本文選題：嵌巖樁 + 數(shù)值模擬　； 參考：《南昌大學》2015年碩士論文

【摘要】：巖溶(karst)是一種由地下水長期溶蝕可溶性巖石而產(chǎn)生巖石內(nèi)部的空洞現(xiàn)象,對建設工程的基礎(chǔ)有著很大影響。巖溶地質(zhì)情況在我國有廣泛分布,貴州、云南存在著可溶性巖石,同時也有普遍的溶蝕現(xiàn)象,廣西地區(qū)的巖溶則已經(jīng)普遍到能作為旅游景點。江西地區(qū)同樣也存在著這樣的情況,巖溶在江西的分布主要在上高、宜春、萍鄉(xiāng)一帶,它分布的廣泛和發(fā)育程度已經(jīng)對橋梁、建筑等的建設產(chǎn)生了很大的影響。江西省是中部的欠發(fā)達地區(qū),其基礎(chǔ)設施尚未建設完善,高速公路、鐵路、城市橋梁的建設規(guī)模會增大,經(jīng)過巖溶地區(qū)的公路將越來越多,橋梁樁基工程需要應對溶洞的情況也會越來越多。然而我國規(guī)范中對于建立在溶洞以上的嵌巖樁的承載力的計算方法并不統(tǒng)一和明確,也就是說,規(guī)范中僅有常規(guī)條件下嵌巖樁承載力的計算式,而缺少存在溶洞情況下的計算式,這對于影響因素頗多、爭議很大的巖溶地區(qū)顯然是不合理的。為指導巖溶地區(qū)橋梁下部結(jié)構(gòu)的設計,給橋梁嵌巖樁極限承載力的計算提供可靠的依據(jù),對巖溶區(qū)嵌巖樁承載力的研究應該達到一個通用的、公式化的水平。本文將基于江西地區(qū)的巖溶地質(zhì)特征,對下伏溶洞的嵌巖樁承載特性做了一些分析和研究,主要內(nèi)容包括:(1)對江西某高速公路設計路線上穿過巖溶區(qū)的橋梁地質(zhì)情況、溶洞分布和發(fā)育特征做了一個比較詳細的統(tǒng)計和總結(jié);(2)查閱文獻,分析巖溶區(qū)嵌巖樁承載和破壞機理;(3)參考資料,選用擴展的DP模型作為巖土本構(gòu)模型,并利用有限元軟件ABAQUS對嵌巖樁力的傳遞機理進行了有效的模擬;(4)對溶洞的數(shù)個幾何與物理參數(shù)進行了敏感性數(shù)值分析,結(jié)論表明:a)嵌入溶洞頂板的樁基破壞模式主要分兩種:頂緣受樁端壓力破壞和底緣受拉破壞,當樁基和溶洞邊界在平面上比較接近時,還容易發(fā)生頂板巖石的剪切破壞;b)溶洞的豎向尺寸對樁基承載力的影響并不明顯,其水平尺寸的影響較為突出;c)嵌巖樁在4m及以下厚度的頂板上時,其前沿深度宜淺不宜深,在5m至8m厚度的頂板,最佳嵌巖深度宜為0.5m~1.0m;d)溶洞頂板上的嵌巖樁極限承載力依溶洞幾何特征的變化規(guī)律可以用二元三次多項式來表示,且本文嘗試了擬合其結(jié)果。(5)對當下溶洞地區(qū)基礎(chǔ)設計做出了個案分析,并提出了施工上的合理的建議。
[Abstract]:Karst (karst) is a kind of cavitation phenomenon in the rock caused by the long-term dissolution of the groundwater soluble rock, which has great influence on the foundation of the construction project. Karst geology is widely distributed in China. There are soluble rocks in Guizhou and Yunnan, but also widespread dissolution phenomenon. The karst in Guangxi has been widely used as a tourist attraction. The distribution of karst in Jiangxi is mainly in Shanggao, Yichun and Pingxiang. Its wide distribution and development degree have had a great influence on the construction of bridges and buildings. Jiangxi Province is an underdeveloped region in the middle of the country. Its infrastructure has not yet been built. The scale of construction of highways, railways and urban bridges will increase, and more highways will pass through karst areas. The bridge pile foundation engineering needs to deal with the karst cave situation will also be more and more. However, the calculation method of bearing capacity of rock-socketed pile built above the cave is not uniform and clear in the code of our country, that is to say, the calculation formula of bearing capacity of rock-socketed pile under conventional conditions is only in the code. However, the lack of calculation formula in the presence of caverns is obviously unreasonable in karst areas where there are many influencing factors. In order to guide the design of bridge substructure in karst area and to provide reliable basis for the calculation of ultimate bearing capacity of rock-socketed pile in karst area, the research on bearing capacity of rock-socketed pile in karst area should reach a general and formulaic level. Based on the characteristics of karst geology in Jiangxi province, this paper makes some analysis and research on the bearing characteristics of rock-socketed piles in buried caverns. The main contents include: (1) the geological conditions of bridges passing through karst areas on the design route of a highway in Jiangxi Province. The distribution and development characteristics of karst caves are summarized in detail. (2) the literature is consulted to analyze the bearing capacity and failure mechanism of rock-socketed piles in karst areas. (3) the extended DP model is selected as the constitutive model of rock and soil. The finite element software Abaqus is used to simulate the transfer mechanism of rock-socketed pile force effectively. (4) the sensitivity numerical analysis of several geometric and physical parameters of the cavern is carried out. The results show that there are two main failure modes of pile foundation embedded in the roof of the cavern: the top edge is damaged by the pressure at the end of the pile and the bottom edge is damaged by tension, when the boundary between the pile foundation and the cave is close in plane, The vertical dimension of the cavern has no obvious effect on the bearing capacity of pile foundation, and the horizontal dimension has a prominent effect on the bearing capacity of pile foundation. When the rock-socketed pile is on the roof with thickness of 4 m or below, the forward depth should be shallow rather than deep. At the thickness of 5 m to 8 m, the optimum depth of rock embedding is 0.5 m ~ 1.0 m / d) the variation of ultimate bearing capacity of rock-socketed pile on the roof of a karst cave can be expressed by the binary cubic polynomial, and the variation of the ultimate bearing capacity of the rock-socketed pile on the roof of the karst cave can be expressed as a binary cubic polynomial. This paper tries to fit the results. (5) A case study of the foundation design in the present karst cave area is made, and some reasonable construction suggestions are put forward.
【學位授予單位】：南昌大學
【學位級別】：碩士
【學位授予年份】：2015
【分類號】：U443.15

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本文編號：2106401