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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
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Analysis of piled raft with nodular pile subjected to vertical load using a Winkler model approach 
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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
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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
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用双曲线切线模量方程计算地基非线性沉降 总被引：10，自引：1，他引：9
提出了一种利用原位试验成果求解非均质非线弹性地基最终沉降的新方法。对分层原状土载荷试验或螺旋板试验成果进行双曲线拟合,建立分层原状土切线模量与竖向附加应力的关系方程;在沉降计算公式中引入附加应力修正系数,以考虑基础埋深、地基非均质非线性特征等因素对应力分布的影响;利用双曲线切线模量方程及附加应力弹性解,可准确求解地基的总沉降。通过对几个压板载荷试验成果的拟合分析,得出了各土类的双曲线切线模量方程,用于求解地基在各级荷载下的沉降。计算结果表明,计算值与实测值吻合得很好。该方法原理简单、参数可靠、结果准确,为地基沉降计算开辟了一条新途径。 相似文献
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劈裂注浆可以有效改善土体的变形参数,大大降低土体在受力状态改变时的变形量,对劈裂注浆后复合土体的等效变形参数进行研究十分重要。在综合分析劈裂注浆扩散机制和工程应用实际的基础上,基于均质化理论提出了劈裂注浆后复合土体的三维单元体几何模型,按等效原则给出了浆-土体积及受力分配关系模型图;接着基于横向各向同性本构关系推导了模型的等效弹性模量和等效泊松比的解析解。然后采用有限元方法取得了模型特定条件下的等效弹性模量和等效泊松比,并与解析结果进行对比分析。最后把模型和相应的解析结果引入Flac3D岩土工程专业分析软件,结合一个热力隧道工程实例对隧道劈裂注浆后关键位置的沉降进行预测分析,并与实测值进行了对比。研究表明：对所提出的计算模型,解析计算与有限元方法计算结果吻合度较高,说明了解析结果的正确性;基于该模型及其解析结果得到的隧道开挖后的沉降预测值与实测值具有良好的一致性,说明所提出的模型和相应的解析计算方法具有一定的可靠性和实用性。 相似文献
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基于Biot饱和多孔介质U-W格式动力控制方程,采用Galerkin法和Fourier变换,推导了饱和土体2.5维有限元方程及黏弹性人工边界,建立了饱和土地基中空沟分析模型,并在波数域中进行求解,通过快速Fourier变换（FFT）进行波数展开,获得三维空间域中结果。算例分析了移动荷载作用下均质饱和土地基、分层饱和土地基、上覆单相弹性层饱和土地基3种饱和土地基模型中空沟的隔振效果。结果表明：饱和土地基中空沟的隔振效果不仅与空沟自身深度有关,还与地基中成层土体的分界面以及土体参数有关,波在不同土体分界面上的透射和反射会影响空沟的隔振效果;饱和土地基中上覆单相弹性层厚度对空沟的隔振效果影响显著,随着上覆单相弹性层厚度的增加,饱和土地基中空沟的隔振效果变好。 相似文献
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The paper deals with modeling the response of pavement systems to subsurface deformations. An analytic formulation is developed in the context of layered elastic theory wherein the bottom boundary is distorted in a prescribed manner – forcing the medium to deform. In the basic case considered, an axisymmetric displacement field is imposed, consisting of vertical and radial components. A version of the model, dealing with a single elastic layer deformed only in the vertical direction (with frictionless bottom), is parametrically interrogated to study the influence of layer thickness and modulus on the resulting surface profile and vertical contact stresses. Furthermore, it is shown that by spatially superposing several axisymmetric solutions, general displacement shapes can be reproduced and analyzed. Such a scheme is demonstrated in an inverse type of analysis to a case study dealing with a sagging runway; using measured surface elevations, an attempt is made to backcalculate subsurface deformations and stress changes at the bottom interface of the structure. 相似文献
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An anisotropic geomechanical model for jointed rock mass is presented. Simultaneously with deriving the orthotropic anisotropy elastic parameters along the positive axis, the equivalent compliance matrix for the deflection axis orthotropic anisotropy was derived through a three-dimensional coordinate transformation. In addition, Singh’s analysis of the stress concentration effects of intermittent joints was adopted, based on two groups of intermittent joints and a set of cross-cutting joints in the jointed rock mass. The stress concentration effects caused by intermittent joints and the coupling effect of cross-cutting joints along the deflection-axis are also considered. The proposed anisotropic mechanics parameters method is applied to determine the deformation parameters of jointed granite at the Taishan Nuclear Power Station. Combined with the deterministic mechanical parameters of rock blocks and joints, the deformation parameters and their variability in jointed rock masses are estimated quantitatively. The computed results show that jointed granite at the Taishan Nuclear Power Station exhibits typical anisotropic mechanical characteristics; the elastic moduli in the two horizontal directions were similar, but the elastic modulus in the vertical direction was much greater. Jointed rock elastic moduli in the two horizontal and vertical directions were respectively about 24% and 37% of the core of rock, showing weakly orthotropic anisotropy; the ratio of elastic moduli in the vertical and horizontal directions was 1.53, clearly indicating the transversely isotropic rock mass mechanical characteristics. The method can be popularized to solve other rock mechanics problems in nuclear power engineering. 相似文献
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G. Ranalli 《Tectonophysics》1994,240(1-4):107-114
The elastic flexural thickness of the lithosphere depends on plate curvature. As curvature increases, the elastic core of the plate is thinned from above (frictional yielding) and from below (plastic creep). Sometimes decoupling between crust and mantle elastic cores can also occur. The mechanical thickness of the lithosphere, on the other hand, is the thickness of the rheologically layered plate having a strength above a critical threshold. In order to estimate the mechanical thickness from a simple uniform-rheology plate model, we adopt a plastic work-hardening constitutive equation, which results in lower stresses in the regions of high strain, relative to the elastic model. It is, therefore, a better approximation to the actual rheology of the flexed lithosphere where there is no lower-crustal decoupling (e.g., in oceanic and in cold continental lithosphere). The equivalent mechanical thickness of the nonlinear plate can be directly obtained, if the curvature is known, from the estimated elastic flexural rigidity or thickness. Comparison with numerical integration of bending moment in rheologically layered lithosphere shows that equivalent mechanical thickness is a good estimation of mechanical thickness. Examination of both oceanic and continental data suggests that mechanical thickness is controlled by the 900 ± 100°C isotherm. This corresponds to a creep strength of the order of 10 MPa in upper mantle material. 相似文献
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水平加筋是广泛应用的软土地基处理方法之一,而水平加筋地基极限承载力的确定是其地基处理设计的重要依据。因此,首先结合条形基础下水平加筋地基的工程特点,在探讨其承载机制和破坏特点的基础上,考虑破坏间断面上筋材与地基土体的变形协调,构建出反映加筋参数变化影响的可变破坏模式及机动允许速度场;然后,在此基础上,通过重点研究筋材的能量耗散分析方法,并引入上限极限分析理论,建立出条形基础下水平加筋地基极限承载力分析模型,再引入序列二次规划优化分析理论,建立出条形基础下水平加筋地基极限承载力确定方法,它能充分反映加筋设计参数对地基破坏模式及承载力的影响;最后,通过试验结果与该方法及现有同类分析模型结果的比较分析,表明了该模型与方法的合理性与可行性。 相似文献
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针对地铁竖向振动在成层地基中的传播,提出了移动荷载作用下层状地基的分析模型。基于该模型,利用狄拉克函数及三重傅里叶变换将时空域内单个移动简谐荷载转换为频率-波数域内的荷载,结合薄层法和移动坐标系法推导了单个移动简谐荷载和移动简谐线荷载作用下三维层状地基动力响应的解析解,并给出了移动简谐线荷载动力响应解析解中参数n的经验取值范围;分析了荷载的移动速度对层状地基动力响应的影响以及弹性模量、泊松比、阻尼比和荷载频率对土体临界速度的影响。结果表明：荷载的移动速度对不同频带的动力响应的影响范围不同;移动速度对低频响应的影响程度大于对高频响应的影响程度;相比于泊松比和阻尼比,弹性模量对土体临界速度的影响最大;频率越接近荷载振动频率的振动响应,其幅值越大,临界速度越小。 相似文献
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针对天津滨海地区围海造陆工程所形成的上软、下硬双层软黏土地基,利用室内载荷试验和数值模拟开展了双层软黏土地基的承载特性及破坏模式研究。研究表明：由于下层沉积土的补强效应,双层软黏土地基的P-S曲线会出现明显的凹凸转折点,其出现的位置与宽厚比密切相关,宽厚比越小,转折点出现的时间越靠后,下层沉积土的补强效果越不明显。数值结果表明：双层软黏土地基破坏模式随着上覆土厚度的变化相差不大,均为整体剪切破坏。随着载荷板宽度的增加,双层软黏土地基以冲剪破坏模式过渡为局部剪切破坏,当载荷板宽度大于3.0 m时,表现为整体剪切破坏。 相似文献
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The effect of tunneling on surrounding environments, especially on existing buried pipelines is a problem that engineers designing and practicing in urban geotechnical environments encounter more frequently than in the past. However, previous studies are usually based on the assumption that the soil is homogeneous. How to reflect soil stratification is the main focus for the problem of tunneling in multi‐layered soils. A displacement controlled coupling numerical method is presented for the displacement analysis of tunnel excavation below existing pipelines in multi‐layered soils. On the basis of the layered soil model, to consider the soil nonhomogeneous characteristic, the finite element method and boundary element method are coupled to simulate the deformation of existing pipelines induced by tunneling. The solutions indicate that good agreements are obtained between the proposed coupling numerical method and the commercial software. The accuracy of the proposed numerical method is better than the two stages method based on the existing closed‐form solutions. Moreover, the results discussed in this paper show that the error obtained by the previous method of weighted average on the basis of homogeneous half space converted from layered soils is not negligible for the obvious difference of elastic parameters among successive layers. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
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A new method of analysis of piles in multi‐layered elastic soil subjected to a torque at the head is developed. The differential equation governing the angle of twist in the pile is derived using the variational principles of mechanics. The method of initial parameters is used to obtain closed‐form solutions of the angle of twist and torque in the pile as a function of depth. The inputs required for the analysis are shear moduli of pile and soil, pile geometry and thickness of soil layers. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
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S. K. Sharan 《国际地质力学数值与分析法杂志》1989,13(5):565-570
A highly efficient technique is presented for the finite element analysis of stresses around underground openings surrounded by an infinite extent of linearly elastic rock mass. The effect of unbounded rock is incorporated in the analysis by using elastic supports around the finite element model. Expressions for stiffnesses of the elastic supports are derived and these are found to depend on the location of elastic supports, the shear modulus and Poisson's ratio of the rock, and the ratio of horizontal to vertical initial stresses. With the use of the proposed technique, the extent of the finite domain to be considered in the analysis is highly reduced. This results in a great computational advantage. The other principal merit of the proposed technique is that a standard finite element code for stress analysis may be used without making any modification. Results of some numerical tests are reported to demonstrate the effectiveness and efficiency of the proposed method. The technique has the potential of being applied to more complex problems of unbounded domains in geomechanics. 相似文献
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This paper presents the analytical layer‐element method to analyze the consolidation of saturated multi‐layered soils caused by a point sink by considering the anisotropy of permeability. Starting from the governing equations of the problem, the solutions of displacements and stresses for a single soil layer are obtained in the Laplace–Hankel transformed domain. Then, the analytical layer‐element method is utilized to further derive the solutions for the saturated multi‐layered soils in the transformed domain by combining with the boundary conditions of the soil system and continuity conditions between adjacent layers. The actual solutions in the physical domain can be acquired by the inversion of Laplace–Hankel transform. Numerical results are carried out to show the accuracy and stability of the proposed method and evaluate the influence of sink depth and anisotropic permeability on excess pore pressure and surface settlement. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
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利用传递-反射矩阵方法和叠加原理推导了双轮胎振动荷载作用下弹性层状公路结构的动力响应解,并利用Hankel数值逆变换技术进行了数值求解。弹性层状结构的传递-反射矩阵同时具有单个矩阵尺寸小、矩阵元素只含有负指数项2个优点,计算结果不受土层单元厚度与荷载频率大小的影响,可以大幅提高计算效率和精度。通过将数值计算与室内模型试验结果进行比较,验证了方法的正确性。在此基础上,分析了面层厚度及模量对层状公路结构动应力、动位移的影响程度和规律,得出了一些有意义的结论。研究结果可为公路路面、路基结构设计提供参考。 相似文献
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成层饱和土中考虑横向惯性的单桩纵向振动 总被引：2，自引：0，他引：2
基于饱和多孔介质理论,研究了成层饱和黏弹性土层中端承桩的纵向振动特性。首先利用Novak薄层法,得到了土层对纵向振动桩的动力阻抗。其次,将桩等效为Rayleigh-Love杆,给出了成层饱和黏弹性土中端承桩纵向振动的一般分析方法和桩头动力复刚度的解析表达式。具体分析了两层饱和黏弹性土中端承桩的纵向振动特性,得到了桩头动刚度因子和等效阻尼随频率的响应特征,讨论了物理和几何等参数对动刚度因子和等效阻尼的影响。结果表明：桩长径比、土层模量比以及桩土模量比等对桩头动刚度因子和等效阻尼有显著的影响。相比于均质土层中的桩,上层土越硬或下层为软弱土层,桩的动刚度因子和等效阻尼振动幅值增大,其周期随长径比显著变化,且对于大直径桩,动刚度因子和等效阻尼随频率呈振动变化。同时,土体与孔隙水相互作用系数和桩泊松比等的影响相对较小。其结果可作为桩基动力基础设计和动力检测等基础数据。 相似文献
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Vertical drains are usually installed in subsoil consisting of several layers. Due to the complex nature of the problem, over the past decades, the consolidation properties of multi‐layered ground with vertical drains have been analysed mainly by numerical methods. An analytical solution for consolidation of double‐layered ground with vertical drains under quasi‐equal strain condition is presented in this paper. The main steps for the computation procedure are listed. The convergence of the series solution is discussed. The comparisons between the results obtained by the present analytical method and the existing numerical solutions are described by figures. The orthogonal relation for the system of double‐layered ground with vertical drains is proven. Finally, some consolidation properties of double‐layered ground with vertical drains are analysed. Copyright © 2001 John Wiley & Sons, Ltd. 相似文献