共查询到20条相似文献，搜索用时 31 毫秒
1.
A simple model for the corrosion‐induced loss of stiffness and strength of the steel strips of earth‐reinforced walls was introduced in a finite element simulation of the long‐term behavior of the wall, in which the backfill‐strips interactions are taken into account by means of a generalized homogenization procedure (called a multiphase model). The results show an initial phase of slow displacements induced by the loss of stiffness, followed after a few decades by a steep acceleration of the displacements, leading to wall failure. The influences of the parameter controlling corrosion, the backfill cohesion and the heterogeneity of the corrosion process are discussed. Results are used to discuss a strategy for reinforced earth wall surveillance. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
2.
强夯加固地基的土体竖向位移计算方法研究 总被引：2，自引：0，他引：2
根据动力分析中应力边界与速度边界之间的关系,将应力边界时程转化为速度边界时程,提出计算土体竖向位移的新方法,并进行了简化和多角度对比性研究。在钱家欢加卸载模型应力和竖向位移计算的基础上,提出将正弦荷载形式和三角形荷载形式分别引入,推导出竖向位移的两种简化计算方法。两种方法概念清楚、物理意义明确,形式简单且相同,区别仅在于系数不同。工程实例表明,两种方法计算出的竖向位移均接近于实测位移,但正弦荷载形式下的位移计算方法更能反映实际情况。 相似文献
3.
Sam Frydman 《Geomechanics and Geoengineering》2020,15(1):54-63
ABSTRACTA simplified approach is presented for estimating permanent displacements in slopes as a result of both vertical and horizontal seismic accelerations. A study of 52 earthquake records showed that the time difference between maximum horizontal and vertical accelerations varied between 0 and 10.3 s. The approach is illustrated for an earth dam embankment by analysing the effects of five of the above earthquake records. The approach combines a pseudo-static slope stability analysis for estimation of the critical (or yield) horizontal-vertical acceleration combinations, and a Newmark type displacement analysis. Guidelines are presented for conservative choice of soil strength parameters of saturated clays for use in the stability analysis. While permanent displacements of up to 40 cm were predicted without considering the vertical acceleration component, no additional displacement above 3.5 cm resulted when this component was included. The predicted additional displacement was consistently less than 10%, and in 50% of the analyses, vertical acceleration led to smaller predicted displacements. The simple approach may be applied in analysis for any slope using real earthquake records. Using existing, empirical expressions for permanent displacement, based only on horizontal accelerations, the effect of the vertical accelerations may be conservatively estimated by increasing the displacement by 10%. 相似文献
4.
The mechanical response of earth structures reinforced with steel strips to loads associated with rail traffic is not well known. In order to better understand the deformations induced by train loads, and to improve design methods, a full-scale structure was built, instrumented, and tested near Rouen, France. Finite-element analyses were performed both in plane-strain and three-dimensional conditions, using different approaches to account for the interaction between the strips and the backfill material. After calibration of the soil-strip interface parameters for a load of 90 kN, simulations of the wall response to a load of 850 kN provided results in good agreement with measurements. Numerical models showed that the soil-strip interface parameters have a major influence on the predicted behavior. The proposed approach could be used for further studies of the influence of geometric and mechanical parameters. 相似文献
5.
The dynamic response of an end bearing pile embedded in a linear visco‐elastic soil layer with hysteretic type damping is theoretically investigated when the pile is subjected to a time‐harmonic vertical loading at the pile top. The soil is modeled as a three‐dimensional axisymmetric continuum in which both its radial and vertical displacements are taken into account. The pile is assumed to be vertical, elastic and of uniform circular cross section. By using two potential functions to decompose the displacements of the soil layer and utilizing the separation of variables technique, the dynamic equilibrium equation is uncoupled and solved. At the interface of soil‐pile system, the boundary conditions of displacement continuity and force equilibrium are invoked to derive a closed‐form solution of the vertical dynamic response of the pile in frequency domain. The corresponding inverted solutions in time domain for the velocity response of a pile subjected to a semi‐sine excitation force applied at the pile top are obtained by means of inverse Fourier transform and the convolution theorem. A comparison with two other simplified solutions has been performed to verify the more rigorous solutions presented in this paper. Using the developed solutions, a parametric study has also been conducted to investigate the influence of the major parameters of the soil‐pile system on the vertical vibration characteristics of the pile. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
6.
Hiroyoshi Hirai 《国际地质力学数值与分析法杂志》2014,38(12):1298-1320
An analytical approach using a Winkler model is investigated to provide analytical solutions of settlement of a rectangular pile subjected to vertical loads in nonhomogeneous soils. For a vertically loaded pile with a rectangular cross section, the settlement influence factor of a normal pile in nonhomogeneous soils is derived from Mindlin's solution for elastic continuum analysis. For short piles with rectangular and circular cross sections, the modified forms of settlement influence factors of normal piles are produced taking into account the load transfer parameter proposed by Randolph for short circular piles. The modulus of subgrade reaction along a rectangular pile in nonhomogeneous soils is expressed by using the settlement influence factor related to Mindlin's solution to combine the elastic continuum approach with the subgrade‐reaction approach. The relationship between settlement and vertical load for a rectangular pile in nonhomogeneous soils is available in the form of the recurrence equation. The formulation of settlement of soils surrounding a rectangular pile subjected to vertical loads in nonhomogeneous soils is proposed by taking into account Mindlin's solution and both the equivalent thickness and the equivalent elastic modulus for layers in the equivalent elastic method. The difference of settlement between square and circular piles is insignificant, and the settlement of a rectangular pile decreases as the aspect ratio of the rectangular pile cross section increases. The comparison of results calculated by the present method for a rectangular pile in nonhomogeneous soils has shown good agreement with those obtained from the analytical methods and the finite element method. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
7.
Reducing vertical acceleration in ballast layers of railways to mitigate geometrical disorders in high‐speed lines 
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下载免费PDF全文 According to field feedbacks from high‐speed lines (HSL), the increase of train operating speeds is responsible for unusual fast evolving geometrical disorders in ballasted tracks. This paper deals with the search of solutions applicable at the design stage to mitigate these disorders. The starting point of the present work relies on the assumption, comforted by the literature, of a strong correlation between disorders and vertical accelerations in the ballast layer induced by the train passages. This led us focus herein on the calculation and the analysis of accelerations in the railway structure. The vertical accelerations (γz) are computed using the in‐house developed numerical program ViscoRail and on the basis of a reference HSL. These are shown to increase strongly with the train speed attesting to the link between the train speed and the geometrical disorders in ballast. Then, other simulations are run varying some structural parameters to evaluate their impact on the acceleration field γz. In that way, we show that decreasing the stiffness of the mechanical connection between the rails and the ballast, increasing the moment of inertia of the rails or the Young modulus of the sub‐ballast layer, leads to a decrease of γz and could provide solutions for the design of future HSL. The solution consisting in the incorporation of an asphalt sub‐ballast layer, as already experimented on sites, is finally examined in more details. Copyright © 2017 John Wiley & Sons, Ltd. 相似文献
8.
Solutions are presented for the problem of isothermal dessiccation shrinkage in a double‐layer porous partially saturated medium. The rheological model taken into account is linear poroelastic. Hence the analysis is mainly focused on hydromechanical coupling effects and contrasts of mechanical and hydraulic properties between two materials: a low thickness skin comprised between the outer boundary and the reference porous material. Three one‐dimensional ideal structures are taken into account: a wall of finite thickness (cartesian geometry), a thick cylinder and a thick sphere. The solution of the time‐dependent problem is arrived at by applying Laplace transforms to the field variables. Exact solutions are obtained in Laplace transform space using Mathematica© to solve the field equations whilst taking into account the continuity equations at the interface and the boundary conditions. The Talbot's modified algorithm has been performed to invert the Laplace transform solutions. A bibliographical and numerical study shows that this method is remarkably precise, stable and close to the analytical inversion. Results are presented using poroelastic data representative of a concrete material and involve a strong coupling effect between hydraulical and mechanical behaviours. A first approach elastic modelling of degradation process have been presented using a thin outer layer. Apart from emphasising the semi‐explicit solution utility due to accurate speed calculation, this paper deals with more complex problems than those which can be solved using purely analytical solutions. Copyright © 2001 John Wiley & Sons, Ltd. 相似文献
9.
Most analytical or semi‐analytical solutions of the problem of load‐settlement response of axially loaded piles are based on the assumption of zero radial displacement. These solutions also are only applicable to piles embedded in either a homogeneous or a Gibson soil deposit. In reality, soil deposits consist of multiple soil layers with different properties, and displacements in the radial direction within the soil deposit are not zero when the pile is loaded axially. In this paper, we present a load‐settlement analysis applicable to a pile with circular cross section installed in multilayered elastic soil that accounts for both vertical and radial soil displacements. The analysis follows from the solution of the differential equations governing the displacements of the pile–soil system obtained using variational principles. The input parameters needed for the analysis are the pile geometry and the elastic constants of the soil and pile. We compare the results from the present analysis with those of an analytical solution that considers only vertical soil displacements. The analysis presented in this paper also provides useful insights into the displacement and strain fields around axially loaded piles. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
10.
Jiao-Long Zhang Herbert A. Mang Xian Liu Yong Yuan Bernhard Pichler 《国际地质力学数值与分析法杂志》2019,43(7):1343-1372
A nonlinear hybrid method is developed for multiscale analysis of a bearing-capacity test of a real-scale segmental tunnel ring subjected to point loads. The structural analysis consists of two parts. Part I refers to modeling of bending-induced tensile cracking of the segments, resulting from the external loading. The segments are subdivided into elements, according to the crack spacing. Each element is either intact or contains one central crack band, flanked by lateral undamaged domains. A multiscale model for tensile softening of concrete is used to describe the progressive deterioration of the crack bands. After iterative determination of their state of damage, the effective bending and extensional stiffnesses of the corresponding elements are quantified by means of Voigt-Reuss-Hill estimates. The effective stiffnesses are used for linear-elastic simulations of the segmental tunnel ring. Part II refers to the relative rotation angles at the joints, which are estimated from monitoring data, using the Bernoulli-Euler hypothesis. Since the validity of this hypothesis is questionable for neck-like joints, the relative rotation angles are post-processed such that they refer to rigid body displacements of the segments. The following conclusions are drawn: The presented approach yields good estimates of crack widths. Relative rotation angles at the joints mainly result in rigid body displacements of the segments, governing the convergences. Because realistic interface models are lacking, hybrid analysis based on displacement-monitoring data allows for performing ultimate-load analysis of segmental tunnel rings. 相似文献
11.
Analysis of piled raft with nodular pile subjected to vertical load using a Winkler model approach 下载免费PDF全文
下载免费PDF全文 Hiroyoshi Hirai 《国际地质力学数值与分析法杂志》2016,40(13):1863-1889
An investigation is made to present analytical solutions provided by a Winkler model approach for analysis of piled rafts with nodular pile subjected to vertical loads in nonhomogeneous soils. The vertical stiffness coefficient along a piled raft with the nodular pile in nonhomogeneous soils is derived from the displacement given by the Mindlin solution for elastic continuum analysis. The vertical stiffness coefficients for the bases of the raft and the nodular part in the nodular pile in a soil are expressed by the Muki solution for the 3‐D elastic analysis. The relationship between settlement and vertical load on the pile base is presented considering the Mindlin solution and the equivalent thickness in the equivalent elastic method. The interaction factor between the shaft of the nodular pile and the soil is expressed taking into account the Mindlin solution and the equivalent elastic modulus. The relationship between settlement and vertical load for a piled raft with the nodular pile in nonhomogeneous soils is obtained by using the recurrence equation of influence factors of the pile for each layer. The percentage of each load carried by both nodular pile and raft subjected to vertical load is represented through the vertical influence factors proposed here. Comparison of the results calculated by the present method for piled rafts with nodular piles in nonhomogeneous soils has shown good agreement with those obtained from the finite element method and a field test. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
12.
Zheng Li Panagiotis Kotronis Sandra Escoffier Claudio Tamagnini 《国际地质力学数值与分析法杂志》2018,42(12):1346-1365
Batter piles are widely used in geotechnical engineering when substantial lateral resistance is needed or to avoid the interference with existing underground constructions. Nevertheless, there is a lack of fast numerical tools for nonlinear soil‐structure interactions problems for this type of foundation. A novel hypoplastic macroelement is proposed, able to reproduce the nonlinear response of a single batter pile in sand under monotonic and cyclic static loadings. The behavior of batter piles (15°, 30°, and 45°) is first numerically investigated using 3D finite element modeling and compared with the behavior of vertical piles. It is shown that their response mainly depends on the pile inclination and the loading direction. Then, starting from the macroelement for single vertical piles in sand by Li et al (Acta Geotechnica, 11(2):373‐390, 2016), an extension is proposed to take into account the pile inclination introducing simple analytical equations in the expression describing the failure surface. 3D finite element numerical models are adopted to validate the macroelement that is proven able to reproduce the nonlinear behavior in terms of global quantities (forces‐displacements) and to significantly reduce the necessary computational time. 相似文献
13.
横观各向同性饱和土体三维粘弹性动力分析 总被引：2，自引：2，他引：0
采用针对横观各向同性饱和土体u-w形式三维粘弹性动力方程,考虑土骨架的粘弹性性质且基于粘弹性理论,通过运用Fourier 展开、Laplace 和Hankel 积分变换方法和引入中间变量,将含有粘弹性参数的六元二阶偏微分运动控制方程组,化为2组各含4个未知变量的常微分方程组,从而给出了柱坐标系下粘弹性横观各向同性饱和土体在非轴对称动力荷载作用下的瞬态反应的土骨架位移分量、孔隙流体相对于土骨架的位移分量瞬态反应一般解。在此基础上,引入初始条件和边界条件,对垂直向和水平向动力荷载作用下半空间边值问题进行了求解。根据动力时域解答的一般解,利用Laplace和Hankel 数值逆变换技术,编制了相应的数值计算程序。并进行了实例验证和弹性、粘弹性解的对比分析。结果表明,在进行横观各向同性饱和土体动力分析时,考虑土骨架的粘弹性是必要的。 相似文献
14.
Considering there is hardly any concerted effort to analyze the pile‐raft foundations under complex loads (combined with vertical loads, horizontal loads and moments), an analysis method is proposed in this paper to estimate the responses of pile‐raft foundations which are subjected to vertical loads, horizontal loads and moments in layered soils based on solutions for stresses and displacements in layered elastic half space. Pile to pile, pile to soil surface, soil surface to pile and soil surface to soil surface interactions are key ingredients for calculating the responses of pile‐raft foundations accurately. Those interactions are fully taken into account to estimate the responses of pile‐raft foundations subject to vertical loads, horizontal loads and moments in layered soils. The constraints of the raft on vertical movements, horizontal movements and rotations of the piles as well as the constraints of the raft on vertical movements and horizontal movements of the soils are considered to reflect the coupled effect on the raft. The method is verified through comparisons with the published methods and FEM. Then, the method is adopted to investigate the influence of soil stratigraphy on pile responses. The study shows that it is necessary to consider the soil non‐homogeneity when estimating the responses of pile‐raft foundations in layered soils, especially when estimating the horizontal responses of pile‐raft foundations. The horizontal loads and the moments have a significant impact on vertical responses of piles in pile‐raft foundations, while vertical loads have little influence on horizontal responses of piles in pile‐raft foundations in the cases of small deformations. The proposed method can provide a simple and useful tool for engineering design. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
15.
冻土路基土体的物理性质与温度有密切关系, 在不同的季节, 路基内的变形场和应力场会相应发生变化. 为了说明路基内变形场和应力场的季节性差异, 以青藏铁路某断面为例, 对冻土路基在有、无列车荷载两种工况下进行了数值模拟, 系统分析了两种工况下路基内的变形场和应力场特点. 结果表明: 路基修筑后, 在自重作用下会产生较大瞬时变形; 由于路基内温度场随时间变化, 路基内各点的位移也随时间发生变化, 且位移时程曲线与温度时程曲线大体呈负相关. 在有、无列车两种工况下路基竖向位移分布都是由道砟中心向路基内部逐渐减小, 但数值明显不同; 由列车荷载引起的最大竖向附加变形发生在路基顶面中心点, 在10月15日、1月15日、4月15日, 变形量分别为-4.94 mm、-3.24 mm、-2.56 mm. 对于路基底面中心点和地基浅层中心点, 由列车荷载引起的附加应力在10月15日最大、1月15日次之、4月15日最小, 附加应力最大达到19.48 kPa; 列车荷载主要影响路基上部土体应力分布, 对下部土体应力分布影响较小. 相似文献
16.
An analysis of a pile vertical response considering soil inhomogeneity in the radial direction under dynamic loads is presented. The solution technique is based on a three‐dimensional axisymmetric model, which includes the consideration of the vertical displacement of the soil. The soil domain is subdivided into a number of annular vertical zones, and the continuity of the displacements and stresses are imposed at both the interface of pile–soil and the interfaces of adjacent soil zones to establish the dynamic equilibrium equations of the pile–soil interaction. Then, the equations of each soil zone and of the pile are solved one by one to obtain the analytical and semi‐analytical dynamic responses at the top of the pile in the frequency domain and time domain. Parametric studies have been performed to examine the influence of soil parameters' variations in the radial direction caused by the construction effect on the dynamic responses of pile. The results of the studies have been summarized and presented in figures to illustrate the influences of the soil parameters as they change radially. The effect of the radius of the disturbed soil zone caused by construction is also studied in this paper. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
17.
鉴于目前城市地下铁路隧道平行、交叠的情况逐年增加,且对多列车耦合荷载作用下地表振动规律尚不清楚,本文建立了大直径盾构隧道下穿双线地铁隧道三维数值分析模型,并通过现有运行列车参数建立了刚体列车模型以及实体轨道模型。采用Hertz接触模拟了运动列车轮与钢轨的接触,通过罚接触与硬接触模拟了隧道与围岩的非线性接触,利用无限元人工边界模拟了无限半空间。使用时域显式整体分析方法模拟了编组列车在隧道内的运行并与实测地表振动加速度结果进行了对比,结果表明本文建立的数值模型能够较好地反映出真实地铁列车运行时地表的振动响应。在此基础上,分析了多线隧道交汇段不同列车运行工况下地表竖向加速度的时频特性以及分布规律。 相似文献
18.
In practical engineering, an applied rectangular area load is not often horizontally or vertically distributed but is frequently inclined at a certain angle with respect to the horizontal and vertical axes. Thus, the solutions of displacements and stresses due to such a load are essential to the design of foundations. This article yields the analytical solutions of displacements and stresses subjected to a uniform rectangular load that inclines with respect to the horizontal and vertical axes, resting on the surface of a cross‐anisotropic geomaterial. The planes of cross‐anisotropy are assumed to be parallel to the horizontal ground surface. The procedures to derive the solutions can be integrated the modified point load solutions, which are represented by several displacement and stresses elementary functions. Then, upon integrations, the displacement and stress integral functions resulting from a uniform inclined rectangular load for (1) the displacements at any depth, (2) the surface displacements, (3) the average displacements in a given layer, (4) the stresses at any depth, and (5) the average stresses in a given layer are yielded. The proposed solutions are clear and concise, and they can be employed to construct a series of calculation charts. In addition, the present solutions clarify the load inclinations, the dimensions of a loaded rectangle, and the analyzed depths, and the type and degree of geomaterial anisotropy profoundly affect the displacements and stresses in a cross‐anisotropic medium. Parametric results show that the load inclination factor should be considered when an inclined rectangular load uniformly distributed on the cross‐anisotropic material. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
19.
Seismic Stability Analysis of a Himalayan Rock Slope 总被引：1，自引：1，他引：0
The seismic slope stability analysis of the right abutment of a railway bridge proposed at about 350 m above the ground level, crossing a river and connecting two huge hillocks in the Himalayas, India, is presented in this paper. The rock slopes are composed of highly jointed rock mass and the joint spacing and orientation are varying at different locations. Seismic slope stability analysis of the slope under consideration is carried out using both pseudo-static approach and time response approach as the site is located in seismic zone V as per the earth quake zonation maps of India. Stability of the slope is studied numerically using program FLAC. The results obtained from the pseudo-static analysis are presented in the form of Factor of Safety (FOS) and the results obtained from the time response analysis of the slope are presented in terms of horizontal and vertical displacements along the slope. The results obtained from both the analyses confirmed the global stability of the slope as the FOS in case of pseudo-static analysis is above 1.0 and the displacements observed in case of time response analysis are within the permissible limits. This paper also presents the results obtained from the parametric analysis performed in the case of time response analysis in order to understand the effect of individual parameters on the overall stability of the slope. 相似文献
20.
Ayhan Gurbuz 《Environmental Earth Sciences》2011,64(3):883-892
A new simplified method based on one-dimensional displacement theory and 2-D finite element (FE) analysis was developed to
predict the vertical displacement behavior of a concrete-faced rockfill dam. The FE analyses were carried out at the end of
construction (EOC) and the end of first filling of reservoir. The proposed method was calibrated by using continuously monitored
vertical displacement of the dam’s body to determine the mobilized modulus of elasticity of the rockfills at the EOC. The
prediction capability of the method was demonstrated using field measurements against the findings from the 2-D FE analysis
simulating characteristics of construction stages of the dam. The validity of the method was also examined on another membrane-faced
rockfill dam by comparing the geodetic measurements of vertical displacement measurements of the dam’s body with the calculated
vertical displacements from 2-D FE analysis at the EOC. 相似文献