【摘要】：我國(guó)高速公路、鐵路建設(shè)迅猛發(fā)展,建設(shè)過程中經(jīng)常會(huì)遭遇大面積軟土問題,而樁承式路堤作為一種有效適應(yīng)于該類不良地基的構(gòu)筑物形式得到普遍應(yīng)用,同時(shí)也引起了學(xué)術(shù)界的廣泛關(guān)注,然而樁承式路堤工作機(jī)理和應(yīng)力應(yīng)變特性非常復(fù)雜。在進(jìn)行土拱效應(yīng)分析時(shí),主要研究以下幾個(gè)關(guān)鍵問題:樁土應(yīng)力比、樁土差異沉降以及基于土拱效應(yīng)的樁承式路堤設(shè)計(jì)方法。已有研究提出了不同的土拱模型及相應(yīng)的計(jì)算方法,然而他們對(duì)土拱效應(yīng)的研究主要集中不同的設(shè)計(jì)參數(shù)對(duì)其發(fā)揮程度的影響,忽略了樁土差異沉降對(duì)土拱效應(yīng)的影響。曹衛(wèi)平、劉漢龍等人分別通過室內(nèi)模型試驗(yàn)以及數(shù)值模擬分析驗(yàn)證了樁土差異沉降與土拱效應(yīng)發(fā)揮程度密切相關(guān)。但是,對(duì)于樁土應(yīng)力比與樁土差異沉降的關(guān)系仍然缺乏具體的理論研究。針對(duì)這一狀況,本文假定等沉面高度,從而判定土拱效應(yīng)的完整程度。其次,將路堤-樁-樁間土作為整體分析,并基于樁承式路堤的變形協(xié)調(diào),提出“樁體向上刺入路堤的體積等于土拱區(qū)體積的壓縮量”的假設(shè),結(jié)合路堤靜力平衡和土拱拱腳處土體的極限狀態(tài),推導(dǎo)出樁土應(yīng)力比以及樁土差異沉降的計(jì)算公式。接著,對(duì)該方法所得結(jié)果進(jìn)行了驗(yàn)證,并分析了樁土面積置換率、填土高度、填土內(nèi)摩擦角對(duì)土拱效應(yīng)發(fā)揮程度以及樁土應(yīng)力比的影響。為了進(jìn)一步驗(yàn)證理論的合理性,采用數(shù)值模擬軟件ABAQUS建立二維分析模型,通過對(duì)模型結(jié)果的應(yīng)力應(yīng)變場(chǎng)分析得到等沉面的高度,即1.4倍樁帽凈距,驗(yàn)證了等沉面高度的假設(shè)。然后,分別改變樁承式路堤設(shè)計(jì)參數(shù),得到路堤高度、填土性質(zhì)、樁間距對(duì)樁土應(yīng)力比以及樁土差異沉降的影響。最后,將數(shù)值模型中應(yīng)力應(yīng)變場(chǎng)隨時(shí)間變化的歷程輸出,可以得到樁土差異沉降對(duì)土拱效應(yīng)發(fā)揮程度的影響。最后,建立了一套基于土拱效應(yīng)的樁承式路堤設(shè)計(jì)方法,通過調(diào)整樁間距及樁帽大小,使路堤達(dá)到相應(yīng)的性能要求,希望對(duì)工程實(shí)踐作出指導(dǎo)。
[Abstract]:With the rapid development of expressway and railway construction in China, large areas of soft soil are often encountered in the process of construction, and pile-supported embankment, as an effective structural form suitable for this kind of bad foundation, has been widely used. At the same time, it has also attracted extensive attention in academic circles. However, the working mechanism and stress-strain characteristics of pile-supported embankment are very complex. In the analysis of soil arch effect, the following key problems are studied: pile-soil stress ratio, pile-soil differential settlement and pile-supported embankment design method based on soil arch effect. Different soil arch models and corresponding calculation methods have been put forward. However, their research on soil arch effect mainly focuses on the influence of different design parameters on the degree of soil arch effect, neglecting the influence of pile-soil differential settlement on soil arch effect. Cao Weiping, Liu Hanlong and others verified that the differential settlement of pile and soil is closely related to the degree of soil arch effect through indoor model test and numerical simulation analysis. However, there is still a lack of specific theoretical research on the relationship between pile-soil stress ratio and pile-soil differential settlement. In view of this situation, this paper assumes the height of equal subsidence surface, so as to determine the integrity of soil arch effect. Secondly, the soil between embankment and pile is taken as the whole analysis, and based on the deformation coordination of pile-supported embankment, the assumption that the volume of pile piercing the embankment upward is equal to the compression of the volume of soil arch area is put forward. Combined with the static balance of embankment and the limit state of soil at the foot of soil arch, the calculation formulas of pile-soil stress ratio and pile-soil differential settlement are derived. Then, the results obtained by this method are verified, and the effects of pile-soil area replacement rate, filling height and internal friction angle on soil arch effect and pile-soil stress ratio are analyzed. In order to further verify the rationality of the theory, a two-dimensional analysis model is established by using the numerical simulation software ABAQUS. The height of the equal sinking surface, that is, 1.4 times the net distance of the pile cap, is obtained by analyzing the stress and strain field of the model results. The hypothesis of equal subsidence surface height is verified. Then, the design parameters of pile-supported embankment are changed respectively, and the effects of embankment height, filling properties and pile spacing on pile-soil stress ratio and pile-soil differential settlement are obtained. Finally, the influence of pile-soil differential settlement on the soil arch effect can be obtained by outputting the stress and strain field in the numerical model with time. Finally, a set of pile-supported embankment design method based on soil arch effect is established. By adjusting the pile spacing and pile cap size, the embankment can meet the corresponding performance requirements, hoping to guide the engineering practice.
【學(xué)位授予單位】：湖南大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2015
【分類號(hào)】：U416.12

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