【摘要】：在巖溶發(fā)育地區(qū),溶洞的形成使得其周?chē)鷰r體的應(yīng)力發(fā)生了重分布,改變了巖體的力學(xué)特征,并嚴(yán)重影響到巖層的承載能力,威脅到橋梁樁基的安全穩(wěn)定,給設(shè)計(jì)和施工也帶來(lái)了很多困難。如何分析和評(píng)估溶洞條件下橋基和持力巖層的穩(wěn)定是工程設(shè)計(jì)及施工必須面對(duì)的關(guān)鍵問(wèn)題。本論文以廣西百色至靖西高速公路BJ-A10合同段的多安大橋?yàn)楣こ桃劳?分別從理論分析和數(shù)值模擬等方面探討了溶洞頂部持力巖層穩(wěn)定性驗(yàn)算方法、橋梁基樁及持力巖層力學(xué)特征、持力層最小安全厚度的確定等,主要工作包括以下幾個(gè)方面:(1)對(duì)廣西境內(nèi)多條公路干線上的橋梁進(jìn)行了調(diào)研,統(tǒng)計(jì)和分析了巖溶區(qū)中小跨徑橋梁的結(jié)構(gòu)形式和病害特征,發(fā)現(xiàn)在巖溶區(qū)樁基基礎(chǔ)應(yīng)用最為廣泛,上部結(jié)構(gòu)一般首選輕型構(gòu)件,基礎(chǔ)變形破壞是巖溶區(qū)中小跨徑橋梁的主要病害形式;(2)分析了巖溶區(qū)橋梁嵌巖樁的失穩(wěn)形式及其穩(wěn)定性的影響因素,討論了橋梁基樁和持力巖層穩(wěn)定性的分析方法,得出了不同的持力巖層最小安全厚度計(jì)算公式;結(jié)合工程實(shí)例,采用了多種力學(xué)模型分別進(jìn)行了抗沖切驗(yàn)算、抗剪切驗(yàn)算和抗彎驗(yàn)算的分析,并與數(shù)值結(jié)果進(jìn)行了對(duì)比,認(rèn)為實(shí)例工程中橋梁基樁持力巖層的受力是較穩(wěn)定的;(3)采用有限差分程序FLAC3D對(duì)不同溶洞形狀、尺寸、位置、上部荷載及持力巖層厚度時(shí)的基樁及持力層力學(xué)特征進(jìn)行了三維模擬,研究了不同條件下,溶洞對(duì)基樁和持力巖層的影響規(guī)律,擬合了不同上部荷載時(shí)基樁端部豎向位移與持力巖層厚度的函數(shù)關(guān)系,提出了根據(jù)持力巖層塑性區(qū)是否貫通和基樁豎向位移是否超過(guò)允許范圍來(lái)確定持力層的最小安全厚度,并結(jié)合工程實(shí)例驗(yàn)證了其持力巖層厚度滿足承載要求。
[Abstract]:In the karst area, the formation of karst cave causes the stress of surrounding rock mass to be redistributed, which changes the mechanical characteristics of rock mass, and seriously affects the bearing capacity of rock layer and threatens the safety and stability of bridge pile foundation. It also brings many difficulties to design and construction. How to analyze and evaluate the stability of bridge foundation and bearing rock is a key problem in engineering design and construction. Based on the Duoan Bridge in the BJ-A10 contract section of Baise to Jingxi Expressway in Guangxi, this paper discusses the method of checking the stability of the rock layer at the top of the karst cave from the aspects of theoretical analysis and numerical simulation. The main work includes the following aspects: (1) the investigation and investigation of the bridges on several main highways in Guangxi, such as the mechanical characteristics of the bridge foundation pile and the bearing rock layer, the determination of the minimum safe thickness of the bearing layer, etc. The structural form and disease characteristics of small and medium span bridges in karst area are statistically analyzed. It is found that the pile foundation in karst area is the most widely used, and the superstructure is generally preferred as light component. Deformation and failure of foundation is the main disease form of medium and small span bridges in karst area. (2) the unstable form of rock-socketed pile and its influencing factors in karst area are analyzed, and the analysis methods of the stability of bridge foundation pile and bearing rock layer are discussed, and different formulas for calculating the minimum safe thickness of bearing rock layer are obtained. Combined with engineering examples, various mechanical models are used to analyze the impact shear calculation, shear resistance checking calculation and bending checking calculation, and the results are compared with the numerical results. It is considered that the bearing force of the bearing rock layer of the bridge foundation pile is relatively stable in the practical engineering. (3) the mechanical characteristics of foundation pile and bearing layer under different shape, size, position, upper load and thickness of bearing rock layer are simulated by finite difference program FLAC3D, and the different conditions are studied. The relationship between vertical displacement at the end of the pile and the thickness of the bearing rock layer under different upper loads is fitted by the influence of the cave on the foundation pile and the bearing rock bed, and the relationship between the vertical displacement of the pile end and the thickness of the bearing rock layer is obtained. The minimum safe thickness of the bearing layer is determined according to whether the plastic zone of the bearing rock layer is through and whether the vertical displacement of the foundation pile exceeds the allowable range.
【學(xué)位授予單位】：廣西大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類(lèi)號(hào)】：U443.15

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