【摘要】：樁基承載力的核心問題是樁-土相互作用問題,然而,現(xiàn)階段,對于泥巖與結構接觸面剪切特性的研究極少,已有的粗粒土、砂土等土質與樁相互作用機理又不適于拿來用于紅層泥巖地層。而泥皮是影響樁-巖相互作用的重要因素,泥皮夾在鉆孔灌注樁與樁側土層之間,形成一薄弱夾層,由于其壓縮性高、抗剪強度低等特點,常常是導致樁側摩阻力降低的主要因素。為解決這一實際工程問題,論文擬從樁-巖相互作用機理出發(fā),結合室內土工參數(shù)試驗、樁-巖接觸面直剪試驗,得到紅層泥巖樁側泥皮土物理力學參數(shù)和樁-巖接觸面剪切特性及其本構,然后采用有限差分軟件建立正常樁和含泥皮樁基數(shù)值模型,研究泥皮效應對紅層泥巖樁基承載性狀的影響,并對含泥皮紅層泥巖樁基承載力公式進行修正。具體包括以下幾個方面研究內容：(1)通過采集紅層泥巖試樣與制作混凝土試塊,進行室內大型樁-巖接觸面剪切試驗,對試驗結果進行分析得到樁-巖接觸面剪切破壞特性,并根據(jù)接觸面剪切試驗結果,建立紅層泥巖樁-巖接觸面本構模型,并推導出其本構方程：(2)通過分析泥皮形成機理,對紅層泥巖樁側泥皮土進行取樣并進行室內土工參數(shù)試驗,得到紅層泥巖樁側泥皮土物理力學參數(shù),主要為后續(xù)建模提供泥皮參數(shù)。調研現(xiàn)有文獻并統(tǒng)計其它地層及泥皮土的物理力學參數(shù),分析泥皮土性狀與原狀土的差異。(3)利用FLAC3D有限差分軟件,建立考慮巖樁-巖接觸面本構的紅層泥巖單樁靜載試驗模型,首先,分析不同樁長情況下,正常樁基與含泥皮樁基承載特性；然后對含泥皮樁基靜載試驗進行參數(shù)敏感性分析,主要研究了泥皮厚度、泥皮彈性模量、泥皮粘聚力、泥皮內摩擦角等因素對含泥皮紅層泥巖樁基承載性狀的影響。(4)通過數(shù)值模擬分析結果,分析了泥皮各因素變化對樁基承載性狀的影響,提出泥皮厚度樁基側摩阻力修正系數(shù),對規(guī)范樁基承載力計算公式進行修正：目前,隨著樁基工程的大規(guī)模開展,關于泥皮缺陷樁承載性狀的問題越來越受到重視,本論文研究成果對實際樁基工程中的含泥皮紅層泥巖樁基設計有一定的參考價值。
[Abstract]:The core problem of pile bearing capacity is pile-soil interaction. However, at present, there are few researches on shear characteristics of mudstone and structural interface. The interaction mechanism of sand and pile is not suitable for red mudstone formation. The mud crust is an important factor affecting the pile-rock interaction. The mud jacket between the bored pile and the pile side soil layer forms a weak interlayer, because of its high compressibility and low shear strength. It is often the main factor that leads to the reduction of pile side friction. In order to solve this practical engineering problem, the paper intends to proceed from the pile-rock interaction mechanism, combined with the indoor geotechnical parameter test, and the direct shear test of pile-rock interface. The physical and mechanical parameters of the mudstone pile side and the shear characteristics of the pile-rock interface and its constitutive structure are obtained, and then the numerical models of the normal pile and the mud-covered pile foundation are established by using the finite difference software. The influence of mud-skin effect on the bearing capacity of red mudstone pile foundation is studied, and the formula of bearing capacity of red mudstone pile foundation with mud-bearing crust is modified. The specific research contents are as follows: (1) through collecting red layer mudstone samples and making concrete test blocks, the shear test of large pile-rock interface is carried out, and the shear failure characteristics of pile-rock contact surface are obtained by analyzing the test results. Based on the shear test results of the contact surface, the constitutive model of the red mudstone pile-rock interface is established, and its constitutive equation is derived: (2) by analyzing the mechanism of mud crust formation, The physical and mechanical parameters of the red mudstone pile side mud soil were obtained by sampling the red mudstone pile side mud soil and carrying out the laboratory geotechnical parameter test, which mainly provided the mud crust parameter for the subsequent modeling. The physical and mechanical parameters of other strata and muddy soil are investigated and the differences between the characteristics of muddy soil and undisturbed soil are analyzed. (3) the static load test model of single red mudstone pile considering the constitutive structure of rock pile-rock interface is established by using FLAC3D finite difference software. Firstly, the load-bearing characteristics of normal pile foundation and mud-covered pile foundation are analyzed under different pile lengths, and then the parameter sensitivity analysis of the static load test of mud-covered pile foundation is carried out, which mainly studies the thickness of mud skin, the elastic modulus of mud skin, and the cohesion of mud skin. The influence of factors such as internal friction angle of mud crust on bearing behavior of mudstone pile foundation with mud skin red layer is discussed. (4) through numerical simulation results, the influence of various factors of mud skin on bearing behavior of pile foundation is analyzed, and the modified coefficient of side friction resistance of pile foundation with mud skin thickness is put forward. The formula for calculating the bearing capacity of pile foundation is revised. At present, with the large-scale development of pile foundation engineering, more and more attention has been paid to the bearing behavior of defective pile with mud and skin. The research results of this paper have certain reference value for the design of mudstone pile foundation with mud skin red bed in actual pile foundation engineering.
【學位授予單位】：西南石油大學
【學位級別】：碩士
【學位授予年份】：2016
【分類號】：TU473.1

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