Axisymmetric fundamental solutions for a finite layer with impeded boundaries

INTRODUCTIONBiot’sconsolidationtheorywasproposedin1 941fromcontinuousmediumfundamentalequations.Thetheorytakingintoaccountthecouplingbetweenthesolidstrainsandporepres suredissipationiscalled“coupledconsolidationtheory” .Thesolutionofgoverningequationso…     

Analysis of 1D consolidation with non-Darcian flow described by exponent and threshold gradient

Numerous experiments have shown that the water flow in fine-grained soils can obey an exponential relationship at small gradients and a linear relationship when the hydraulic gradient exceeds a certain limit. Based on the non-Darcian flow described by exponent and threshold gradient, the theory of 1D consolidation is modified in this paper to consider a linear variation in the vertical total stress with depth and the effect of ramp loading. The numerical solutions were derived in detail by the finite difference method for excess pore water pressure and the average degree of consolidation. Finally, the influence of various parameters on consolidation behavior was investigated. The results show that the rate of consolidation is reduced when non-Darcian flow described by exponent and threshold gradient is adopted in the theory of 1D consolidation. As well the distribution of vertical total stress has a great influence on the dissipation of excess pore water pressure, either for pervious top and pervious bottom （PTPB） or for pervious top and impervious bottom （PTIB）. For the case of PTIB, the distribution of vertical total stress in a foundation has a great influence on the rate of consolidation; however, for the case of PTPB, the rate of consolidation is independent of the distribution of vertical total stress. The rate of consolidation is dependent on the ratio of the thickness of a soil layer to the equivalent head of the final average vertical total stress; the greater the value of this ratio, the slower the rate of consolidation. Finally, an increase in construction time reduces the consolidation rate of a foundation. Thus, consolidation behavior of 1D consolidation with non-Darcian flow has been thoroughly acquainted in this paper.     

Study on one-dimensional consolidation of soil under cyclic loading and with varied compressibility

This paper presents a semi-analytical method to solve one dimensional consolidation problem by taking consideration of varied compressibility of soil under cyclic loading. In the method, soil stratum is divided equally into n layers while load and consolidation time are also divided into small parts and time intervals accordingly. The problem of one-dimensional consolidation of soil stratum under cyclic loading can then be dealt with at each time interval as one-dimensional linear consolidation of multi-layered soils under constant loading. The compression or rebounding of each soil layer can be judged by the effective stress of the layer. When the effective stress is larger than that in the last time interval, the soil layer is compressed, and when it is smaller, the soil layer rebounds. Thus, appropriate compressibility can be chosen and the consolidation of the layered system can be analyzed by the available analytical linear consolidation theory. Based on the semi-analytical method, a computer progra     

In-plane creep buckling of concrete-filled steel tubular arches

The creep-induced deformation of the arch rib of concrete-filled steel tubular （CFST） arches under a sustained load can increase the bending moment, which may lead to earlier stability failure called creep buckling. To investigate the influences of concrete creep on the buckling strength of arches, a theoretical analysis for the creep buckling of CFST circular arches under distributed radial load is performed. The simplified Arutyunyan-Maslov （AM） creep law is used to model the creep behavior of concrete core, and the creep integral operator is introduced. The analytical solutions of the time-dependent buckling strength under the sustained load are achieved and compared with the existing formula based on the age-adjusted effective modulus method （AEMM）. Then the solutions are used to determine the influences of the steel ratio and the first loading age on the creep buckling of CFST arches. The results show that the analytical solutions are of good accuracy and applicability. For CFST arches, the steel ratio and the first loading age have significant influences on creep buckling. An approximate log-linear relationship between the decreased degrees of the creep buckling strength and the first loading age is found. For the commonly used parameters, the maximum loss of the buckling strength induced bv concrete creen is close to 40%     

梯度饱和土层的一维固结度的计算

研究了梯度饱和土层在外荷载下的固结作用,利用Biot理论给出了固结的基本微分方程,一些材料常数假设为指数模型,当梯度系数为零时,退化为一维均匀饱和土层的固结,利用分离变量等方法,得到透水和不透水边界条件下孔隙压力,给出了固结度曲线。当梯度系数不为零时,给出了梯度饱和土在外荷载下的孔隙压力,利用固结度的定义,数值算例出了梯度饱和土层的固结度变化曲线,分析和讨论了梯度系数等对固结度的影响。这些结果对地基下沉量计算和预测有一定的理论价值和意义。     

Nonlinear analytical solution for one-dimensional consolidation of soft soil under cyclic loading

INTRODUCTION Conventional consolidation analysis based on Terzaghi’s one-dimensional theory neglects the non-linearity of soil for the sake of mathematical expediency, which is considered to be one of the theory’s shortcomings. Many researchers have pro-posed one-dimensional (1D) consolidation models where the coefficient of volume compressibility mv, coefficient of permeability kv, and coefficient of consolidation cv, vary with either depth or time. Schiffman (1958), Davis and Raymon…     

Cubic Spline Solutions of Nonlinear Bending and Buckling of Circular Plates with Arbitrarily Variable Thickness

The cubic B-splines taken as trial function, the large deflection of a circular plate with arbitrarily variable thickness,as well as the buckling load, have been calculated by the method of point collocation. The support can be elastic. Loads imposed can be polynomial distributed loads, uniformly distributed radial forces or moments along the edge respectively or their combinations. Convergent solutions can still be obtained by this method under the load whose value is in great excess of normal one. Under the action of the uniformly distributed loads, linear solutions of circular plates with linearly or quadratically variable thickness are compared with those obtained by the parameter method. Buckling of a circular plate with identical thickness beyond critical thrust is compared with those obtained by the power series method.     

Stable response of axisymmetric two-phase water-saturated soil

Biot's dynamic consolidation equations and Hankel transform were used to derive the integral solutions of stress and displacement for axisymmetric harmonic excitations in the two-phase saturated soil with subjacent rock-stratum. The influence of the coefficient of permeability and loading frequency on the soil displacement at the ground surface were studied. The results showed that higher loading frequency led to more dynamic characteristics; and that the effect of the soil permeability was more obvious at higher frequencies.     

Stable response of axisymmetric two-phase water-saturated soil

Biot's dynamic consolidation equations and Hankel transform were used to derive the integral solutions of stress and displacement for axisymmetric harmonic excitations in the two-phase saturated soil with subjacent rock-stratum. The influence of the coefficient of permeability and loading frequency on the soil displacement at the ground surface were studied. The results showed that higher loading frequency led to more dynamic characteristics; and that the effect of the soil permeability was more obvious at higher frequencies.     

城市滨河湿地植物群落调查

调查了绵阳市安昌江滨河湿地植物的群落类型及物种多样性,结果显示,滨河湿地植物有79种,分属36科,主要由草本构成,乔、灌、藤本植物较少.安昌江滨河湿地植物按优势种为代表可划分为空心莲子草、马唐、青蒿、马鞭草、构树、狗牙根等6个主要植物群落类型,以上6类群落类型对研究区域湿地生态系统的物质循环起着主要作用.研究区域内植物群落的垂直结构较简单,层次单一,在水平结构上表现出明显的镶嵌性,这可能与滨河湿地生境的多样化和破碎化有关.对整个滨河湿地群落不同层次的多样性指数（H＇）分析显示,草本层（3.97）＞乔木层（1.79）＞灌木层（1.61）;均匀度指数（E）为草本层（0.82）＞乔木层（0.79）＞灌木层（0.38）,灌木层分布不均匀.人类干扰引起的湿地环境的变化和旱生物种入侵是影响该区生物多样性的重要因素.     

Axisymmetrical Nonlinear Bending and Buckling of a Circular Plate Under Large Load

With the terms of the exact series solution taken as trial functions, the method of point collocation was used to calculate the large deflection of a circular plate. The axisymmetrical bending formulae were developed for the calculation of a circular plate subjected to polynomial distributed loads, a concentrated load at the center, uniform radial forces and moments along the edge or their combinations. The support may be elastic. The buckling load was calculated. Under action of uniformly distributed load, central load or their compound load, solutions were compared with those obtained by other methods, Buckling beyond critical thrust was compared with that calculated by the power series method. The method presented in this paper has advantages of wide convergent range, high precision and short computing time. Moreover, the computing time is nearly independent of the complexity of the loads.     

浅析CFG桩复合地基设计计算

简述CFG桩复合地基的基本概念,分析CFG桩复合地基承载力计算和CFG桩复合地基变形计算,以及单桩竖向承载力特征值的取值要求和褥垫层厚度确定。     

Critical cyclic stress ratio of undisturbed saturated soft clay in the yangtze estuary under complex stress conditions

There exists a critical cyclic stress ratio when sand or clay is subjected to cyclic loading. It is an index distinguishing stable state or failure state. The soil static and dynamic universal triaxial and torsional shear apparatus developed by Dalian University of Technology in China was employed to perform different types of tests on saturated soft marine clay in the Yangtze estuary. Undisturbed samples were subjected to undrained cyclic vertical and torsional coupling shear and cyclic torsional shear after three-directional anisotropic consolidation with different initial consolidation parameters. The effects of initial orientation angle of major principal stress, initial ratio of deviatoric stress, initial coefficient of intermediate principal stress and stress mode of cyclic shear on the critical cyclic stress ratio were investigated. It is found that the critical cyclic stress ratio decreases significantly with increasing initial orientation angle of major principal stress and initial ratio of deviatoric stress. Compared with the effects of the initial orientation angle of major principal stress and initial ratio of deviatoric stress, the effect of initial coefficient of intermediate principal stress is less evident. Under the same consolidation condition, the critical cyclic stress ratio from the cyclic coupling shear test is lower than that from the cyclic torsional shear test, indicating that the stress mode of cyclic shear has an obvious effect on the critical cyclic stress ratio. The main reason is that the continuous rotation in principal stress directions during cyclic coupling shear damages the original structure of soil more than the cyclic torsional shear does.     

Analytical layer-element solutions for a multi-layered transversely isotropic elastic medium subjected to axisymmetric loading

This paper presents an analytical layer-element method used to analyze the displacement of a multi-layered transversely isotropic elastic medium of arbitrary depth subjected to axisymmetric loading. Based on the basic constitutive equations and the HU Hai-chang’s solutions for transversely isotropic elastic media, the state vectors of a multi-layered transversely isotropic medium were deduced. From the state vectors, an analytical layer element for a single layer (i.e., a symmetric and exact stiffness matrix) was acquired in the Hankel transformed domain, which not only simplified the calculation but also improved the numerical efficiency and stability due to the absence of positive exponential functions. The global stiffness matrix was obtained by assembling the interrelated layer elements based on the principle of the finite layer method. By solving the algebraic equations of the global stiffness matrix which satisfy the boundary conditions, the solutions for multi-layered transversely isotropic media in the Hankel transformed domain were obtained. The actual solutions of this problem in the physical domain were acquired by inverting the Hankel transform. This paper presents numerical examples to verify the proposed solutions and investigate the influence of the properties of the multi-layered medium on the load-displacement response.     

Nonlinear analysis of consolidation with variable compressibility and permeability

INTRODUCTION Since the development of the conventionalconsolidation theory by Terzaghi (1943) in 1923,many attempts have been made to present some solu-tions for the problems considering more realistic as-sumptions on the practical geotechnical engineering.Some efforts have been made to avoid limitation ofthe assumptions in the Terzaghi’s theory. During theconsolidation of soil, it is obvious that the coefficientof volume compressibility mv and the coefficient ofpermeability kv ar…     

一类非线性中立型双曲微分方程的振动性

研究一类具有连续分布滞量的非线性中立型双曲方程解的振动性质.利用Jensen不等式和直接分析方法,获得了一类具连续分布滞量的非线性中立型双曲微分方程所有解振动的若干充分条件.     

人炎性阑尾肌层生长抑素免疫组化研究

用免疫组织化学PAP法观察33例人阑尾肌层生长抑素(SS)样免疫反应(-IR)神经。阑尾炎组25例(单纯组7例,慢性组6例,化脓组7例,坏疽组5例);对照组8例。结果:各组阑尾肌层中均有SS-IR神经分布,环肌层较多,各阑尾炎组SS-IR神经丛及神经细胞数密度均较对照组减少(P<0.05,P<0.01),坏疽组SS-IR神经丛数密度较单纯组、慢性组减少(P<0.05)。本文结果提示:阑尾肌层SS-IR神经参与了阑尾炎的神经调理。     

基于循环经济的"农家乐"旅游思考

发展循环经济是实施可持续发展战略的重要途径,文章结合循环经济理论与“农家乐”旅游在可持续发展中面临的问题,探讨了循环经济对“农家乐”旅游可持续发展的作用,提出了运用循环经济促进我国“农家乐”旅游可持续发展的具体措施。     

波在周期磁化等离子体圆波导中的传播特性

电磁波与等离子体之间的相互作用是等离子体物理学和高功率微波器件研究的重点,加载等离子体可以大幅度提高微波器件的输出功率和效率．文章提出了一种加载周期磁化变化等离子体圆波导的周期慢波结构,即加载轴向周期磁化正弦变化等离子体圆波导的介质周期结构,并研究了电磁波在该介质结构中的传播特性,根据严格的理论推导得出电磁波在其中传播的色散方程,并进行了数值计算和分析．     

Excitation of axisymmetric and non-axisymmetric guided waves in elastic hollow cylinders by magnetostrictive transducers

Ultrasonic guided waves have been successfully applied in nondestructive evaluation (NDE) and structural health monitoring (SHM) of pressure vessels and pipelines due to their advantages, such as long detection range and high inspection efficiency. Compared with other ultrasonic guided wave actuators, magnetostrictive transducers are more cost-effective, involve simpler fabrication process, and have higher possible transduction efficiency. The normal mode expansion (NME) method is adopted to analyze the forced response and perturbation analysis of elastic hollow cylinders with respect to magnetostrictive loadings, including partial loading, axial array loading, and circular array loading. The phase velocity and frequency spectra of axisymmetric/non-axisymmetric guided waves excited by magnetostrictive transducers are analyzed. The theoretically predicted trends are verified by finite element numerical simulations and experiments.