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In-situ tests for subgrade resilient modulus characterization.

机译：用于路基弹性模量表征的现场测试。

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摘要

Subgrade soil characterization, expressed in terms of resilient modulus (MR) has become crucial for pavement design. For a new design, MR values are generally obtained by conducting repeated triaxial tests on reconstituted/undisturbed cylindrical specimens. Because of the complexities encountered with the test, in-situ tests would be desirable if reliable correlation can be established. In pavement evaluation to arrive at the type of rehabilitation required, laboratory tests for subgrade MR are even more complex and costly since coring through pavement structure is required. The main focus of this study is to determine subgrade MR employing in-situ techniques, namely Dynamic Cone Penetrometer (DCP) and Falling Weight Deflectometer (FWD). To accomplish this objective MR test results on field cores are compared with both DCP-based and FWD-based resilient modulus values. Concurrently, another objective is to analytically study the effect of soil parameters on Dynamic Cone Penetration resistance.; Twelve as-built test sections reflecting typical subgrade soil materials of Mississippi are selected and tested for DCP and FWD before and after pavement construction. Undisturbed samples are extracted using a Shelby tube, and tested in a repeated triaxial machine for MR. Other routine laboratory tests are conducted to determine physical properties of the soil. In analyzing the data, the soils tested are categorized into two groups, fine-grain and coarse-grain soils.; DCP results (DCP index, penetration/blow) froth tests conducted directly in the prepared subgrade are employed to develop regression models for laboratory MR predictions. A unique feature of the modulus is that physical soil properties are included in the models. The predictability of the models is substantiated by repeating DCP tests at an independent site.; The laboratory MR values are also compared with backcalculated moduli determined from deflections measured directly on prepared subgrade as well as atop the pavement surface. The backcalculated moduli from FWD deflection measurements on the prepared subgrade are in agreement with laboratory M R. In contrast, the backcalculated modulus derived from deflection measurements atop pavement surface is consistently larger than the laboratory MR with two distinct ratios, one for fine- and another for coarse-grain soil.; Employing pore collapse and cavity expansion analyses, the effect of different soil parameters on Dynamic Cone Penetration resistance is investigated. Among the various parameters, the friction angle in conjunction with initial porosity, significantly, affect the dynamic penetration resistance.
机译：以弹性模量（M R ）表示的路基土壤表征对于路面设计至关重要。对于新设计，通常通过对重构的/未受扰动的圆柱试样进行重复的三轴测试来获得M R 值。由于测试遇到的复杂性，如果可以建立可靠的相关性，则将需要进行原位测试。在进行路面评估以达到所需的修复类型时，由于需要通过路面结构取芯，因此对M R 路基的实验室测试更加复杂且成本更高。这项研究的主要重点是利用现场技术，即动态圆锥渗透仪（DCP）和落锤挠度仪（FWD）确定路基M R 。为了实现这一目标，将现场磁芯上的M R 测试结果与基于DCP和基于FWD的弹性模量值进行了比较。同时，另一个目的是分析研究土壤参数对动态锥穿度的影响。选择了十二个反映密西西比州典型路基土壤材料的竣工测试段，并在路面施工前后对DCP和FWD进行了测试。使用谢尔比管提取未受干扰的样品，并在重复三轴仪中测试M R 。进行其他常规实验室测试以确定土壤的物理性质。在分析数据时，将测试的土壤分为两类：细粒土壤和粗粒土壤。直接在准备好的路基中进行的DCP结果（DCP指数，渗透/打击）泡沫测试被用于建立实验室M R 预测的回归模型。模量的独特之处在于模型包含了土壤的物理性质。通过在独立地点重复进行DCP测试，可以证实模型的可预测性。还将实验室的M R 值与通过直接在准备好的路基以及人行道表面上测得的挠度确定的反算模量进行比较。在准备好的路基上从FWD挠度测量得出的反算模量与实验室M R 一致。相反，从路面表面挠度测量得出的反算模量始终大于实验室M R ，具有两个不同的比率，一个用于细土，另一个用于粗粮土。利用孔隙塌陷和空洞膨胀分析，研究了不同土壤参数对动态锥渗透性的影响。在各种参数中，摩擦角和初始孔隙率会显着影响动态抗穿透性。

著录项

  • 作者

    Abd El-Rahim, Ashraf Mohamed.;

  • 作者单位

    The University of Mississippi.;

  • 授予单位 The University of Mississippi.;
  • 学科 Engineering Civil.
  • 学位 Ph.D.
  • 年度 2001
  • 页码 146 p.
  • 总页数 146
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 建筑科学;
  • 关键词

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