【摘要】：隨著經(jīng)濟(jì)的迅速發(fā)展,國(guó)家為改善二、三線城市特別是滇西北地區(qū)的交通出行問題,為高速公路的建設(shè)投入大量資金,這有利于推進(jìn)滇西北旅游業(yè)的發(fā)展,促成邊區(qū)實(shí)現(xiàn)跨越式發(fā)展和構(gòu)建小康社會(huì)。工程實(shí)踐中常會(huì)遇到群樁樁距距過小的情況,傳統(tǒng)的理論分析和室內(nèi)試驗(yàn)明顯滯后于工程實(shí)踐的需求。因此在保證橋梁工程的安全性并充分發(fā)揮群樁承載性能的同時(shí),對(duì)小間距群樁樁基的承載性狀進(jìn)行深入研究是非常有必要的。論文在分析國(guó)內(nèi)外室內(nèi)試驗(yàn)和理論計(jì)算的基礎(chǔ)上,通過建立有限元三維數(shù)值模型對(duì)云南某橋梁工程的小間距群樁豎向承載特性展開分析,主要研究工作及成果如下:(1)基于查閱國(guó)內(nèi)外群樁基礎(chǔ)的相關(guān)文獻(xiàn)基礎(chǔ)上介紹了計(jì)算單樁承載力、群樁承載力、群樁沉降、有效樁長(zhǎng)的方法,對(duì)比分析幾種常用經(jīng)典計(jì)算方法的優(yōu)缺點(diǎn)及適用范圍,并在此基礎(chǔ)上對(duì)群樁承載力采用群樁效應(yīng)系數(shù)法和極限平衡法、群樁沉降采用分層總和法、有效樁長(zhǎng)采用樁頂沉降控制法分別進(jìn)行計(jì)算。(2)對(duì)有限元軟件在巖土工程中的適用性進(jìn)行了簡(jiǎn)要分析,簡(jiǎn)明闡述本論文Abaqus數(shù)值模擬軟件的建模步驟及分析材料本構(gòu)模型的選用:樁體采用線彈性模型、土體采用摩爾-庫倫模型、相互作用采用摩擦接觸(切向行為采用罰函數(shù)、法向行為采用硬接觸)和綁定接觸,面-面離散化的方法。(3)采用Abaqus有限元軟件,對(duì)小間距低承臺(tái)群樁基礎(chǔ)進(jìn)行三維數(shù)值模擬計(jì)算,探討不同樁距、樁長(zhǎng)、樁數(shù)、樁徑等工況對(duì)群樁豎向承載性狀的影響,并就不同樁距工況下采用數(shù)值計(jì)算和理論計(jì)算得出的群樁效應(yīng)系數(shù)進(jìn)行對(duì)比分析,通過分析荷載-沉降曲線得出結(jié)論:在豎向荷載較小時(shí),不同工況下的群樁沉降差別不大;當(dāng)豎向荷載增大,樁距在2d-6d工況下沉降量由大變小;樁長(zhǎng)由50m增至80m工況下群樁豎向承載力逐步增大,沉降變形逐步減小,但樁長(zhǎng)增加到一定程度后再增加長(zhǎng)度,群樁承載力和沉降變化幅度較低;隨樁數(shù)增加,荷載-沉降曲線呈現(xiàn)較大變化,但樁數(shù)增加到一定量時(shí),沉降減小幅度趨于平穩(wěn)。對(duì)比分析數(shù)值計(jì)算和理論計(jì)算不同樁距工況下的群樁效應(yīng)系數(shù)相差不大,驗(yàn)證了采用數(shù)值模擬的可行性。(4)對(duì)依托工程分別采用以群樁效應(yīng)系數(shù)法和極限平衡法兩種不同方法來計(jì)算群樁豎向承載力,并對(duì)結(jié)果進(jìn)行了對(duì)比分析,驗(yàn)證了有限元數(shù)值計(jì)算出的群樁效應(yīng)系數(shù)的適用性;對(duì)依托工程群樁沉降、有效樁長(zhǎng)分別采用理論計(jì)算和數(shù)值計(jì)算進(jìn)行對(duì)別分析,得出群樁設(shè)計(jì)的合理性。
[Abstract]:With the rapid economic development, in order to improve the transportation and travel problems of the second and third tier cities, especially in northwest Yunnan, the state has invested a large amount of money in the construction of highways, which is conducive to promoting the development of tourism in northwest Yunnan. Promote the border region to achieve leapfrog development and build a well-off society. In engineering practice, the group pile spacing is often too small, and the traditional theoretical analysis and indoor test obviously lag behind the demand of engineering practice. Therefore, while ensuring the safety of bridge engineering and giving full play to the bearing capacity of pile groups, it is necessary to deeply study the bearing behavior of small spacing pile groups. Based on the analysis of indoor tests and theoretical calculations at home and abroad, the vertical bearing characteristics of small spacing pile groups in a bridge project in Yunnan Province are analyzed by establishing a finite element three-dimensional numerical model. The main research work and results are as follows: (1) based on the reference of the domestic and foreign pile group foundation, the method of calculating the bearing capacity, settlement and effective pile length of single pile group is introduced. The advantages and disadvantages of several classical calculation methods are compared and analyzed. On this basis, the pile group effect coefficient method and limit equilibrium method are adopted for pile group bearing capacity, and the stratified summation method is used for pile group settlement. The effective pile length is calculated by means of pile top settlement control method. (2) the applicability of finite element software in geotechnical engineering is analyzed briefly. In this paper, the modeling steps of Abaqus numerical simulation software and the selection of material constitutive model are briefly described. The pile body adopts linear elastic model, the soil body adopts Moore Coulomb model, the interaction adopts friction contact, and the tangential behavior adopts penalty function. (3) Abaqus finite element software is used to simulate the pile group foundation with small spacing and low cap, and the different pile spacing, pile length and pile number are discussed. The influence of pile diameter and other working conditions on the vertical bearing behavior of pile group is analyzed, and the effect coefficient of pile group under different pile-spacing conditions is compared and analyzed by numerical calculation and theoretical calculation. Through the analysis of load-settlement curve, it is concluded that the settlement of pile group under different working conditions is not different when the vertical load is small, and when the vertical load increases, the settlement of pile spacing changes from large to small under 2d-6d condition. When the pile length increases from 50 m to 80 m, the vertical bearing capacity of pile group increases gradually, the settlement deformation decreases gradually, but the pile length increases to a certain extent, and the variation range of bearing capacity and settlement of pile group is lower, which increases with the number of piles. The load-settlement curve varies greatly, but when the pile number increases to a certain amount, the settlement decreases steadily. There is no significant difference in the effect coefficient of pile group between the numerical calculation and the theoretical calculation under different pile-spacing conditions. The feasibility of numerical simulation is verified. (4) pile group effect coefficient method and limit equilibrium method are used to calculate the vertical bearing capacity of pile group respectively, and the results are compared and analyzed. The applicability of the effect coefficient of pile group calculated by finite element method is verified, and the rationality of pile group design is obtained by theoretical calculation and numerical calculation of effective pile length for pile group settlement of relying engineering.
【學(xué)位授予單位】：長(zhǎng)安大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類號(hào)】：U443.15

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