本文選題：樁-土相互作用 + 虛土樁��； 參考：《浙江大學(xué)》2013年博士論文

【摘要】：目前,國內(nèi)外研究樁與樁底土相互作用關(guān)系的模型,大多數(shù)是非連續(xù)模型,且缺乏對樁底土作用的研究。為了建立樁與樁底土的嚴(yán)格耦合關(guān)系,本文提出了一種改進(jìn)的虛土樁法。并基于該方法,分析了樁底土對單樁縱向振動特性的影響,研究了焊縫在多級混凝土管樁完整性檢測中的作用及不同條件下靜鉆根植竹節(jié)樁這一新樁型的動力特性。主要的工作與創(chuàng)新成果如下： (1)基于地基中圓形豎向荷載下的Mindlin附加應(yīng)力,提出了考慮應(yīng)力擴(kuò)散效應(yīng)的虛土樁法。進(jìn)一步結(jié)合平面應(yīng)變模型,通過Laplace變換和卷積定理等數(shù)學(xué)方法,求得任意激振力作用下的樁體振動頻域響應(yīng)解析解和時域響應(yīng)半解析解。通過分析樁底土體參數(shù)對樁動力響應(yīng)的影響,發(fā)現(xiàn)土體剪切模量是決定樁底支撐剛度的重要因素,土體模量提高,將引起樁底支撐剛度和阻尼顯著增大。樁底土對樁身動力響應(yīng)的影響存在臨界厚度,約5-7倍的樁體半徑,在此范圍內(nèi),樁體剛度與樁底土層厚度成反比關(guān)系,阻尼與之成正比關(guān)系。 (2)將虛土樁法從平面應(yīng)變模型發(fā)展到軸對稱連續(xù)土體模型中,考慮土體的徑向和豎向兩相位移,建立三維波動效應(yīng)下的樁土體系縱向振動模型。通過引入位移勢函數(shù)和Laplace變換的手段,采用分離變量法將豎向和徑向位移進(jìn)行解耦,進(jìn)而通過阻抗傳遞法求得樁體的頻域響應(yīng),通過Laplace逆變換得到樁體的時域響應(yīng)。根據(jù)所求得的解,對比了軸對稱連續(xù)模型與平面應(yīng)變模型下虛土樁法的差異,發(fā)現(xiàn)軸對稱模型能更好地反映樁土體系的自振頻率。 (3)提出了混凝土管樁焊接縫的簡化模型,將影響焊縫質(zhì)量的物理因素轉(zhuǎn)化到等效的剛度體系中,從而實現(xiàn)了可對焊縫進(jìn)行理論擬合的目的。借助本文所提出的虛土樁法,求得多級混凝土焊接管樁樁頂?shù)膭恿憫?yīng)。經(jīng)過分析有效焊接斷面、焊接高度等參數(shù)的大小對樁頂速度響應(yīng)的影響,表明焊接深度不應(yīng)小于5mm,焊縫高度宜控制在2mm范圍內(nèi)。實測數(shù)據(jù)的擬合結(jié)果表明,該簡化模型能有效地反映焊縫質(zhì)量對管樁反射波信號的影響,可為樁基完整性檢測提供指導(dǎo)。 (4)根據(jù)靜鉆根植竹節(jié)樁的成樁機(jī)理,確立了徑向非均質(zhì)理論與虛土樁法相結(jié)合的樁土動力模型。結(jié)合系數(shù)矩陣傳遞法,求得徑向非均質(zhì)土體下竹節(jié)形根植樁的樁頂動力響應(yīng)。分析了竹節(jié)及樁周水泥土等對樁頂動力響應(yīng)的影響,結(jié)果表明樁體剛度與竹節(jié)密度和竹節(jié)半徑成正比,樁側(cè)水泥土的硬化程度越高,樁頂剛度越大,阻尼越小,且泥漿的水泥配合比為40%時,性價比較高。通過對工程數(shù)據(jù)的反演擬合驗證了樁側(cè)水泥土的硬化規(guī)律。 完善地模擬樁與樁底土的作用關(guān)系是本文的核心,即文中提出的虛土樁法。以此來解決工程中出現(xiàn)的實際問題是本文的目的�；诖�,本文提出的新方法、得到的新結(jié)論可為樁基工程設(shè)計及檢測工作提供參考。
[Abstract]:At present, most of the models used to study the interaction between piles and subsoil are discontinuous models and lack of research on pile-subsoil interaction. In order to establish a strict coupling relationship between pile and subsoil, an improved virtual soil pile method is proposed in this paper. Based on this method, the effect of pile bottom soil on the longitudinal vibration characteristics of single pile is analyzed, and the role of weld seam in the integrity detection of multistage concrete pipe pile and the dynamic characteristics of the new type of pile with static drilling and planting bamboo section pile under different conditions are studied. The main results of work and innovation are as follows: 1) based on the Mindlin additional stress under the circular vertical load in the foundation, a fictitious soil pile method considering the stress diffusion effect is proposed. Combined with plane strain model, by means of Laplace transform and convolution theorem, the analytical and semi-analytical solutions of vibration frequency domain response and time domain response of pile subjected to arbitrary excitation force are obtained. By analyzing the influence of soil parameters on pile dynamic response, it is found that the shear modulus of soil is an important factor in determining the supporting stiffness of pile bottom, and the increase of soil modulus will result in a significant increase in the stiffness and damping of pile bottom bracing. The influence of pile soil on the dynamic response of pile body has a critical thickness, about 5-7 times of the radius of the pile body. In this range, the stiffness of the pile is inversely proportional to the thickness of the soil layer of the pile bottom, and the damping is proportional to it. 2) the pseudo-soil pile method is developed from plane strain model to axisymmetric continuous soil mass model. Considering the radial and vertical two-phase displacement of soil, the longitudinal vibration model of pile-soil system under three-dimensional wave effect is established. By introducing the displacement potential function and Laplace transform, the vertical and radial displacements are decoupled by the method of separating variables, and the frequency domain responses of the piles are obtained by the impedance transfer method, and the time-domain responses of the piles are obtained by the Laplace inverse transformation. According to the obtained solution, the difference between the axisymmetric continuous model and the plane strain model is compared. It is found that the axisymmetric model can better reflect the natural frequency of pile-soil system. The simplified model of welding joint of concrete pipe pile is put forward. The physical factors affecting weld quality are transformed into the equivalent stiffness system, so that the purpose of theoretical fitting of weld seam can be realized. The dynamic response of multistage concrete welded pipe pile top is obtained by using the virtual soil pile method proposed in this paper. The effect of effective welding section, welding height and other parameters on the velocity response of the pile top is analyzed. The results show that the welding depth should not be less than 5mm, and the weld height should be controlled within the range of 2mm. The fitting results of measured data show that the simplified model can effectively reflect the influence of weld quality on the reflected wave signal of pipe pile and can provide guidance for pile foundation integrity detection. 4) according to the pile forming mechanism of static drilling and planting bamboo section pile, the dynamic model of pile and soil is established, which combines radial heterogeneity theory with fictitious soil pile method. Based on the coefficient matrix transfer method, the dynamic response of the pile top of the bamboo-shaped root pile under the radial heterogeneous soil is obtained. The influence of bamboo section and cement soil around pile on the dynamic response of pile top is analyzed. The results show that the stiffness of pile is proportional to the density and radius of bamboo section, the higher the hardening degree of cement soil is, the greater the stiffness of pile top is and the smaller the damping is. And when the cement mixture ratio of mud is 40, the ratio of performance to price is higher. The hardening law of cement soil on the pile side is verified by inverse fitting of engineering data. It is the core of this paper to simulate the interaction between pile and soil perfectly, that is, the virtual soil pile method proposed in this paper. The purpose of this paper is to solve the practical problems in engineering. Based on this, the new method and the new conclusion can provide reference for the design and testing of pile foundation engineering.
【學(xué)位授予單位】：浙江大學(xué)
【學(xué)位級別】：博士
【學(xué)位授予年份】：2013
【分類號】：TU473.1

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