本文選題：CFG樁復(fù)合地基 + 固結(jié)　； 參考：《湖南大學(xué)》2014年碩士論文

【摘要】：近年來復(fù)合地基技術(shù)在地基處理中得到了廣泛應(yīng)用，復(fù)合地基理論也成為了巖土工程領(lǐng)域重要的研究課題。CFG樁(水泥-粉煤灰-碎石樁的簡稱)復(fù)合地基作為其中的一種常用技術(shù)，具有施工簡單、質(zhì)量可靠和成本低等優(yōu)點，用于軟基處治時，可顯著提高地基承載力，減少其沉降，并能變廢(粉煤灰)為寶，經(jīng)濟和社會效益明顯。但目前有關(guān)CFG樁復(fù)合地基的理論研究整體上仍落后于其工程實踐，特別是對深厚軟土中未打穿CFG樁復(fù)合地基(由樁長范圍的加固區(qū)和樁長以下的下臥層組成)的研究更是鮮見報道。為此，本文進一步探討了未打穿CFG樁復(fù)合地基的固結(jié)和沉降特性，并完成了數(shù)值模擬分析，具體工作主要如下： 首先，結(jié)合復(fù)合地基及CFG樁復(fù)合地基的已有研究基礎(chǔ)和發(fā)展現(xiàn)狀，針對CFG樁復(fù)合地基的承載變形性狀、作用機理、褥墊層設(shè)置、承載力確定及設(shè)計計算方法等方面，進行了較為系統(tǒng)深入的討論和分析。 其次，將未打穿CFG樁復(fù)合地基簡化為雙層地基，，基于雙層地基一維固結(jié)理論，考慮樁體滲透和不滲透兩種情況，分別建立出未打穿CFG樁復(fù)合地基的固結(jié)方程，通過引入相應(yīng)的邊界條件，導(dǎo)得了不同工況下按沉降與按孔壓定義的未打穿CFG樁復(fù)合地基固結(jié)度計算公式。在此基礎(chǔ)上，基于MATLAB編制出相應(yīng)的計算程序，進而分析了樁長、樁體壓縮模量、樁體貫入比和面積置換率等參數(shù)對于固結(jié)過程的影響規(guī)律，并證實了“對于未打穿復(fù)合地基，按沉降定義的固結(jié)度不等于按孔壓定義的固結(jié)度”這一結(jié)論。 第三，基于所導(dǎo)得的未打穿CFG樁復(fù)合地基固結(jié)度計算公式，由固結(jié)度的定義，得到了考慮時效性的CFG樁復(fù)合地基的沉降計算公式，并通過算例對比分析，驗證了本文方法的可行性。 最后，基于FLAC3D軟件平臺，建立了未打穿CFG樁復(fù)合地基的三維數(shù)值分析模型，通過改變幾何力學(xué)參數(shù)進行對比分析，獲得了荷載水平、樁間土體模量、下臥層土體模量和樁長等參數(shù)對未打穿CFG樁復(fù)合地基沉降的影響規(guī)律曲線，可供工程實踐參考。
[Abstract]:In recent years, composite foundation technology has been widely used in foundation treatment. The theory of composite foundation has also become an important research subject in geotechnical engineering field. As a common technology, CFG pile (short for cement-flyash gravel pile) composite foundation has the advantages of simple construction, reliable quality and low cost. When used in soft foundation treatment, the bearing capacity of the foundation can be significantly increased, its settlement can be reduced, and the waste (fly ash) can be changed into a treasure. The economic and social benefits are obvious. However, at present, the theoretical research on CFG pile composite foundation is still lagging behind its engineering practice. Especially, the study of CFG pile composite foundation (composed of the reinforcement zone in the long range of pile and the lower horizontal layer below the pile length) in the deep soft soil is rarely reported. Therefore, this paper further discusses the consolidation and settlement characteristics of CFG pile composite foundation, and completes the numerical simulation analysis. The main work is as follows: first, Combined with the existing research foundation and development status of composite foundation and CFG pile composite foundation, aiming at the bearing deformation behavior, action mechanism, cushion setting, bearing capacity determination and design calculation method of CFG pile composite foundation, etc. Then, the CFG pile composite foundation is simplified as a double-layer foundation. Based on the one-dimensional consolidation theory of the double-layer foundation, the seepage and impermeability of the pile body are considered. The consolidation equations of CFG pile composite foundation without penetration are established respectively. By introducing the corresponding boundary conditions, the formulas for calculating the consolidation degree of CFG pile composite foundation under different working conditions are derived according to the definition of settlement and pore pressure. On this basis, the corresponding calculation program based on MATLAB is worked out, and the influence of pile length, pile compression modulus, pile penetration ratio and area replacement ratio on the consolidation process is analyzed. The conclusion that the degree of consolidation defined by settlement is not equal to the degree of consolidation defined by pore pressure ". Third, based on the derived formula for calculating the degree of consolidation of CFG pile composite foundation, the definition of consolidation degree is derived from the definition of consolidation degree. The formula for calculating the settlement of CFG pile composite foundation considering time effect is obtained, and the feasibility of this method is verified by comparison and analysis of examples. Finally, based on the software platform of FLAC3D, The three-dimensional numerical analysis model of CFG pile composite foundation is established. By changing the geometric mechanical parameters, the load level and the soil modulus between piles are obtained. The influence of soil modulus and pile length on the settlement of CFG pile composite foundation can be used as a reference for engineering practice.
【學(xué)位授予單位】：湖南大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2014
【分類號】：TU470

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