本文關(guān)鍵詞： 軟土地基 被動(dòng)樁 堆載 土體側(cè)移 修正劍橋模型　出處：《福州大學(xué)》2014年碩士論文　論文類型：學(xué)位論文

【摘要】：在路基和橋梁等建設(shè)工程中,往往因地基土的工程性質(zhì)較差,使得在土體上的堆載誘發(fā)土體發(fā)生較大側(cè)向位移,使鄰近樁基礎(chǔ)受到附加水平荷載甚至豎向摩阻力的作用,嚴(yán)重影響樁的承載性能乃至上部結(jié)構(gòu)的破壞,這類樁即稱作“被動(dòng)樁”。被動(dòng)樁問(wèn)題有著深刻的工程背景和慘痛的經(jīng)驗(yàn)教訓(xùn),特別是近年來(lái)橋梁堆載問(wèn)題日益突出。本文首先利用有限元軟件Geo-Studio進(jìn)行軟基上堆載對(duì)鄰近橋梁樁基的受力形狀二維模擬分析,主要討論了不同堆載高度、寬度、位置、樁徑大小、樁長(zhǎng)、樁身彈性模量、凈空高度、軟土層厚度和樁頂荷載等因素對(duì)被動(dòng)樁的位移變化、樁身應(yīng)力和彎矩分布規(guī)律的影響,研究發(fā)現(xiàn)：(1)堆載大小和軟土層厚度對(duì)于樁基位移影響較大,起到至關(guān)重要的作用,橋梁尺寸和樁頂荷載等對(duì)樁基位移也有一定的影響,但影響不大,說(shuō)明與樁基位移直接相關(guān)聯(lián)的是樁側(cè)軟基沉降的大小。(2)樁身應(yīng)力大小受堆載大小、樁身彈性模量、凈空高度、樁頂荷載等因素影響較大。在左樁基的軟基段左側(cè),樁底持力層交界處右側(cè),右樁基軟基段左側(cè),樁底持力層交界處右側(cè),以及系梁部位的應(yīng)力較大,出現(xiàn)一定程度應(yīng)力集中現(xiàn)象。(3)樁身彎矩大小與堆載大小、位置、樁長(zhǎng)、彈性模量、凈空高度、軟土層厚度和樁頂荷載等因素關(guān)系較大,在軟土層以下約1 Om左右位置和樁底嵌入持力層處彎矩均較大。其次,針對(duì)福州閩侯荊溪特大橋的6個(gè)墩位的堆載問(wèn)題進(jìn)行了相應(yīng)分析,根據(jù)相關(guān)鉆探資料和設(shè)計(jì)資料建立相關(guān)模型,通過(guò)計(jì)算結(jié)果發(fā)現(xiàn),69#橋墩處位移較大,達(dá)到5.4cm。因此,結(jié)合相應(yīng)的橋梁加固設(shè)計(jì)規(guī)范提出了不同的加固和治理措施；同時(shí),對(duì)橋側(cè)軟基上堆載問(wèn)題提出了不同的預(yù)防措施,認(rèn)為采用復(fù)合地基加固軟基的方式能夠最有效地防治堆載所引起的的樁側(cè)位移,而采用卸載、換填土、隔離樁和樁基加固等方法,只適合于堆載較小或樁基位移較小的情況。說(shuō)明若要明顯改善堆載對(duì)橋梁樁基的影響,應(yīng)著手于改善軟土地基的承載力狀況,減小軟土地基沉降,從而減少軟基變形對(duì)橋梁樁基帶來(lái)的影響。
[Abstract]:In the subgrade and bridge construction projects, because of the poor engineering properties of the foundation soil, the surcharge on the soil caused a larger lateral displacement of the soil. The adjacent pile foundation is subjected to additional horizontal load or even vertical friction, which seriously affects the bearing capacity of the pile and even the damage of the superstructure. This kind of pile is called "passive pile". The problem of passive pile has profound engineering background and painful experience and lessons. Especially in recent years, the problem of bridge surcharge is becoming more and more serious. Firstly, the finite element software Geo-Studio is used to simulate the stress shape of adjacent bridge piles on soft foundation. This paper mainly discusses the displacement change of passive pile with different heaped height, width, position, pile diameter, pile length, elastic modulus of pile body, clearance height, soft soil layer thickness and pile top load. Under the influence of stress and bending moment distribution of pile body, it is found that the size of pile load and the thickness of soft soil layer play an important role in influencing the displacement of pile foundation. The bridge size and pile top load also have some influence on the pile foundation displacement, but the influence is not obvious, which shows that the pile displacement is directly related to the pile side soft foundation settlement. The elastic modulus of pile, clearance height and load on top of pile have great influence on the left side of the soft foundation, the right side at the junction of the bottom bearing layer, the left side of the soft foundation section of the right pile foundation, and the right side of the bearing layer at the bottom of the pile. The bending moment and pile load size, position, pile length, elastic modulus, clearance height of pile body are larger than that of tie beam, and the phenomenon of stress concentration occurs to a certain extent, I. E. pile bending moment and pile load size, position, pile length, elastic modulus and clearance height. The thickness of soft soil is related to the pile top load and so on. The bending moment is larger at about 1 Om below the soft soil layer and at the pile bottom embedded in the bearing layer. Secondly. Based on the relevant drilling data and design data, this paper analyzes the surcharge problem of 6 piers of Fuzhou Minhou Jingxi Bridge, and establishes the relevant model. Through the calculation results, it is found that the displacement at the pier of Gui69# bridge is large. Therefore, combined with the corresponding design code for bridge reinforcement, different reinforcement and treatment measures are put forward. At the same time, different preventive measures are put forward to the problem of pile load on the soft foundation of bridge side. It is considered that the composite foundation can be used to strengthen the soft foundation effectively to prevent the pile side displacement caused by the surcharge, and the unloading method is adopted to replace the fill. The method of separating pile and strengthening pile foundation is only suitable for the case of small heaped load or small displacement of pile foundation. It shows that if the influence of pile load on bridge pile foundation is to be improved obviously, the bearing capacity of soft soil foundation should be improved. The settlement of soft soil foundation is reduced, and the influence of soft foundation deformation on bridge pile foundation is reduced.
【學(xué)位授予單位】：福州大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2014
【分類號(hào)】：U443.15

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