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1.
An analytical solution for the wave-induced soil response is developed for a seabed of finite thickness subject to a three-dimensional (3-D) wave system produced by two intersecting waves of equal properties. These 3-D exact solutions for the pore pressure and effective stresses, proposed for a non-cohesive soil matrix of finite depth in a homogeneously unsaturated and anisotropic condition, are readily reducible to the limiting two-dimensional cases of progressive and standing waves, for which no explicit solutions are available for finite thickness. The effects of soil isotropy, degree of saturation, seabed thickness and grain size on the wave-induced pore pressure are discussed in detail. The explicit solutions presented in this study for the wave-induced pore pressure and effective stresses should benefit the laboratory experiments and field monitoring programs carried out in soil of finite depth. 相似文献
2.
In this study, analytical solutions for tide-induced pore pressure, seepage force and water inflow into a subaqueous drained tunnel are developed. The results are compared with numerical solutions from a commercial software. The effects of the soil permeability, shear modulus, lining thickness and buried depth of the tunnel on tide-induced pore pressure, seepage force and water inflow are discussed. Larger tide-induced pore pressure and seepage force are obtained for smaller tunnel depth and higher soil permeability. The phase lags of the maximal tide-induced pore pressure at different depths are determined and investigated. 相似文献
3.
A standing wave in front of a seawall may reach a height more than twice of its incident component. When excess pore pressure occurs, it may even induce seabed instability, hence endangering the structure. This issue was studied previously using only linear wave theory. In this paper, standing‐wave theory to a second‐order approximation is applied, in order to demonstrate the differences between these two solutions. The spatial and temporal variations in the instantaneous pore pressure are first calculated, in addition to their vertical distributions. The effects of wave height, water depth and the degree of soil saturation on pore pressure distributions are then discussed, followed by the net pore pressure averaged over one wave cycle. The results suggest the existence of a residual pore pressure in the seabed and its net pore pressure can be used to estimate the wave‐induced liquefaction potential in a soil column. It also indicates that, in deep water, the second‐order solution predicts that a negative pore pressure at an antinode which may be greater than a positive pressure. Overall, the second‐order solution is found to agree better with the experimental results of the pore pressures available, compared to the linear solution. Copyright © 2000 John Wiley & Sons, Ltd. 相似文献
4.
运动荷载附近有限层厚软土地基的振动研究 总被引：4，自引：4，他引：0
基于Biot多孔弹性介质的波动理论,研究了运动荷载附近软土地基的振动问题。假设一条形均布荷载作用在地基表面,则该模型可视为平面应变问题进行分析。通过引入4个势函数和Helmholtz原理,并利用Fourier变换及逆变换技术,获得了运动荷载作用下软土地基的应力、位移和孔隙水压力的解答。利用离散Fourier逆变换得到数值计算结果,分析了荷载速度,频率以及软土的渗透系数及多孔弹性参数对运动荷载作用下地表竖向位移及土体中任一点孔隙水压力分布的影响。 相似文献
5.
The settlement and excess pore pressure are calculated for a column of water-saturated clay in which the permeability and/or shear modulus vary with depth. Several fairly general laws of variation are investigated. In each case, the soil is assumed to have a permeable top surface and to rest on an impervious substrate. For all the variations examined, in which the shear modulus increases with depth below the surface but the permeability of the soil remains constant, the deflection at a given instant after imposition of the load decreases and the degree of settlement increases with increasing rate at which the change with depth takes place. It is found that, when the variation over the height of the column is one order of magnitude or less, the curve of degree-of-consolidation versus time is reasonably wellapproximated by the curve for a homogeneous soil whose modulus equals the depth-averaged value. When, in addition, the permeability decreases with depth, the approximation becomes less accurate. The same approximation, for moderate increase in shear modulus with depth, predicts satisfactorily the process of dissipation of excess pore pressure at a given depth, but breaks down when the variation in modulus is large. Finally, it is shown that the effect of variable modulus on the settlement is greater than of a comparable variation in permeability. 相似文献
6.
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
7.
A theoretical study is made of the consolidation of a composite foundation reinforced by columns. A more reasonable initial condition for the consolidation of a composite foundation is derived from the equilibrium equation and the equal strain assumption. Then, the general analytical solutions for excess pore water pressures in the column and in the surrounding soil are obtained using this new initial condition under the influence of several important factors. These factors include: the gradual variation of horizontal permeability in the disturbed soil, the change in the total average stress in a composite foundation with depth, and the effect of time-dependent external loads. The general expressions for the overall average degree of consolidation of a composite foundation, both in terms of stress and in terms of deformation, are then derived. On the basis of the above theory, the explicit solutions for a particular case, which considers ramp loading and a linear change of total stress with depth, are given in detailed forms. Finally, a parametric study and a comparison of some available solutions are made. The results show that the average degree of consolidation obtained in terms of stress and in terms of deformation is the same; the increase in construction time, the disturbance intensity during column construction and the size of the disturbed zone reduce the consolidation rate of a composite foundation. For the case of PTIB (pervious top surface and impervious bottom surface), the increase in the ratio of top total stress to bottom total stress in the composite foundation accelerates consolidation. 相似文献
8.
简谐荷载作用下饱和土体中圆形衬砌隧道三维动力响应分析 总被引：2，自引：0，他引：2
研究了全空间饱和土体中圆形衬砌隧道在径向简谐点荷载作用下的三维动力响应,将衬砌用无限长圆柱壳来模拟,土体用Biot饱和多孔介质模型来模拟,引入两类势函数来表示土骨架的位移和孔隙水压力,并利用修正Bessel方程来求解各势函数,结合边界条件,得到频率-波数域内衬砌和土骨架位移、孔隙水压力的解答,最后进行Fourier逆变换得到时间-空间域内的响应。通过算例分析了荷载振动频率和土体渗透性对土体和衬砌位移响应及土体孔压的影响。结果表明,饱和土体和弹性土体的位移响应具有明显区别。随着荷载频率的增大,土体和隧道位移幅值减小,土体孔压幅值增大;随着土体渗透性增大,土体位移及孔压幅值减小。 相似文献
9.
Recently, very strong vertical ground motions have been recorded during several earthquakes. The vertical motions are the consequence of compressional stresses which are mainly transmitted by pore fluids. For linear elastic analysis of a submerged soil layer, the permeability has a very minor effect on shear-wave response for which pore fluids are not taken into account. But on compressional-wave response, the permeability dominates the damping effect and is thought as the principal influential factor from pore fluids. In this study, the effect of changing permeability on damping is explored. In practice it is harder to obtain the coefficient of permeability, κ, than to measure the void ratio, e. In order to evaluate the permeability and explore its influence on vertical shaking, the formula relating κ–e for the saturated soil is selected for a 1D submerged pore-elastic model subjected to vertical sine-wave loading. The random, linear, linear-plus-random, logarithmic, and log-plus-random depth functions of void ratio are taken into account in this study. The intrinsic error due to the use of the arithmetic mean of permeability for a certain area with a heterogeneous distribution of permeability has also been assessed. Numerical simulations show that the five depth distributions of void ratio all result in the extra viscous forces. The damping effect on vertical shaking is mainly controlled by the harmonic mean of permeability and spatial distribution of permeability rather than the arithmetic mean of permeability. The harmonic mean is more appropriate than the arithmetic mean to be the representative permeability, because the damping coefficient is inversely proportional to permeability. 相似文献
10.
The subject of wave-induced soil response in a real seabed has attracted the attention of geotechnical and coastal engineers over the last three decades, for which several basic theories have been developed. However, the evaluation of soil liquefaction has not been attempted theoretically in a seabed with multiple sub-layers, in which homogeneity in soil properties can be assumed within each layer. In this study, a semi-analytical approach is presented for obtaining solutions for the pore pressure and effective stresses in a non-cohesive layered seabed of finite thickness subject to a system of three-dimensional waves. Based on the numerical results for a layered seabed, influences of soil characteristics (relative layer thickness, permeability ratio and shear modulus) on seabed responses are described. Special attention is given to the effect of placing a coarser material as a top layer for protecting an underlayer of finer sediment. Although only a three-layered seabed is explicitly solved in this study, the procedure outlined can readily be extended to a multi-layered soil system. The three-dimensional solutions can also be applied to the two-dimensional progressive or standing wave systems. 相似文献
11.
基于一维固结理论,研究了土层物理力学性质沿深度非均匀连续变化的固结问题。首先,利用分离变量法,获得了渗透系数和压缩系数随深度按指数函数变化的非均匀地基一维固结方程的解析表达式; 然后与Terzaghi固结理论的经典解答进行了比较,获得了两种解答之间的相似转换关系。这样,非均匀地基固结问题就可以用相同荷载以及边界条件下的均匀地基固结的经典解线性表示。因此,非均匀地基固结问题的求解转化为对相似转换系数的计算。该系数集中反映土层非均匀性对地基固结的影响,从而为解决非均匀地基一维固结问题提供了便捷途径。 相似文献
12.
A closed form analytical solution for two‐dimensional plane strain consolidation of unsaturated soil stratum 
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下载免费PDF全文 This paper discusses the excess pore‐air and pore‐water pressure dissipations and the average degree of consolidation in the 2D plane strain consolidation of an unsaturated soil stratum using eigenfunction expansion and Laplace transformation techniques. In this study, the application of a constant external loading on a soil surface is assumed to immediately generate uniformly or linearly distributed initial excess pore pressures. The general solutions consisting of eigenfunctions and eigenvalues are first proposed. The Laplace transform is then applied to convert the time variable t in partial differential equations into the Laplace complex argument s. Once the domain is obtained, a simplified set of equations with variable s can be achieved. The final analytical solutions can be computed by taking a Laplace inverse. The proposed equations predict the two‐dimensional consolidation behaviour of an unsaturated soil stratum capturing the uniformly and linearly distributed initial excess pore pressures. This study investigates the effects of isotropic and anisotropic permeability conditions on variations of excess pore pressures and the average degree of consolidation. Additionally, isochrones of excess pore pressures along vertical and horizontal directions are presented. It is found that the initial distribution of pore pressures, varying with depth, results in considerable effects on the pore‐water pressure dissipation rate whilst it has insignificant effects on the excess pore‐air pressure dissipation rate. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
13.
假定土体在固结过程中压缩性和渗透性的变化成正比,基于 - 及 - 关系,推导出饱和软土成层地基一维非线性固结解析解,分别给出了按沉降定义和按有效应力定义的每层土平均固结度及整个土层总固结度的计算公式。采用Fortran语言编制了相应的计算程序,将计算得到的结果与已有双层地基一维非线性固结解析解计算结果进行比较,验证该解析解的正确性。利用该程序分析成层地基一维非线性固结性状,分别讨论了初始竖向渗透系数、初始体积压缩系数、荷载值及土层厚度对地基固结性状的影响。分析结果表明：在成层地基一维非线性固结过程中,初始竖向渗透系数对超静孔压的影响较为复杂,对上下层地基固结速率影响不同;初始体积压缩系数增大,超静孔压增大,固结速率变小;所加荷载值越大,超静孔压消散越慢,固结发展越慢;超静孔压消散速率不仅取决于土层厚度,同时取决于各层土渗透性的相对大小。 相似文献
14.
This paper presents a simple analytical solution to Fredlund and Hasan's one‐dimensional (1‐D) consolidation theory for unsaturated soils. The coefficients of permeability and volume change for unsaturated soils are assumed to remain constant throughout the consolidation process. The mathematical expression of the present solution is much simpler compared with the previous available solutions in the literature. Two new variables are introduced to transform the two coupled governing equations of pore‐water and pore‐air pressures into an equivalent set of partial differential equations, which are easily solved with standard mathematical formulas. It is shown that the present analytical solution can be degenerated into that of Terzaghi consolidation for fully saturated condition. The analytical solutions to 1‐D consolidation of an unsaturated soil subjected to instantaneous loading, ramp loading, and exponential loading, for different drainage conditions and initial pore pressure conditions, are summarized in tables for ease of use by practical engineers. In the case studies, the analytical results show good agreement with the available analytical solution in the literature. The consolidation behaviors of unsaturated soils are investigated. The average degree of consolidation at different loading patterns and drainage conditions is presented. The pore‐water pressure isochrones for two different drainage conditions and three initial pore pressure distributions are presented and discussed. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
15.
目前对渗透系数取极端值情况下饱和土中两类压缩波物理本质的理解尚不够清晰,比如文献中对渗透系数无穷大情况下饱和土中两类压缩波波速的求解有不同的结果。结合Zienkiewicz给出的土动力学基本方程,深入讨论了流体运动方程的建立,推导了饱和土一维压缩弹性问题的动力控制方程及其 - 、 - 形式,进而得出渗透系数取0和取无穷大这两种极端情况下饱和土中压缩波的波速,解释了其物理意义。提出了惯性耦合力的概念,指出两相体动力分析时土骨架和孔隙水之间的相互作用包含渗透力和惯性耦合力两项,并重点讨论了衡量惯性耦合力的参数孔隙度对压缩波波速的影响。 相似文献
16.
基于Biot多孔介质波动理论,建立孔隙率、密度、剪切模量和渗透系数相互耦合且同时沿深度变化的非均匀饱和半空间模型,引入量化的非均匀梯度表征地基非均匀程度。在柱坐标系下构建以土骨架位移和孔隙压力为基本未知量的三维动力控制方程,采用算子运算和Hankel积分变换求解控制方程,推导出简谐集中力作用下半空间地基振动响应的积分解。将所得结果分别退化到均匀饱和半空间和弹性半空间与经典Lamb解做了对比,验证了结果的正确性。利用已有研究结论,给出孔隙率、密度、剪切模量和渗透系数之间的耦合关系式,代入推导结果进行数值计算。分别对水饱和地基和气饱和（干土）地基的动力响应进行分析,给出两类地基在动力作用下的振动位移和孔隙压力分布,并对非均匀性的影响作出分析。结果表明：4参数沿地基深度耦连变化对地基的动力响应产生一定程度影响,振动位移和孔隙压力在地层中的衰减速度由此加快。由于水的黏滞性远大于气体,所以水饱和地基中的振动衰减更快。非均匀程度越高,耦合效应的影响越明显。 相似文献
17.
采用Barron轴对称固结及大变形固结问题的某些简化与假定,推导建立了砂井地基大变形固结控制方程,利用建立的双层砂井地基大变形固结方程及编制的计算程序,通过引入软土渗透系数、有效应力与孔隙比之间的幂函数关系k =ced与e=a( )b,对瞬时加载下双层砂井地基固结性状进行算例计算。结果表明：（1）双层软土幂函数渗透关系及压缩关系中诸参数对双层砂井地基固结性状有重要影响：随着两层软土幂函数渗透关系中参数c1、c2的增加（渗透性增加）、或幂函数压缩关系中参数a1、a2的增加,各土层水平径向与竖向孔隙比减小更快,沉降发展速率与超静孔压消散速率也相应增加,且沉降发展速率快于孔压消散速率。（2）两层土在分界面处的孔隙比及平均超静孔压均出现明显的突变,将沿深度分布曲线分成形状不同的两段,表现出不同的固结性状。 相似文献
18.
由于非饱和土的渗透系数是基质吸力的函数,使得控制方程带有强非线性的特征,进而使得控制方程的解析求解变得十分困难。同伦分析法对级数基函数和辅助线性算子的选择具有更大的自由性、灵活性,且收敛性的控制和调节更加容易实现,求解强非线性微分方程时在选择线性算子以及辅助参数上具有明显的优势。因此,针对非饱和土固结方程的非线性特征,对于处于地表浅层的非饱和土层,假设孔隙气压力为大气压力,在Richard经验公式与非饱和土一维固结理论的基础上,推导了非饱和一维固结无量纲控制方程;应用同伦分析法,通过选取适当的初始猜测解与辅助参数,将该非线性方程转换为线性的微分方程组并求解得到固结问题的级数解。此外,以压实高岭土为研究对象,在收集相关试验参数基础之上,将由同伦分析法求得的固结问题的近似解析解与有限差分法数值结果相对比,分析结果验证了解析解的正确性。 相似文献
19.
The analytical solution of soil pore pressure accumulations due to a progressive wave is examined in detail. First of all, the errors contained in a published analytical solution for wave‐induced pore pressure accumulation are addressed, and the correct solution is presented in a more general form. The behaviour of the solution under different soil conditions is then investigated. It is found that the solution for deep soil conditions is sensitive to the soil shear stress in the top thin layer of the soil. However the solution is significantly influenced by the shear stress in the thin layer of soil near the impermeable base, for shallow and finite depth soil conditions. It is also found that a small error in the soil shear stress can lead to a large error in the accumulated pore pressure. An error analysis reveals the relationships between the accuracy of the pore pressure accumulation and the accuracy of the soil shear stress. A numerical solution to the simplified Biot consolidation equation is also developed. It is shown that the error analysis is of significant value for the numerical modelling of pore pressure buildup in marine soils. Both analytical and numerical examples are given to validate the error estimation method proposed in the present paper. Copyright © 2001 John Wiley & Sons, Ltd. 相似文献
20.
Tsunami runup and drawdown can cause liquefaction failure of coastal fine sand slopes due to the generation of high excess
pore pressure and the reduction of the effective over burden pressure during the drawdown. The region immediately seaward
of the initial shoreline is the most susceptible to tsunami-induced liquefaction failure because the water level drops significantly
below the still water level during the set down phase of the drawdown. The objective of this work is to develop and validate
a numerical model to assess the potential for tsunami-induced liquefaction failure of coastal sandy slopes. The transient
pressure distribution acting on the slope due to wave runup and drawdown is computed by solving for the hybrid Boussinesq—nonlinear
shallow water equations using a finite volume method. The subsurface pore water pressure and deformation fields are solved
simultaneously using a finite element method. Two different soil constitutive models have been examined: a linear elastic
model and a non-associative Mohr–Coulomb model. The numerical methods are validated by comparing the results with analytical
models, and with experimental measurements from a large-scale laboratory study of breaking solitary waves over a planar fine
sand beach. Good comparisons were observed from both the analytical and experimental validation studies. Numerical case studies
are shown for a full-scale simulation of a 10-m solitary wave over a 1:15 and 1:5 sloped fine sand beach. The results show
that the soil near the bed surface, particularly along the seepage face, is at risk to liquefaction failure. The depth of
the seepage face increases and the width of the seepage face decreases with increasing bed slope. The rate of bed surface
loading and unloading due to wave runup and drawdown, respectively, also increases with increasing bed slope. Consequently,
the case with the steeper slope is more susceptible to liquefaction failure due to the higher hydraulic gradient. The analysis
also suggests that the results are strongly influenced by the soil permeability and relative compressibility between the pore
fluid and solid skeleton, and that a coupled solid/fluid formulation is needed for the soil solver. Finally, the results show
the drawdown pore pressure response is strongly influenced by nonlinear material behavior for the full-scale simulation. 相似文献