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Stress distribution and displacement in multi-layer soil system.

机译：多层土体系中的应力分布与位移。

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摘要

In this research project an axisymmetric-two dimensional finite element model was developed in ANSYS program to predict the vertical stress distribution and surface displacement for threes type of uniform soil profiles and four different sequences of layered soil profiles. Three air dry soils, silt clay loam, silt loam and sand soil, having different mechanical properties and at initial loose conditions were employed in the simulation and measurement. In the case of uniform soil profile agreement between Boussinesq's vertical stress distribution and that obtained from the finite element model was good. Differences between the various treatments of different soil type and the linear and nonlinear soil behaviors on the vertical stress predicted by the model for case of uniform soil profile were small. The measured vertical stress was higher and extended to deeper depth compared to model prediction. Surface displacements predicted by the model were influenced greatly by the soil type and the simulated soil behaviors. Linear soil behavior obtained from one-D confined test showed lowest surface displacement while the nonlinear soil behavior obtained from semi-confined tests gave the largest values. Margin of discrepancy in the predicted surface displacements between the treatments of soil type, linear and nonlinear soil behavior was large. Measured surface displacement was higher than the predicted one, but the margin of discrepancy between the two was reduced for the case of uniform soil profile of silt clay loam soil with nonlinear soil behavior at high load levels.; In the case of layered soil profile the vertical stress distribution pattern predicted by the model was affected by the type of soil make up the layered system and by the simulated soil behaviors. Soft soil overlaid by stiff soil tends to produce predicted stress higher than Boussinesq's solution especially with nonlinear soil behavior and larger load levels; while stiffer soil underlie by softer soil gives opposite results. Laboratory measured vertical stress at depth 20 cm-30 cm showed higher values than the predicted. Surface displacement for the layered soil profile was influenced mainly by the surface layer in the system and the simulated soil behavior. Model prediction was closer to the measured surface displacement for a layered profile having a soft surface soil with nonlinear behavior at higher load levels. Results indicate that the soil test method that allowed large strain were more suitable to simulate agricultural soil behavior. Also, a 50 percent difference between the model prediction or measured vertical stress and the theoretical Boussinesq's solution was used as a base for evaluate how well the measured results correlated to the predicted one. Percentage of computed differences between showed that laboratory measured vertical stress and the finite element model prediction was close better to each other compared to the differences between the measured results and Boussinesq's solution. Result of the percentage of computed differences between the measured surface displacement and the finite element indicate that the measured surface displacements were close to the finite element prediction than to Boussinesq's estimations. Results indicate that the finite element model can be used effectively to examine and evaluate the pattern of stress distribution and surface displacement under wide range of soil and load conditions. (Abstract shortened by UMI.)
机译：在本研究项目中，在ANSYS程序中开发了轴对称二维有限元模型，以预测三种类型的均匀土壤剖面和四种不同层状土壤剖面的垂直应力分布和表面位移。在模拟和测量中，使用了三种具有不同机械性能并在初始松散条件下的风干土，粉质粘土壤土，粉质壤土和沙土。在均匀土壤剖面的情况下，Boussinesq的竖向应力分布与从有限元模型获得的竖向应力分布之间的一致性很好。在均匀土壤剖面的情况下，该模型预测的不同土壤类型的各种处理与线性和非线性土壤行为在垂直应力上的差异很小。与模型预测相比，测得的垂直应力更高，并且延伸到更深的深度。该模型预测的表面位移受土壤类型和模拟土壤行为的影响很大。从一维密闭试验获得的线性土壤行为显示出最低的表面位移，而从半密闭试验获得的非线性土壤行为给出了最大值。在土壤类型，线性和非线性土壤行为的处理之间，预测表面位移的差异幅度较大。测得的表面位移高于预测值，但在高负荷水平下具有非线性土壤特性的粉质粘土壤土的土壤剖面均匀的情况下，两者之间的差异幅度减小了。在分层土壤剖面的情况下，模型预测的垂直应力分布模式会受到组成分层系统的土壤类型和模拟土壤行为的影响。硬土覆盖的软土往往会产生比Boussinesq解更高的预测应力，特别是在非线性土性和较大荷载水平的情况下；而较硬的土壤在较软的土壤下会产生相反的结果。实验室在20 cm-30 cm深度处测得的垂直应力显示出比预期更高的值。分层土壤剖面的表面位移主要受系统表层和模拟土壤行为的影响。对于具有高负荷水平下具有非线性行为的软表面土壤的分层剖面，模型预测更接近于所测得的表面位移。结果表明，允许大应变的土壤测试方法更适合于模拟农业土壤行为。同样，将模型预测值或测得的垂直应力与理论Boussinesq解之间的50％差异用作评估测量结果与预测值的相关程度的基础。两者之间的计算差异百分比表明，与测量结果与Boussinesq's解之间的差异相比，实验室测得的垂直应力与有限元模型预测值之间的相互接近性更好。所测量的表面位移与有限元之间的计算差异百分比的结果表明，所测量的表面位移更接近于有限元预测，而不是Boussinesq的估计。结果表明，有限元模型可以有效地用于检查和评估在大范围的土壤和载荷条件下的应力分布和表面位移模式。 （摘要由UMI缩短。）

著录项

  • 作者

    Al-Azzawe, Isam Ahmad.;

  • 作者单位

    Colorado State University.;

  • 授予单位 Colorado State University.;
  • 学科 Geotechnology.; Engineering Environmental.
  • 学位 Ph.D.
  • 年度 1996
  • 页码 201 p.
  • 总页数 201
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 地质学;环境污染及其防治;
  • 关键词

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