【摘要】：摘要：樁的動(dòng)力響應(yīng)研究是樁支承建筑物抗震設(shè)計(jì)和樁基完整性檢測(cè)的理論基礎(chǔ)。由于問題的復(fù)雜性,已往研究大多將樁側(cè)土簡(jiǎn)化為單相或飽和兩相彈性介質(zhì)。眾所周知,工程環(huán)境所處的近地表土層往往處于非飽和狀態(tài),為固、液、氣三相的多孔介質(zhì)材料。因此,本文在非飽和土動(dòng)力學(xué)最新研究成果的基礎(chǔ)上,基于三相多孔介質(zhì)波動(dòng)方程,充分考慮各相材料間的慣性和粘性耦合效應(yīng)以及毛細(xì)壓力作用,通過理論分析和模型試驗(yàn)對(duì)非飽和土-樁動(dòng)力相互作用問題,非飽和土彈性半空間中埋置振源時(shí)的基本解以及樁的長(zhǎng)期荷載循環(huán)特性進(jìn)行了系統(tǒng)的研究,主要研究?jī)?nèi)容包括以下幾個(gè)方面： (1)針對(duì)半空間埋置振源下的三維Lamb問題,運(yùn)用方位角的Fourier級(jí)數(shù)展開和徑向Hankel變換技術(shù),直接對(duì)頻域內(nèi)的非飽和土波動(dòng)方程進(jìn)行求解,并結(jié)合地基表面的邊界條件以及荷載作用面上的連續(xù)性條件,求得了非飽和均質(zhì)彈性半空間內(nèi)部作用任意振源時(shí)的動(dòng)力Green函數(shù),退化到飽和土中的解與已有文獻(xiàn)的結(jié)果相吻合。 (2)考慮基質(zhì)吸力對(duì)土體動(dòng)剪切模量的影響,建立了豎向簡(jiǎn)諧振動(dòng)作用下非飽和土和單樁耦合動(dòng)力響應(yīng)模型,求解了軸對(duì)稱條件下非飽和土體的動(dòng)力控制方程和基樁的一維波動(dòng)方程,根據(jù)樁土界面銜接條件以及樁端不同支承形式,給出了嵌巖樁和非端承樁的樁頂復(fù)動(dòng)剛度、速度導(dǎo)納以及土層阻抗在頻域內(nèi)的解答。 (3)通過Helmholtz矢量分解及分離變量法解耦波動(dòng)方程,并將樁等效為能考慮其剪切變形的Timoshenko桿件,采用Novak三維連續(xù)介質(zhì)模型對(duì)非飽和土中端承樁的穩(wěn)態(tài)水平振動(dòng)進(jìn)行了研究；同時(shí)利用半空間水平動(dòng)力Green函數(shù),建立了非飽和土中水平受荷單樁的Fredholm積分方程,得到了單樁動(dòng)力阻抗的封閉形式解答,考察了樁身位移、彎矩和剪力沿深度的分布規(guī)律。 (4)在Novak平面應(yīng)變模型的基礎(chǔ)上,利用散射域中的水平位移衰減函數(shù),通過位移場(chǎng)的疊加考慮樁-樁間的波動(dòng)干擾和群樁效應(yīng),推導(dǎo)了水平穩(wěn)態(tài)諧振下非飽和土中單樁及群樁基礎(chǔ)的阻抗函數(shù)以及各單樁分擔(dān)的荷載,并討論了飽和度、頻率和樁間距等參數(shù)對(duì)基礎(chǔ)振動(dòng)特性的影響。 (5)推導(dǎo)了兩種不混溶流體飽和多孔介質(zhì)中Rayleigh波的彌散特征方程,討論了波速、自由場(chǎng)位移分布及粒子運(yùn)動(dòng)軌跡,隨后在求得非飽和土半空間自由波場(chǎng)解的基礎(chǔ)上,采用Winkler地基梁模型,考慮上部結(jié)構(gòu)慣性力的作用,對(duì)頻域內(nèi)全埋入單樁和部分埋入單樁在Rayleigh波作用下的橫向動(dòng)力響應(yīng)進(jìn)行了研究,分析了飽和度、軸向荷載和自由段樁長(zhǎng)等因素與樁的地震反應(yīng)之間的相互影響關(guān)系。 (6)通過開展紅黏土中單樁軸向循環(huán)荷載模型試驗(yàn),對(duì)不同循環(huán)荷載比和加載頻率下樁的長(zhǎng)期動(dòng)力特性進(jìn)行了研究,并從樁側(cè)土剪切剛度和側(cè)阻退化兩方面出發(fā),對(duì)循環(huán)荷載作用下樁頂累積沉降機(jī)理進(jìn)行了分析。在FLAC3D中,實(shí)現(xiàn)了能夠反映剪切剛度疲勞退化的修正Hardin-Drnevich(H-D)模型,并對(duì)常法向剛度(CNS)循環(huán)剪切下側(cè)阻退化進(jìn)行了數(shù)值模擬。
[Abstract]:Abstract: The dynamic response of the pile is the theoretical basis of the seismic design and the integrity test of the pile foundation. Because of the complexity of the problem, most of the research has simplified the pile-side soil into single-phase or saturated two-phase elastic medium. It is well known that the near-earth surface soil layer in the engineering environment is often in an unsaturated state, and is a solid, liquid and gas three-phase porous medium material. Therefore, on the basis of the latest research results of unsaturated soil dynamics, based on the three-phase porous medium wave equation, the inertia and the viscous coupling effect and the capillary pressure effect among the phase materials are fully considered. Based on the theoretical analysis and model test, the basic solution and the long-term load cycle characteristics of the pile in the unsaturated soil-pile dynamic interaction problem, the unsaturated soil elastic half-space and the long-term load cycle characteristics of the pile are studied. The main research contents include the following aspects: (1) Aiming at the three-dimensional Lamb problem under the half-space embedded vibration source, using the Fourier series expansion and the radial Hankel transformation technique of the azimuth angle, the non-saturated soil wave equation in the frequency domain is directly solved, and the boundary condition on the surface of the foundation and the continuity strip on the load acting surface are combined. In this paper, the dynamic Green's function in unsaturated homogeneous elastic half-space is obtained, and the degeneracy to the saturated soil is the same as that of the existing literature. (2) Considering the influence of matrix suction on the dynamic shear modulus of soil, the dynamic response model of unsaturated soil and single pile under the action of vertical simple harmonic vibration is established, and the dynamic control equation of unsaturated soil and one-dimensional wave of the foundation pile are solved. The dynamic equation, according to the interface condition of the pile and the different bearing form of the pile end, gives the pile top complex dynamic stiffness, the velocity admittance and the soil layer impedance in the frequency domain. (3) Uncoupling the wave equation by the Helmholtz vector decomposition and the separation variable method, and the pile is equivalent to the Timoshenko rod which can take into account the shear deformation of the pile, and the steady-state horizontal vibration of the non-saturated soil middle-end bearing pile is carried out by using the Novak three-dimensional continuous medium model. In this paper, the Fredholm integral equation of horizontal load-bearing single pile in unsaturated soil is established by using the Green's function of the semi-space, and the closed form solution of the dynamic impedance of the single pile is obtained. The displacement, bending moment and shearing force of the pile are also studied. (4) On the basis of the Novak plane strain model, using the horizontal displacement attenuation function in the scattering field, the fluctuation of the pile-pile is taken into account by the superposition of the displacement field. In this paper, the impedance function of single pile and pile foundation in unsaturated soil under the horizontal steady-state resonance and the load of each single pile are derived, and the parameters such as saturation, frequency and pile spacing are also discussed. In this paper, the dispersion characteristic equation of Rayleigh wave in two immiscible fluid saturated porous media is derived, and the wave velocity, the free field displacement distribution and the particle motion trail are discussed, and then, on the basis of obtaining the free wave field solution of the unsaturated soil semi-space, Win The transverse dynamic response of a single pile and a partially embedded single pile in the frequency domain under the action of Rayleigh wave is studied by the kler foundation beam model considering the action of the inertial force of the upper structure, and the factors such as saturation, axial load and length of free segment pile and the seismic response of the pile are analyzed. (6) The long-term dynamic characteristics of the pile under different cycle load ratio and loading frequency are studied by carrying out the model test of single-pile axial circulation load in red clay. On the basis of the two aspects of side resistance and degradation, the pile top under the action of cyclic load The cumulative settlement mechanism is analyzed. In the FLAC3D, a modified Harin-Drnovich (H-D) model, which can reflect the fatigue degradation of the shear stiffness, is realized, and the normal method is subjected to cyclic shear of the stiffness (CNS).
【學(xué)位授予單位】：中南大學(xué)
【學(xué)位級(jí)別】：博士
【學(xué)位授予年份】：2013
【分類號(hào)】：TU473.1

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