连续排水边界条件及其固结分析

Consolidation theory is a key problem of soil mechanics. Most of the research focused on the consolidation equation and initial conditions, the boundary conditions are seldom studied. But the boundary conditions have important effects on the consolidation behaviour. By analyzing the expression characteristics of calssic consolidation analytical solution and the relationship of boundary pore pressure and time from consolidation test, model test and field test, continuous drainage boundary conditions associated with time and the method to determine its parameter are proposed. Use the methods of mathematical physics (separation of variables, Fourier transform and Lee transform etc.) to derivate a series of analytical solutions of one-dimensional and part of axisymmetrical consolidation with continuous drainage boundary conditions. And use transfer matrix method to obtain the consolidation solution of layered foundation. Using UMAT in ABAQUS to develop the subroutine of continuous drainage boundary condition achieve consolidation finite element analysis. The influence of boundary conditions on the consolidation behavior are discussed, including two aspects of the problem: time ratio to achieve the same degree of consolidation and the degree of consolidation ratio at the same time. Foundation design method with continuous drainage boundary condition is presented. This research will solve the contradiction between the boundary condition and initial condition of consolidation problem. Due to simulate boundary condition accurately, the whole consolidation process will be simulated more accurately. The research has important theoretical and engineering application value for the enrichment and development of consolidation theory and guiding the engineering practice.

固结理论是土力学的核心问题，大部分研究集中在固结方程和初始条件，对边界条件研究得较少，但边界条件对固结性状有很重要影响。在已有成果基础上，本项目拟首先通过对经典固结解析解表达式的剖析和对固结试验、模型试验和现场试验中孔压与时间测试结果的分析，提出与时间相关联的连续排水边界条件及其参数确定方法；采用分离变量、傅立叶变换和李氏比拟法等数学物理方程方法，推导系列基于连续排水边界条件的一维和部分轴对称固结解析解，并采用传递矩阵法给出成层地基的固结解答；同时利用ABAQUS中UMAT开发连续排水边界条件子程序，实现基于连续排水边界条件的固结数值分析；最后探讨边界条件对软土地基固结性状的影响，提出基于连续排水边界条件的软基设计方法。本研究拟解决固结理论存在的边界条件与初始条件的矛盾，能精确地模拟边界条件，进而准确地模拟土体内部固结全过程，对丰富和发展固结理论与指导工程实践具有重要的理论与工程应用价值。

固结理论是土力学的核心问题，大部分研究集中在固结方程和初始条件，对边界条件研究的较少，但边界条件对固结性状有很重要影响。在已有成果基础上，申请人通过对经典固结解析解表达式的剖析和对固结试验、模型试验和现场试验中孔压与时间测试结果的分析，提出与时间相关联的连续排水边界条件及其参数确定方法。采用分离变量、傅立叶变换和拉普拉斯变换法等数学物理方程方法，推导系列基于连续排水边界条件的一维和部分轴对称固结解析解，并采用传递矩阵法给出成层地基的固结解答；同时利用ABAQUS开发连续排水子程序，实现基于连续排水边界条件的固结数值分析；最后探讨边界条件对软土地基固结性状的影响，提出基于连续排水边界条件的软基设计方法。本研究能够解决固结理论存在的边界条件与初始条件的矛盾，能精确地模拟边界条件，进而准确地模拟土体内部固结全过程，对丰富和发展固结理论与指导工程实践具有重要的理论与工程应用价值。. 通过研究，得到四点新认识：（1）排水边界参数是界面参数，与上下界面材料性质有关；（2）固结度不再是时间因子的单值函数，还与界面参数有关，且时间因子仅是归一化方法；（3）可描述上下面排水性能略有差别的情况下固结分析；（4）土层双面排水之间的不排水对称面，不仅与双面排水的性能有关，而且与初始条件有关，甚至不是一个固定的位置。