本文選題：超長(zhǎng)樁　切入點(diǎn)：承載特性　出處：《遼寧工程技術(shù)大學(xué)》2015年碩士論文

【摘要】：近年來(lái)高層建筑、大型橋梁、港口等建設(shè)中廣泛應(yīng)用大直徑超長(zhǎng)樁,給樁基理論這一傳統(tǒng)課題提出了新的挑戰(zhàn)。研究發(fā)現(xiàn)當(dāng)樁頂受荷水平臨近極限承載力時(shí),超長(zhǎng)樁樁端附近摩阻力有突然增大的現(xiàn)象,且在不同樁周土強(qiáng)度與樁土接觸面性質(zhì)的影響下,這種增大效果的發(fā)揮也不同。深入研究此種增強(qiáng)作用的原因及機(jī)理,對(duì)超長(zhǎng)樁的理論研究和實(shí)際應(yīng)用具有十分重要的意義。本文設(shè)計(jì)實(shí)施了超長(zhǎng)樁室內(nèi)模型試驗(yàn),分析了模型樁在不同樁頂荷載下荷載與沉降的關(guān)系、樁身軸力隨深度的變化、樁側(cè)摩阻力隨深度的變化以及樁頂荷載與樁端土壓力的關(guān)系。利用ADINA軟件建立了對(duì)應(yīng)于模型試驗(yàn)的有限元模型,將有限元模擬結(jié)果與試驗(yàn)結(jié)果進(jìn)行對(duì)比分析,并研究了樁端阻力與樁側(cè)阻力相互作用的機(jī)理。在考慮樁側(cè)阻力與樁端阻力的相互作用的基礎(chǔ)上,提出用Mindlin解對(duì)樁側(cè)阻力增強(qiáng)值進(jìn)行計(jì)算,并結(jié)合彈性理論法對(duì)模型樁承載力進(jìn)行了計(jì)算,對(duì)比了模型樁樁側(cè)摩阻力修正前后的計(jì)算結(jié)果。通過(guò)以上研究,得到了如下結(jié)論：(1)超長(zhǎng)樁的樁頂沉降較大,在設(shè)計(jì)超長(zhǎng)樁的極限承載力時(shí),以沉降控制較為合理；豎向荷載沿超長(zhǎng)樁樁身向下傳遞的過(guò)程中,上部樁側(cè)土分擔(dān)了較多的樁頂荷載,樁端承受的荷載相對(duì)較��；超長(zhǎng)樁樁側(cè)摩阻力發(fā)揮作用的主要部位在樁身上部以及樁底以上10d范圍內(nèi),樁身中部側(cè)摩阻力相對(duì)較小。當(dāng)樁頂荷載增加至一定值時(shí),樁端附近出現(xiàn)側(cè)摩阻力增強(qiáng)現(xiàn)象；在樁頂荷載達(dá)到1093N時(shí),試驗(yàn)?zāi)Ｐ蜆兜臉抖俗枇蜆秱?cè)阻力在樁端附近均出現(xiàn)增強(qiáng)現(xiàn)象。(2)有限元模擬可以反映出超長(zhǎng)模型試驗(yàn)中樁土作用的實(shí)際情況；樁端阻力對(duì)樁側(cè)土的水平應(yīng)力有增強(qiáng)作用,增大范圍約為樁端以上5d范圍內(nèi)；樁側(cè)阻力對(duì)樁端土5d范圍內(nèi)的應(yīng)力也具有增強(qiáng)作用,提高了樁端土的極限承載力；樁側(cè)阻力對(duì)樁端阻力的強(qiáng)化作用并不明顯,考慮樁端與樁側(cè)阻力相互作用的超長(zhǎng)樁承載力計(jì)算,關(guān)鍵在于準(zhǔn)確計(jì)算樁側(cè)阻力的增強(qiáng)值。(3)應(yīng)用Mindlin解對(duì)樁端阻力產(chǎn)生的樁側(cè)水平應(yīng)力進(jìn)行計(jì)算,并根據(jù)滑動(dòng)摩擦力與法向應(yīng)力呈直線關(guān)系,得到了考慮樁端阻力作用下的樁側(cè)附加摩阻力計(jì)算方法。(4)當(dāng)樁頂作用荷載較大時(shí),彈性理論法計(jì)算的樁側(cè)摩阻力與試驗(yàn)值在樁端附近存在偏離。結(jié)合附加側(cè)摩阻力進(jìn)行修正后得到的計(jì)算側(cè)摩阻力與試驗(yàn)值接近,說(shuō)明此種計(jì)算方法對(duì)正確計(jì)算超長(zhǎng)樁的側(cè)摩阻具有一定的理論意義和工程價(jià)值。
[Abstract]:In recent years, large diameter super-long piles have been widely used in high-rise buildings, large bridges, ports and so on, which presents a new challenge to the traditional problem of pile foundation theory. It is found that when the load level of pile top is near the ultimate bearing capacity, The frictional resistance near the end of super-long pile increases suddenly, and under the influence of different soil strength around pile and pile-soil interface, the effect of this increase is also different. It is very important for the theoretical research and practical application of super-long pile. In this paper, the indoor model test of super-long pile is designed and implemented, and the relationship between load and settlement of model pile under different pile top loads is analyzed, and the axial force of pile body changes with depth. The variation of pile side friction with depth and the relationship between pile top load and soil pressure at the end of pile are studied. The finite element model corresponding to the model test is established by using ADINA software, and the results of finite element simulation and test are compared and analyzed. The mechanism of interaction between pile end resistance and pile side resistance is studied. On the basis of considering the interaction between pile side resistance and pile end resistance, the Mindlin solution is proposed to calculate the pile side resistance enhancement value. Combined with elastic theory, the bearing capacity of model pile is calculated, and the calculated results before and after the modification of frictional resistance on the side of model pile are compared. Through the above study, it is concluded that the settlement of the pile top of the super-long pile is larger than that of the super-long pile. In the design of ultimate bearing capacity of super-long pile, the settlement control is more reasonable, and in the process of vertical load passing down the pile body, the upper pile side soil shares more pile top load, and the load on the pile end is relatively small. The main part of the lateral friction of super-long pile is in the pile body and above the pile bottom for 10 days, the friction of the middle side of the pile is relatively small. When the load on the top of the pile increases to a certain value, the phenomenon of increasing the side friction near the pile end appears. When the load on the top of the pile reaches 1093N, both the pile tip resistance and the lateral resistance of the test model pile are enhanced near the pile tip. The finite element simulation can reflect the actual situation of pile-soil action in the super-long model test. The resistance at the end of the pile enhances the horizontal stress of the soil on the side of the pile, the increasing range is about 5 days above the end of the pile, and the resistance of the side of the pile also increases the stress in the range of 5 days, which improves the ultimate bearing capacity of the soil at the end of the pile. The reinforcement effect of pile side resistance on pile tip resistance is not obvious. The bearing capacity of super-long pile considering the interaction between pile end and pile side resistance is calculated. The key lies in accurately calculating the enhancement value of pile side resistance. The Mindlin solution is used to calculate the horizontal stress of pile side caused by resistance at the end of the pile, and according to the relationship between sliding friction force and normal stress, the horizontal stress of pile side is calculated in a straight line. The calculation method of additional frictional resistance of pile side considering the resistance of pile tip is obtained. 4) when the load on the top of pile is large, The pile side friction calculated by the elastic theory method deviates from the test value near the pile end, and the calculated side friction resistance is close to the test value after modified with the additional side friction. It is shown that this method has certain theoretical significance and engineering value for correctly calculating the lateral friction of super-long piles.
【學(xué)位授予單位】：遼寧工程技術(shù)大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2015
【分類號(hào)】：TU473.1

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本文編號(hào)：1700126