【摘要】：鹽漬土在我國西北地區(qū)分布較廣，對高速公路工程建設(shè)產(chǎn)生很多危害，而隨著西部大開發(fā)持續(xù)推進，高速公路和高速鐵路大規(guī)模建設(shè)，這對鹽漬化軟土地基處理技術(shù)提出了更高的要求。礫石樁是一種重要的鹽漬化軟土地基加固方法，具有效果良好、施工簡便和造價經(jīng)濟等優(yōu)點，，但目前對于鹽漬化軟土地區(qū)礫石樁復(fù)合地基的研究仍處于“應(yīng)用領(lǐng)先于理論”的階段，因此本文通過三維拉格朗日有限差分法、室內(nèi)外試驗和理論分析相結(jié)合的方法，深入研究了路堤下礫石樁復(fù)合地基的工作性狀（附加應(yīng)力場特性和變形規(guī)律），并通過具體工程實例進行了驗證。本文主要研究成果簡述如下： （1）說明礫石樁處理鹽漬化軟土地基的施工機械和施工技術(shù)，分析了鹽漬土工程性質(zhì)研究現(xiàn)狀，綜述了路堤荷載下樁體復(fù)合地基附加應(yīng)力特性和變形場規(guī)律的研究現(xiàn)狀，并指出其中存在的問題。 （2）通過三維拉格朗日有限差分法模擬研究了路堤荷載下礫石樁復(fù)合地基附加應(yīng)力場特性。明確了樁身應(yīng)力、樁側(cè)摩阻力沿深度變化規(guī)律；相比于均質(zhì)地基，礫石樁復(fù)合地基在樁頂和樁端附近附加應(yīng)力梯度較大；在路堤下樁體承擔(dān)了更多的荷載，減少了樁間土附加應(yīng)力，從而有效控制了沉降；并基于路堤下充分發(fā)揮樁體作用的思路，提出褥墊層的厚度和模量。 （3）通過三維拉格朗日有限差分法研究了路堤荷載下礫石樁復(fù)合地基沉降規(guī)律和側(cè)向變形規(guī)律。路堤荷載下樁土存在相對位移，樁頂沉降和樁間土沉降隨著填土高度的增加均逐漸增大，填土結(jié)束后的樁頂沉降和樁間土沉降隨固結(jié)時間仍逐漸增大直至趨于穩(wěn)定；側(cè)向位移沿深度呈弓形分布，最大側(cè)向位移發(fā)生在軟土層內(nèi)。 （4）依托具體工程實例對礫石樁加固鹽漬化軟弱土地基的效果進行了分析，并通過室內(nèi)外試驗對路堤下礫石樁復(fù)合地基工作性狀進行了進一步分析，結(jié)果表明現(xiàn)場試驗與采用FLAC3D計算的結(jié)果基本一致，驗證了本研究數(shù)值模擬計算的正確性和可靠性，較為全面的揭示了鹽漬化軟土地區(qū)礫石樁復(fù)合地基的工作性狀。
[Abstract]:Saline soil is widely distributed in the northwest of China, causing a lot of harm to highway engineering construction. However, with the continuous development of the western region, the large-scale construction of expressway and high-speed railway has been carried out on a large scale. This puts forward higher requirements for the treatment technology of salinized soft soil foundation. Gravel pile is an important reinforcement method of salinized soft soil foundation, which has the advantages of good effect, simple construction and economical cost. However, the research on gravel pile composite foundation in salinized soft soil area is still in the stage of "applying ahead of theory", so this paper combines the method of three-dimensional Lagrangian finite difference method, indoor and outdoor test and theoretical analysis, In this paper, the working behavior of gravel pile composite foundation under embankment (additional stress field and deformation law) is deeply studied and verified by a concrete engineering example. The main research results of this paper are summarized as follows: (1) the construction machinery and construction technology of gravel pile for treating salinized soft soil foundation are explained, and the research status of the engineering properties of saline soil is analyzed. This paper summarizes the research status of additional stress characteristics and deformation field law of pile composite foundation under embankment load, and points out the existing problems. (2) the additional stress field characteristics of gravel pile composite foundation under embankment load are studied by means of three-dimensional Lagrangian finite difference method. Compared with homogeneous foundation, the additional stress gradient of gravel pile composite foundation near pile top and pile tip is larger than that of homogeneous foundation. The pile under the embankment bears more loads, reduces the additional stress of soil between the piles, thus effectively controls the settlement, and puts forward the thickness and modulus of the cushion based on the idea of giving full play to the role of the pile under the embankment. (3) the law of settlement and lateral deformation of gravel pile composite foundation under embankment load is studied by means of three-dimensional Lagrangian finite difference method. Pile-soil displacement exists under embankment load. Pile top settlement and inter-pile soil settlement gradually increase with the increase of filling height. The pile top settlement and inter-pile soil settlement after filling are still increasing with consolidation time and then tend to be stable. The lateral displacement is arcuate along the depth, and the maximum lateral displacement occurs in the soft soil layer. (4) based on concrete engineering examples, the effect of gravel pile strengthening salinized soft soil foundation is analyzed, and the working behavior of gravel pile composite foundation under embankment is further analyzed through indoor and outdoor tests. The results show that the results of field tests are basically consistent with those calculated by FLAC3D, which verifies the correctness and reliability of the numerical simulation in this study, and reveals the working behavior of gravel pile composite foundation in salinized soft soil area in an all-round way.
【學(xué)位授予單位】：長安大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2014
【分類號】：U416.1

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