面向对象方法在Biot固结有限元程序中的应用

面向对象程序设计方法应用于有限元程序编制带来了相当大的优越性。但迄今为止，这种方法在岩土工程中的应用实例很少。至于用面向对象方法进行土力学中常见的Biot固结有限元分析软件的开发，尚未见报道。现将面向对象有限元方法引入Biot固结有限元程序编制中，用C＋＋语言编制中一个Biot固结有限元程序实例。和结构化程序设计方法相比较，采用面向对象方法进行Biot固结有限元程序的编制，使程序的可维护性、可再生性、可扩充性和程序开发的效率都得到了很大的提高。指出将面向对象程序设计方法引入了Biot固结有限元程序的编制等岩土工程的数值计算领域，是今后的发展方向。     

确定固结系数的固结速率半对数法

基于太沙基一维固结理论,推导了固结速率与固结时间的解析关系,为固结系数的求解开辟了新方法。该方法避免了图解法的缺陷,消除了初始沉降和次固结的影响。求解中采用最小二乘法原理,便于计算机数据处理。通过与现有方法比较,发现该方法准确、可靠和简便,可以在实际工程中推广应用。     

无单元法在三维断裂力学中的应用

介绍了无单元法在三维断裂力学问题中的应用。无单元法基于滑动最小二乘拟合,只需结点信息就可建立离散模型。采用罚函数法来满足无单元法的本征边界条件。用可视准则来处理裂纹面对高斯点影响域的隔离作用,推导了裂纹两表面的相互作用对整体平衡方程组的贡献方程。利用单点位移公式来计算三维裂纹前缘点的应力强度因子。通过算例验证了应用该法确定三维裂纹前缘应力强度因子的有效性。     

改进的最小二乘法在水文分析计算中的应用

在水分析计算中，经常涉及到变量之间的线性或非线性拟合，而在拟合各种特性曲线时，通常应用以实测资料与拟合曲线间的误差平方和最小作为目标函数的方法——最小二乘法，但这种方法忽视了所有实测点应与拟合曲线间的相对误差尽量不超过某一百分比的原则，为了达到上述要求，提出了非线性的加权最小二乘法及线性相关方程的最小距离平方和法，探讨改进了传统的最小二乘法达到优化的效果。最小距离平方和法与常用的图解法相比，本法所得成果较为客观；与传统的单方向(x或y方向)最小二乘回归法相比，所求线性方程不会因坐标系的选取而改变。最后应用算例进行了初步讨论。     

求前期固结应力的数学模型研究及应用

前期固结应力是土体的一个重要指标。从e-logp曲线形状入手,分析了既有数学模型存在的不足,提出了用著名的Harris模型来拟合e-logp曲线的思路,通过分析对比发现,该模型比传统的3次甚至4次多项式模型更优越。采用0.618法和最小二乘拟合法编写了求前期固结应力的程序,其输入数据简单,计算结果精度高。实例计算表明所提出的曲线模型具有一定的参考价值。     

利用滑动平均剩余重力异常确定深度的最小二乘法

本文提出一种利用滑动平均剩余重力异常测定隐伏构造深度的最小二乘法。该方法主要是拟合简单的模型，用观测重力数据的所谓滑动平均滤波器进行褶积。本方法不仅能用于剩余异常，也可以适用于剖面不长的布格重力数器。该方法适用于有随机误差及不带随机误差的综合资料。由美国和塞内加尔两个野外实便作了详细检验，证明该方法是有效的。     

排水固结法在高速公路路基处理中的应用

高速公路的某些地段，土层变形较大，变形历时过长，必须进行路基处理以满足设计要求。在大量现场试验和监测结果的基础,皮肤软土地基变形机理的分析，提出并采用排水固结法的地基处理方案，设计了加压系统和排水系统。加压系统中的第一级荷载和排水井径计算的正确与否是该方法能否成功的关键。     

偏最小二乘回归法在库岸再造预测中的应用

简述了单因变量偏最小二乘回归法的基本原理和计算步骤.针对水库库岸再造预测的特点,将三峡库区巫山县段的岩质库岸划分为漫滩段、枯-洪水位变幅带、常见洪水位以上段3种类型.建立了坡角与岩体类型、力学性质、地形地貌之间的3个偏最小二乘回归方程.计算结果表明,组成岸坡的岩体类型、性质是决定库岸再造的最主要因素,地形地貌因素次之.应用偏最小二乘回归模型,可提高库岸再造预测的准确度,为土地利用提供决策支持.     

基于丹麦法稳健估计在地铁变形监测中的应用

变形监测在工程项目中是一项非常重要且必不可少的环节,因此,获得原始监测数据并进行有效的处理和预测对项目的安全实施具有关键作用。本文以长春某段地铁监测数据为例,分别用丹麦法稳健估计法和最小二乘法进行数据处理,得出丹麦法稳健估计在单一状态抗拒粗差方面优于最小二乘法的结论。     

An analytical solution of one-dimensional consolidation for soft sensitive soil ground

An analytical solution of one-dimensional consolidation for soft sensitive soil ground is presented. The moving boundary is introduced to indicate the notable change of consolidation behaviour of sensitive soil with the increase of stress level. It is assumed that the soil structure of the upper subsoil gradually destroys downwards with the dissipation of pore pressure, and the coefficient of consolidation as well as the coefficient of permeability of the upper subsoil become small, which hinders the dissipation of pore pressure of the lower subsoil. The consolidation degree curve obtained from the present solution is found to lie between the two curves obtained from Terzaghi one-dimensional consolidation solution with the parameters of the undisturbed soil and the remolded soil. The calculated results provide a new explanation for a general phenomenon in the consolidation of soft sensitive soil ground, as that for high loadings the consolidation is longer than for small ones. It should be pointed out from this study that both the deep mixing method and the long vertical drains methods are effective techniques for improving deep sensitive soil ground. Copyright © 2004 John Wiley & Sons, Ltd.     

One-dimensional consolidation of soil under multistage load based on continuous drainage boundary

In engineering practice, a rapid loading rate can result in ground failure when the strength of soft soils is relatively low, and a multistage loading scheme is always utilized to deal with this situation. Firstly, under a multistage load and the continuous drainage boundary, an analytical solution of excess pore-water pressure and consolidation degree is obtained by virtue of the superposition formula of excess pore-water pressure, and a more general continuous drainage boundary under arbitrary time-dependent load is developed. Then, a comparison with existing analytical solutions is conducted to verify the present solution. A preliminary attempt on applying the continuous drainage boundary into the finite element model is made, and the feasibility of the numerical model for the one-dimensional consolidation under the continuous drainage boundary is verified by comparing the results calculated by FEM with that from present analytical solution. Finally, the consolidation behavior of soil is investigated in detail for different int erface parameters or loading scheme. The results show that, in land reclamation projects, a horizontal drain should be placed close to the boundary with a smaller interface parameter to improve the consolidation efficiency. The degree of consolidation is also related to the applied time-dependent load and interface parameters.     

Exact solutions for one‐dimensional consolidation of single‐layer unsaturated soil

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.     

A simple analytical solution to one‐dimensional consolidation for unsaturated soils

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.     

连续渗透边界下非饱和土竖井地基固结解析解EI北大核心CSCD

基于非饱和土轴对称固结理论和等应变假设,引入连续渗透边界条件,采用边界条件齐次化、本征函数法,推导得到瞬时均布荷载下非饱和土竖井地基三维固结解析解。通过与双面完全渗透边界条件下已有解析解进行对比,验证了所得解析解的正确性。对所得解进行算例分析发现:通过设置合理上、下界面参数,所得解可用于模拟实际上、下边界透水透气任意分布的情况,弥补了目前无法考虑上、下边界渗透性介于渗透与不渗透之间或不对称分布的不足;在井径比及井深适当的前提下,当径、竖向渗透系数比大于2时,竖向渗流对于超孔隙压力消散的影响较小;当考虑竖向渗流时,上述影响随着上、下边界渗透性能的增强而愈加明显。     

广义节点无网格法在土力学固结分析中的应用

借鉴流形方法思想,引入广义节点的概念,对传统的无网格法进行了改进,建立了可具有任意高阶多项式插值函数的广义节点无网格方法.与传统无网格方法相比,广义节点无网格方法更具有一般性,当选取0阶广义节点位移插值函数时便可得到传统的无网格法.结合土工固结问题,通过推导建立了Blot固结方程的数值计算列式,对静态固结问题进行数值计算,通过对比分析验证了所建议方法的可行性.     

三维径向点插值无网格法及其在流固耦合中的应用

径向基函数点插值无网格法(radial point interpolation method,RPIM)是一种新型的无网格法,其形函数具有插值特性,且形式简单,易于施加本质边界条件。文中介绍了径向基函数点插值无网格法的基本原理,推导了三维情况下点插值无网格法的基本公式。从变分原理出发,结合比奥固结理论,建立了流-固耦合的三维点插值无网格法基本方程和数值积分方法,并开发了相应计算程序。通过三维悬臂梁和单向固结问题的数值试验,验证了该方法对三维弹性问题和流-固耦合问题的适用性和有效性     

软土动力排水固结的室内模型试验研究

以广州国际会展中心一期工程动力排水固结软基处理项目为工程背景进行了室内模型试验,重点观察和分析了插设塑料排水板过程中、全部夯击过程中及夯击完成后饱和软黏土内的孔压响应。结果表明,塑料排水板插设完毕时刻与各个位置孔压达到峰值时刻不同步,孔压增长体现出滞后性特点。夯击过程中,离夯击点越近,其孔压增长越快,孔压增长幅度也越大,达一定夯击击数后浅部孔压增长趋于平缓,而深部处全部夯击完毕后其孔压依然继续增加,但各个位置孔压消散情况基本一致。