【摘要】：我國巖溶地區(qū)分布廣泛,隨著工程建設(shè)規(guī)模逐步擴(kuò)大,在巖溶地區(qū)修建各類工程設(shè)施成為必然,人們也逐漸認(rèn)識到巖溶地質(zhì)對結(jié)構(gòu)物的危害性,特別是在橋梁樁基施工過程中遇到埋藏型巖溶地層,一般考慮將樁基作用在溶洞頂板之上。因此,溶洞頂板穩(wěn)定性研究工作被提到重要議程。本文以益婁高速公路埋藏型巖溶工程特性及處治技術(shù)研究項目為依托,開展對巖溶溶洞頂板與橋梁樁基的相互作用機(jī)理及其穩(wěn)定性研究,為后續(xù)工程的設(shè)計以及安全施工提供一定的借鑒作用,具有很大應(yīng)用價值。論文所做的主要工作及研究成果如下：(1)本文首先介紹了埋藏型巖溶的特征,通過對模型做出基本的假設(shè),將基樁與頂板的模型進(jìn)行分類簡化,得到了10種熟悉的力學(xué)結(jié)構(gòu)模型,在此基礎(chǔ)上,采用彈性力學(xué)中的薄板理論對溶洞頂板與橋梁樁基荷載系統(tǒng)模型做了詳細(xì)的受力分析,得出了對應(yīng)的頂板厚度檢驗公式。(2)根據(jù)建設(shè)工程中對基巖洞穴頂板的實際處理經(jīng)驗,分析了溶洞頂板穩(wěn)定性影響因素,經(jīng)分析可知：溶洞處于某一埋藏深度時,頂板跨度越大,其允許最小安全厚度越大：而溶洞洞深越深,其最小安全厚度更小；得出頂板跨度是溶洞穩(wěn)定的非常不利因素,而溶洞的洞深是其穩(wěn)定的有利因素。(3)從溶洞失穩(wěn)的原因著手分析了巖溶失穩(wěn)機(jī)理,引入巖石強度理論,建立巖溶失穩(wěn)模型對其機(jī)理進(jìn)行分析,分析得出,其實巖溶失穩(wěn)機(jī)理即為力學(xué)機(jī)理：荷載作用導(dǎo)致巖土體強度失效以致失穩(wěn)。(4)從上述結(jié)構(gòu)模型中選取梁板模型來進(jìn)行模擬分析,并結(jié)合該模型的特點對不同樁徑下頂板的穩(wěn)定性做了抗沖切、抗剪切以及抗彎驗算。經(jīng)驗算可知,由基樁和頂板組成的類梁板模型整體呈安全穩(wěn)定狀態(tài),其計算結(jié)果能指導(dǎo)工程設(shè)計與施工。(5)本文采用數(shù)值軟件FLAC-3D,對益婁高速公路第10合同段石壩沖大橋位于K81+843和K81+878橋墩下的基樁和溶洞頂板穩(wěn)定性進(jìn)行了模擬分析。通過分析,筆者建議采用套筒加固技術(shù)對K81+878處的基樁進(jìn)行加固,研究結(jié)論可以作為益婁高速公路橋基工程設(shè)計與施工的依據(jù)。此外,數(shù)值模擬對于此類問題的分析實用可靠,值得更深入研究。
[Abstract]:Karst area is widely distributed in China. With the expansion of engineering construction scale, it is inevitable to build various kinds of engineering facilities in karst area. People also gradually realize the harmfulness of karst geology to structure. Especially in the process of bridge pile foundation construction, when the buried karst strata are encountered, it is generally considered that the pile foundation should be acted on the roof of the karst cave. Therefore, the study of cavern roof stability has been raised to the important agenda. Based on the research project of buried karst engineering characteristics and treatment technology of Yiluo Expressway, the interaction mechanism and stability of karst cave roof and bridge pile foundation are studied in this paper. It can be used for reference for the design and safety construction of the subsequent engineering, and has great application value. The main work and research results are as follows: (1) this paper firstly introduces the characteristics of buried karst and simplifies the model of foundation pile and roof by making the basic assumptions of the model. On the basis of 10 familiar mechanical structural models, the load system model of roof and bridge pile foundation of cavern is analyzed in detail by using thin plate theory in elastic mechanics. The corresponding test formula of roof thickness is obtained. (2) according to the practical treatment experience of bedrock cave roof in construction project, the factors influencing the stability of karst cave roof are analyzed. The analysis shows that the roof span of karst cave is larger when it is in a certain buried depth. The greater the allowable minimum safe thickness is, the deeper the cave is, and the smaller the minimum safe thickness is, the more the roof span is the most disadvantageous factor for the stability of the cave. The cave depth is a favorable factor for its stability. (3) the mechanism of karst instability is analyzed from the reasons of cave instability. The rock strength theory is introduced, and the mechanism of karst instability is analyzed by establishing a karst instability model. In fact, the mechanism of karst instability is mechanical mechanism: the failure of strength of rock and soil caused by load causes instability. (4) the beam and plate model is selected from the above structural model to simulate and analyze. Combined with the characteristics of the model, the stability of the roof under different pile diameter is calculated by anti-punching, shearing and bending. The empirical calculation shows that the beam-like plate model composed of foundation pile and roof is in a safe and stable state as a whole. The calculation results can guide the design and construction of the project. (5) in this paper, the stability of the foundation pile and the roof of the karst cave located under the piers of K81,843 and K81 878 is simulated and analyzed by using the numerical software FLAC-3D in the 10th contract section of Yilu Expressway. Through the analysis, the author suggests that the foundation pile at K81,878 should be strengthened with sleeve reinforcement technology, and the research conclusion can be used as the basis for the design and construction of the bridge foundation of Yiluo Expressway. In addition, the numerical simulation is practical and reliable for the analysis of this kind of problems, which is worthy of further study.
【學(xué)位授予單位】：長沙理工大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2015
【分類號】：U443.15

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