本文選題：多節(jié)鉆擴灌注樁 + 構(gòu)造優(yōu)化��； 參考：《山東大學》2017年碩士論文

【摘要】：變徑灌注樁以其高承載力、施工簡易等特點越來越多的應(yīng)用于工程建設(shè)中。多節(jié)鉆擴灌注樁作為一種支盤樁、DX樁的優(yōu)化發(fā)展樁型,其成樁質(zhì)量可靠,施工效率高,承載力提高顯著,但是其樁身構(gòu)造設(shè)置和豎向承載力機理亟待開發(fā)與研究,本文采用數(shù)值模擬并結(jié)合理論分析的方法,研究并完善了鉆擴樁構(gòu)造優(yōu)化設(shè)置及豎向承載力理論,取得結(jié)論如下:1、基于理論推導(dǎo),明確了鉆擴樁擴徑體剖面幾何形狀為星形線與圓弧組合而成,推導(dǎo)了具體擴徑體幾何形狀的數(shù)學模型公式;通過對比模型試驗,判斷出鉆擴樁最佳盤徑樁徑比D/d取值宜為2～2.5,單樁最佳擴徑體數(shù)量約為2～3個,且宜設(shè)置在靠下的堅硬土層上,相鄰擴徑體最小間距約為2.5D～3.5D。2、通過對比分析,發(fā)現(xiàn)鉆擴樁抗壓時,擴徑體上部影響段摩阻力產(chǎn)生軟化減小,下部影響段產(chǎn)生硬化增大,綜合而言,設(shè)置擴徑體后承載力得到增強,但擴徑體對其臨近側(cè)摩阻力產(chǎn)生弱化效應(yīng);考慮擴徑體對鄰近區(qū)域摩阻力的影響,提出新型抗壓承載力計算公式,驗證結(jié)果良好。3、結(jié)合荷載傳遞法,取樁側(cè)、樁端、擴徑端為雙曲線函數(shù),求解出鉆擴樁非線性沉降預(yù)測方法,并對側(cè)阻參數(shù)進行變量分析;在擴徑端引入圓孔擴張理論,推導(dǎo)分析出考慮擴徑體幾何特征的擴徑端力與位移關(guān)系,得出受壓面水平內(nèi)壓力ph的分布規(guī)律;在此基礎(chǔ)上應(yīng)用荷載傳遞法,重新計算出樁頂沉降曲線,并與前者對比,發(fā)現(xiàn)新方法相對于傳統(tǒng)方法能更精準的預(yù)測中前期樁頂沉降,更能體現(xiàn)承載力對擴徑體特征的敏感性,傳統(tǒng)方法得到的擴徑端阻力小于實際值,但可以考慮塑性屈服,存在極限值,而新方法由于未考慮塑性條件,僅有彈性情況,使得其對擴徑端阻力的后期預(yù)測明顯偏大,后期沉降值會小于實際值。4、通過對比分析,發(fā)現(xiàn)鉆擴樁抗拔時,擴徑體上部影響段摩阻力產(chǎn)生硬化增大,下部影響段產(chǎn)生軟化減小,綜合而言,抗拔擴徑體對其臨近側(cè)摩阻力產(chǎn)生強化效應(yīng);考慮擴徑體對鄰近區(qū)域摩阻力的影響,提出新型抗拔承載力計算公式,驗證結(jié)果良好。
[Abstract]:Variable diameter cast-in-place pile is more and more widely used in engineering construction because of its high bearing capacity and easy construction. As a kind of optimum development pile type of branch disc pile and DX pile, multi-section drilling-expansion pile is of reliable quality, high construction efficiency and remarkable improvement of bearing capacity. However, the structure of pile body and the mechanism of vertical bearing capacity need to be developed and studied urgently. In this paper, numerical simulation and theoretical analysis are used to study and perfect the theory of structural optimization and vertical bearing capacity of drilling-expanding pile. The conclusions are as follows: 1, based on theoretical derivation. In this paper, it is clear that the geometric shape of the expanding body section of drill pile is the combination of star line and circular arc, the mathematical model formula of the geometric shape of the concrete expanding body is derived, and the comparison model test is carried out. It is found that the optimum diameter ratio D / d is 22.5, and the optimum number of single pile is about 2 ~ 3, and the minimum distance of adjacent diameter expanding is about 2.5 DX 3.5D.2. it is found that when drilling and expanding piles are compressed, the minimum distance between them is about 2.5 DX 3.5D.2.The results show that the optimum diameter ratio is about 2.5 DX / d, and the optimum diameter expansion is about 2 ~ 3, and the minimum distance between the two piles is about 2.5 DX 3.5D.2. The frictional resistance of the upper part of the expanding body decreases, and the lower part of the body harms and increases. In a word, the bearing capacity of the upper part of the expanding body is enhanced, but the effect of the expanding body on the adjacent side friction is weakened. Considering the influence of the expanding body on the frictional resistance of the adjacent region, a new formula for calculating the compressive bearing capacity is put forward. The result is good .3. combined with the load transfer method, the pile side, the pile end and the expanding end are taken as hyperbolic functions. The nonlinear settlement prediction method of drilling and expanding pile is solved, and the variable analysis of lateral resistance parameter is carried out, and the expansion theory of circular hole is introduced into the expanding end, and the relationship between the expanding end force and displacement considering the geometric characteristics of the expanding body is deduced and analyzed. On the basis of this, the settlement curve of pile top is recalculated by using load transfer method, and compared with the former, it is found that the new method can predict the settlement of pile top more accurately than the traditional method The resistance of the traditional method is smaller than the actual value, but the plastic yield can be considered and the limit value exists. However, the new method is only elastic because it does not consider the plastic condition. The later prediction of the resistance to the expanding end is obviously larger, and the later settlement value will be less than the actual value .4.Through comparison and analysis, it is found that the friction of the upper influence section of the expanding body increases while the lower part of the expanding pile softens when the pile is pulled out. To sum up, the anti-pull-out expanding body has a strengthening effect on the frictional resistance of the adjacent side, and considering the influence of the expanding body on the frictional resistance of the adjacent region, a new formula for calculating the pull-out bearing capacity is put forward, and the results are good.
【學位授予單位】：山東大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：TU473.1

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