth pressure Kp, but is greater than coefficient of earth pressure at rest K0. A concave upward behavior can be seen from load transfer curve. Friction stress concentration on the upper fixed end results from an anchor of Z/D<10, hence do not place the free length of anchor in 10D. From the process of yielding soil surround the fixed end can be found, soil surround bottom of an anchor reaches yield first due to stress relaxation, the range of yielding soil above fixed length is larger than the range of yielding soil below fixed length, the yielding range upon fixed end will reaches structural wall if an anchor is placed in shorter free length. The yielding range will develop to ground surface when overburden depth of an anchor is less than 8D, so do not placed those anchors in this area. |
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| 相關連結： | http://ethesys.lib.cyut.edu.tw/ETD-db/ETD-search-c/view_etd?URN=etd-0827103-085139 | |