本文選題：重力錨 + 鈣質(zhì)砂　； 參考：《天津大學》2014年碩士論文

【摘要】：對鈣質(zhì)土的研究始于上世紀60年代,由埃索(ESSO)石油公司在Bass Strait建設(shè)的一組石油平臺,在1970年施工過程中發(fā)現(xiàn)樁極易貫入,在約0.67m的樁段進行了拉拔實驗,結(jié)果表明其實際值只有設(shè)計值的20%,造成了重大損失,因而引起了人們的關(guān)注。國內(nèi)對鈣質(zhì)土的研究始于上個世紀80年代,國家科委把南海鈣質(zhì)土的研究列為“八五”科技攻關(guān)項目,對鈣質(zhì)土以及建于其上的結(jié)構(gòu)物的研究引起人們的重視。由于鈣質(zhì)土的物理力學性質(zhì)特殊,一般的錨固形式不適用于這種土質(zhì)條件,作為一種古老的錨固形式--重力錨卻能很好的適用于此類土質(zhì)條件,而在國內(nèi),重力錨研究的相對較少,目前也沒有太多的資料針對鈣質(zhì)砂中的重力錨,有關(guān)重力錨的規(guī)范僅給出了重力錨的大體設(shè)計要求,對于重力錨承載力特性沒有明確的研究。本文對鈣質(zhì)土(包括鈣質(zhì)砂以及礁灰?guī)r)的物理力學性質(zhì)進行相關(guān)的研究以及對錨固場址的土質(zhì)進行了總結(jié),討論了不同錨固形式的使用條件,最后確定重力錨為最佳選擇。通過規(guī)范給出的重力錨設(shè)計原則以及相關(guān)計算公式,可以初步確定重力錨尺寸,并計算得到重力錨的水平承載力,與有限元計算的結(jié)果進行比較,可以發(fā)現(xiàn)兩個結(jié)果一致,進一步驗證了有限元模型的可靠性,通過有限元對重力錨在水平荷載作用下破壞機理的研究,可以發(fā)現(xiàn)重力錨水平承載力影響因素,最終確定重力錨的最佳尺寸,然后進行局部結(jié)構(gòu)的計算以及整體抗傾覆計算,最后采用有限元對串錨進行模擬與計算,得到其水平承載力特性。通過錨固場址土質(zhì)條件的分析和有限元分析重力錨在水平荷載作用下破壞機理得到以下結(jié)論:(1)對鈣質(zhì)砂尤其是帶礁灰?guī)r層的土質(zhì)條件,作為錨固形式,重力錨優(yōu)于其他形式的錨,如拖曳錨、樁錨、平板錨。(2)通過有限元模擬,當土體參數(shù)不變,重力錨體積以及其他參數(shù)不變時,僅改變錨底面面積,錨的水平承載力先是隨底面積面積增加而增加,隨后隨面積的增加而減小,并且正方形底面優(yōu)于矩形底面。其原因是破壞機理不一樣,底面積較小時主要是土體局部破壞,面積較大則是土體淺層破壞。除底面積外,最敏感的影響因素是錨底與土的摩擦系數(shù),水平承載力隨摩擦系數(shù)增加呈線性增加。(3)有剪力鍵或裙板的重力錨水平承載力明顯高于平底重力錨,這是因為安裝剪力鍵或裙板后,錨底土體破壞模式發(fā)生改變,由淺層破壞向下發(fā)展,滑動破壞面變大,承載力也就提高了。研究表明剪力鍵最優(yōu)道數(shù)為12道。(4)通過對串錨的模擬,可以發(fā)現(xiàn),串錨中的錨單元受力不同于單個錨的受力,破壞形式不同于單個重力,水平承載力不是簡單的單個錨水平承載力的疊加。
[Abstract]:The research on calcareous soil began in the 1960s. A group of oil platforms constructed by Essos ESSO oil company in Bass Strait. During the construction in 1970, it was found that the piles were easy to penetrate, and the drawing experiments were carried out at about 0.67 m. The results show that the actual value is only 20% of the design value, which has caused great losses, and has attracted people's attention. The research on calcareous soil in China began in the 1980s. The research of calcareous soil in the South China Sea has been listed as the scientific and technological research project of the eighth Five-Year Plan by the State Science and Technology Commission, and the study of calcareous soil and the structure on which it is built has attracted people's attention. Because of the special physical and mechanical properties of calcareous soil, the general form of anchoring is not suitable for this kind of soil condition. As an ancient form of anchorage-gravity anchor can be well applied to this kind of soil condition, but in our country, There are few researches on gravity anchors, and there is not much data for gravity anchors in calcareous sand. The general design requirements of gravity anchors are only given in the criterion of gravity anchors, and the bearing capacity characteristics of gravity anchors are not clearly studied. In this paper, the physical and mechanical properties of calcareous soil (including calcareous sand and reef limestone) are studied and the soil quality of anchoring site is summarized. The application conditions of different anchoring forms are discussed, and the optimum choice of gravity anchor is determined. Through the design principle of gravity anchor and relevant calculation formula, the size of gravity anchor can be preliminarily determined, and the horizontal bearing capacity of gravity anchor can be calculated. Comparing with the result of finite element calculation, it can be found that the two results are consistent. The reliability of the finite element model is further verified. Through the study of the failure mechanism of the gravity anchor under horizontal load, the factors affecting the horizontal bearing capacity of the gravity anchor can be found and the optimum size of the gravity anchor can be determined. Then the local structure and the whole anti-overturning calculation are carried out. Finally, the finite element method is used to simulate and calculate the anchor, and the horizontal bearing capacity is obtained. The failure mechanism of gravity anchor under horizontal load is analyzed by means of the analysis of soil quality and finite element analysis of the anchoring site. The following conclusion is drawn: 1) the soil condition of calcareous sand, especially the limestone bed with reef, is regarded as the form of anchoring. Gravity anchors are superior to other anchors, such as towed anchors, pile anchors, flat anchors. Through finite element simulation, when soil parameters are constant, gravity anchor volume and other parameters are invariant, only the floor area of anchor is changed. The horizontal bearing capacity of the anchor increases firstly with the increase of the bottom area, then decreases with the increase of the area, and the square bottom is better than the rectangular bottom. The reason is that the failure mechanism is different, the small bottom area is mainly the local failure of soil, and the larger area is the shallow failure of soil. In addition to the bottom area, the most sensitive factor is the friction coefficient between the anchor bottom and the soil. The horizontal bearing capacity increases linearly with the increase of the friction coefficient. The horizontal bearing capacity of the gravity anchor with shear bond or skirt plate is obviously higher than that of the gravity anchor with flat bottom. This is because after installing the shear bond or skirt plate the failure mode of the soil under the anchor is changed from shallow failure to downward and the sliding failure surface becomes larger and the bearing capacity is increased. The results show that the optimum number of shear keys is 12 channels. 4) through the simulation of anchor, it is found that the force of anchor element in anchor is different from that of single anchor, and the failure form is different from that of single gravity. The horizontal bearing capacity is not a simple superposition of the horizontal bearing capacity of a single anchor.
【學位授予單位】：天津大學
【學位級別】：碩士
【學位授予年份】：2014
【分類號】：TU476

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1 李颯;段高松;李懷亮;黃山田;王曉飛;;復(fù)合荷載作用下重力錨的抗滑穩(wěn)定計算[J];土木建筑與環(huán)境工程;2018年02期

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本文編號：1831357