【摘要】：陡坡段雙樁柱式橋梁與平地常規(guī)橋梁的基樁相比,在受荷機(jī)理和受力情況上都有很大的差異,基樁受到陡坡土體傳遞來(lái)的橫向荷載及樁頂組合荷載的共同作用,同時(shí)樁身對(duì)樁側(cè)巖土體產(chǎn)生抗力,構(gòu)成繁雜的陡坡土體-基樁互相影響的系統(tǒng)。本文結(jié)合江西省交通運(yùn)輸廳科技項(xiàng)目(編號(hào):2016C0006)進(jìn)行雙樁柱式橋梁的基樁對(duì)陡坡安全性及樁身屈曲穩(wěn)定性的研究。(1)對(duì)于陡坡段的均質(zhì)巖土體,構(gòu)建一個(gè)陡坡巖土體與雙樁柱式橋墩及橫梁的計(jì)算模型,分析其受力情況得出系統(tǒng)勢(shì)能,并基于最小勢(shì)能理論可得到下滑土體發(fā)生位移后達(dá)到穩(wěn)定時(shí)產(chǎn)生的虛位移,以此計(jì)算安全系數(shù)用于評(píng)價(jià)陡坡穩(wěn)定性。在系統(tǒng)總勢(shì)能中,本文著重考慮了雙樁柱式橋墩及橫梁的應(yīng)變能及樁土摩擦的能量。研究表明,本文結(jié)果稍大于邊坡安全系數(shù),說(shuō)明雙樁柱式橋墩對(duì)陡坡安全性是有利影響。在對(duì)陡坡安全性系數(shù)進(jìn)行敏感性分析中,發(fā)現(xiàn)彈性模量對(duì)安全系數(shù)的增長(zhǎng)影響不大;樁徑增大,樁土相互作用面積增大,導(dǎo)致安全系數(shù)增大;將基樁布置于坡頂至跛腳水平距離一半的位置時(shí)安全系數(shù)最大,此位置兩側(cè)布置安全系數(shù)逐漸減小;陡坡段土體粘聚力和內(nèi)摩擦角增大,陡坡安全系數(shù)隨之增大。(2)通過(guò)改進(jìn)的遺傳算法對(duì)臨界滑裂面進(jìn)行確定。通過(guò)五個(gè)參數(shù)進(jìn)行控制所構(gòu)建的三維橢球面,以安全系數(shù)作為目標(biāo)函數(shù),計(jì)算最小安全系數(shù)所對(duì)應(yīng)的參數(shù)最優(yōu)值構(gòu)成的最危險(xiǎn)滑移面,完成滑移面搜索。為避免局部最優(yōu)解情況,本文采用優(yōu)化后的遺傳算法進(jìn)行操作,即通過(guò)加入小生境技術(shù),極大限度的避免了局部最優(yōu)解的出現(xiàn),保證了搜索滑裂面結(jié)果的可靠性。通過(guò)在設(shè)定區(qū)域范圍內(nèi)改變參數(shù)進(jìn)行搜索,結(jié)果表明參數(shù)對(duì)滑移面的形狀影響并不大。(3)對(duì)于陡坡段橋梁基樁容易發(fā)生屈曲穩(wěn)定的問(wèn)題,通過(guò)滑移面與基樁的模型確定不同受荷類型區(qū)域長(zhǎng)度,并根據(jù)每段受力情況計(jì)算包括樁身自重產(chǎn)生能量在內(nèi)的系統(tǒng)能量,基于能量法可求變分特征方程特征根,得出一種用樁身臨界荷載判斷樁身屈曲穩(wěn)定性的方法。通過(guò)對(duì)樁身屈曲穩(wěn)定敏感性研究,發(fā)現(xiàn)嵌固段長(zhǎng)度增長(zhǎng),臨界荷載增大;在樁身自由段長(zhǎng)度過(guò)長(zhǎng)和樁徑過(guò)小的情況下,基樁極易發(fā)生屈曲穩(wěn)定性破壞。
[Abstract]:Compared with the foundation pile of the conventional bridge on the flat ground, there are great differences in the mechanism of loading and the stress on the foundation pile in the steep slope. The pile is subjected to the lateral load transmitted by the steep slope soil and the combined load on the top of the pile. At the same time, the pile body has the resistance to the soil on the side of the pile, forming a complicated system of interaction between the steep slope soil and the foundation pile. In this paper, the safety and buckling stability of foundation piles of double-piling bridge on steep slopes are studied in conjunction with the Science and Technology Project of Jiangxi Provincial Communications and Transportation Department (No. 2016C0006). (1) for homogeneous rock and soil mass in steep slope, A calculation model of steep slope rock soil and double pile column bridge piers and beams is constructed, and the system potential energy is obtained by analyzing its stress. Based on the theory of minimum potential energy, the fictitious displacement of sliding soil can be obtained when the displacement is stable. The safety factor is calculated to evaluate the stability of steep slope. In the total potential energy of the system, the strain energy of piers and beams and the energy of pile-soil friction are considered in this paper. The results show that the safety factor of the slope is slightly larger than that of the bridge piers, which indicates that the double-piling bridge piers have a beneficial effect on the safety of steep slopes. In the sensitivity analysis of the safety coefficient of steep slope, it is found that the elastic modulus has little effect on the increase of safety factor, and the increase of pile diameter and pile-soil interaction area leads to the increase of safety factor. When the pile is arranged at the half of the horizontal distance from the top of the slope to the crippling foot, the safety factor is maximum, and the safety factor on both sides of the position decreases gradually, and the cohesive force and the angle of internal friction of the soil in the steep slope increase. The safety factor of steep slope increases accordingly. (2) the critical slip surface is determined by improved genetic algorithm. The three dimensional ellipsoid is controlled by five parameters and the safety factor is taken as the objective function to calculate the most dangerous slip surface formed by the optimum value of the parameters corresponding to the minimum safety factor and to complete the search of the slip surface. In order to avoid the situation of local optimal solution, this paper uses the optimized genetic algorithm to operate, that is, by adding niche technology, the appearance of local optimal solution is avoided to a great extent, and the reliability of the result of searching slip surface is ensured. The results show that the parameters have little effect on the shape of slip plane. (3) for the bridge pile in steep slope section, buckling stability is easy to occur. Based on the model of sliding plane and pile, the length of different types of load is determined, and the system energy, including the energy generated by pile weight, is calculated according to the stress condition of each section, and the characteristic root of variational characteristic equation is obtained based on energy method. A method for judging the buckling stability of pile body by critical load is obtained. Through the study of the stability sensitivity of pile buckling, it is found that the length of the fixed block increases and the critical load increases, and the buckling stability of the pile is easily destroyed when the length of the free section of the pile is too long and the diameter of the pile is too small.
【學(xué)位授予單位】：江西理工大學(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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