本文選題：樁網(wǎng)結(jié)構(gòu)路基 + PFC離散元�。� 參考：《北京交通大學(xué)》2015年碩士論文

【摘要】：樁網(wǎng)結(jié)構(gòu)路基的樁、加筋墊層和土體相互作用強(qiáng)烈,尤其路基高度較低時(shí),基床受列車荷載影響較大,路基中的土拱效應(yīng)及張拉膜效應(yīng)會(huì)發(fā)生變化從而影響樁網(wǎng)結(jié)構(gòu)路基功能的發(fā)揮。研究列車荷載下樁網(wǎng)結(jié)構(gòu)低路基土拱效應(yīng)及墊層中土工格柵特性具有重要的理論意義和工程價(jià)值。 本文運(yùn)用PFC3d離散元軟件建立了樁網(wǎng)結(jié)構(gòu)路基簡化模型對土拱效應(yīng)進(jìn)行了細(xì)觀研究分析,進(jìn)而基于遂渝線現(xiàn)場動(dòng)車試驗(yàn)測試斷面運(yùn)用ABAQUS有限元軟件建立三維樁網(wǎng)結(jié)構(gòu)路基動(dòng)力模型,對列車荷載作用下樁網(wǎng)結(jié)構(gòu)低路基的土拱效應(yīng)和土工格柵受力及變形開展研究,本文主要內(nèi)容及結(jié)論如下： 1、運(yùn)用PFC3d軟件建立樁網(wǎng)結(jié)構(gòu)路基簡化模型模擬土拱效應(yīng),對顆粒間的接觸力鏈,顆粒的豎向及橫向位移,路基的豎向應(yīng)力分布等進(jìn)行分析,表明樁土發(fā)生差異沉降后路基中會(huì)形成應(yīng)力拱,應(yīng)力拱內(nèi)包含多個(gè)虛擬土拱。動(dòng)荷載作用時(shí)路基中會(huì)形成動(dòng)力土拱,動(dòng)力土拱的高度與動(dòng)荷載的大小有關(guān)且動(dòng)力土拱高度要低于靜力土拱。位移拱范圍內(nèi)樁頂上方顆粒的橫向位移較大,向四周逐漸減小。等沉面形成與位移拱有關(guān),位移拱范圍內(nèi)樁頂上方顆粒擠入樁間土區(qū)域從而導(dǎo)致位移拱范圍外樁頂上方顆粒豎向位移增大而樁間土上方顆粒豎向位移減小。 2、運(yùn)用ABAQUS軟件建立三維樁網(wǎng)結(jié)構(gòu)低路基動(dòng)力模型,采取相應(yīng)方法對列車荷載、動(dòng)力邊界等條件進(jìn)行設(shè)定�，F(xiàn)場動(dòng)車測試與模擬計(jì)算的動(dòng)應(yīng)力、動(dòng)位移結(jié)果對比驗(yàn)證了本文所建模型的可靠性。 3、基于動(dòng)力有限元模型分析列車荷載作用下樁網(wǎng)結(jié)構(gòu)路基中豎向應(yīng)力分布、等沉面高度、樁土應(yīng)力比等變化規(guī)律,表明列車荷載作用下路基中動(dòng)應(yīng)力的分布會(huì)受到土拱效應(yīng)影響,表現(xiàn)為樁間土上方的動(dòng)應(yīng)力轉(zhuǎn)移到樁頂上方且在土工格柵附近轉(zhuǎn)移現(xiàn)象最明顯。列車荷載作用過程中,樁土應(yīng)力比峰值逐漸減小且趨于穩(wěn)定。布置樁體縱斷面的等沉面高度大于沒有布置樁體縱斷面的等沉面高度,且沿路基中心到路肩同一類型縱斷面的等沉面高度降低,列車荷載作用后路基中心處的等沉面高度升高。另外分析了樁間距、路基高度、樁端土體模量等因素對土拱效應(yīng)分析參數(shù)及其在列車荷載作用后變化的影響規(guī)律。 4、分析列車荷載作用下的土工格柵受力及變形規(guī)律,表明路基中心處樁頂上方土工格柵豎向位移要小于樁間土上方土工格柵豎向位移。橫向土工格柵豎向變形量及變形變化量要大于縱向土工格柵。垂直樁帽邊的縱向土工格柵動(dòng)位移要大于平行樁帽邊的縱向土工格柵動(dòng)位移,橫向土工格柵動(dòng)位移從路基中心到坡腳呈現(xiàn)遞減規(guī)律。路基中心樁帽邊緣處土工格柵拉力及動(dòng)拉力大于樁間土及樁帽中心處土工格柵,橫向土工格柵最大拉力及動(dòng)拉力大于縱向土工格柵。墊層布置雙層土工格柵相對單層土工格柵能夠減小路基沉降及不均勻沉降,能夠提高路基抵抗列車荷載造成路基不均勻沉降的能力,并有利于土工格柵在列車荷載下的受力穩(wěn)定。另外分析了樁間距、路基高度、樁端土體模量等因素對土工格柵拉力及變形及其在列車荷載作用后變化大小的影響規(guī)律。
[Abstract]:Pile net structure subgrade pile, reinforcement cushion and soil interaction are strong, especially when the height of subgrade is low, the foundation bed is influenced by train load, soil arch effect and tensioned effect in subgrade will change to influence the function of pile network structure subgrade. The characteristics of grille have important theoretical significance and engineering value.
In this paper, a simplified model of pile net structure subgrade is established by using PFC3d discrete element software, and the soil arch effect is studied and analyzed. Then the dynamic model of the three dimensional pile network structure is established based on the test section of the field train test and test section of the Suu Yu line, and the soil arch effect of the Low Subgrade under the load of the pile network under the load of the train. The main contents and conclusions of this study are as follows:
1, using the PFC3d software to establish the simplified model of pile net structure to simulate the soil arch effect. The contact force chain, the vertical and lateral displacement of particles, the vertical stress distribution of the subgrade are analyzed. It shows that the stress arch will be formed in the Subgrade after the difference settlement of the pile and soil, and several virtual soil arches are included in the stress arch. The subgrade of the subgrade is the dynamic load. The dynamic soil arch is formed, the height of the dynamic soil arch is related to the size of the dynamic load and the height of the dynamic soil arch is lower than that of the static soil arch. The lateral displacement of the particles above the top of the pile is larger and gradually decreases to the surrounding area. The formation of the equal subsidence surface is related to the displacement arch, and the particles in the top of the pile top are squeezed into the soil area between the piles and thus lead to the soil region. The vertical displacement of particles above the top of the pile outside the displacement arch range increases, while the vertical displacement of the particles above the pile decreases.
2, the dynamic model of the Low Subgrade of three dimensional pile network structure is established by using ABAQUS software. The corresponding method is adopted to set the train load and the dynamic boundary conditions. The dynamic stress and the dynamic displacement results of the field EMU test and the simulation results verify the reliability of the model built in this paper.
3, based on the dynamic finite element model, the vertical stress distribution in the subgrade of the pile net structure under the load of the train is analyzed. The variation law of the height of the subsidence surface and the stress ratio of the pile and soil shows that the distribution of the dynamic stress in the subgrade under the load of the train will be influenced by the soil arch effect, which shows that the dynamic stress above the pile soil is transferred above the pile top and in the geotextile. The transfer phenomenon near the gate is most obvious. In the course of the train load, the stress of the pile and soil decreases gradually and tends to be stable. The height of the equal subsidence surface is greater than that without the longitudinal section of the pile body, and the height of the equal subsidence surface along the same type of longitudinal section along the center of the roadbed is reduced, and the Subgrade after the train load is loaded. In addition, the analysis parameters of the pile spacing, the height of the subgrade and the soil modulus of the pile end on the analysis parameters of the soil arch effect and its influence on the change after the train load are also analyzed.
4, the stress and deformation law of geogrid under the load of train indicates that the vertical displacement of the geogrid above the pile top is less than the vertical displacement of the geogrid above the pile. The vertical deformation and deformation of the lateral geogrid is greater than that of the longitudinal geogrid. The dynamic displacement of the longitudinal geogrid is greater than that of the parallel pile cap. The dynamic displacement of the lateral geogrid is decreasing from the center of the subgrade to the foot of the slope. The tensile force and the dynamic tension of the geogrid at the edge of the pile cap at the center of the subgrade is greater than the geogrid at the center of the pile and the pile cap. The maximum pulling force and the dynamic pulling force of the lateral geogrid are greater than the longitudinal geogrid. The layout of the double layer geogrid relative to the single layer geogrid can reduce the settlement and uneven settlement of the roadbed, which can improve the ability of the subgrade to resist the uneven settlement of the subgrade by the train load, and is beneficial to the stability of the geogrid under the train load. In addition, the pile spacing, the height of the subgrade and the soil modulus of the pile end are also analyzed. The influence of grid tension and deformation on the change of train load is discussed.

【學(xué)位授予單位】：北京交通大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2015
【分類號】：U416.1

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