共查询到17条相似文献，搜索用时 156 毫秒
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目前考虑土体非线性压缩及渗透特性的双层地基非线性固结解均假定土体固结系数保持不变,能反映固结系数变化的双层地基非线性固结解还很鲜见。引入经典的e- 和e- 非线性关系描述土体的非线性压缩、渗透特性,在假定双层地基上、下土层压缩指数与渗透指数比值 相等且不等于1的基础上,得到变荷载下考虑土体固结系数变化的双层地基一维非线性固结近似解。该解答在 1条件下可退化为已有的 1时双层地基一维非线性固结解。基于此解探讨了双层地基上、下土层参数的相对比值对非线性固结性状的影响。结果表明：单面排水条件下 越小,下层土与上层土的相对压缩性越低、相对渗透性越高,则双层地基非线性固结速率越快;减小 值,增加双层地基中压缩性小、渗透性高的土层的厚度,会加快地基的固结速率。 相似文献
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在土中渗流遵循非达西渗流定律的前提下,考虑软土在固结过程中的非线性固结特性,根据饱和土体一维固结的连续条件,推导出基于非达西渗流的软土一维非线性固结控制方程。利用半解析方法对其进行求解,并与差分计算结果进行对比,验证半解析方法的可靠性。最后,着重分析非达西渗流与达西定律之间非线性固结性状的差别,以及不同自重应力分布方式对固结速率的影响。结果表明,考虑非达西渗流下的非线性固结速率比达西定律下要慢,且指数和临界水力坡降越大,非线性固结速率越慢。而且,作用的外荷载越小、地基土层越厚,非达西渗流下非线性固结速率的减慢愈明显。自重应力均匀分布下的非线性固结速率要比自重应力线性分布下慢,但随着荷载的增大、土层的变薄,两者之间的差别会越来越小。 相似文献
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Laplace变换解双层地基固结问题 总被引：1，自引：0，他引：1
连云港地区的软土是海相淤泥和淤泥质土.在连云港软土地区修筑高速公路时,通常采用水泥土搅拌桩地基处理方法使路基强度和变形满足工程的要求.该类软土压缩沉降量大,排水固结缓慢,地基稳定性差,造成高速公路建设中及建成后工程问题频繁出现.从江苏海相软土的工程实例出发,将经水泥土搅拌桩处理后的高速公路路基简化为双层地基,借助Laplace变换求解了二级加荷下的双层地基一维固结问题,为克服对固结方程进行Laplace逆变换的困难,在Laplace逆变换中运用Stehfest算法进行数值求解,该双层地基固结沉降计算结果与实际观测数据基本一致. 相似文献
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《岩土力学》2021,(5)
目前考虑土体非线性压缩及渗透特性的双层地基非线性固结解均假定土体固结系数保持不变,能反映固结系数变化的双层地基非线性固结解还很鲜见。本文引入经典的e-lgσ'和e-lgk_(v)非线性关系描述土体的非线性压缩、渗透特性,在假定双层地基上、下土层C_(c)_(i)/C_(k)_(i)值相等且不等于1的基础上,得到变荷载下考虑土体固结系数变化的双层地基一维非线性固结近似解。该解答在C_(c)/C_(k)→1条件下可退化为已有的C_(c)/C_(k)=1时双层地基一维非线性固结解。最后,基于本文解探讨了双层地基上、下土层参数的相对比值对非线性固结性状的影响。结果表明：单面排水条件下,C_(c)/C_(k)越小,下层土与上层土的相对压缩性越低、相对渗透性越高,则双层地基非线性固结速率越快;减小C_(c)/C_(k)值,增加双层地基中压缩性小、渗透性高的土层的厚度,会加快地基的固结速率。 相似文献
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饱和软土的自重固结涉及许多复杂的非线性问题,而现有分析方法一般基于线性假设,将固结控制方程简化,在沉降变形较大的情况下并不合理。基于Gibson大变形固结方程,推导在单面排水和双面排水条件下的边界条件,综合考虑饱和软土的自重特性与非线性压缩、渗透关系,采用稳定性较好的Crank-Nicolson型差分格式离散并求解非线性控制方程,并从孔隙比、沉降、孔隙水流速3个方面将数值解与CS2固结数值模型进行对比验证。结合工程实例,研究土层不同初始厚度和初始孔隙比对自重固结的影响。结果表明：初始厚度与初始孔隙比较大土层最终沉降也较大。与传统方法相比,该方法所得出的数值解精度较高,实现了高度非线性固结方程的快速求解,其成果更能广泛运用于实际工程的分析之中。 相似文献
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考虑土中指数形式渗流定律以及土体的非线性固结特性,以超静孔隙水压力为变量在拉格朗日坐标系内建立了软土一维大变形固结问题的控制方程及其求解条件,并运用有限差分法获取其数值解答。在指数形式渗流定律退化为达西定律下,通过将差分解与已有的半解析解进行对比,验证了数值计算的可靠性。最后对指数形式渗流定律下软土一维非线性大变形固结性状进行计算分析,结果表明： 1时,软土的非线性大变形固结速率会随外载增大而减慢; 1时,软土的非线性大变形固结速率会随着外荷载的增加而加快;软土非线性大变形固结速率要比非线性小变形固结速率快,且差别会随荷载增大而加剧;此外,大变形固结理论的最终沉降值要小于小变形固结理论,且差别会随着荷载的增大而加剧。 相似文献
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基于太沙基一维固结理论,采用有限差分法对室内固结试验进行了数值分析,编制了室内固结试验的C++数值程序和自动求解固结系数的Matlab拟合程序,该程序能够模拟不同尺寸（排水高度）软土试样的固结过程。讨论了试样尺寸、渗透系数和初始固结应力对模拟结果的影响。数值结果显示随着排水高度和渗透系数的增加,由时间平方根法和时间对数法求解的固结系数比不断减小,且排水高度较小时固结系数比变化较快。土体初始应力越小,主固结完成所需的时间越长。与日本广岛重塑土大尺寸试样固结试验结果进行了比较分析。研究结果表明所采用的数值方法能够较好地模拟软土的固结试验过程,可以进行一定条件下大尺寸软土试样的固结特性研究,研究成果对于揭示软土的固结变形发展有一定的理论价值和实际意义。 相似文献
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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
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实验室软土多级固结蠕变试验成果表明,海积软土具有非线性、不可逆的、与时间相关的固结变形特性。在此基础上,提出了时间效应系数的概念,并构造了反映海积软土一维固结蠕变的本构关系。 相似文献
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以结构性较强的天然饱和软黏土为研究对象,考虑了沉积作用对其自重应力的影响,以及压缩性和渗透性的非线性变化,推导了任意加载条件下结构性土一维大应变固结控制方程,并采用半解析的方法对方程进行求解计算。再将其退化为无结构性的饱和软黏土固结解,与已有的大应变固结解进行了对比,验证了该解的正确性。最后将该半解析解计算结果与小应变固结理论解、不考虑结构性的固结理论解计算结果进行对比分析。结果表明：大应变固结理论的沉降计算值大于小应变固结理论的计算值,且二者的差值随着荷载的增加而增加;当考虑土体的结构性时,地表沉降计算值小于不考虑土体结构性的沉降计算值。 相似文献
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A method for the analysis of the consolidation of a horizontally layered soil under plane conditions is developed. The method depends upon the transformation of the governing equations by a Fourier trasform. This transformation has the effect of reducing the partial differential equations of consolidation to ordinary differential equations. The ordinary differential equations are then solved using a finite layer or finite difference approach. Once the solution in the transformed plane has been found, the actual solution is synthesized by Fourier inversion. The method leads to a considerable reduction in the amount of core storage necessary for solution and enables the solution of quite significant problems to be obtained on a mini-computer. 相似文献
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The governing equations for the coupled processes of consolidation and creep of two-layered soft soils are established. The Nishihara rheological model is adopted to simulate the elasto-viscoplastic characteristics of soft soils, disregarding the effects of the soil self-gravity. A semi-analytical theory combined with numerical and analytical methods is introduced to solve the governing equations of the one-dimensional rheological model. The computational procedure and the approximate solutions for two-layered soft soils subjected to surface loading are obtained for two drainage conditions. The solutions and the computational procedure are used to study the effects of the two layers and constitutive parameters on rheological consolidation behavior of soft soils. It can be concluded that two layers affect the rate of excess pore water pressure dissipation and settlement development. The parametric studies show that when the parameters of the upper layer remain constant, increases in the permeability and elastic modulus in the lower layer accelerate the dissipation of the excess pore water pressure, and meanwhile increases in the viscosity coefficient and viscoplastic limit slows down the dissipation of the excess water pressure. 相似文献
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Based on the Fredlund consolidation theory of unsaturated soil, exact solutions of the governing equations for one‐dimensional consolidation of single‐layer unsaturated soil are presented, in which the water permeability and air transmission are assumed to be constants. The general solution of two coupled homogeneous governing equations is first obtained. This general solution is expressed in terms of two functions psi1 and ψ2, where ψ1 and ψ2, respectively, satisfy two second‐order partial differential equations, which are in the same form. Using the method of separation of variables, the two partial differential equations are solved and exact solutions for three typical homogeneous boundary conditions are obtained. To obtain exact solutions of nonhomogeneous governing equations with three typical nonhomogeneous boundary conditions, the nonhomogeneous boundary conditions are first transformed into homogeneous boundary conditions. Then according to the method of undetermined coefficients and exact solutions of homogenous governing equations, the series form exact solutions are put forward. The validity of the proposed exact solutions is verified against other analytical solutions in the literature. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
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软土的次固结对于软土的变形量非常重要。在软土次固结计算中,通常以次固结系数作为计算参数,但该系数不能反映荷载变化的影响,而且只适用于正常固结土。由于工程中所遇到的大都为超固结土,对超固结土的次固结计算还缺少合理的方法。通过室内试验开展了软土次固结沉降相关研究,进行了多组原状软土试样的分级加载次固结试验,试验结果表明,对于软土次固结计算,建议从次固结应变与时间关系的角度,采用双曲线形式进行拟合,并分别对正常固结和超固结状态的次固结应变参数进行分析,建立了一维次固结的经验模型公式,提出了一种考虑压力对次压缩影响的次固结沉降计算方法,并将该方法应用于现场工程项目,验证了该方法可以适用于正常固结土和超固结土,使得软土次固结沉降量的计算能够更好地反映实际工程问题。 相似文献
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In the present work, a simplified model has been developed to study the behavior of stone column-supported embankment under axi-symmetric loading condition. The rate of consolidation of stone column-reinforced soft ground under axi-symmetric condition has also been presented in the paper. Mechanical model elements such as Pasternak shear layer, spring–dashpot system are used to model the different components such as granular layer, soft soil, stone columns etc. The governing differential equations are solved by finite difference technique. Parametric study has also been carried out to show the effect of different model variables on the settlement, stress concentration ratio of the foundation system. It is observed that for lower diameter ratio, at a particular time, the degree of consolidation predicted by the present method for axi-symmetric loading condition is almost same or lower than the degree of consolidation obtained by unit cell approach, but as the diameter ratio increases present analysis predicts higher degree of consolidation as compared to the unit cell approach. The maximum settlement decreases as the modular ratio increases and beyond the modular ratio value 30, the reduction rate of settlement decreases. 相似文献
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Conceptual data model and method of settlement calculation for deformation and water release from saturated soft soil 总被引：2，自引：0，他引：2
Research on the seepage deformation of saturated soft soil has resulted in many achievements based, mainly, on existing seepage-deformation control equations. In reality, however, these control equations and related parameters suffer from many problems. The conductivity coefficient in the seepage control equation and the consolidation coefficient in the consolidation equation clearly resemble each other in form. However, in existing regulations and practice, soil deformation is rarely calculated by substituting the conductivity coefficient obtained from field hydrogeological experiments for the consolidation coefficient. Similarly, seepage is seldom calculated by substituting the conductivity coefficient with the consolidation coefficient obtained from consolidation experiments. This can be attributed to the fact that the two coefficients have some obvious differences. Moreover, the settlement deformation of soil calculated using the existing seepage and consolidation models does not agree very well with the measured deformation. Also, the values calculated using different models usually deviate markedly. Research indicates that these problems derive from the fact that the seepage and consolidation equations are based on different concepts of elementary volume. This study proposes using two separate elementary volume concepts: deformation elementary volume and control elementary volume. The concepts are adopted for saturated soft soil and the results used to analyze the relationships and differences between the two concepts. Moreover, we developed a conceptual data model (CDM) for the water released from and the deformation of the saturated soil. The model discloses the differences between the consolidation and conductivity coefficients both in their physical significances and magnitudes. The inter-relationship between the two coefficients is also revealed. An analytical solution for the deformation and water released from saturated soft soil is deduced based on the CDM model and the relationship between the hydrogeological and consolidation deformation parameters is established. A physical test model for saturated soft soil under certain conditions is also designed to verify the analytical solution using a method of curve fitting. Seepage and deformation tests and case studies show that the parameters calculated using the consolidation model are in agreement with those obtained from the CDM seepage model based on the measured data for flux and settlement vs. time. Furthermore, the relationship between conductivity and consolidation coefficients is verified. The method suggested in this paper is generally applicable to problems involving the consolidation coefficient, volume compressibility, conductivity coefficient, hydraulic conductivity, and specific storage of saturated soft soil, etc. Thus, its potential applications are numerous. 相似文献